RECORD OF DECISION (RODS) · Environmental Restoration Program. Final Record . Final Record of...

Whiteman Air Force Base

Environmental Restoration Program Final RecordFinal Record

of Decisionof Decision

for Sites SS-06, SD-07/SS-40, LF-08,

SS-15, ST-17, ST-19, ST-20, OT-23,

ST-26, DP-32, and SS-35

USAF Contract No. F41624-03-D-8595

Project No. YWHG2005-7020/7020A

Task Order 0220

Prepared for

Whiteman Air Force Base Missouri

July 2006

Final Record of Decision

Sites SS-06, SD-07/SS-40, LF-08, SS-15, ST-17, ST-19, ST-20, OT-23,

ST-26, DP-32, and SS-35

Whiteman Air Force Base Knob Noster, Missouri

Prepared by

Air Combat Command Langley Air Force Base, Virginia

July 2006

Contents

Section Page Acronyms and Abbreviations ..........................................................................................................v 1. Declaration Summary........................................................................................................1-1

1.1 Site Name and Location.........................................................................................1-1 1.2 Statement of Basis and Purpose ...........................................................................1-1 1.3 Description of Selected Remedy...........................................................................1-1 1.4 Statutory Determinations ......................................................................................1-2 1.5 Authorizing Signatures .........................................................................................1-2

2. Decision Summary .............................................................................................................2-1 2.1 Site Name, Location, and Description .................................................................2-1 2.2 Site History and Enforcement Activities.............................................................2-2

2.2.1 Site SS-06.....................................................................................................2-2 2.2.2 Site SD-07/SS-40........................................................................................2-2 2.2.3 Site LF-08 ....................................................................................................2-3 2.2.4 Site SS-15.....................................................................................................2-4 2.2.5 Site ST-17 ....................................................................................................2-5 2.2.6 Site ST-19 ....................................................................................................2-5 2.2.7 Site ST-20 ....................................................................................................2-6 2.2.8 Site OT-23 ...................................................................................................2-7 2.2.9 Site ST-26 ....................................................................................................2-8 2.2.10 Site DP-32....................................................................................................2-8 2.2.11 Site SS-35.....................................................................................................2-9

2.3 Community Participation......................................................................................2-9 2.4 Scope and Role of Response Action...................................................................2-10 2.5 Site Characteristics ...............................................................................................2-11

2.5.1 Whiteman AFB Characteristics..............................................................2-11 2.5.2 Site-specific Characteristics....................................................................2-12

2.6 Current and Potential Future Land and Resource Uses .................................2-31 2.6.1 Land Use...................................................................................................2-31 2.6.2 Groundwater Resources .........................................................................2-33

2.7 Site Risks ................................................................................................................2-34 2.7.1 Human Health .........................................................................................2-34 2.7.2 Ecological..................................................................................................2-38

2.8 Documentation of Significant Changes.............................................................2-42 3. Responsiveness Summary ................................................................................................3-1

3.1 Stakeholder Comments and Lead Agency Responses ......................................3-1 3.2 Technical and Legal Issues....................................................................................3-1

4. References ............................................................................................................................4-1

MKE\061930001 RECORD OF DECISION JULY 2006

III

1

CONTENTS

Appendix A Administrative Record Index

Table Potential Exposure Scenarios Evaluated in Human Health Risk Assessments ....... 2-35

Figures 2-1 Base Location Map 2-2 Site Location Map 2-3 Site SS-06 Site Features Map 2-4 Site SD-07/SS-40 Site Features Map 2-5 Site LF-08 Site Features Map 2-6 Site SS-15 Site Features Map 2-7 Site ST-17 Site Features Map 2-8 Site ST-19 Site Features Map 2-9 Site ST-20 Site Features Map 2-10 Site OT-23 Site Features Map 2-11 Site ST-26 Site Features Map 2-12 Site DP-32 Site Features Map 2-13 Site SS-35 Site Features Map

MKE\061930001 JULY 2006 RECORD OF DECISION IV

Acronyms and Abbreviations

1,2-DCA 1,2-dichloroethane AFB Air Force Base AFCEE Air Force Center for Environmental Excellence AST aboveground storage tank bgs below ground surface CALM Cleanup Levels for Missouri CEC Civil Engineer Compound CERCLA Comprehensive Environmental Response, Compensation, and Liability Act CFR Code of Federal Regulations cis-1,2-DCE cis-1,2-dichloroethene COC chemical of concern COPC chemical of potential concern CSR Code of State Regulations DPT direct-push technology ELCR excess lifetime cancer risk ERA ecological risk assessment ERP Environmental Restoration Program gpm gallons per minute HHRA human health risk assessment HI hazard index HQ ACC/A7VR Headquarters Air Combat Command, Environmental Restoration Office LUST leaking underground storage tank μg/L micrograms per liter MDNR Missouri Department of Natural Resources mg/kg milligram per kilogram mg/L milligram per liter PAH polycyclic aromatic hydrocarbon ppbv parts per billion by volume RAB Restoration Advisory Board RCRA Resource Conservation and Recovery Act RfD reference dose RI remedial investigation ROD Record of Decision SF slope factor SVOC semivolatile organic compound TCE trichloroethene TCLP toxicity characteristic leaching procedure TS treatability study USAF United States Air Force USEPA United States Environmental Protection Agency UST underground storage tank VOC volatile organic compound


V

1. Declaration Summary

1.1 Site Name and Location Whiteman Air Force Base (AFB) is located in Knob Noster, Johnson County, Missouri. The sites of this Record of Decision (ROD) are similar in that their evaluation concluded that the residual contamination at the sites did not present a risk under the current and anticipated future industrial scenario or the possible future residential scenario. The following sites are included in this ROD:

• Site SS-06 (Drum Storage Area) • Sites SD-07/SS-40 (Aircraft Wash Rack Drains/Spill Site) • Site LF-08 (Landfill 1) • Site SS-15 (Drum Burial Area) • Site ST-17 (Facility 92 Underground Storage Tank [UST] Area) • Site ST-19 (Facility 101/102) • Site ST-20 (Facility 158) • Site OT-23 (Firing Range) • Site ST-26 (Facility 94 Communications Building) • Site DP-32 (Old Hospital Incinerator) • Site SS-35 (Hobby Shop Spill Site)

1.2 Statement of Basis and Purpose This ROD presents the selected remedy for Sites SS-06, SD-07/SS-40, LF-08, SS-15, ST-17, ST-19, ST-20, OT-23, ST-26, DP-32, and SS-35 at Whiteman AFB, Missouri. The selected remedy was chosen in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) of 1980, as amended by the Superfund Amendments and Reauthorization Act of 1986, and, to the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan. This decision is based on the Administrative Record file for the sites listed above and complies with 40 Code of Federal Regulations (CFR), Part 300.

The lead agency, United States Air Force (USAF), in conjunction with the Missouri Department of Natural Resources (MDNR), have determined that no action is necessary to protect public health or welfare or the environment. The United States Environmental Protection Agency has declined to actively participate.

1.3 Description of Selected Remedy The no further response action selected in this ROD applies to site media at Sites SS-06, SD-07/SS-40, LF-08, SS-15, ST-17, ST-19, ST-20, OT-23, ST-26, DP-32, and SS-35. The no further action selected remedy was presented in the Proposed Plan for Sites SS-06, SD-07/SS-40, LF-08, SS-15, ST-17, ST-19, ST-20, OT-23, ST-26, DP-32, and SS-35 (CH2M HILL


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1.3 Description of Selected Remedy The no further response action selected in this ROD applies to site media at Sites 5S-06, SD-W/5540, LF-llB, 55-15, Sr-17, ST-19, ST-20, OT-23, ST-26, DP-32, and 55-35. The no further action selected remedy was presented in the Proposed Plan for Sites 55-06, SD-D7/5540, LF-llB, 55-15, ST-17, ST-19, ST-20, OT-23, ST-26, DP-32, and 55-35 (CH2M HILL 2005a). The Proposed Plan was distributed to the community and a public availability session was held May 19, 2005. The session was held to give citizens the opportunity to comment on the Proposed Plan. No comments were received from the community regarding the Proposed Plan.

1.4 Statutory Determinations Remedial investigations for the sites included. in this ROD have concluded that the residual contamination at the sites does not present a risk under the current and anticipated future indushia1 scenario or the possible future residential scenario. Therefore, no remedial action or further review is necessary to ensure protection of human health and the environment.

1.5 Authorizing Signatures

-PJ~~d&", q.'~''''/8.Zt:1J'~TGELLER Date Missouri Department of Natural Resources

~~~---- Date

Director of Installations

______________________________________ __________

__________________________________________ ___________

SECTION 1—DECLARATION SUMMARY

2005a). The Proposed Plan was distributed to the community and a public availability session was held May 19, 2005. The session was held to give citizens the opportunity to comment on the Proposed Plan. No comments were received from the community regarding the Proposed Plan.

1.4 Statutory Determinations Remedial investigations for the sites included in this ROD have concluded that the residual contamination at the sites does not present a risk under the current and anticipated future industrial scenario or the possible future residential scenario. Therefore, no remedial action or further review is necessary to ensure protection of human health and the environment.

1.5 Authorizing Signatures

ROBERT GELLER Date Missouri Department of Natural Resources

PATRICK A. BURNS Date Brigadier General, USAF The Civil Engineer, Air Combat Command

MKE\061930001 WHITEMAN AIR FORCE BASE JULY 2006 1-2

2. Decision Summary

This decision summary describes Sites SS-06, SD-07/SS-40, LF-08, SS-15, ST-17, ST-19, ST-20, OT-23, ST-26, DP-32, and SS-35 at Whiteman AFB. It also summarizes legal and public involvement issues.

2.1 Site Name, Location, and Description Whiteman AFB is located in west central Missouri, in Johnson County, approximately 2 miles south of Knob Noster (Figure 2-1). The base is approximately 9 miles east of Warrensburg, 22 miles west of Sedalia, and 70 miles southeast of Kansas City.

USAF is the lead agency and is working in conjunction with MDNR. USAF, through the Environmental Restoration Program (ERP), has financially supported site studies and development of the remedy for the sites listed below. The sites included in this decision are briefly described below and depicted in Figures 2-2 through 2-13. Additional site details are presented in Section 2.2.

Site SS-06 (Drum Storage Area) consisted of a drum storage area located on the eastern side of Building 9 and a maintenance facility located along the western edge of the flight line and aircraft apron.

Sites SD-07/SS-40 (Aircraft Wash Rack Drains/Spill Site) is a former aircraft wash rack area and drainage ditches, which conveyed water from the wash rack area to a lake located at the north end of the base.

Site LF-08 (Landfill 1) is located on the northern portion of the base and consists of an old drainageway that was partially filled with waste material during the 1940s and 1950s.

Site SS-15 (Drum Burial Area) is a suspected burial area along Brewer Branch Creek north of Bennett Lake. The buried debris is located within gully or trench features and is scattered over the surface of the site.

Site ST-17 (Facility 92 UST Area) was a complex of 12 USTs removed in 1991 as part of the reconstruction of the taxiway and hangar system in support of the B-2 bombers.

Site ST-19 (Facility 101/102) included five 25,000-gallon and five 1,000-gallon USTs that were used for storing diesel fuel and gasoline (Facility 101) and one 125,000-gallon aboveground storage tank (AST) (Facility 102) used to store jet petroleum (JP)-8 aviation fuel. Site ST-19 is located at the north end of the base.

Site ST-20 (Facility 158) is a former fuel tank farm consisting of three 12,000-gallon USTs. Site ST-20 is located in the central area of the base.

Site OT-23 (Firing Range) consists of soil excavated from two separate areas from firing ranges and consolidated in the northeast area of the base.


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SECTION 2—DECISION SUMMARY

Site ST-26 (Facility 94 Communications Building) is a former UST, which was excavated in 1992, at the Communications Building located near the eastern boundary of the base.

Site DP-32 (Old Hospital Incinerator) is a former water treatment plant and possible burn pit, centrally located near the intersection of Barksdale Lane and Minuteman Drive.

Site SS-35 (Hobby Shop Spill Site) is the location of a former Hobby Shop used primarily for vehicle maintenance until it burned down in 1970. Site SS-35 is located on the northern half of the base.

2.2 Site History and Enforcement Activities Details regarding the site-specific history and studies conducted at the sites are presented in the following sections. Appendix A presents the Administrative Record Index, which is an index of documents used to make the no further response action decision.

2.2.1 Site SS-06 Site SS-06 is a former drum storage area. Chemicals used at the facility included oils, hydraulic fluids, solvents, and degreasers (Ecology & Environment 1988a). These chemicals may have been stored in drums placed on the ground surface or on a gravel pad in the drum storage area. Numerous small spills were reported, and the drum storage area was abandoned in 1988.

An Installation Restoration Program Phase II, Stage 1 investigation of Site SS-06 was conducted in 1988 and a Phase II, Stage 2 investigation in 1991. Both investigations identified environmental impacts to the soil. Following the investigations, soil at the site was reportedly excavated, but the extent of the soil excavation was not documented. To verify that the affected soils had been removed, additional verification sampling was conducted in 1992 in support of the Remedial Investigation (RI) (Halliburton 1997a). In 2004, Site SS-06 was reviewed as part of the RI Work Plan (CH2M HILL 2005b), which presented a summary of known information, updated the human health risk assessment (HHRA) and ecological risk assessment (ERA), and recommended path forward for the site.

A summary of the contamination at Site SS-06 is provided in Section 2.5.2.1 of this ROD. A summary of site risks is provided in Section 2.7.1.

2.2.2 Site SD-07/SS-40 Site SD-07/SS-40 is a combination of two previously identified sites—Site SD-07, Aircraft Wash Rack Drains, and Site SS-40, Spill Site. The sites were combined because the activities related to the sites overlap. Site SD-07/SS-40 represents an aircraft wash rack and pump house and drainageways from the wash rack. The facilities operated until the late 1970s. In the 1950s and 1960s, the aircraft wash rack area was used for degreasing aircraft. Drainage from the cleaning operation flowed through a pipe to a nearby oil/water separator.

Water with dissolved solvent discharged from the separator by storm drain and drainage ditches to a base lake. Some of the cleaning solvent reportedly emulsified in the water and was discharged into the storm drain, prompting complaints from residents downstream of the wash rack area (Black & Veatch 1991). The solvent used predominantly for degreasing at



the wash racks was PD-680 (Stoddard Solvent, 85 percent nonane and 15 percent trimethylbenzene). In 1985, investigations began into the area and surface soil samples were collected. Results indicated the presence of volatile organic compounds (VOCs) and metals (a.k.a. inorganics). Subsequent investigations included sediment and surface water samples from the drainageways.

The aircraft wash rack and oil/water separator were removed following the Stage 2 investigation. During the early 1990s, soil in the Site SS-40 area was regraded, and a portion of the soil may have been excavated and removed from the area. Building 1 was constructed over the footprint of the wash rack. The drainage system was completely reconstructed, and the open ditches that conveyed water from the oil/water separator to the current parking lot north of Alert Road were replaced with storm sewer pipes. The underground pipes resurface south of Arnold Avenue, and the conveyed water flows through a culvert under Arnold Avenue to a lake on the north side of the road.

In 2004, Site SD-07/SS-40 was reviewed as part of the RI Work Plan (CH2M HILL 2005b). The work plan presented a summary of known information, updated the HHRA and ERA, and recommended path forward for the site. A summary of contamination at Site SD-07/SS-40 is provided in Section 2.5.2.2 of this ROD. A summary of site risks is provided in Section 2.7.2.

2.2.3 Site LF-08 Site LF-08 (Landfill 1) is known to have operated during the 1940s and 1950s. Subsurface waste was encountered during excavation of utility lines and building foundations around Buildings 160 and 154. According to Ecology and Environment (1988a), the 1947 aerial photograph showed dumping activities in the southwest corner of the Civil Engineer Compound (CEC) extending west across McConnell Lane (previously named Doolittle Road). Waste is purported to have been deposited into existing topographic swales, and a low area is evident in the 1940 aerial photograph. Dumping is also visible in the 1952 aerial photograph on the west side of McConnell Lane to the south of the current location of Building 167. The CEC was completed by 1958, and no further dumping is observed in the 1958 or subsequent aerial photographs. A vehicle wash area, which was a potential source of contamination, was located on the site and is included as part of Site LF-08 (Whiteman AFB 2002).

Fill material was observed along McConnell Lane in several places during the performance of the Phase I and Phase II investigations, and seeps were observed along McConnell Lane (Ecology and Environment 1988a; Black & Veatch 1991). This area was regraded during construction of the Officer’s Club (Building 3008) in the early 1990s. According to base personnel, surficial waste material was exposed during construction and this material was removed from the site and disposed of at an offsite landfill. An asphalt parking lot currently covers the majority of the area south of the Officer’s Club and west of the former CEC. Drainage ditches were also reconstructed at this time, and culverts were installed along Third Street and parts of McConnell Lane. No waste is visible and there is no evidence of active seepage upgradient of the drainageways.

Geophysical investigations were performed during the Phase I Investigation (Ecology and Environment 1988a), the Phase II Investigation (Black & Veatch 1991), the Resource


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Conservation and Recovery Act (RCRA) Field Investigation (Halliburton 1994), and as part of a data gap investigation (Geotechnology 1996). According to the Phase I Investigation Report, the preliminary geophysical investigation was performed between July 30 and August 6, 1985. Electrical conductivity and magnetometer techniques were used to locate or confirm the locations of buried materials. The preliminary survey did not identify any linear anomalies.

Geophysical surveys conducted during the Phase II Investigation did not detect fluctuations in terrain conductivity, which would suggest the presence of substantial accumulations of buried metallic material debris. The magnetometer survey detected what may be a scattered presence of minor amounts of metallic material. However, due to interference from manmade objects, such as power lines and buried electrical conduits, no distinct geophysical patterns could be identified. An electromagnetic survey performed during the RCRA Field Investigation indicated an anomalous area west of McConnell Lane, near the intersection with First Street. Geotechnology performed a ground penetrating radar and electromagnetic survey. The ground penetrating radar, which proved to be more accurate, indicated conductive features, possibly refuse, at a variety of depths ranging from 2 to 16 feet. In summary, none of these geophysical investigations were able to conclusively determine the existence or limits of waste material.

In 1998, Jacobs Engineering performed an additional investigation to provide data for the Vacuum-Assisted Dual-Phase Extraction Pilot Study. The investigation included installing soil borings to further define the nature and extent of trichloroethene (TCE) in groundwater and wells for groundwater extraction and geotechnical analyses of soil samples. Portions of this data and the 1996 geophysical investigation are presented in the 1998 Summary of Borehole Geophysical Investigation Report (Jacobs 1998a).

In 2004, Site LF-08 was reviewed as part of the RI Work Plan (CH2M HILL 2005b). The work plan presented a summary of known information, updated the HHRA and ERA, and recommended path forward for the site. A summary of contamination at Site LF-08 is provided in Section 2.5.2.3 of this ROD. A summary of site risks is provided in Section 2.7.3.

2.2.4 Site SS-15 A detailed history of Site SS-15 is unknown. The site was initially identified when equipment operators uncovered evidence of drums during excavation activities. Investigations into the area began with an aerial photograph review and geophysical survey. Photographs showed several lineations west of the suspected drum burial area, identified as suspected gullies and a possible trench oriented in a north-south direction. The trench area contained construction fill at the ground surface. The geophysical survey defined areas that may contain buried conductive, possibly metallic, material throughout the northern, northwestern, and western parts of the site (Black & Veatch 1991). A 1958 aerial photograph reveals a disturbed area, including possible trenches in the western part of the site. Subsequent investigations indicated the presence of buried metallic debris and VOCs, semivolatile organic compounds (SVOCs), and inorganics in soil and groundwater.

Environmental samples collected during historical investigations provided the basis for the Decision Document (Halliburton 1996). The selected remedial action was institutional



controls and monitoring for groundwater. No further action was recommended for the soil, sediment, and surface water.

Groundwater, soil, and soil gas sampling have been conducted at Site SS-15 since the preparation of the Decision Document. In 2004, a supplemental investigation and an interim investigation were conducted. The supplemental investigation was conducted north of the Site SS-15 limits, at MDNR’s request, because of the observation of disturbed areas in several historical aerial photographs (Black & Veatch 2004b). The interim investigation was conducted to confirm the presence and valence state of chromium in surface water and to determine soil gas concentrations of acrolein for use in evaluating the indoor air vapor intrusion pathway in the HHRA. Results of the interim investigation were presented in the RI Work Plan (CH2M HILL 2005b).

A summary of contamination at Site SS-15 is provided in Section 2.5.2.4 of this ROD. A summary of site risks is provided in Section 2.7.4.

2.2.5 Site ST-17 Site ST-17 is located between the north and south sets of B-2 hangars and is flanked by the operations apron and the runway. The 1-acre site, formerly known as the Underground Fuel Storage Tank Area, was a complex of 12 USTs outside the pump house in Building S-92 (Ecology and Environment 1988a). Testing in 1988 indicated the integrity of the tanks had not been compromised, but releases may have occurred during fuel transfer operations (Ecology and Environment 1988b).

In 1991 as part of the reconstruction of the taxiway and hangar system, the tanks were removed. Following tank removal, confirmation soil samples were collected within each of the 12 tank areas (PACE 1991). Exact location and depth of confirmation soil samples are unknown. There was no available information regarding the disposition of soil excavated as part of the UST removal. MDNR approved the completion of the UST closure in a letter dated August 29, 1990.

Environmental samples were collected in 1985 as part of Phase II Stage 1 for the site, and documentation in support of no further action was prepared in August 1988. The investigation was performed while Building S-92 was operational, and the location of the borings was dictated by underground utilities and safety requirements. The samples provided the basis for the decision document (Jacobs 1998b). No further activity has been conducted at the site since the decision document was prepared.

In 2004, Site ST-17 was reviewed as part of the RI Work Plan (CH2M HILL 2005b). The work plan presented a summary of known information, updated the HHRA and ERA, and recommended path forward for the site. A summary of contamination at Site ST-17 is provided in Section 2.5.2.5 of this ROD. A summary of site risks is provided in Section 2.7.5.

2.2.6 Site ST-19 Site ST-19, known as Facility 101/102, is located at the north end of the base between Arnold and Vandenberg avenues. The site consisted of two adjacent facilities: Facility 101 and Facility 102.


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Facility 101 had five 25,000-gallon USTs that were used for storing diesel fuel and gasoline (Jacobs 1999a). When in operation, the tanks were filled from a dispensing area located on the east side of the facility. When empty, the USTs reportedly were filled with a rust-inhibiting solution. A fuel spill was reported to have occurred in the mid-1980s when heavy rainfall flooded the tanks, displacing fuel and contaminating the surrounding soil (Halliburton 1997b). The USTs were removed in 1998 and closed in accordance with the MDNR’s UST Closure Guidance Document. A total of 2,130 cubic yards of soil was excavated during the tank closure, 1,250 cubic yards of which were determined to be contaminated and were disposed or treated at Show Me Landfill and Central Missouri Landfill. A total of 880 cubic yards of non-contaminated soil was returned to the tank area along with an additional 1,500 cubic yards of clean backfill.

The excavation conducted for the UST removal effort revealed a concrete vault below the Facility 101 dispensing area that contained five closed-in-place 1,000-gallon USTs. The concrete vault with the USTs was left in place (Gehm 1998). In a letter dated October 19, 1998, MDNR determined that no additional investigation or remedial action was required with regard to closure of the USTs at Site ST-19.

Facility 102 had one 125,000-gallon AST that was used for JP-8 aviation fuel storage. No information is available on the operational history of the facility. In 1992, the AST reportedly was demolished and removed from the site. In 1997, new ASTs were installed with spill and leak containment at the Facility 102 location. No documentation of historical spills, installation details, or details of the soil excavation prior to installation of new ASTs exists for Facility 102.

A drainage channel located north of the two facilities received surface water runoff from both. Historically, storm sewer piping conveyed surface water from the facilities to this ditch. The drainage channel is still present and carries storm water in a northerly direction.

Environmental samples were collected in 1993 as part of a RI of the site, and a RI report was prepared in June 1997 (Halliburton 1997b). The samples, in addition to those collected during the UST removal, provided the basis for the Decision Document for No Further Action (Jacobs 1999a). No further activity has occurred since the decision document was prepared.


2.2.7 Site ST-20 Site ST-20 is located near the Base Transportation Support shop along 4th Street. The site surface is relatively flat and is paved. The site is a former fueling station known as Fuel Tank Farm Facility 158. The fueling station consisted of three USTs, two of which (Tank 158-1 and Tank 158-2) contained gasoline; the third (Tank 158-3) held diesel fuel.

In August 1992, tightness testing indicated that the southernmost UST (Tank 158-3) was leaking. The three 12,000-gallon USTs at Site ST-20 were removed (Tank 158-3 in late 1997 and the other two in early 1998). The excavation depth for the 1997 removal was reported to be 12 feet below ground surface (bgs) and reported as 8 feet bgs for the others. The pump



island was also removed, and the closure report indicates that part of that area was excavated to a depth of 8 feet bgs. Excavated soils and excavation side walls were sampled, and analytical results were less than leaking underground storage tank (LUST) soil cleanup guidelines. The removal of the USTs and RI work conducted at Site ST-20 led to the preparation of a Tank Closure Report in 1999 (Jacobs 1999b). The Tank Closure Report was submitted to the UST Section of MDNR for comment. MDNR’s comments on the Closure Report were addressed and the area immediately adjacent to the USTs was closed. In 2000, an RI/FS and risk assessment were completed recommending no further action with long-term maintenance (LTM). In 2001, a Decision Document for No Further Action for Site ST-20 documenting the results of the FS and UST closure was submitted to the Federal Facilities Section of MDNR (Montgomery Watson 2001). Formal response to the decision document was not received.


2.2.8 Site OT-23 Site OT-23 consists of two separate inactive firing ranges that contained lead-contaminated soil resulting from pistol, rifle, and machine-gun practice. Range A is an abandoned rifle range located on Johnson County Road at the eastern base boundary. Range B is an abandoned pistol range located at the northeast intersection of 10th Street and Spaatz Road, located at the southwestern part of the base. The ranges include affected soil berms located behind the target designed to capture projectiles. The berms at Ranges A and B were located outside and open to the weather.

Based upon results of a 1991 RCRA facility assessment, Site OT-23 was added to the ERP list. Samples collected in 1991 from the berms at each range indicated elevated lead concentrations, and in 1996, Ranges A and B were decommissioned. In 1996, 3 feet of soil and part of the soil berm were excavated at Range A. In March 1997, 1,300 cubic yards of affected soil were excavated from Range B and placed with the affected soil at Range A. The soil was stockpiled on Range A prior to screening and stabilization. Stabilization of soils consisted of using a patented chemical treatment process (MAECTITE®) that converts leachable metals (e.g., lead) into insoluble minerals. A total of 5,379.5 tons of lead-contaminated soil was stabilized, and confirmation samples were collected for every 100 cubic yards of soil treated. Confirmation soil samples were collected and analyzed using the RCRA Toxicity Characteristic Leaching Procedure (TCLP), and all but one sample had concentrations below the 5 milligrams per liter (mg/L) limit. The sample above the limit contained 15.5 mg/L.

The treated soil was used as fill in the excavated area. Clean soil from the berm was spread and compacted to form a 2-foot-thick cover over the treated soil. The clean soil cover provides a barrier against future contact and reduces rainwater infiltration. Since the soil remained onsite, MDNR required groundwater monitoring, and Site OT-23 was included in the long-term monitoring program from 1998 through 2004. As part of the program, three monitoring wells were installed at Site OT-23 in May 1998. A fourth well was installed in December 2002 per request by MDNR.


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In 2004, Site OT-23 was reviewed as part of the RI Work Plan (CH2M HILL 2005b). The work plan presented a summary of known information, updated the HHRA and ERA, and recommended path forward for the site. A summary of contamination at Site OT-23 is provided in Section 2.5.2.8 of this ROD. A summary of site risks is provided in Section 2.7.8.

2.2.9 Site ST-26 Site ST-26 is the location of a former UST at the Communications Building, near the eastern boundary of the base. The UST was used to store diesel fuel from 1961 to 1992, at which time it was removed from service because it was suspected of leaking. The UST was excavated in 1992, and the excavation was filled with clean backfill. A RI was conducted in 1993 that included collecting grab groundwater samples. The groundwater samples collected indicated the presence of VOCs. Based on the tank removal and soil remediation activities at the site, no further action was proposed by USAF, and closure documents were submitted to MDNR.

MDNR did not approve the closure at that time because of the presence of monocyclic aromatics. Monocyclic aromatics have relatively high volatilization and solubility rates, are considered to be highly mobile in soil, and are expected to migrate through the soil and potentially leach to the groundwater. Based on a concern that the sampling locations were not near the source, MDNR requested additional data, and Site ST-26 was added to the long-term monitoring program.

Groundwater monitoring took place at Site ST-26 from October 1999 through April 2004. As reported in the latest groundwater summary monitoring report (Black & Veatch 2004a), TCE was detected in one monitoring well (at 17 micrograms per liter [μg/L]) above the regulatory drinking water standard of 5 μg/L. Over time, the concentrations of TCE in groundwater have been decreasing. A supplemental investigation was performed in January 2004 in accordance with discussions with MDNR to address identified data gaps to allow site closure. That investigation consisted of five direct-push technology borings (DPTs) and groundwater sampling (Black & Veatch 2004b). MDNR approved the investigation and the conclusion that the site had been characterized in 2004.

In 2004, Site ST-26 was reviewed as part of the RI Work Plan (CH2M HILL 2005b). The work plan presented a summary of known information, updated the HHRA and ERA, and recommended path forward for the site. A summary of contamination at Site ST-26 is provided in Section 2.5.2.9 of this ROD. A summary of site risks are provided in Section 2.7.9.

2.2.10 Site DP-32 Site DP-32 is a former water treatment plant and possibly a burn pit site (identified in some documents as an incinerator) for solid/liquid waste from the flight line. The site, located near the intersection of Barksdale Lane and Minuteman Drive, was transformed into a playground surrounded by military family housing. Recently, however, the base began demolishing the housing surrounding the site. Upon demolition completion, Site DP-32 will be used as parade grounds.

Site DP-32 was once part of a natural wooded area containing three drainage channels, remnants of which are still present at the site. Site DP-32 is characterized by a topographic



high that gradually slopes downgradient to the north, west, and southwest toward the primary drainage channel and the southern tributary.

In March 2004, a treatability study was conducted to evaluate a potential remedial alternative to address chemicals encountered in the primary drainage channel in the northern portion of the site. An organic mulch biowall was studied as a remedial alternative (CH2M HILL 2004). Monitoring events as part of the treatability study have been ongoing since March 2004. They will continue until March 2006.

In late 2004, Site DP-32 was reviewed as part of the RI Work Plan (CH2M HILL 2005b). The work plan presented a summary of known information, updated the HHRA and ERA, and recommended path forward for the site. A summary of contamination at Site DP-32 is provided in Section 2.5.2.10 of this ROD. A summary of site risks is provided in Section 2.7.10.

2.2.11 Site SS-35 Site SS-35 is the site of a former Hobby Shop located in the northern half of the flight line facilities, west of the aircraft parking apron. The site is east of Building 115, north of Building 116, and along Lockbourne Terrace. The Hobby Shop was used primarily for vehicle maintenance until it burned down in 1970. It is now used for vehicle parking and equipment storage. The area around the Hobby Shop footprint is primarily an asphalt parking area with intermittent sections of grass or gravel. Storm water drains into a swale to the north where it enters the base storm water system.

In 2004, Site SS-35 was reviewed as part of the RI Work Plan (CH2M HILL 2005b). The work plan presented a summary of known information, updated the HHRA and ERA, and recommended path forward for the site. A summary of contamination at Site SS-35 is provided in Section 2.5.2.11 of this ROD. A summary of site risks is provided in Section 2.7.11.

2.3 Community Participation Regulations under CERCLA require public participation to occur before and at the completion of the ROD (e.g., 40 CFR § 300.430[f][3]; see also, Community Relations Superfund: A Handbook [USEPA 1992]). To meet these obligations, USAF and MDNR regularly provide the community with information regarding the cleanup of sites at Whiteman AFB through meetings of the Restoration Advisory Board (RAB). In addition, USAF provides a public information repository, meeting announcements, fact sheets, and public notices published in the local newspapers.

The public was encouraged to attend RAB meetings, which were held semiannually from mid-1990s until 2003; since then, RAB meeting have been held annually. The location, date, and time of the meetings are published in the local newspapers. At these meetings, community members review and discuss the ERP progress and are encouraged to provide USAF with their ideas and opinions regarding studies and cleanup options at the various ERP sites. Published ERP reports are made available to the public at the information repository located in Warrensburg, Missouri, at the Central Missouri State University Library Government Documents Room. The Whiteman AFB ERP Manager is responsible for


2-9


maintaining the repositories and ensuring that documents are added to the information file as work continues at the site.

A public comment period for the Proposed Plan, which corresponds to this ROD, began on April 22, and ended on May 31, 2005. The Proposed Plan was mailed directly to the Whiteman AFB mailing list for public review. The Proposed Plan included information announcing the public comment period and associated public meeting. A public notice summarizing the Proposed Plan and announcement of the public comment period and associated public availability session was also printed in local newspapers. In addition, postcards announcing the public availability session were distributed to base residences.

Representatives from USAF, MDNR, and CH2M HILL were available to answer questions regarding the ERP at Whiteman AFB. MDNR distributed general environmental information for the State of Missouri. No comments or community attendance was received at the public availability session, which was held May 19, 2005.

2.4 Scope and Role of Response Action The proposed no further action remedy in this ROD will be the final action for Sites SS-06, SD-07/SS-40, LF-08, SS-15, ST-17, ST-19, ST-20, OT-23, ST-26, DP-32, and SS-35. USAF and MDNR have determined that no further response action is necessary to protect public health or welfare or the environment.

The no further response action is based on the conclusions of the risk assessment presented in the approved RI Work Plan. One element of the risk assessment was the determination that the domestic groundwater use pathway is not complete. This determination was based on the fact that the shallow groundwater is not currently used for domestic purposes, does not have sufficient yield to serve as a primary component of a public or private water supply, and has an institutional control restricting use. The State of Missouri Well Construction Code (10 CSR 23-3) defines the area in which Whiteman AFB is located as Area 1 and the regulations stipulate that “[a]ll persons engaged in drilling domestic wells in Area 1…shall..[s]et no less than eighty feet (80’) of casing, extending not less than thirty feet (30’) into bedrock.” This prevents the installation of drinking water wells within the shallow aquifer and effectively eliminates the beneficial use of that aquifer. To further prevent non-compliant groundwater extraction at the base, the Base General Plan contains the following language:

“All drinking water wells will be constructed in accordance with the Missouri Department of Natural Resources rules for Well Construction (10 CSR 23-3). This requirement prevents the use of potentially contaminated groundwater in the shallow aquifer and provides protection for deep aquifers at the base.”

Wells installed at Whiteman AFB for domestic use are located in a deep aquifer and future wells, if necessary, would also be installed in this deep aquifer which has not been affected by activities at these sites.

In addition, the locations of the shallow groundwater plumes for the no further response action sites will be added to the base general plan to document their location in the event

2-10 MKE\061930001 WHITEMAN AIR FORCE BASE JULY 2006


that future risk assessment methodologies or assumptions change and new evaluations are necessary.

2.5 Site Characteristics This section describes the pertinent physical characteristics of Whiteman AFB and the specific sites to be closed. This is followed by a summary of the nature and extent and fate and transport of contamination based on environmental sampling data from the site-specific investigations.

2.5.1 Whiteman AFB Characteristics 2.5.1.1 Geology The regional geology generally consists of unconsolidated overburden underlain by bedrock. Unconsolidated overburden consists of thin alluvial deposits over loess and residual soils. The alluvium consists of stratified deposits of sand, gravel, silty clay, and silty clay loam (Stohr et al. 1981). Beneath the alluvium are loess and residual soil deposits. Loess consists of wind-blown silt deposits, but the loess may be absent because of erosion or nondeposition. Residual soils consist of soil from in-place weathering and decomposition of bedrock. The residual soils are thickest on gentle slopes, and usually consist of clayey silt or sandy silty clay with occasional sand or gravel. A moderately weathered light brown to gray clayey shale is generally observed beneath the unconsolidated overburden materials at Whiteman AFB. The competent bedrock under the clayey shale consists of shale and sandstone units of the Lagonda Formation, Cherokee Group, Desmoinesian Series, and Pennsylvanian System.

2.5.1.2 Hydrogeology Two potentially significant aquifers and three low-yielding groundwater bearing zones occur in the area of Whiteman AFB:

• A Quaternary-age unconsolidated overburden water-bearing unit consisting of alluvium, loess, and residual soil (low-yielding)

• Pennsylvanian-age, Cherokee Group shales, sandstones, and limestones (low-yielding)

• Mississippian-age limestones (low-yielding)

• Ordovician-age aquifers, specifically sandstones in Central Missouri (used for base water supply)

• Cambrian-age aquifers, specifically dolomite (used for base water supply)

Shallow groundwater within the unconsolidated overburden appears to be under semiconfined conditions within a clay with sand and gravel or clayey shale at the soil/bedrock interface. These units vary in thickness and do not appear to be continuous beneath the sites (as evidenced by their absence at Site SS-06).

MKE\061930001 2-11 RECORD OF DECISION JULY 2006


2.5.1.3 Surface Water Whiteman AFB is drained by several small perennial streams and creeks that flow to either the Blackwater or Lamine rivers (Metcalf and Eddy 1991). Both rivers are part of the Missouri River drainage basin. Base streams are not classified by MDNR for the protection of aquatic life (10 Code of State Regulations [CSR] 20-7.031), nor are they used as sources of potable water (Ecology and Environment 1988). Because of the low relief and poor infiltration capacity of the soils, intense rainfall commonly causes localized flooding in parts of the base.

2.5.2 Site-specific Characteristics Geology at the base is consistent; therefore, a site-specific geologic discussion is unnecessary. Subsequent sections describe the hydrogeology, surface water conditions, nature and extent and fate and transport of contamination, risk assessments, and the conceptual site model.

The nature and extent and fate and transport of site contaminants aid in understanding the current distribution of the contaminants, as well as assessing the potential for exposure if no remedial actions are taken at the site. The chemical and physical properties of these types of contaminants and fate and transport processes are described in detail within the RI Work Plan (CH2M HILL 2005b).

Chemicals of potential concern (COPCs) and chemicals of concern (COCs) were identified through the performance of the HHRA as part of the RI Work Plan (CH2M HILL 2005b). COPCs are chemicals found at concentrations greater than conservative screening levels, identified as a potential threat to human health or the environment, and further evaluated in the baseline risk assessment. The nature and extent and fate and transport discussions below focus on the COPCs identified at each site.

2.5.2.1 Site SS-06 Site SS-06 Hydrogeology Based on one monitoring well at the site and monitoring wells at Site SS-40, which are immediately to the northwest of Site SS-06, groundwater flow is to the northeast. The original depth to groundwater after installing the monitoring well was recorded as 24 to 25 feet bgs and rose to approximately 6 feet bgs (Halliburton 1997a). This rise in groundwater indicates that semiconfined conditions exist at Site SS-06.

Site SS-06 Surface Water There are no wetlands or surface water bodies present at or adjacent to Site SS-06. The site is located on the flight line and associated aircraft apron. Therefore, a portion of the site is concrete pavement with some grassy infield areas. The pavement storm water drains to the grassy infield areas.

Site SS-06 Nature and Extent of Contamination No COPCs were identified in soil or groundwater at Site SS-06. Water bodies are not present at the site; therefore, no surface water or sediment samples are present.

Site SS-06 Fate and Transport of Contamination A discussion of fate and transport of contamination is not applicable because there were no COPCs identified in soil and groundwater at Site SS-06.



2.5.2.2 Site SD-07/SS-40 Site SD-07/SS-40 Hydrogeology Historic groundwater flow across the southern portion of the site generally is toward the west and northwest. The occurrence of groundwater is most prevalent in the clay with sand and gravel, which appears to be semiconfining. This is supported by the fact that a rise in groundwater is observed in monitoring wells screened in this unit, as opposed to those screened in the overlying lean clay.

Site-specific information is not available to calculate groundwater flow velocities, but based on other sites, groundwater velocities on the order of 10 feet/year are common at the base.

Site SD-07/SS-40 Surface Water Historically, drainage from the cleaning operation at Site SD-07 flowed through a pipe to a nearby oil/water separator. Water with dissolved solvent discharged from the separator to a base lake and eventually Clear Fork Creek through the open drainage ditch. The open drainage ditch has since been replaced by a pipe and filled with soil, and the area has been paved. The habitat that was previously in the open drainage ditch thus was removed. The base lake, which is downgradient of the former drainage ditch and downgradient of the piped discharge could have received input from Site SD-07/SS-40. A portion of the drainage ditch is still present to the north.

Site SD-07/SS-40 Nature and Extent of ContaminationSoil Lead, an inorganic, and 3,3’-dichlorobendizine, a SVOC, were identified as COPCs in soil.

Lead was detected in two samples at concentrations of 483 milligrams per kilogram (mg/kg) and 673 mg/kg. Both samples were collected in 1985, prior to base construction and removal and reworking of soil in the area; therefore, samples were collected again in 2002. Samples collected during the 2002 investigation did not exhibit lead concentrations greater than the screening level.

3,3’-Dichlorobenzidine was detected in two borings installed north of the former wash rack and not directly downgradient. Concentrations from the 0- to 2-foot bgs interval were 0.041F and 0.051F mg/kg. Concentrations from the 6- to 8-foot bgs interval were 0.09F and 0.048F mg/kg.

Groundwater TCE, cis-1,2-dichloroethene (cis-1,2-DCE), and selenium were identified as COPCs in groundwater.

TCE, which is a VOC, was detected at concentrations above the screening level in four groundwater monitoring wells, ranging from 5.3 to 80.5 μg/L. The extent of TCE is bounded by groundwater sample locations exhibiting concentrations either below detection or below the screening level in the upgradient, downgradient, and cross gradient to the northeast position. The extent is not bounded by a groundwater sample location in the cross-gradient position to the southwest, but the concentration of TCE decreases cross-gradiently northeast to southwest.

cis-1,2-DCE, a degradation product of TCE, was detected at concentrations above its screening level in two wells, ranging from to 95 to 412.6 μg/L. The extent of cis-1,2-DCE is



bounded by groundwater sample locations exhibiting concentrations either below detection or below the screening level in the upgradient, cross-gradient location to the northeast, and downgradient location. The extent is not bounded by a groundwater sample location in the cross-gradient position to the southwest, but the concentration of cis-1,2-DCE decreases cross-gradiently northeast to southwest.

Selenium, an inorganic, was detected in five monitoring wells. The extent of the elevated concentrations is bounded by groundwater samples with concentrations below the screening level. The cross-gradient locations are not bounded, but the concentrations of dissolved selenium decrease northeast and southwest from the locations that exhibited the highest concentrations of dissolved selenium.

Surface Water There were no COPCs identified for site surface water.

Sediment There were no COPCs identified for site sediment.

Site SD-07/SS-40 Fate and Transport of Contamination Chemicals classified as VOCs, SVOCs, and inorganics were evaluated as site COPCs.

Fate and Transport of VOCs The distribution of VOCs suggests that spillage from the former wash rack is the probable source. The released TCE volatilized to the atmosphere and leached to groundwater. TCE and cis-1,2-DCE were not found in soils at concentrations exceeding screening levels.

The main migration and fate pathways for the VOCs found in groundwater are:

• Migration and degradation in groundwater • Volatilization from groundwater

Migration and Degradation in Groundwater. TCE degrades most rapidly in soil and groundwater under anaerobic conditions. The reductive dechlorination follows the sequential pathway of TCE to cis-1,2-DCE to vinyl chloride to carbon dioxide, chloride, and water. cis-1,2-DCE and very low concentrations of vinyl chloride are found in groundwater within the small TCE plume boundaries. This is indicative that reductive dechlorination has occurred. Both VOCs are present below screening levels within 250 feet of the most elevated concentrations.

The VOC plume is migrating to the north, although there is some uncertainty as to whether the site groundwater ultimately discharges to surface water features to the north or northwest. In either case, the discharge areas are more than 2,400 feet from the current TCE plume boundaries. Site-specific estimates of TCE migration velocity are not available, but using the typical migration velocity of approximately 10 feet/year for the base, it would take more than 200 years for the plume to discharge to surface water. Given this long travel time, it is unlikely the plume will reach a discharge zone before attenuating to concentrations below screening levels. Even if the plume eventually reached the creek, there would be significant volatilization upon discharge and detectable concentrations in the creek are unlikely.



Volatilization from Groundwater. In general, volatilization from groundwater does not result in significant loss of the plume contaminant mass for most plumes. However, volatilization can occur from the upper few feet of the saturated zone and can be accentuated in slowly moving plumes where there are wide fluctuations in the water table. Quantification of this pathway is performed as part of the risk assessment to assess impacts on human health.

Fate and Transport of SVOCs 3,3’-Dichlorobenzidine is characterized by very low rates of volatilization (Henry’s Law coefficient = 4 × 10-9 atm-m3/mole) and moderate adsorbability (Koc = 724). Normally 3,3’-dichlorobenzidine would be expected to persist in soil, but its very low concentration of 0.051 mg/kg suggests very little attenuation is needed before it drops to detectable levels of about 0.04 mg/kg. Migration may occur through soil erosion. The site is well vegetated, and movement of 3,3’-dichlorobenzidine with future erosion of soil particles with adsorbed 3,3’-dichlorobenzidine is considered to be an insignificant migration pathway. Leaching to groundwater has not occurred because it has not been detected in groundwater. Further leaching to groundwater at levels of concern is not expected.

Fate and Transport of Inorganics The lead soil data are 19 years old and represent surface soil that has since been excavated or reworked during base construction. Resampling near select locations with elevated lead concentrations has demonstrated lower concentrations. As a result, the concentrations are likely lower as a result of mixing with soil from outside the former drainageway.

Lead has limited volatility and would be expected to persist in soil. The main migration pathway for lead at Site SD-07/SS-40 is erosion of soil containing adsorbed lead. The site is covered with pavement or is well vegetated, and movement of lead adsorbed to soil particles is considered to be an insignificant migration pathway.

Leaching of lead from soil to groundwater is not considered a significant pathway. Lead has not been detected above screening levels in groundwater samples collected for Site SS-40. As a result, leaching of lead does not appear to have resulted in impacts to groundwater.

Selenium is rarely seen in groundwater at levels of concern. It is somewhat uncertain whether it is actually present in groundwater or whether sample turbidity or laboratory analytical problems is the reason for its presence. Its distribution is roughly similar to that of TCE, so it cannot be discounted entirely. Selenium migration is difficult to assess without details on the groundwater geochemistry and the species of selenium. Elemental selenium is virtually insoluble and would not be the form found in groundwater, but very soluble forms such as sodium selenide or potassium selenate could be present. Its distribution suggests its movement to date has paralleled that of the TCE plume.

2.5.2.3 Site LF-08

Site LF-08 Hydrogeology Groundwater generally flows toward the drainageway that parallels McConnell Lane and continues north of 1st Street. This results in northeasterly flow in the area on the west side of McConnell Lane and northwesterly flow from the CEC area. Depth to groundwater generally is less than 5 feet bgs in the CEC area and up to 10 feet bgs in the Site LF-08 area, though the depth to groundwater becomes shallower toward the ditch discharge area. Slug



test results indicate a groundwater velocity of 9.5 feet per year based on an average hydraulic conductivity of 0.13 feet per day, an effective porosity of 0.15, and a gradient across the site of 0.03. Slug tests performed at nearby Site SS-30, indicated a groundwater velocity ranging from 1 to 14 feet per year.

Site LF-08 Surface Water Surface water is present at the site within a drainageway present along the east side of McConnell Lane and open ditches and culverts in the area west of Building 166 and north of Building 160. This drainageway carries surface water to a culvert under 1st Street and to a creek that conveys surface water north and ultimately to Clear Fork Creek.

Site LF-08 Nature and Extent of Contamination Waste Geophysical investigations have not conclusively determined the existence or limits of waste associated with Site LF-08, former Landfill 1. The bulk of this material may have been removed during the construction of Building 3008. In addition, a detailed review of the soil borings completed to date provides very little evidence of the presence of waste in the soil borings. The extent of landfill waste material has not been confirmed, but the work to date at Site LF-08 has documented that only trace waste material remains at the site.

Soil Lead, an inorganic, was identified as a COPC in soil.

Lead was detected at a concentration of 306 mg/kg in a sample collected from at depth of 1 to 2 feet bgs. Waste material was also observed within the sample. This sample was collected prior to the excavation of soil in the area for the construction of Building 3008.

Groundwater VOCs, benzene, TCE, cis-1,2-DCE, and vinyl chloride were identified as COPCs in groundwater.

Benzene was detected at a concentration of 117 μg/L at one location located west of Building 168.

TCE-contaminated groundwater forms a plume in the CEC area. cis-1,2-DCE and vinyl chloride, products from the degradation of TCE, were observed in groundwater at concentrations greater than the screening levels within the TCE plume. These chemicals are found at much lower concentrations and much less frequently than TCE. The concentrations of cis-1,2-DCE are less than its screening level of 70 μg/L, except at one location where the concentration is 79.27 μg/L. Vinyl chloride is present at a concentration above its screening level of 2 μg/L in one monitoring well at 2.4 μg/L.

The TCE plume exceeding screening levels is relatively wide (about 600 feet), most likely indicative of multiple release points. This eastern half of the plume is much lower in concentration (generally between 5 and 10 μg/L). The more concentrated part of the plume that is above 500 μg/L is relatively narrow (about 75 feet wide) and oriented parallel to the groundwater flow direction. The plume does not extend beyond the ditch discharge location along McConnell Lane and 1st Street.

Surface Water No COPCs were identified in surface water at the site.



Sediment No COPCs were identified in sediment at the site.

Site LF-08 Fate and Transport of Contamination VOCs in groundwater and one inorganic in soil were evaluated as site COPCs.

Fate and Transport of VOCs The location and distribution of VOCs suggests one or more historic spills or similar releases in the CEC area. One or more spills likely released TCE to soil where it volatilized to the atmosphere and leached to groundwater. TCE was not found in site soils at concentrations exceeding screening levels. Release of pure phase solvent is unlikely because of the lack of the solvents in the soil and the fact that the maximum dissolved phase concentrations of TCE (2,000 μg/L) is far below its solubility (1,100,000 μg/L) in groundwater. There are an estimated 45 pounds of TCE in the dissolved phase in groundwater and adsorbed on the surrounding soils.



Migration and Degradation in Groundwater. cis-1,2-DCE and vinyl chloride are found at much lower concentrations and much less frequently than TCE. Aerobic conditions currently exist in groundwater, as indicated by the presence of dissolved oxygen and nitrate in most of the plume monitoring wells. These data indicate that while some biodegradation of TCE has occurred, it is not occurring to a substantial degree in most of the TCE plume.

Recently, an enhanced reductive dechlorination treatability study (TS) was conducted at the CEC area to create reducing conditions through the injection of vegetable oil to serve as an organic substrate. The TS was not entirely successful because of the difficulty in getting adequate distribution of the substrate in the very low permeability soils. However, it is expected that some reducing conditions will occur in the future in the more concentrated parts of the plume and result in reductive dechlorination of TCE. Beyond the area of injection, however, degradation of TCE may not be significant because of the lack of anaerobic conditions.

The VOC plume is discharging to the ditch located along the east side of McConnell Lane and along the north side of 1st Street. The estimated plume discharge flow to the ditch is 0.06 gallons per minute (gpm), and the estimated TCE mass flux to the ditch is 0.15 pound/year. At these low mass flux rates and the minimal water depth (a few inches) and flow in the ditch, there would be significant volatilization at the groundwater/surface water interface and in the ditch. The ditch has been sampled four times and only trace concentrations of TCE have been observed. TCE was found in one sample from a seepage depression at a concentration of 20 μg/L during one sampling episode. The TCE concentrations in this sample indicate groundwater conditions rather than surface water conditions. However, seepage is no longer present at the location. TCE was not found at several downstream sample locations where more volatilization is expected.

The lack of a continuing source of VOCs to groundwater will result in diminishing concentrations over time as the plume migrates downgradient and discharges to the ditch.



The historical groundwater data indicate a declining trend in groundwater concentrations at locations that are closer to the most likely original source areas. Increases in TCE concentrations have occurred at downgradient locations nearer the discharge zone and are expected as the plume migrates to the discharge location. The trends in TCE concentration near the discharge location are expected to begin declining as the plume continues to migrate and discharge to the ditch. The travel time for the remainder of the TCE plume to travel 1,000 feet from the original source area north of 3rd Street to the ditch was estimated to be 100 years, assuming no degradation. Dispersion and volatilization from the upper few feet of the saturated zone is expected to occur and will also result in diminished TCE plume concentrations before discharge to the ditch.

In summary, the TCE plume is expected to discharge slowly to the ditch over the next 10 decades. The mass flux of groundwater and TCE to the ditch is very small (about 0.06 gpm and less than 0.15 pound/year), and the TCE is expected to continue to be present at minimal or immeasurable concentrations in the ditch downstream of the site.

Volatilization from Groundwater. As described in Section 2.5.2.2 above.

Fate and Transport of Inorganics The single elevated lead sample was located within waste material near Building 3008. Lead persists in soil and does not readily dissolve in groundwater or volatilize into air. Because of its tendency to adsorb to soil particles, the most likely transport mechanism is by windborne contaminated dust or soil erosion, rather than migration through groundwater. It is also important to note that the elevated lead level was observed in soil that may have been removed during the construction of Building 3008 or is currently located beneath an asphalt driveway.

2.5.2.4 Site SS-15 Site SS-15 Hydrogeology Groundwater flow across the site generally is toward the north/northwest. Groundwater near Brewer Branch Creek flows towards the creek. Groundwater is most prevalent in the clay with sand and gravel as opposed to the overlying lean clay.

Groundwater velocities are expected to be less than 10 feet/year based on estimates for other similar sites on base.

Site SS-15 Surface Water A creek emanating from the Bennett Lake spillway bisects the site from the south to the north. A drainageway is located on the western part of the site and drains storm water from the base housing complex located to the west of the site.

Site SS-15 Nature and Extent of Contamination Soil The soil COPCs identified for site soil were acrolein and lead.

Acrolein, a VOC, was detected above its screening level at a concentration of 0.29 mg/kg at one location from 8 to 10 feet bgs. Fill material was present from ground surface to 10 feet bgs at the location, which is located in a geophysical anomaly area in the western part of the site. Debris was not encountered at the sample location.



Lead was detected at low concentrations in 40 of 41 soil samples collected from Site SS-15. It exceeded its screening level in one soil sample with a concentration of 500 mg/kg from 8 to 10 feet bgs.

Groundwater VOCs, 1,3,4-trimethylbenzene, and TCE were identified as COPCs for site groundwater.

1,3,4-Trimethylbenzene was detected above its screening level at one location at a concentration of 26 μg/L, but below the screening level at three additional samples.

TCE was detected above the screening level in one monitoring well during four groundwater monitoring events at concentrations ranging from 29 to 32 μg/L.

Surface Water No COPCs were identified in surface water at the site.

Sediment No COPCs were identified for site sediment.

Soil Gas One COPC, acrolein, was identified as present at a concentration in soil that could result in elevated concentrations of site soil gas. Soil gas samples were collected and acrolein was detected at a concentration of 1.07 parts per billion by volume (ppbv) from 4 to 5 feet bgs in one of two soil gas samples. The concentration of acrolein in the soil gas sample was above the screening level of 0.87 ppbv.

Site SS-15 Fate and Transport of Contamination VOCs in soil and groundwater and one inorganic in soil were evaluated as site COPCs.

Fate and Transport of VOCs Acrolein was identified as a COPC in soil. The migration pathways of potential concern for this chemical are volatilization to ambient or indoor air or leaching to groundwater. It was not detected in groundwater, even though sufficient time has elapsed for leaching to groundwater to have occurred. Additional migration is not expected to occur at levels that would affect groundwater quality.

TCE and 1,3,4-trimethylbenzene were identified as COPCs in groundwater. Neither was detected in soil samples collected at the site. The VOCs in groundwater may migrate and could ultimately discharge to the creek, or they could volatilize to ambient or indoor air. Neither VOC has been detected in surface water. This is likely a combination of volatilization to the atmosphere at the groundwater-surface water interface and dilution into the creek water. It is expected that VOC concentrations will continue to be immeasurable in the creek at the site, particularly given the low concentrations in groundwater (less than 35 μg/L in each case).

Fate and Transport of Inorganics Lead was identified as a COPC in soil. Lead has limited volatility and would be expected to persist in soil. The main migration pathway for lead at Site SS-15 is leaching of lead to groundwater. The movement of lead adsorbed to soil particles is considered to be an insignificant migration pathway.



2.5.2.5 Site ST-17 Site ST-17 Hydrogeology Groundwater has not been observed within the lean to fat clay. Based on the groundwater flow direction at Sites SS-06 and SS-40, located northwest of the Site ST-17, the anticipated groundwater flow direction beneath Site ST-17 is northward. Groundwater velocities are expected to be less than 10 feet/year based on estimates for other similar sites on base.

Site ST-17 Surface Water Surface water bodies do not exist at or near the site. Site ST-17 drains to the east, towards the runway.

Site ST-17 Nature and Extent of Contamination Soil There were no COPCs identified for site soil.

Groundwater Groundwater sampling was to be part of the subsurface investigation, but insufficient groundwater was available for analysis and so groundwater samples were not collected.

Surface Water Surface water samples were not collected because no surface water bodies exist at or near the site.

Sediment Sediment samples were not collected because no surface water bodies exist at or near the site.

Site ST-17 Fate and Transport of Contamination A discussion of fate and transport of contamination is not applicable because there were no COPCs identified in soil at Site ST-17.

2.5.2.6 Site ST-19 Site ST-19 Hydrogeology Groundwater flow at Site ST-19 is generally toward the northwest to northeast. The groundwater velocity is expected to be less than 10 feet per year based on estimates from other similar sites on base.

Site ST-19 Surface Water A drainage channel located north of the two facilities received surface water runoff from both. Historically, storm sewer piping conveyed surface water from the facilities to this ditch. The drainage channel is still present and carries storm water in a northerly direction.

Site ST-19 Nature and Extent of Contamination Soil Benzene and lead were retained as COPCs in soil.

Benzene, a VOC, was detected in six soil samples at Site ST-19. Benzene was detected above its screening level in three confirmation soil samples with the following concentrations: 0.1622, 0.1347, and 0.6410 mg/kg. Exact confirmation soil sample depths were not reported,



but the samples were collected from below the respective UST; therefore, it is assumed that the sample depth is below 10 feet bgs.

Lead was detected above the screening level in one sample, located adjacent to the former AST, at a concentration of 373 mg/kg from 0 to 1 foot bgs.

Groundwater There were no COPCs identified for site groundwater.



Site ST-19 Fate and Transport of Contamination Chemicals in soil classified as a VOC and an inorganic were evaluated as site COPCs.

Fate and Transport of VOCs The main migration and fate pathways for benzene found in soil are migration and degradation in soil. In subsurface soil, benzene may leach to groundwater prior to aerobic biological degradation. However, aerobic biological degradation is relatively rapid with half lives on the order of 1 month. If benzene leaches to groundwater, it typically does not migrate far in aerobic aquifers because of the biological degradation. Most subsurface soil at Whiteman AFB, as well as the groundwater, is aerobic.

Fate and Transport of Inorganics Lead has limited volatility and would be expected to persist in soil. The main migration pathway for lead at Site ST-19 is erosion of soil with adsorbed lead. Leaching of lead is not expected to be significant, and lead has not been detected in groundwater. The location where lead was present at a concentration above its screening level occurred near the area of the former AST, beneath a concrete pad that provides spill containment for new storage tanks. As such, the lead is protected from future erosion and contact with surface water, and it is not expected to migrate from the site.

2.5.2.7 Site ST-20 Site ST-20 Hydrogeology Groundwater at the site has a radial flow in directions ranging from northwest to northeast to southeast. Groundwater is most prevalent in the clay with sand and gravel. Slug tests performed at Site LF-08 and Site SS-30, which are near Site ST-20, indicate a groundwater velocity of 9.5 feet per year and 1 to 14 feet per year, respectively.

Site ST-20 Surface Water There are no surface water bodies at the site. The site is a flat paved parking lot that appears to drain to a grassy area to the east.

Site ST-20 Nature and Extent of Contamination Soil



1,3,4-Trimethylbenzene was identified as a COPC in soil.

1,3,4-Trimethylbenzene (1.1 mg/kg) was detected at a concentration above the screening level at one location immediately southeast of the former fill stand at a depth of 11 to 13 feet bgs.

Groundwater VOCs, 1,2-dichloroethane (1,2-DCA), and benzene were retained as a COPC in groundwater.

1,2-DCA was detected at a concentration of 20 μg/L at one DPT location. No other detections above the screening level of 1,2-DCA have occurred in groundwater at Site ST-20. The detection is an isolated occurrence, roughly 300 feet east and side-gradient of the suspected source area. The extent of 1,2-DCA in groundwater was not delineated because data were not collected to the north and east. 1,2-DCA was not detected at elevated concentrations in numerous groundwater samples collected between this location and the suspected source area, so it is doubtful that the chemical is related to the tank area.

Benzene was detected at concentrations in groundwater above its screening level in three monitoring wells at concentrations ranging from 6 to 280 μg/L.



Site ST-20 Fate and Transport of Contamination The COPCs related to the site are VOCs and SVOCs in soil and VOCs in groundwater.

Fate and Transport of VOCs 1,3,4-Trimethylbenzene was found in one soil sample south of the former UST area at a concentration of 1.1 mg/kg, and benzene was found in groundwater samples around a former tank. In addition, an elevated concentration of 1,2-DCA was encountered in one sample 300 feet east of the tank area. The fuel is likely the source of the 1,3,4-trimethylbenzene and benzene contamination. The source of 1,2-DCA in groundwater is unknown, but the relatively low concentrations may be related to a small spill of solvents.

1,3,4-Trimethylbenzene was encountered at an elevated concentration at a depth of 11 to 13 feet bgs in one sample collected south of the UST excavation. The likely fate and transport pathway for this chemical is to leach to groundwater. 1,3,4-Trimethylbenzene was detected in five groundwater samples across the site at concentrations well below the groundwater screening level. Each analytical result was flagged “F” to indicate that the concentration is greater than the method detection limit but less than the reporting limit. Because decades have elapsed since the release most likely occurred, further leaching significant enough to result in groundwater contamination exceeding screening levels is not expected to occur in the future.



As noted, the concentration of benzene has declined in the three wells in which it was detected. By November 1995, the concentration had reduced to 14 μg/L in the well where benzene was still observed. Benzene degrades rapidly under aerobic conditions, and the groundwater data indicate that biodegradation is occurring. Site ST-20 is not located near receiving streams. With the slow groundwater velocities, degradation is expected to occur before there is significant movement of the benzene in groundwater. Given the large previous declines in benzene and the 9 years elapsed since the last sample, benzene may no longer be detectable in groundwater.

1,2-DCA degrades most rapidly in soil and groundwater under anaerobic conditions and is not expected to migrate appreciably. A surface water discharge location has not been observed within 1,000 feet of Site ST-20; however, if concentrations of 1,2-DCA were to migrate to a surface water body, it is expected to volatilize rapidly at the groundwater/surface water interface and be undetectable in the surface water.

2.5.2.8 Site OT-23 Site OT-23 Hydrogeology Groundwater flow beneath Site OT-23 is to the southwest. Groundwater was observed in both the lean clay and the clay with gravel. The occurrence of groundwater in the clay with gravel is more prevalent.

No slug tests have been performed to date at Site OT-23 to determine groundwater velocity. Based on estimated groundwater velocities at other sites on base, the velocity is likely less than 10 feet/year.

Site OT-23 Surface Water Surface water features are not present at or adjacent to Site OT-23. The site is a minor topographic high; therefore, storm water drains outward from each of the site boundaries.

Site OT-23 Nature and Extent of Contamination Soil Lead was identified as a preliminary COPC in soil. One of 19 confirmatory soil samples of the stabilized soil exhibited a TCLP lead concentration of 15.565 mg/L, which is greater than the TCLP limit of 5 mg/L. In addition, nine soil samples were collected from four monitoring well borings in May 1998 and December 2002. The nine samples were analyzed for lead, and none exhibited concentrations of lead in soil above the screening level. Lead was not retained as a COPC because it has been rendered no longer bioavailable.

Groundwater There were no COPCs identified for site groundwater.



Site OT-23 Fate and Transport of Contamination



The COPC related to the site is lead in soil.

Since the lead in the soil was chemically treated and stabilized, it will not leach from the treated soil. Overland erosion is not considered a likely transport pathway, because the treated soil has a 2-foot cover with vegetation.

2.5.2.9 Site ST-26 Site ST-26 Hydrogeology Groundwater flow at Site ST-26 is radial, due to the presence of gravel fill up to 12 feet in thickness within UST excavation area. The gravel is acting as a local recharge area and has produced a mounding effect. The regional groundwater flow is to the southeast. Groundwater velocities are expected to be less than 10 feet/year based on estimates for other similar sites on base.

Site ST-26 Surface Water There are no surface water bodies or wetlands at or adjacent to Site ST-26. Storm water from the site drains to a grassy area to the southwest.

Site ST-26 Nature and Extent of Contamination Soil There were no COPCs identified for site soil.

Groundwater TCE and cis-1,2-DCE were identified as COPCs in groundwater.

TCE was detected at elevated concentrations ranging from 6.2 to 23 μg/L in 10 samples from two monitoring wells. TCE also was detected, in low concentrations, in 19 samples from five monitoring wells onsite over time, at concentrations ranging from 0.32F to 4.8 μg/L. TCE concentrations decreased away from the site in all directions. This is consistent with the groundwater radial flow direction for the site.

cis-1,2-DCE was detected at a concentration above the screening level of 70 μg/L with a concentration of 72 μg/L at one location in one of 10 samples. The limits of the cis-1,2-DCE are horizontally bounded by locations where cis-1,2-DCE either was not detected or was detected below the screening level.

TCE and cis-1,2-DCE are solvents and are not related to the storage of diesel fuel in the former UST. The presence of the VOCs is likely the result of small spills.



Site ST-26 Fate and Transport of Contamination VOCs in groundwater were evaluated as site COPCs.

Fate and Transport of VOCs



The COPCs related to the site are VOCs in groundwater. Their presence does not appear to be related to the USTs at the site and is likely the result of small spills. cis-1,2-DCE is a degradation product of TCE, and its presence appears to be linked to the TCE contamination. There is minimal TCE present in the groundwater. The mass of TCE is estimated at 0.007 pound (CH2M HILL 2005b).

The main fate and transport pathways for the VOCs are:


Migration and Degradation in Groundwater. TCE degrades primarily under anaerobic reducing conditions which are not typically present in groundwater at Whiteman AFB. The concentration of TCE at the site has not changed significantly over multiple sampling events. However, the presence of cis-1,2-DCE indicates that some degradation has occurred. The migration velocity for TCE is estimated to be about 8 feet/year (CH2M HILL 2005b). Given the slow groundwater migration rates and minimal TCE in groundwater, the mass flux of TCE away from the site is less than 0.0007 pound/year. As a result, minimal additional migration is expected before the TCE diminishes to below the screening levels. There are no surface water features within 1,000 feet of the site; therefore, migration to surface water is not a concern.

Volatilization from Groundwater. As described in Section 2.5.2.2.

2.5.2.10 Site DP-32 Site DP-32 Hydrogeology Groundwater flow across the site generally is to the west/southwest toward the primary drainage channel. Depth to groundwater across the site ranged from 1.22 to 13.36 feet bgs with an average depth of 6 feet bgs. Groundwater flow on the west side of the primary drainage channel is expected to be to the east, toward the channel.

The clay with sand and gravel appears to intersect the northeastern part of the primary drainage channel downgradient of the storm sewer outfall, resulting in the continuous discharge of groundwater to the channel. Groundwater flow in this northern part of the site area appears to be more to the north/northwest, as evidenced by the presence of water in the primary drainage channel, even when runoff from the storm sewer is low.

Based on slug tests conducted in the northeastern portion of the site, a groundwater gradient of 0.023 feet/foot, and an inferred average effective porosity of 0.20, the average linear velocity for the clay with sand and gravel soils located in the northern part of Site DP-32 is 16 feet/year. The hydraulic conductivity of the soils in the southwestern part of Site DP-32 is much lower and little groundwater flow is expected in this area.

Site DP-32 Surface Water Site DP-32 was once part of a natural wooded area containing three drainage channels, remnants of which are still present at the site. The primary drainage channel flows from northeast to southwest in an arc, where it connects with a secondary drainage channel (southern tributary) before continuing southwest. The southern tributary is smaller and flows east to west. The third, smaller drainageway (referred to as the tertiary drainage channel) runs from north to south and enters the primary drainage channel at the northwest limits of



Site DP-32. A storm sewer was constructed within the northeast part of the primary drainage channel and the eastern part of the secondary drainage channel. The topography of Site DP-32 is characterized by a topographic high that gradually slopes downgradient to the north, west, and southwest toward the primary drainage channel and the southern tributary. The primary channel eventually flows into Brewer Branch Creek.

Site DP-32 Nature and Extent of Contamination Soil The COPCs identified for site soil were TCE, cis-1,2-DCE, and 3,3’-dichlorobenzidine.

TCE was present in one soil sample (10 to 12 feet bgs) at a concentration greater than its screening level. The soil sample was collected from the saturated zone and may represent TCE that has migrated either from overlying soils or from upgradient groundwater. The location is located roughly in the center of the site and is bounded by soil samples with TCE concentrations below the screening level, and therefore the extent of TCE in soil at Site DP-32 is defined.

cis-1,2-DCE was present in one soil sample (8 to 10 feet bgs) at a concentration greater than the screening level. The soil sample was collected from the saturated zone and may represent cis-1,2-DCE that has migrated either from overlying soils or from upgradient groundwater. Concentrations of cis-1,2-DCE are bounded by soil samples with concentrations were below their screening levels.

One SVOC, 3,3’-dichlorobenzidine, was detected at a concentration greater than the screening level. 3,3’-Dichlorobenzidine was detected in two soil samples at locations collected 0 to 2 feet bgs. Although these sample locations are considered isolated, 3,3’-dichlorobenzidine was retained as a COPC. 3,3’-Dichlorobenzidine may be associated with pressurized spray containers of paint, lacquers, or enamels that could have been disposed of at the site.

Groundwater The COPCs identified for groundwater were TCE, cis-1,2-DCE, vinyl chloride, methyl chloride, and dichloromethane.

TCE and its degradation products cis-1,2-DCE and vinyl chloride are present at varying concentrations above screening levels throughout Site DP-32. The highest historical concentrations of VOCs observed were 4,300 μg/L of TCE, 1,180 μg/L of cis-1,2-dichloroethene, and 67.8 μg/L of vinyl chloride. The distribution of TCE and its degradation products is characterized by two areas of elevated concentrations: one northeast of the site and one in the southwest. TCE degradation products are more prevalent in the southwestern part of the site. The extent of TCE and its degradation products has been defined.

Methyl chloride was detected in one groundwater grab sample at a concentration above its screening level. This sample location is bounded by groundwater samples with methyl chloride concentrations below its screening level, and therefore the extent of methyl chloride in groundwater is defined.

Dichloromethane was detected in one monitoring well sample at a concentration slightly above its screening level. This sample location is bounded by groundwater samples with



dichloromethane concentrations below its screening level, and therefore the extent of dichloromethane in groundwater is defined.

Surface Water TCE, vinyl chloride, and 3,3’-dichlorobenzidine were retained as COPCs in surface water.

TCE and its daughter product vinyl chloride were observed in samples collected from the primary drainage channel. No elevated concentrations of VOCs were observed in the secondary drainage channel. Surface water TCE concentrations above the screening level have a maximum concentration located at the upstream end of the creek. TCE declines from the historical maximum of 194 μg/L at each subsequent downstream sampling location. TCE at the location farthest downstream, about 500 feet, was 4.6 μg/L. Vinyl chloride was also detected in a sample collected from the upstream end of the creek at a concentration of 2.3 μg/L, above its screening level of 2 μg/L.

An upgradient source of the surface water in the primary channel is groundwater. The extent of elevated levels of TCE and its degradation products in surface water is physically bounded on the upgradient end by this contributing source. VOC concentrations gradually decrease in downstream samples to concentrations below screening levels. Therefore, the extent of TCE and its degradation products is characterized. The decrease in concentrations of chemicals in surface water downgradient of the groundwater/surface water interface near the northeast plume supports the fact that the southwestern area of the plume is not a primary contributor to surface water in the channel. An organic mulch biowall was installed to evaluate a remedial alternative that would address VOC concentrations in the primary drainage channel. The objective of the biowall is to intercept and treat VOC-contaminated groundwater before discharging into the channel (i.e., surface water).

3,3’-Dichlorobenzidine was detected in one surface water sample at a concentration above its screening level. The presence of 3,3’-dichlorobenzidine in surface water may not be site-related based on its presence in sediment from the secondary drainage channels; however, it was retained as a COPC.

Sediment Sediment COPCs include benzo(a)pyrene, benzo(b)fluoranthene, and arsenic.

The SVOCs were detected in multiple sediment samples but were randomly distributed in the stream channels, and their distribution is not obviously site related.

The distribution of arsenic in sediment appears to be random and does not appear to be site related; however, arsenic was retained as a COPC.

Site DP-32 Fate and Transport of Contamination VOCs in groundwater were evaluated as site COPCs. VOCs and SVOCs in surface water were evaluated as site COPCs. Arsenic in sediment was evaluated as a site COPC.

Fate and Transport of VOCs The most prevalent VOCs are TCE, cis-1,2-DCE, and vinyl chloride. Methyl chloride and dichloromethane were detected at single locations at concentrations above screening levels. The location and distribution of the VOCs suggests a historic spill or similar release at Site DP-32. Given the two areas of the TCE plume with high concentration, there may have been separate releases. Release of pure phase solvent is unlikely because of the absence of



these solvents in unsaturated zone soil and the fact that the maximum dissolved phase concentrations of TCE (5,282 μg/L) is far below its solubility in groundwater (1,100,000 μg/L). There is an estimated 12 pounds of TCE in the dissolved phase in groundwater and adsorbed on the aquifer soils (CH2M HILL 2005b).

TCE released to the soil volatilized to the atmosphere and leached to underlying soils and the groundwater. TCE in soil was found only at one location at a concentration above its screening level. Concentrations of cis-1,2-DCE and vinyl chloride also were above screening levels in only one sample at one location. In each case, the sample was taken from the saturated zone. These VOCs were not found in unsaturated zone soil samples at these locations or any other unsaturated zone samples at Site DP-32. As a result, the VOCs found in soil probably are present as a result of migration in the groundwater and are not indicative of ongoing leaching of VOCs to groundwater. Their fate and transport are discussed within the groundwater media.

The main migration and fate pathways for the VOCs in groundwater and surface water are:

• Migration and degradation in groundwater • Volatilization from surface water • Volatilization from groundwater

Migration and Degradation in Groundwater. cis-1,2-DCE and vinyl chloride are found in groundwater, indicating that some reductive dechlorination has occurred at the site. Chloride, though present in groundwater, is not indicative of a plume resulting from degradation of TCE. Reducing conditions in groundwater have not historically been present, based on groundwater sampling. The VOC plume is discharging to the primary drainageway along the northeastern part of the site. The estimated plume discharge flow to the drainageway is only 0.05 gpm (CH2M HILL 2005b), and the estimated TCE mass flux to the ditch is 0.4 pound/year. The absence of a continuing source of VOCs to groundwater will result in diminishing concentrations over time as the plume migrates downgradient and discharges to the drainageway.

Volatilization from Surface Water. TCE is present in the drainageway as a result of the plume discharge. The shallow stream depth (varying from 1 to 6 inches in depth) allows TCE to rapidly volatilize to the atmosphere. It volatilizes out of the stream over a distance of 500 feet based on the consistent decline in concentrations from about 200 μg/L at the most upstream location to the screening level of 5 μg/L at the farthest downstream location.


Fate and Transport of SVOCs One SVOC, 3,3’-dichlorobenzidine, was a COPC in soil and surface water. Two polycyclic aromatic hydrocarbons (PAHs) were COPCs in sediment.

3,3’-Dichlorobenzidene is a SVOC with an organic carbon partion coefficient (Koc) of 724, indicating a tendency to adsorb to soils and to have relatively low mobility. Henry’s Law constant is 4 × 10-9 atm-m3/mole, which is indicative of minimal volatility. Information on its biodegradability is not available. In general it would be expected to persist in soil and not to leach to groundwater. It also would be expected to adsorb to stream sediments, though to an



extent somewhat less than the PAHs. The occurrence of 3,3’-dichlorobenzidene in surface water is minimal and is expected to volatilize to the atmosphere at a moderate rate.

PAHs were found at concentrations above screening levels in sediment samples collected along the drainageway. PAHs do not dissolve readily in groundwater or volatilize into air. Because of their tendency to adsorb to soil particles, the most likely transport mechanism is streambed erosion. PAHs also do not biodegrade readily, indicating they are likely to persist for a long time in the drainageway sediments. They could be eroded downstream or covered with new sediments.

PAHs were not observed at concentrations above screening levels in soil or groundwater from the site. It is possible that the PAHs in sediment have accumulated as a result of runoff from nearby roadways. Some of the major sources of PAHs in the urban environment are asphalt and vehicular emissions.

Fate and Transport of Arsenic Arsenic was the only inorganic detected and retained as a COPC in sediment. It persists in sediment and does not dissolve readily in surface water or volatilize into air, nor does it degrade. Because of the tendency to adsorb to soil particles, the most likely transport mechanism is streambed erosion.

The distribution of arsenic in sediment does not appear to be site-related, and sediment at Site DP-32 could receive arsenic from upgradient or other anthropogenic sources such as runoff from Barksdale Lane, which crosses the drainage ditch.

2.5.2.11 Site SS-35 Site SS-35 Hydrogeology Groundwater flow across the site generally is toward the north, with northwesterly and northeasterly components near the site boundaries. Groundwater velocities are expected to be less than 10 feet per year based on estimates from other similar sites on base.

Site SS-35 Surface Water There are no surface water bodies or wetlands at or adjacent to Site SS-35. Storm water from paved areas drain to grassy areas within the site. Although Site SS-35 and surrounding areas are relatively flat, the area drains to the north.

Site SS-35 Nature and Extent of Contamination Soil TCE, cis-1,2-DCE, and vinyl chloride were identified as COPCs in soil.

TCE (0.208F mg/kg) was detected in one sample at 17 to 18 feet bgs at a concentration above its screening level. That depth is within the saturated zone. The TCE likely is present as a result of transport in groundwater rather than leaching from soil. The extent of TCE in soil at SS-35 is bounded horizontally since it is surrounded by results that are either below detection or below the screening levels.

cis-1,2-DCE (0.793 mg/kg) and vinyl chloride (0.212F mg/kg) were detected in one sample at 11 to 12 feet bgs at a concentration above the screening levels. That depth is in the saturated zone. As with the TCE, cis-1,2-DCE and vinyl chloride are likely present as a result of transport in groundwater rather than leaching from soil. The extent of cis-1,2-DCE



and vinyl chloride in soil are bounded horizontally since the elevated concentrations are surrounded by results that are either below detection or below the screening levels.

Groundwater Carbon tetrachloride, TCE, cis-1,2-DCE, and vinyl chloride were identified as COPCs in groundwater.

Carbon tetrachloride was detected at a location northeast of the approximate location of the former Hobby Shop, at a concentration of 7.21 μg/L, which is above its screening level. The extent of carbon tetrachloride in groundwater was not delineated because the location was not downgradient of the former Hobby Shop and more than 150 feet east. Borings immediately surrounding the former Hobby Shop area do not have evidence of carbon tetrachloride in soil or groundwater, so the constituent may not be related to activities at the Hobby Shop area.

TCE was detected at concentrations ranging from 0.26 to 133.4 μg/L in 13 groundwater samples. TCE concentrations decreased away from the Hobby Shop toward the north, northwest, and northeast. This is consistent with the groundwater flow direction for the area, indicating that constituents originating near the former Hobby Shop are migrating downgradient.

cis-1,2-DCE was detected in one groundwater sample located north-northwest of the approximate location of the former Hobby Shop at a concentration of 815.3 μg/L, which exceeds its screening level. cis-1,2-DCE was detected in seven other groundwater samples, at concentrations ranging from 0.14 to 18.85 μg/L. The limits of the cis-1,2-DCE are bounded by locations where cis-1,2-DCE either was not detected or was detected below the screening level.

Vinyl chloride was detected in one groundwater sample located north of the former Hobby Shop at a concentration of 155.4 μg/L, which exceeds the screening level. Vinyl chloride was detected in two additional samples at concentrations of 0.98F and 0.19 μg/L. The location where the concentration was above the screening level is bounded by samples that do not contain concentrations above the detection limit, so the extent of the vinyl chloride detected above the screening level was delineated.



Site SS-35 Fate and Transport of Contamination VOCs in soil and groundwater were determined to be COPCs.

The location and distribution of the VOCs suggests a historic spill or similar release in the former Hobby Shop area. One or more spills likely released TCE to soil where it volatilized to the atmosphere and leached to groundwater. TCE was not found in the unsaturated zone soils at concentrations exceeding screening levels. The presence of TCE in saturated zone soils is likely a result of transport in groundwater.



Release of pure phase solvent is unlikely because these solvents are not present in the soil and because the maximum dissolved phase concentrations of TCE (133.4 μg/L) is far below its solubility (TCE solubility = 1,100,000 μg/L ) in groundwater. There is an estimated 5 pounds of TCE in the dissolved phase in groundwater and adsorbed on the aquifer soils (CH2M HILL 2005b).



Migration and Degradation in Groundwater. Carbon tetrachloride was identified in groundwater at a concentration of 7 μg/L, just above the screening level of 5 μg/L. Carbon tetrachloride degrades in a manner similar to TCE and is not expected to migrate appreciably.

cis-1,2-DCE and vinyl chloride are found in higher concentrations than TCE in one groundwater sample from near the source area, indicating that significant reductive dechlorination has occurred. Downgradient of the source, the two degradation products diminish by more than one order of magnitude. The three VOCs are below screening levels within 250 feet of the most elevated concentrations.

The VOC plume is migrating to the north towards a small creek located about 1,500 feet downgradient. The travel time for TCE to the creek, assuming no further biodegradation, is more than 100 years (CH2M HILL 2005b). Given the long travel time, it is unlikely that the plume will reach the creek. Also the estimated flow rate of the plume groundwater is less than 0.1 gpm, and the estimated TCE mass flux is 0.01 pound/year. Even if the plume did eventually reach the creek, at the low mass flux rates, there would be significant volatilization as the plume discharged to the creek and detectable concentrations in the creek are unlikely.


2.6 Current and Potential Future Land and Resource Uses 2.6.1 Land Use The anticipated current and future land use at the sites is industrial. Nonetheless, the sites are also below established risk thresholds for the unrestricted (residential) and industrial scenario based on current groundwater conditions, as described in Section 2.6.2.

Whiteman AFB is an active USAF installation encompassing 4,677 acres of government-owned, leased, or easement land. The base is bordered by agricultural land to the south and east, Knob Noster State Park and low-density residential areas to the west, and the community of Knob Noster to the north. Site-specific current and future land uses are presented below.



2.6.1.1 Site SS-06 Site SS-06 is located along the western edge of the flight line and aircraft apron. Therefore, the current and future uses of Site SS-06 and surrounding areas are flight line activities. There are no wetlands or surface water bodies present at or adjacent to Site SS-06.

2.6.1.2 Site SD-07/SS-40 Site SD-07/SS-40 is located along the northwestern edge of the flight line and aircraft apron. Therefore, the current and future uses of the site and surrounding areas are flight line operations. The northern portion of Site SD-07/SS-40 contains Arnold Avenue, a parking lot, and grassy drainage area. The surface water drainage area drains to a small lake, which is part of Clear Fork Creek.

2.6.1.3 Site LF-08 Site LF-08 consists of the Officer’s Club (Building 3008) and associated driveways and parking lots. McConnell Lane and 1st Street run through the site. Maintenance facilities and a recycling center are located in the southeast portion of the site. Drainage ditches and culverts are located along 1st Street and parts of McConnell Lane. The drainage ditch conveys water ultimately to Clear Fork Creek.

2.6.1.4 Site SS-15 Site SS-15 consists of an open grass field with trees concentrated in one main section north of the site. The field is maintained and mowed. The presence of a picnic area and playground adjacent to Site SS-15 suggests that the area is maintained and used regularly by residents. Brewer Branch Creek, which flows to the north, bisects the site from the south to the north. The site is bound by 12th Street to the south, Vandenberg to the east, a base housing complex to the west and a playground/picnic area to the north. A second surface water body, on the western part of the site, drains storm water from the base housing complex west of the site.

2.6.1.5 Site ST-17 Site ST-17 is a 1-acre site located between the north and south sets of B-2 hangars and is flanked by the operations apron and the runway. Therefore, the current and future uses of Site ST-17 and surrounding areas are flight line activities. There are no wetlands or surface water bodies present at or adjacent to Site ST-17.

2.6.1.6 Site ST-19 Site ST-19 is bounded by Arnold Avenue to the east and 2nd Street to the south. The site consists of two facilities: Facility 102 and 175. ASTs with spill and leak containment are present at the site. Most of the area is paved; the unpaved areas are characterized by patchy, mowed grass. A drainage channel located north of the two facilities received surface water runoff from both. The drainage channel is still present and carries storm water in a northerly direction. Industrial facilities surround Site ST-19. Future uses of the site are consistent with current uses.

2.6.1.7 Site ST-20 The site is a paved parking lot adjacent to Building 159, an industrial facility. Surrounding areas are of industrial nature. There are no wetlands or surface water bodies present at or



adjacent to Site ST-20. The parking lot drains to the grassy areas surrounding the paved area. Future uses of the site are consistent with current uses.

2.6.1.8 Site OT-23 Site OT-23 consists of and is surrounded by relatively flat grassy fields, enclosed by fences. The site it located within a restricted access area. Future uses of the site are consistent with current uses.

2.6.1.9 Site ST-26 Site ST-26 is the location of the Communications Building and associated parking lot and mowed grass, which is enclosed by a fence. The site is remote and surrounded by mowed, grassy fields. The site drains to the southwest. There are no surface water bodies or wetlands at or adjacent to Site ST-26.

2.6.1.10 Site DP-32 The site consists of a playground, pavilion, grass and Barksdale Lane. Currently, the base is in the process of demolishing surrounding base housing. In the future, Site DP-32 will be used by the base to practice parade drills. Subsurface excavation at the site is not anticipated once demolition is completed. Areas surrounding Site DP-32 will be used for administrative operations, which may include building construction. These activities are not expected to affect the site or the location of the biowall.

Site DP-32 contains three drainage channels. The primary drainage channel flows from northeast to southwest and ultimately flows into Brewer Branch Creek. The secondary channel flows east to west. The third is a drainageway running from north to south.

2.6.1.11 Site SS-35 Site SS-35 is used for vehicle parking and equipment storage. The site consists of Buildings 110, 114, 115, and 139, Lockbourne Terrace, and asphalt parking areas with intermittent sections of grass or gravel. There are no surface water bodies or wetlands at or adjacent to Site SS-35. Storm water drains into a swale to the north where it enters the base storm water system. There are no surface water bodies or wetlands at or adjacent to Site SS-35.

2.6.2 Groundwater Resources As stated in Section 2.5.1.2, shallow groundwater within the unconsolidated overburden appears to be semiconfined within clay with sand and gravel and/or clayey shale at the soil/bedrock interface. Groundwater within the overlying low-permeability clays and clayey shale is not used for domestic or agricultural purposes nor is it likely to be used as such in the future. Well surveys indicate that the shallow groundwater under and in the vicinity of Whiteman AFB is not and nor will it be used for domestic purposes as restricted by Title 10, Division 23, Chapter 3, of the Missouri Code of State Regulations. Furthermore, the base obtains its domestic water supply from water supply wells constructed at depths of 1,000 feet or greater in bedrock and the construction of shallow wells for domestic use is not allowed by the base or state regulations. Therefore, it is unlikely that complete exposure pathways could exist for consumption of groundwater by future residents.



2.7 Site Risks 2.7.1 Human Health The HHRAs for the sites were conducted as part of the RI Work Plan (CH2M HILL 2005b) following USEPA’s Risk Assessment Guidance for Superfund (USEPA 1989) and AFCEE Guidance for Risk Assessment (AFCEE 1997). The risk assessments were performed using a phased process that included a risk screening analysis. The baseline HHRA for each site comprised the following components:

• Identification of COPCs. Review of chemicals identified in the site-specific nature and extent evaluations to determine if they should be retained as COPCs for further evaluation in the HHRA. If no COPCs were identified, a HHRA was not prepared for that site.

• Exposure Assessment. Identifying potential pathways by which exposure could occur, characterization of potentially exposed populations (e.g., workers or residents), and estimation of the magnitude, frequency, and duration of exposures.

Each site is situated on property used for industrial purposes. For the purpose of the HHRA, future land use at each site was evaluated as both residential and industrial. Residential use is the most conservative land use assumption for purposes of estimating human health risks because potential exposure durations under residential land use are longer and provide higher COPC intake rates than those used to evaluate risk associated with industrial land use. Potential receptors associated with residential land use are adult and child residents. Potential receptors associated with industrial land use include workers at a future industrial facility and construction workers performing onsite excavation or maintenance activities. Trespassers are not a realistic receptor at the site because of the high-level, 24-hour security at the base and the presence of the 6-foot-tall fence with barbed wire surrounding it, and so they were not quantitatively evaluated in the HHRAs.

Following the review of COPCs, potential site risks were evaluated for media with potentially complete exposure pathways as presented in Table 1.

• Toxicity Assessment. Identifying the types of adverse health effects associated with exposure to COPCs, along with available toxicity factors (e.g., cancer slope factors [SFs] and reference doses [RfDs]), and summarizing the relationship between magnitude of exposure and occurrence of adverse health effects.

• Risk Characterization. Integrating the results of the exposure assessment and toxicity assessment to estimate the potential risks to human health; specifically, the HHRA calculated the total site risks for each exposure media for residents, industrial workers, and construction workers. The total site risks and predicted blood lead levels were then compared with the risk thresholds (1 × 10-5 excess lifetime cancer risk [ELCR], noncancer hazard index [HI] of 1, and 5 percent of the population with a blood lead level greater than 10 μg/dL) to determine if a recommendation of no further action is appropriate for the site.

• Uncertainty Assessment. Identifying sources of uncertainty associated with the data, methodology, and values used in the HHRA estimation.



TABLE 1 Potential Exposure Scenarios Evaluated in Human Health Risk Assessments Record of Decision

Potential Exposure Media Pathways Receptor Notes

Groundwater Inhalation of VOCs in indoor air

Dermal contact Inhalation of VOCs in excavations

Soil Incidental Ingestion Inhalation of VOCs in ambient air and indoor air Inhalation of Fugitive Dust Dermal contact

Incidental Ingestion Inhalation of VOCs in ambient air Inhalation of Fugitive Dust Dermal contact

Surface Water Dermal contact

Sediment Dermal contact

Residents Industrial Workers

Construction Workers

Residents Industrial Workers

Construction Workers

Residents Industrial Workers Construction Workers

Residents Industrial Workers Construction Workers

Shallow groundwater underneath the base will not be used as a drinking water supply. Indoor air vapor intrusion may occur at sites where shallow groundwater is affected by VOCs.

Invasive soil activities could bring construction workers into intermittent contact with groundwater and volatile emissions in excavations.

Outdoor activities could result in contact with soil. At sites with sediment, outdoor activities could result in occasional contact with sediments in intermittent drainage ditches and surface depressions. Indoor air vapor intrusion may occur at sites where soil is affected by VOCs.

Outdoor excavation activities could result in worker contact with soil. At sites with sediment, outdoor activities could result in occasional contact with sediments in intermittent drainage ditches and streams, as well as shallow ponds.

At sites with surface water, outdoor activities could result in occasional contact with surface water in drainage ditches, streams, or ponds.

At sites with sediments below surface water, outdoor activities could result in occasional contact with surface water in drainageways and creeks.

Source: CH2M HILL

The HHRA concluded that risks to human health were below the risk thresholds in site media for the unrestricted (residential) or industrial land use. Site-specific discussions are presented below.

2.7.1.1 Site SS-06 Based on review of relevant data collected to date, the soil and groundwater at Site SS-06 have not been affected by former site activities. The site-specific HHRA concluded that no human health COCs were identified for site media (CH2M HILL 2005b).

2.7.1.2 Site SD-07/SS-40 The calculated ELCR is 1 × 10-7 for a resident and the noncancer HIs are 0.009 (child resident) and 0.004 (adult resident). The percentage of the child population with a blood lead level



greater than 10 μg/dL is 0.06, which is an acceptable level. For the industrial worker, the calculated ELCR is 3 × 10-8 and the noncancer HI is 0.002. The percentage of the worker population with a fetal blood lead level greater than 10 μg/dL is 1.4, which is an acceptable level. The calculated ELCR for the construction worker is 2 × 10-8 and the noncancer HI is 0.03. The percentage of the construction worker population with a fetal blood lead level greater than 10 ug/dL is expected to be 2.2 percent (1.4 percent x 1.6), which is within acceptable levels.

In summary, calculated ELCRs, HIs, and modeled blood lead levels are below established risk thresholds for the potential receptors (child and adult residents, industrial workers, and construction workers) evaluated in the HHRA.

2.7.1.3 Site LF-08 Potential exposures to lead in soil were calculated. The percentage of the child population with a blood lead level greater than 10 μg/dL is 0.016, which is an acceptable level. The percentage of the industrial worker population with a fetal blood lead level greater than 10 μg/dL is 1.5, which is an acceptable level. The ELCR for construction worker exposure to groundwater is 1 × 10-6, and the noncancer HI is 0.9. The percentage of the construction worker population with a fetal blood lead level greater than 10 μg/dL is expected to be 2.4 percent (1.5 percent x 1.6), which is within acceptable levels.

The calculated human health risks are within established risk thresholds for residential, industrial, and construction worker scenarios.

2.7.1.4 Site SS-15 Potential exposures to COPCs in soil, groundwater, and soil gas were calculated. For residents, the ELCR is 1 × 10-8 and the noncancer HIs are 0.004 (child resident) and 0.002 (adult resident). The percentage of the child population with a blood lead level greater than 10 μg/dL is 0.02, which is an acceptable level. For the industrial worker, the ELCR is 4 × 10-9, and the noncancer HI is 0.0008. The percentage of the worker population with a fetal blood lead level greater than 10 μg/dL is 1.3, which is an acceptable level. Potential construction worker exposures to COPCs in soil and groundwater were calculated. The ELCR is 9 × 10-9, and the noncancer HI is 0.4.

The calculated ELCRs and HIs are below established risk thresholds for the potential receptors (child and adult residents, industrial workers, and construction workers) evaluated in the HHRA.

2.7.1.5 Site ST-17 Discussion of human health risk assessment at Site ST-17 is not applicable, because no COPCs were identified in soil.

2.7.1.6 Site ST-19 The calculated noncancer HIs are 0.06 (child resident) and 0.02 (adult resident), and the ELCR is 3 × 10-6, which are within acceptable levels. The percentage of the child population with a blood lead level greater than 10 μg/dL is 0.1, which is an acceptable level. The industrial worker noncancer HI and ELCR are 0.01 and 8 × 10-7, respectively, which are



within acceptable levels. The percentage of the worker population with a fetal blood lead level greater than 10 μg/dL is 1.5, which is an acceptable level. The construction worker noncancer HI and ELCR are 0.002 and 7 × 10-9, respectively, which are within acceptable levels. The percentage of the construction worker population with a fetal blood lead level greater than 10 μg/dL is expected to be 2.4 percent (1.5 percent × 1.6), which is within acceptable levels.

In summary, calculated ELCRs and HIs are below established risk thresholds for the potential receptors (child and adult residents, industrial workers, and construction workers) evaluated in this HHRA. Modeled blood lead levels are also less than regulatory criteria for the potential receptors evaluated in the HHRA.

2.7.1.7 Site ST-20 The calculated ELCR is 3 × 10-7 for a resident and the noncancer HIs are 0.02 (child resident) and 0.01 (adult resident). For the industrial worker, the calculated ELCR is 8 × 10-8 and the noncancer HI is 0.004. The calculated ELCR is 4 × 10-7 for the construction worker and the noncancer HI is 0.1.

The calculated HIs are below established risk thresholds for the potential receptors (child and adult residents, industrial workers, and construction workers) evaluated in the HHRA.

2.7.1.8 Site OT-23 The MAECTITE process has rendered the lead no longer bioavailable through ingestion, dermal, or inhalation exposures. As a result, there are no potential exposures of concern from a human health standpoint.

2.7.1.9 Site ST-26 The calculated ELCR for the resident is 1 × 10-8 and the noncancer HIs are 0.002 (child resident) and 0.001 (adult resident). The calculated ELCR for an industrial worker is 3 × 10-9

and the noncancer HI is 0.0004. The calculated ELCR is 6 × 10-9 for the construction worker and the noncancer HI is 0.007. Since the estimated risks are below risk thresholds, potential risks are within acceptable levels and there are no risk drivers.

Calculated ELCRs and HIs are below established risk thresholds for the potential receptors (child and adult residents, industrial workers, and construction workers) evaluated in the HHRA.

2.7.1.10 Site DP-32 The ELCR is 1 × 10-5 for a resident and the noncancer HIs are 0.7 (child resident) and 0.3 (adult resident). The calculated ELCR is 3 × 10-6 for the industrial worker and the noncancer HI is 0.1. The calculated ELCR is 9 × 10-7 for the construction worker and the noncancer HI is 0.3.

Calculated ELCRs and HIs are below established risk thresholds for the potential receptors (child and adult residents, industrial workers, and construction workers) evaluated in the HHRA. As a result, a remedial alternative is not necessary. However the biowall, as part



of the treatability study, will be completed for a better understanding of how this technology can be applied elsewhere.

2.7.1.11 Site SS-35 For a resident, the ELCR is 7 × 10-6 and the noncancer HIs are 0.1 (child resident) and 0.06 (adult resident). The ELCR is 2 × 10-6 for an industrial worker, while the noncancer HI is 0.02. The ELCR is 3 × 10-6 for a construction worker, while the noncancer HI is 0.1. The calculated risks and HIs are below established risk thresholds for the potential receptors (child and adult residents, industrial workers, and construction workers) evaluated in the HHRA.

2.7.2 Ecological An evaluation of the potential for ecological risk at Whiteman AFB was conducted according to MDNR’s Cleanup Action Levels for Missouri (CALM) guidance document (MDNR 2001). The CALM process was developed for hazardous substance contamination that is remediated under Missouri’s Voluntary Cleanup Program laws and regulations (10 CSR 25-15.010) administered by the MDNR Hazardous Waste Program. No unacceptable ecological risks were identified at any of the sites.

2.7.2.1 Site SS-06 On August 12, 2004, CH2M HILL scientists conducted an ecological site reconnaissance. Site SS-06 is located behind the fenced boundary of the runway, which limits access to the site by potential terrestrial receptors. Although there are areas of mowed grass at and adjacent to the site, most of Site SS-06 and the adjacent areas are surrounded by either base buildings or pavement. There are no potential aquatic receptors, because there are no water bodies present at or adjacent to the site. Based upon the ecological evaluation, there are no significant ecological habitats or ecological receptors present at or adjacent to Site SS-06, and thus there is no potential for ecological exposure.

2.7.2.2 Site SD-07/SS-40 An ecological risk assessment was performed for Site SD-07 in 1991. The 1991 ecological risk assessment concluded that wildlife could be exposed to site-related chemicals from the ingestion of surface water, soil, or prey in the former wash rack drainage. It was noted, however, that the low quality of the drainage habitat would reduce the overall potential for exposure. An updated evaluation of the potential for ecological risk at Site SD-07 was conducted according to the MDNR CALM guidance document (MDNR 2001). An ecological risk assessment for Site SS-40 was conducted in October 2003 as part of the RI (CH2M HILL 2003), in accordance with MDNR’s CALM guidance for ecological risk assessments (MDNR 2001).

In 2004, ecological and physical characteristics were evaluated at Site SD-07 to determine whether ecologically important habitats and potential ecological receptors are present. The revised ecological evaluation concluded that there was no contact with ecological receptors at Site SD-07. There is no potential for ecological exposure or risk at Site SS-40.



2.7.2.3 Site LF-08 A risk assessment was performed for Site LF-08 in 1996. No sensitive environments or receptors were identified in that assessment. However, an updated evaluation of the potential for ecological risk at Site LF-08 was completed in 2004. A semiquantitative risk evaluation was completed due to the potential co-occurrence of ecological receptors and complete exposure pathways. The ERA concluded that the risks to receptors are virtually negligible based on the conservative assumptions used in this screening level assessment. Risk to higher trophic level predators is similarly considered to be negligible. In summary, no unacceptable risk was identified for ecological receptors.

2.7.2.4 Site SS-15 An ecological risk assessment was performed for Site SS-15 in 1997. It was concluded that ecological receptors could be exposed to site-related contaminants in soil and surface water at Site SS-15 (i.e., concentrations in excess of toxicological benchmarks for surface soil). However, these constituents were determined to be present at concentrations consistent with background conditions and therefore were not site related.

An updated evaluation of the potential for ecological risk at Site SS-15 was conducted according to the MDNR CALM guidance document (MDNR 2001). The purpose of the updated Tier 1 ecological exposure assessment was to determine whether the site is likely to pose a risk to ecological receptors. The quantitative ERA (Tier 2) was completed to determine whether receptors and habitats at or adjacent to the site were at potential risk from coming in contact with a chemicals on or near the site. This evaluation included an assessment of the types of habitats on or near the site and the presence or absence of receptors and migratory pathways for chemicals to potentially reach media where ecological receptors could be potentially exposed (e.g., surface water bodies, surface soils, etc.).

The results of the risk characterization indicate there is likely to be no significant risk to plants, terrestrial invertebrates, short-tailed shrews, or killdeer at Site SS-15, and thus the risk to higher trophic level mammalian and avian receptors that might access the site is also negligible.

2.7.2.5 Site ST-17 On August 12, 2004, CH2M HILL scientists conducted a Tier 1 ecological exposure assessment site reconnaissance of Site ST-17. Based on Tier 1 results, a Tier 2 assessment was not needed. Site ST-17 is located between the north and south sets of the B-2 hangars and is flanked by the operations apron and the runway. The 1-acre site is covered by an 8-inch-thick concrete taxiway. No wetlands or surface water bodies are present at or adjacent to the site. The absence of habitat at and adjacent to Site ST-17 is due to its location on an active runway. The ecological risk characterization indicates that there are likely no receptors at the site.

2.7.2.6 Site ST-19 An ecological risk assessment for Site ST-19 was performed in 1997 (Halliburton 1997b). Based on no unacceptable risks to ecological receptors, a Decision/Closure Document for No Further Action was submitted in 1999. The ecological risk assessment concluded that terrestrial organisms are not expected to experience significant exposure to surface soil at



the site because (1) the site lies within a highly developed area, (2) parts of the site are enclosed by a fence that limits access by larger terrestrial animals, (3) conditions at the site do not provide adequate food and cover for wildlife, and (4) the site is not located near existing habitats. In addition, drainage ditches and small ponded areas at the site are not expected to support substantial aquatic populations.

An updated evaluation of the potential for ecological risk at Site ST-19 was conducted according to the MDNR CALM guidance document (MDNR 2001). On August 11, 2004, CH2M HILL scientists conducted an ecological site reconnaissance of Site ST-19. Most of the area is paved. The unpaved areas are characterized by patchy, mowed grass.

Previous investigations at Site ST-19 documented that fill material was observed at depths ranging from near ground surface to 10 feet bgs. It is likely that if terrestrial receptors such as invertebrates and small plants were present, their exposure would be limited to the surficial layer of topsoil and fill rather than to any affected subsurface soil. There are no surface water bodies present at or adjacent to Site ST-19. Based upon the ecological evaluation, there are no significant ecological habitats or ecological receptors present at or adjacent to Site ST-19. Offsite migration of residual chemicals in soil or groundwater is not anticipated since the soil matrix consists primarily of fine-grained clays. Therefore, an ecological exposure pathway evaluation (Phase II) is not necessary. In summary, there are no significant ecological habitats or ecological receptors present at or adjacent to Site ST-19.

2.7.2.7 Site ST-20 On August 12, 2004, CH2M HILL scientists conducted an ecological site reconnaissance at Site ST-20. Site ST-20 is covered with asphalt and secured by a chainlink fence. There are no surface water bodies at the site, and it is not expected to provide a suitable habitat for ecological receptors. Although native vegetation and other potential ecological receptors are present at Knob Noster State Park, located along the northern border of Whiteman AFB, there are no complete exposure pathways between residual site chemicals and such receptors.

2.7.2.8 Site OT-23 A qualitative ecological risk assessment of Site OT-23 performed in 1997 (Halliburton 1997a) did not identify sensitive environments at the site. The assessment concluded that terrestrial ecological receptors could experience adverse effects from exposure to contaminants in surface soil at Site OT-23.

An updated evaluation of the potential for ecological risk was conducted in accordance with MDNR’s CALM guidance document (MDNR 2001). On August 11, 2004, CH2M HILL scientists conducted an ecological site reconnaissance of Site OT-23. Site OT-23 consists of relatively flat grassy fields. The entire site is surrounded by fences because it lies within a restricted access area. These fences could inhibit potential terrestrial receptors from accessing the site and being exposed to site-related contaminants. However, small terrestrial receptors and plants could be present at Site OT-23. Offsite migration of residual chemicals in soil or groundwater is not anticipated since the soil matrix consists primarily of lean clay ranging from near ground surface to a maximum depth of 36 feet bgs (Jacobs 1998a).



Since ecological receptors could occur in habitats at Site OT-23, the site was evaluated to determine whether receptors and habitats at or adjacent to the site were at potential risk from coming in contact with a chemicals on or near the site. Although lead is present in soil at Site OT-23, it is sequestered and not bioavailable following stabilization using the MAECTITE process. Therefore, there are no potentially complete exposure pathways for receptors at Site OT-23.

2.7.2.9 Site ST-26 On August 11, 2004, CH2M HILL scientists conducted an ecological site reconnaissance of Site ST-26. The UST at Site ST-26 was excavated and the excavation was filled with clean soil. The UST area is characterized by patchy, mowed grass. Because clean fill has been placed at the site, surface soil samples have not been collected as the samples would be representative of the clean fill rather than potentially affected soils. It is likely that if terrestrial receptors such as invertebrates and small plants were present, their exposure would be limited to the surficial layer of topsoil and fill rather than to any historically affected subsurface soil.

There are no surface water bodies or wetlands at or adjacent to Site ST-26. The area at and around Site ST-26 does not provide high quality habitat for potential ecological receptors because of its small size and maintained grasses, and the presence of adjacent industrial sites. Offsite migration of residual chemicals in soil or groundwater is not anticipated since the soil matrix consists primarily of fine-grained clay. Based upon the ecological evaluation, there are no significant ecological habitats or ecological receptors present at or adjacent to Site ST-26.

2.7.2.10 Site DP-32 As part of the RI, a CH2M HILL ecologist visited the site on February 26 and 27, 2002, and characterized it based on the considerations listed in the MDNR CALM guidance for ecological risk assessment (MDNR 2001). It was concluded that there is potential for Site DP-32 to support ecological receptors (CH2M HILL 2003). The primary habitats identified were the small stream, grassland, scrub/shrub, and wooded areas on or directly adjacent to the site.

A Phase II ecological exposure pathway analysis determined that receptors or habitats on or adjacent to the site could be exposed to chemicals from Site DP-32. The information compiled as part of the historical site use and potential sources of contamination has suggested that the primary chemicals are likely those related to historical waste incineration operations at the site (e.g., PAHs, other SVOCs, inorganics).

Based on the results of the Tier 1 qualitative ecological risk assessment, it was determined that a semiquantitative risk evaluation was warranted for Site DP-32. Benthic invertebrates (e.g., aquatic insects) or biota in the water column (e.g., fish, aquatic insects, and amphibians) might be exposed to chemicals in sediment and surface water. Therefore, the direct contact exposure route was considered in the risk evaluation for these lower trophic level receptors.

Characterization of potential ecological risk for constituents measured in environmental media at Site DP-32 suggests that minimal risk exists through direct exposure and food web



exposure for most constituents at Site DP-32. The ecological risk characterization indicates that there is likely no risk to receptors that might access the site.

2.7.2.11 Site SS-35 As part of the RI for Site SS-35, a CH2M HILL ecologist visited the site on February 26 and 27, 2002, and characterized the site based on the considerations listed in the MDNR CALM guidance for ecological risk assessment. The Tier I qualitative ecological risk assessment concluded that there is no habitat at or adjacent to Site SS-35. Based on the absence of habitat on or surrounding Site SS-35, there is likely no risk to receptors that might access the site.

2.8 Documentation of Significant Changes There are no changes in this ROD from the Proposed Plan.


29

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Record of Decision Whiteman Air Force Base, Missouri

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INSTALLATION BOUNDARY RECORD OF DECISION SITE LIMITS WHITEMAN AIR FORCE BASE, MISSOURI

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155 19 509 140 5070

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FIGURE 2-5 SITE LF-08 SITE FEATURES MAP RECORD OF DECISION WHITEMAN AIR FORCE BASE, MISSOURI

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3. Responsiveness Summary

The public comment period for the Proposed Plan began on April 22, 2005, and ended on May 31, 2005, as described in Section 2.3. No comments were received on the Proposed Plan. The public availability session regarding the Proposed Plan was held on May 19, 2005. No questions were received because there was no community participation.

3.1 Stakeholder Comments and Lead Agency Responses None.

3.2 Technical and Legal Issues None.


3-1

4. References

Air Force Center for Environmental Excellence (AFCEE). 1997. Headquarters Air Force Center for Environmental Excellence Technical Services Quality Assurance Program, Air Force Center for Environmental Excellence Guidance for Contract Deliverables, Appendix D: Risk Assessment Methods, Version 1.0.

Black & Veatch. 1991. Installation Restoration Program, Stage 2 Remedial Investigation/Feasibility Study, Whiteman Air Force Base, Knob Noster, Missouri.

Black & Veatch. April 2004a. Final Groundwater Summary Report – Long Term Monitoring. April.

Black & Veatch. 2004b. Final Supplemental Investigation Report—Long Term Monitoring at Sites SS-15 and ST-26.

CH2M HILL. 2005a. Proposed Plan for Twelve Environmental Restoration Sites, Whiteman Air Force Base, Missouri.

CH2M HILL 2005b. Final Remedial Investigation Work Plan.

CH2M HILL. 2004. Treatability Study Implementation and First Quarter Evaluation Report for Site DP-32.

CH2M HILL. 2003. Final Remedial Investigation Report for Sites DP-32, SS-40, SS-41, and SS-44.

Ecology and Environment Inc. 1988a. IRP Phase II: Confirmation/Quantification, Stage 1 –Final Report.

Ecology and Environment, Inc. 1988b. Technical Document to Support No Further Action Record of Decision.

Gehm Environmental. 1998. Whiteman Air Force Base – Facility 101 USTs #1– #5 Closure Report.

Geotechnology, Inc. 1996. Geophysical Survey.

Halliburton NUS Corporation. 1994. Installation Restoration Program, Draft RCRA Facilities Investigation: Volumes I, II, III.

Halliburton NUS Corporation. 1996. Draft Decision Document for SS-15 Suspected Drum Burial Area.

Halliburton NUS Corporation. 1997a. Remedial Investigation Report for ST-06, Building F-9.

Halliburton NUS Corporation. 1997b. Remedial Investigation for Site ST-19, Tank Farm Facilities 101 and 102.

Jacobs Engineering Group, Inc. 1998a. Summary of Borehole Geophysical Investigation.

Jacobs Engineering Group, Inc. 1998b. Decision/Closure Document for No Further Action.


4-1

SECTION 4—REFERENCES

Jacobs Engineering Group, Inc. 1999a. Decision Document for No Further Action, Installation Restoration Program, Tank Farm Facilities 101 and 102, Site ST-19.

Jacobs Engineering Group, Inc. 1999b. Site ST-20, Base Transportation Closure UST.

Metcalf and Eddy, Inc. August 23, 1991. Final RCRA Preliminary Assessment Report for Whiteman Air Force Base. August 23.

Missouri Department of Natural Resources (MDNR). 2001. Cleanup Levels for Missouri (CALM) Guidance Document. Division of Environmental Quality Hazardous Waste Program.

Montgomery Watson. 2001. Decision Document for No Further Action for Site ST-20.

PACE Incorporated. 1991. Confirmation Soil Sampling Analytical Results.

Stohr, C. J., et al. 1981. Geologic Aspects of Hazardous-Waste Isolation in Missouri. Missouri Department of Natural Resources Engineering Geology Report 6.

U.S. Environmental Protection Agency (USEPA). 1989. Risk Assessment Guidance for Superfund, Volume 1, Human Health Evaluation Manual (Part A). USEPA/540/1-89/002.

U.S. Environmental Protection Agency (USEPA). 1992. Risk Assessment Guidance for Superfund (RAGS).

Whiteman Air Force Base. 2002. Management Action Plan. Whiteman Air Force Base, Missouri.


Appendix A Administrative Record Index

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