EPA Superfund Explanation of Significant Differences - United States Environmental ... ·...

EPA/ESD/R04-05/040 2005

EPA Superfund

Explanation of Significant Differences:

MARINE CORPS LOGISTICS BASE EPA ID: GA7170023694 OU 06 ALBANY, GA 08/09/2005

10116013

United States Environmental Protection AgencyRegion 4

Arhnta Federal Center61 Forcyth St. SW, Atlanta, GA 30303-8960

CERTIFIED MAILRETURN RECEIPT REQUESTED

4WD

Colonel John P. LopezCommanding OfficerMarine Corps Logistics Base, Albany814 Radford BoulevardSTE20315Albany, Georgia 31704-0315

SUBJ: Explanation of Significant DifferencesOperable Unit 6 MCLB, Albany

Dear Col. Lopez:

The United States Environmental Protection Agency (EPA) Region 4 has reviewed the abovesubject decision document and concurs with the Explanation of Significant Differences (ESD)for the Remedial Action at OU 6. This remedy is supported by the previously completedRemedial Investigation, Feasibility Study and Baseline Risk Assessment Reports.

-- The ESD involves the changing of source controls and groundwater treatment technologyselected in the September 2001 Record of Decision (ROD). The changes include:

- Change in groundwater treatment technology from in situ enhanced bioremediation to insitu abiotic treatment of chlorinated volatile organic compounds (cVOCs);

- Change in the configuration of the Evapotranspiration (ET) Cover at the Northern PlumeArea (NPA);

- Elimination of a clay cap as a contingency remedy for the ET Cover;- Delay in construction of the ET cover to allow for heavy equipment transport for

groundwater treatment technology;- No additional maintenance or replacement of the Depot Maintenance Area (DMA)

pavement (cap) required.

Page I of 3

This remedial action is protective of human health and the environment, complies withFederal and State requirements that are legally applicable or relevant and appropriate to theremedial action and is cost effective.

Sincerely,

Winston A. SmithDirectorWaste Management Division

cc: Mr. Dan Ownens, SOUTHDIVMr. Billy Hendricks, GEPDMr. Albert Wilson, GEPD

Page 2 of 3

be: Martha Brock, EPA OEAPatricia Goldberg, FFBLila Llamas, FFB

EXPLANATION OF SIGNIFICANT DIFFERENCESto the

Final Record of Decision for Operable Unit 6Marine Corps Logistics Base NPL Site

Albany, GeorgiaEPA ID# GA7170023694

May 2005

I. INTRODUCTION AND STATEMENT OF PURPOSE

This Explanation of Significant Differences (ESD) has been prepared to document significantchanges to the Final Record of Decision (ROD) for Operable Unit 6 (OU 6) at the Marine CorpsLogistics Base (MCLB) Albany, Georgia (Base)(ROD executed on September 19, 2001). This ESDwill change several of the remedy components selected in the Final ROD for OU 6 (Basewidegroundwater). The source control and/or groundwater treatment areas described at the end ofthis Section are illustrated on Figure 1-1.

As the lead agency for this National Priorities List (NPL) Site, the United States Department ofthe Navy (the Navy) is issuing this ESD pursuant to public participation requirements specifiedin Section 117(c) of the Comprehensive Environmental Response, Compensation and LiabilityAct (CERCLA) and Section 300.435(c)(2)(i) of the National Contingency Plan (NCP). TheUnited States Environmental Protection Agency (EPA) and the State of Georgia Department ofNatural Resources - Environmental Protection Division (EPD) are the support agencies for thisSite. This ESD document will become part of the Administrative Record for the Site pursuant toNCP Section 300.825(a)(2). The Administrative Record for the Site is available for public reviewduring normal business hours at the following locations:

- the Environmental Branch Office, Installation and Logistics Division, Building 5501, MCLBAlbany, GA;

- the information repository in the Dougherty County Public Library, 2nd Floor-ReferenceSection, 300 Pine Street, Albany, GA.

Documents cited in this ESD are part of the Administrative Record and are available for reviewat the above locations.

The ROD for OU 6 specifies two types of response actions at the Base: source control andgroundwater treatment. Source control described in the ROD is specific to each area of theBase, consisting principally of capping or covering an area with soil. The purpose of sourcecontrol is either to mitigate infiltration of surface water through contaminated soil and/orburied wastes, or to prevent dermal contact with wastes. The ROD also specifies groundwatertreatment for each area of the Base, consisting of enhanced bioremediation

MCLB Albany ESD final 0070605 Page 1 of 16

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and/or monitored natural attenuation (MNA). The purpose of groundwater treatment is toreduce contaminant concentrations to target levels within specified timeframes. After signingthe ROD, the Navy conducted pilot tests at MCLB Albany of both source control methods andthe planned groundwater remedy (enhanced bioremediation). The source control testsdemonstrated that an evapotranspiration cover (ET cover) is more effective than a traditionalclay cap at controlling infiltration. The groundwater pilot tests showed that abiotic treatmentmay be more effective than enhanced bioremediation for groundwater treatment.

Source control and/or groundwater treatment activity is specified for eight (8) potential sourcesof contamination (PSCs) within three (3) areas of the Base (see Figure 1-1), as follows:

1) Northern Plume Area (NPA)- PSC 1, East Disposal Area- PSC 3, Long Term Landfill- PSC 26, Contaminant Berm Area

2) Depot Maintenance Activity (DMA) Plume Area- PSC 10, Central Repair Division of the DMA (including Building 2200 and associated shop

areas)- PSC 12, Industrial Wastewater Treatment Plant (IWTP)- PSC 13, Industrial Wastewater Pipeline (IWP)- PSC 22, DMA Storage Area

3) PSC 4- PSC 4, Warehouse Disposal Area

II. SITE HISTORY AND THE SELECTED REMEDY

OU 6 is an operable unit comprised of all groundwater underlying the Base. The boundaries ofthe groundwater contaminant plumes, including both on-Base and off-Base areas, define thelimits of OU 6. Groundwater within OU 6 occurs in the Upper Floridan Aquifer that locallyoccurs within the Ocala Limestone. The Ocala Limestone contains an Upper Water BearingZone (UWBZ) and a Lower Water Bearing Zone (LWBZ). OU 6 contains three geographic areasof contamination (plumes) identified as the NPA, the DMA, and PSC 4. The plume areas withinOU 6 contain chemicals of concern (COCs) in concentrations that exceed EPA risk criteria, orFederal or State maximum contaminant levels (MCLs) for drinking water.

The NPA, DMA, and PSC 4 area exhibit a history of varied uses and multiple contaminantreleases, but the principal contaminants are chlorinated solvents. The source of the contaminantplumes at the NPA was burial (in shallow trenches or pits) of waste materials containingsolvents. The source of the contaminant plumes at the DMA was spills and other releases ofsolvents from workshops and wastewater sewers. Infiltrating rainwater leached the solventsdown through the subsurface soil and created contaminant plumes in OU 6. (see Figures 2-1and 2-2 [figures renumbered from Planteco Environmental Consultants, LLC,


September 2004]). The dissolved contaminants migrated from the source areas bothhorizontally within the UWBZ, and vertically into the underlying LWBZ. To date, the principalmass of contaminants is contained in plumes within the UWBZ; solvents have been detectedonly at low levels in the upper part of the LWBZ.

Sampling by the EPA indicates that COCs have not exceeded MCLs in any offsite residentialwells. However, the Base in 1998, in cooperation with EPA and EPD, sent a letter to allresidents living within one mile of PSC 3 offering to provide free connection to the Albanywater supply. The Base implemented in 1999 residential water-supply connections as aprecaution to eliminate the potential for human exposure to contaminated groundwater. TheBase also offered to fund all costs associated with permanently plugging and abandoning wellsthat were replaced by municipal water connections; however, no residential wells werepermanently abandoned by the Base.

The Base holds a Georgia Hazardous Waste Facility Permit (Permit Number HW-009 [S&D]) forstorage of hazardous waste and for post-closure care of three surface impoundments. The Basewas placed on the EPA's National Priority List of Superfund sites in 1990. In July 1991, theNavy entered into a Federal Facilities Agreement (FFA) with the EPD and EPA Region 4 toestablish a procedural framework and schedule for developing, implementing, and monitoringappropriate response actions at the facility. Any response actions would be in accordance withCERCLA; Resource Conservation and Recovery Act (RCRA); the NCP; and the GeorgiaHazardous Waste Management Act.

The Final ROD specifies source control by capping and covering, and in-situ treatment ofgroundwater to achieve cleanup goals within 10 years for off-Base areas and 20 years for on-Base areas. The major components of the Navy's selected remedy for this Site include:

• Source Control at NPA, DMA, and PSC 4

At NPA: Evapotranspiration (ET) coverAt DMA: Characterization of potential source areas within the DMA and control of thesesources with an appropriately designed cap, and repair and/or re-lining of subsurfacepiping, manholes, and associated pipe junctionsAt PSC 4: Twelve inches of soil cover

• Groundwater Treatment at NPA, DMA, and PSC 4

Primary remedy for the UWBZ at NPA and DMA: enhanced bioremediationContingency remedy for the UWBZ at NPA and DMA: conventional pumping and ex-sitntreatment

- Contingency remedy for the LWBZ at NPA, DMA, PSC 4: conventional pumping and ex-situ treatment

- Primary remedy for the UWBZ at PSC 4 and the LWBZ at NPA, DMA, PSC 4: MNAContingency remedy for the UWBZ at PSC 4 : enhanced bioremediation.

MCLB Albany ESD final 0070605 Page f> of 16

III. BASIS FOR THE DOCUMENT

Source Control at NPA

In accordance with the ROD, the objective of source control at the NPA is to reduce the flow ofwater through the soil and buried wastes, thereby isolating contaminants above the water table.The ROD specifies an evapotranspiration (ET) cover as the primary source-control remedy atthe NPA, and a traditional clay cap as a contingency remedy. The ROD also specifies aperformance criterion: the ET cover must achieve an infiltration rate of lxlO~5 centimeters persecond (cm/sec) or less. The Base conducted a 3-year pilot study (Alternative CoverAssessment Project - ACAP) comparing the performance of an ET cover and a conventionalclay cap. The ACAP study showed the performance of the ET cover was superior to aconventional clay cap. The results of the pilot study are documented in the TechnicalMemorandum (TM) entitled Project Path Forward - Source Area Capping Remedy, Potential Sourceof Contamination (PSC) 1, 3 and 26, Operable Unit 6 (CH2M HILL, November 2002). The TM is thebasis for the source control design at the NPA. Because of the expense and time required toimplement an ET cover, this ESD removes the contingency remedy of a traditional clay cap. Inagreement with the EPA and the EPD, the Base will implement an ET cover as the sole source-control remedy at the NPA.

The ROD requires that the selected source-control remedy be implemented by September 2004,which is 3 years from the date of signing the ROD for OU 6. However, the implementation ofthe ET cover has been delayed to allow completion of groundwater treatment. Without thedelay, heavy equipment required for the groundwater treatment would damage the new ETcover. It is anticipated that the ET cover will be installed by the end of 2006. The ET coverdesign is currently in progress, with the most recent design described in the document, "DraftRemedial Design for Evapotranspiration Cover (ET)for the Northern Plume Area (NPA) at MarineCorps Logistics Base (MCLB), Albany, GA" (CH2M HILL, May 2004). Performance of the ETcover will be evaluated semi-annually as part of the corrective action effectiveness/naturalattenuation reporting process, and during the CERCLA Five-Year Review.

PSC 2

Harding Lawson and Associates (HLA) reported that PSC 1 (Figure 1-1) is an inactive landfillmeasuring approximately 100 feet by 300 feet, located near the western edge of the Indian LakeRefuge Area and south of North Shaw Road (HLA, Remedial Investigation and Baseline RiskAssessment Report, Operational Unit 6, Marine Corps Logistics Base Albany, Georgia, 2000). Between1958 and 1959, approximately 10,000 tons of wastes including solvents were reportedlydisposed and burned in trench-and-fill operations. The wastes were subsequently compacted,covered with soil, and planted with pine trees. The site is currently covered by a mature standof pine trees mixed with shrubs and a few mature hardwoods.

The ROD specifies an ET cover as the source-control remedy for PSC 1 to reduce infiltration ofprecipitation into the wastes, and thus, to reduce the potential migration of contaminants togroundwater. Multiple investigations at PSC 1 indicate the most probable disposal area has nolandfill wastes or other sources of contamination to depths of 8 feet bgs. The results show the


existing soil and vegetation cover is equivalent to an ET cover. Furthermore, recentgroundwater analyses indicate that cVOC concentrations are substantially lower than 10 yearsago. For these reasons, an ET cover is not needed at PSC 1 to reduce the migration ofcontaminants to groundwater. This ESD removes the implementation of an ET cover at PSC 1.More details of the studies at PSC 1 are provided in the following paragraphs.

A geophysical survey in 1992 found a potential disposal area in the south-central portion ofPSC 1 (ABB Environmental Services Inc. Bench-Scale Treatability Study, TM Operational Unit 2,Marine Corps Logistic Base Albany, Albany, Georgia, 1994). A subsequent soil gas survey detectedchlorinated volatile organic compounds (cVOCs) including trichloroethene (TCE), cis-1,2-dichloroethene (DCE), and carbon tetrachloride in 5 of 50 soil gas points (Target EnvironmentalServices Inc., So/7 Gas Survey, PSC 1 Marine Corps Logistic Base, Albany, Georgia prepared for ABBEnvironmental Services Inc., 1992). These two investigations indicated that a 0.75-acre area inthe southeastern portion of PSC 1 might be a disposal (source) area. This area was laterconfirmed as a source area based on cVOC detections in soil samples (HLA, OU 6 FeasibilityStudy for Marine Corps Logistic Base, Albany, Georgia, 2000).

Based on this information, CH2M HILL in December 2003 advanced 15 soil borings andinstalled 3 soil-gas monitoring points to locate the buried wastes. Fourteen borings wereadvanced to 8 feet below ground surface (bgs), and one boring was advanced to 15 feet bgs. Nolandfill wastes or disturbed soil were encountered in the soil borings and only low to moderateresponses were observed while screening soil samples with an OVA meter. Subsequent vapormonitoring of the soil gas points did not indicate the presence of landfill materials (CH2MHILL, TM Basis for Deletion ofEvapotranspiration Cover at PSC 1, 2004).

Benzene, TCE, cis 1,2-DCE, and vinyl chloride have been detected above their MCL in thePSC 1 groundwater plume. Older (pre-2000) groundwater analyses indicate the followingmaximum concentrations:

• TCE at 1,200 micrograms per liter (ug/L) (at ALB01-08B, sampled on 11/05/92),• cis 1,2-DCE at 7,600 ug/L (reported as Total 1,2-DCE, ALB01-08B, sampled on 11/05/92),

and• vinyl chloride at 900 ug/L (at ALB01-6B, sampled on 12/04/97).

In March 2004, CH2M HILL collected and analyzed groundwater samples from 20 monitoringwells at PSC 1 to evaluate current plume conditions. The March 2004 results (CH2M HILL, Basisfor Deletion ofEvapotranspiration Cover at PSC 1, Marine Corps Logistics Base, Albany, Georgia,April 12, 2004; CH2M HILL, ET Cover Draft Design, May 13, 2004) indicate maximum TCEconcentrations are approximately one order of magnitude (10X) lower than the historicalmaximum concentrations. The results also indicate the UWBZ contaminant plume has notmigrated into the LWBZ. Based on these results, there is no continuing source of TCE (andother COCs) at PSC 1.

PSC 3

PSC 3 (Figure 1-1) is the former long-term landfill. The ROD specifies source control using anET cover, in situ groundwater treatment of the UWBZ plume, and natural attenuation with

MCLB Albany ESD final (XJ706U5 Page 8 of IA

monitoring of the LWBZ plume. No changes to these remedies are planned. A previousinvestigation of PSC 3 that identified contaminant source areas (HLA, TerraProbe ™ LandfillCharacterization Report, May 2000). This source area will receive an ET cover beginning in 2006.Groundwater treatments (see below) are planned to start in 2005. Semi-annual monitoring ofthe UWBZ and LWBZ at PSC 3 is ongoing.

PSC 26

PSC 26 (Figure 1-1) is the containment berm area that was suspected of containing buriedwastes. The ROD specifies source control using an ET cover, in situ groundwater treatment ofthe UWBZ plume, and natural attenuation with monitoring of the LWBZ plume. Treatment ofthe UWBZ plume is planned (see below), and natural attenuation with semi-annual monitoringof the UWBZ and LWBZ is ongoing. The only change to the ROD is elimination of the ET cover.The following paragraph explains why no ET cover will be constructed at PSC 26.

PSC 26 was extensively investigated using geophysical methods, soil gas surveys, and soilsampling and analysis (ABB-ES, Remedial Investigation and Baseline Risk Assessment [BRA] ReportAddendum for Oil 1, May 1997). The geophysical investigation found no evidence of buriedwastes. Neither the soil gas survey nor soil sampling indicated the potential presence ofsurface or subsurface contamination that might act as a source for groundwater contamination.The BRA for PSC 26 determined that both cancer and non-cancer risks posed by soilcontaminants under current land use were within the acceptable range (ABB-ES, 1997). Under apotential residential land-use scenario, the cancer risk was within the acceptable range, but thenon-cancer risk for a resident child exceeded a hazard index (HI) of 1. The two "contaminants"contributing significantly to the HI were iron and manganese. However, concentrations of theseelements were similar to background soil concentrations, and neither is known to be associatedwith a waste release at PSC 26 (ABB-ES, 1997, Sec. 6.2.1.8). Therefore, no ET cover is required atPSC 26.

Source Control at the DMA

The source control remedy for the DMA (Figure 1-1) is comprised of two parts: 1)Characterization of potential source areas within the DMA and control of these sources with anappropriately designed cap, to minimize potential for leaching of contaminants in soil togroundwater; and, 2) repair/replacement of leaking subsurface pipelines that could provideinfiltration of water and potentially new contaminants to soil and groundwater. The ROD statesthat both defective/leaking pipes and incomplete or cracked pavement over soil source areaswould be repaired or replaced. The ROD includes additional source characterization as part ofthe remedy, and this work was done to define the area(s) to be maintained as a cap. Sourcecharacterization included identification of subsurface pipelines, examination of subsurfacepiping for defects and leaks, and testing subsurface soil in areas with potentially high levels ofcontamination.

Summary of DMA Source Characterization Study

In 2001, the Base conducted subsurface characterization studies at the DMA. The scope of workis detailed in two documents: 1) Work Plan Addendum (WPA) No. 07, Source Characterization of


the Depot Maintenance Activity Area (Rev. 01, CH2M HILL, October 2001); and, 2) WPA No. 06,Pavement and Floor Drain Investigation at the Depot Maintenance Activity Area (Rev. 01, CH2MHILL, February 2002). The results of the source characterization are provided in a TM, DMASource Characterization (CH2M HILL, Revision No. 01, September 2003). The results of thesubsurface piping investigation are provided in a TM, DMA Piping System Investigation (CH2MHILL, July 2003).

The objective of the source characterization was to identify high levels of soil contamination inthe vadose zone that might serve as a source of groundwater contamination. Particular focuswas directed toward the "shop areas," where various solvents and paints are routinely usedand stored. Shop areas targeted for subsurface soil tests were identified in the report, Phase IEnvironmental Site Assessment of the Depot Maintenance Activity Area (CH2M HILL, April 2001).Five new monitoring wells were installed into the UWBZ, 83 soil borings were completed usingdirect push methods, and 166 soil samples were chemically analyzed.

The source characterization indicated there are low levels of cVOC-contaminated soil beneathDMA buildings. With few exceptions, the concentrations of cVOCs in soil decreased withdepth. These results indicate there have been a few releases of small amounts of solventswithin the shops. The results showed there are no large scale or ongoing potential sources ofcontamination in soil beneath the shop areas. Results of this investigation supported findings ofprevious work that indicated releases from industrial wastewater sewers contributed to thecontaminant plume in the UWBZ (ABB-ES, Remedial Investigation and Baseline Risk Assessment[RI/BRA] Report for OU 4, January 1998).

During the ABB-ES investigation, low levels of TCE and other VOCs were detected in theshallow soil beneath the industrial wastewater sewers, but higher concentrations were detectedat greater depths (approximately 30-45 feet). The sewers were installed in the early 1950s usingclay pipe, but have been rehabilitated by the Insituform™ process in 1990. Following therehabilitation work the sewer pipe has not developed any substantial defects in integrity. Also,since 1990, the DMA has greatly reduced its use of chlorinated solvents and has improved itsefforts to minimize wastes. These practices have reduced both the concentrations of chlorinatedsolvents in wastewater and the volume of wastewater flow in the industrial sewer system. Thedistribution of cVOCs in soil suggests that the pipe rehabilitation, along with decreased use ofchlorinated solvents and waste minimization efforts have been effective source controls for theDMA. This conclusion is further substantiated by the widespread, diffuse nature of thegroundwater plume at DMA, and the associated decreasing or stable trend of cVOCs ingroundwater over time (Planteco Environmental Consultants, LLC, Monitored NaturalAttenuation Results, December 2003 Sampling of Groundwater Monitoring Wells for the Former SludgeDrying Beds at the Industrial Wasteii'ater Treatment Plant, and Operable Unit 6, Marine CorpsLogistics Base Albany, Albany, Georgia, draft version 1.2, March 17, 2004).

The results of the piping investigation indicate that, although the industrial wastewater pipesare in relatively good condition, there is evidence of defects and some potential for leakagewhere service connections have been made. The use of "hammer taps" - new connections madeto existing pipes by physically "breaking" into the line and re-grouting the area around the newconnection - has created numerous connections that probably are not leak tight. The pipinginvestigation also noted that the interior surfaces of some of the service laterals, manholes, and

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pipe-junction structures have not been lined, and therefore do not provide the same level ofmoisture and/or chemical resistance as the Insituform™ lining. Although no leakage orsurface defects were noted, there is a potential for leakage from these structures because theexposed brick and mortar surfaces are not impervious to liquids.

Conclusions of the DMA Source Characterization Studies

The results of the subsurface soil investigation indicate a few isolated, shallow zones of soilcontamination, apparently associated with small-volume, accidental releases in the shop areas.Soil contamination identified by ABB-ES (1998) at depths greater than 20 feet bgs is related topre-1990 releases from the wastewater sewers, not to ongoing releases from shop areas. Thesource characterization results identified no existing surface or near surface sources ofcontamination that represent a current or future threat to groundwater beneath the DMA. Forthese reasons, no additional maintenance of the DMA pavement (cap) is required to protectgroundwater. Service connections to the industrial sewers are potential release locations.Therefore, all connection points between services/lateral piping and the industrial sewers willbe repaired or replaced as required by the ROD.

Source Control at PSC 4

According to the ROD, the primary remedy for source control at PSC 4 is a soil cover to preventhuman and ecological receptors from coming into contact with contaminants in surface soil.This soil cover will be installed as specified in the ROD.

Groundwater Treatment at the NPA and DMA

The ROD specifies enhanced bioremediation as the primary groundwater treatment remedy forthe UWBZ at the NPA and DMA. Enhanced bioremediation would be implemented in-situ(within the aquifer) by injecting chemicals to accelerate natural biological reactions that destroythe cVOCs. In order to evaluate the effectiveness of enhanced bioremediation, the Navyconducted in 2001 a bench-scale study, and in 2002, two field-scale pilot tests of enhancedbioremediation at PSC 3. The pilot tests demonstrated that enhanced bioremediation wasineffective in reducing cVOC concentrations within the first year after injections, and thatmultiple injections would be required to achieve cleanup. The Navy concluded from the teststhat enhanced biodegradation is not likely to achieve the ROD cleanup goals within thetimeframes required. The results of the pilot studies are documented in the TM, SummaryReport, Abiotic and Biological Pilot Tests at DMA and PSC 3 (CH2M HILL, June 2003).

As discussed in the TM, the Navy also conducted pilot tests to evaluate in situ abiotic (non-biological) treatment of cVOCs. These tests measured the effectiveness of injecting chemicals(potassium permanganate and zero valent iron [ZVI]) that destroy cVOCs on contact. The testresults showed that abiotic treatment was very effective: cVOC concentrations in the test areawere reduced >90% within a matter of weeks. Also, the tests showed that the chemicals couldbe delivered to the UWBZ fairly efficiently and that only one injection would likely be requiredto achieve the cleanup goals. For this reason, abiotic chemical treatment will be used to addressgroundwater impacts at both the NPA and the DMA. The approach to groundwater treatmentat the NPA and the DMA is described in the Remedial Action Work Plan for Operable Unit 6-Baseunde Groundwater, Marine Corps Logistics Base Albany, Georgia (CH2M HILL, November

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2004).

The OU 6 ROD (Table 1-3) specifies groundwater remedial goals for three trace metals -antimony, cadmium, and thallium. These metals have been detected above their respectiveMCL numerous times since 1992:

Parameter MCL Years of Number Number Number of Number of Number of(ug/L) Sampling of Wells of GW Results Wells w/ >1 Exceedances

on Base analyses Exceeding Exceedance Dec2003-Sampled MCL Jun2004

Antimony

Cadmium

Thallium*

6

5

2

1992-2004

1992-2004

1 992-2004

249

252

251

1,020

1,015

1,021

52

40

26

1

7

2

0

0

0

* During the DMA pilot test, the permanganate color (purple) induced false positives in analysis of groundwater samples from thepilot test site. Values do not include multiple false positives for thallium in these samples.

However, close examination of the data indicate that very few of the exceedances occurred inthe same well or even in the same area of the Base. The exceedances are scattered across theBase and over the first 11 years of the sampling period (1992-2003). These results indicate anessentially random pattern of detections that cannot be associated with a release, and no metalsplumes have been identified. The data further indicate that the majority of the exceedancesoccurred in the 1990s and that the most recent sampling (December 2003 and June 2004) foundno MCL exceedances. In summary, the available data indicate that there is no plume of metalcontaminants at MCLB Albany to be remediated, and that natural attenuation processes haveachieved the ROD goals for these metals. For these reasons, this ESD removes the metals fromfurther routine monitoring.

The ROD specifies MNA as the remedy for the LWBZ at both DMA and NPA. Ongoinggroundwater monitoring by the Base indicates that the LWBZ continues to show little or nocVOC contamination, even without treatment in the UWBZ. MNA is unchanged as the remedyfor the LWBZ at NPA and DMA.

Groundwater Treatment at PSC 4

The ROD specifies MNA as the groundwater-treatment remedy for both the UWBZ and LWBZat PSC 4. Ongoing MNA testing by the Base shows that the plume at PSC 4 has nearlydisappeared. MNA is unchanged as the remedy for groundwater at PSC 4.

IV. DESCRIPTION OF SIGNIFICANT DIFFERENCES

The following table summarizes the significant changes to response actions specified in theFinal ROD. These changes are described is some detail in the following paragraphs.

Remedial Action

NPA Source Control

ROD Response Action

ET Cover placed on PSC 1,

Changed Response Action

ET Cover placed on PSC 3

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PSC 3, and PSC 26. only. Work will begin aftergroundwater treatments, sothat injection work will notdamage ET cover.

Repair and/or re-lining ofsubsurface piping, manholes,and piping junctions.

DMA Source Control Characterization of sourceareas & control of thesesources w/appropriatelydesigned cap, and repairand/or re-lining of subsurfacepiping, manholes, and pipingjunctions.

Groundwater Treatment ofUWBZ at NPA

Use enhanced bioremediationfor plume treatment.

Use injections of sodiumpermanganate (on TCE plume)or zero valent iron (on carbontetrachloride plume) for plumetreatment.

Groundwater Treatment ofUWBZ at DMA

Use enhanced bioremediationfor plume treatment.

Use injections of sodiumpermanganate for plumetreatment.

Source Control at NFA

The ROD specifies that source-control at NPA would be implemented using an ET cover. ThisESD removes the contingency source-control remedy of a traditional clay cap. The 3-year ACAPstudy showed the performance of the ET cover was superior to a conventional clay cap (CH2MHILL, Project Path Forward - Source Area Capping Remedy, Potential Source of Contamination (PSC)1, 3 and 26, Operable Unit 6, Marine Corps Logistics Base Albany, Georgia, November 2002). Basedon the ACAP results, and in agreement with the EPA and the EPD, the Base will implement anET cover as the sole source-control remedy at NPA. This change is not expected to have anysignificant effect on the UWBZ contaminant plumes and there are no estimated savings. An ETcover will be implemented at PSC 3 following groundwater treatment. This is necessarybecause the heavy equipment needed to perform the groundwater treatment would damage thenew ET cover. Currently, construction of the ET cover at PSC 3 is scheduled to begin in the Fallof 2005.

No ET cover will be implemented over PSC 1 or PSC 26. Recent drilling and testing at PSC 1(CH2M HILL, Basis for Deletion of Evapotranspiration Cover at PSC 1, Marine Corps Logistics BaseAlbany, Georgia, April 12, 2004; CH2M HILL, ET Cover Draft Design, May 13, 2004) found noburied wastes (active sources of contamination) to depths of 8 ft bgs, indicating the existing soiland vegetation cover is equivalent to an ET cover. Based on extensive characterization of PSC26 (ABB-ES, Remedial Investigation and Baseline Risk Assessment Report Addendum for Oil I, May1997), there are no waste disposal areas or highly-contaminated soil (sources) that require

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capping. The decision not to construct an ET cover at PSC 1 and PSC 26 is expected to have noadverse impact on the UWBZ contaminant plumes. There are no buried wastes (sources) at PSC26, so additional cover is not needed. The existing soil and vegetation cover at PSC 1 isequivalent to an ET cover, and contaminant levels in the UWBZ have decreased significantly inthe last 10 years. Contaminant plumes in the UWBZ will be treated at PSCs I, 3, and 26 (CH2MHILL, Remedial Action Work Plan for OU 6, November 2004) to achieve the ROD cleanupgoals. The estimated cost avoidance of eliminating the ET covers at PSC 1 and PSC 26 is $5million.

Source Control at DMA

The ROD specifies the source control remedy is composed of two parts: 1) Characterization ofpotential source areas within DMA and control of these sources with an appropriately designedcap, and 2) repair and/or re-lining of subsurface piping, manholes, and associated pipingjunctions. Based on extensive subsurface soil testing, no vadose zone sources were identified.Therefore, no special maintenance or replacement of the existing pavement to function as a capis warranted. Repairs/relining of subsurface piping and manholes will be performed, asrequired in the ROD, to prevent new releases to soil and groundwater. The estimated costavoidance by eliminating maintenance of the pavement cover at DMA is $10 million.

Groundwater Treatment at the DMA and NPA

The ROD specifies enhanced bioremediation as the primary groundwater remedy for theUWBZ at the NPA and the DMA. Pilot tests (CH2M HILL, Pilot Test Summary Report of Abioticand Biological Pilot Tests at DMA and PSC 3, June, 2003) showed that abiotic treatment may bemore effective than enhanced bioremediation. Field-scale pilot studies showed that injection ofchemicals (potassium permanganate and zero valent iron) will rapidly destroy cVOCs in theUWBZ. The test results indicate that a single injection will likely be sufficient to treat the sourceareas of the OU 6 plumes. The permanganate, a strong oxidizing agent, was effective atdistances greater than 50 feet from the point of injection. ZVI, a strong reducing agent, waseffective at distances greater than 25 feet from the point of injection. During remedyimplementation, injections of permanganate and ZVI will occur at a spacing of no more than100 ft and 50 ft, respectively (CH2M HILL, Remedial Action Work Plan for Operable Unit 6 -Baseit'ide Groundwater, Marine Corps Logistics Base Albany, Georgia, November 2004). Althoughpotassium permanganate was used in the pilot studies, sodium permanganate is being used forfull-scale implementation due to ease of application. The sodium permanganate iscommercially available in liquid form (40% solution) that is easily diluted with water.Potassium permanganate is only available as a dry chemical that must be vigorously mixedwith water prior to use. Also, the maximum concentration of a potassium permanganatesolution is only 5%. If necessary, the sodium permanganate may be injected at higherconcentrations to achieve greater treatment effectiveness. Permanganate will be injected to treatplumes of chlorinated alkenes, such as PCE and TCE; and ZVI will be used to treat plumes ofchlorinated alkanes, such as carbon tetrachloride.

Results of ongoing MNA testing being performed by the Navy show that the untreated parts ofthe OU 6 plumes will naturally attenuate and achieve the ROD cleanup goals within thetimeframes specified (Planteco Environmental Consultants, LLC, Monitored Natural Attenuation


Results, December 2003 Sampling of Groundwater Monitoring Wells for the Former Sludge DryingBeds at the Industrial Wastezvater Treatment Plant, and Operable Unit 6, Marine Corps Logistics BaseAlbany, Albany, Georgia, draft version 1.2, March 17, 2004; CH2M HILL, Remedial Action WorkPlan for Operable Unit 6 - Basewide Groundwater, Marine Corps Logistics Base Albany, Georgia,November 2004). Results of MNA monitoring in 2003 and 2004 indicate that levels of antimony,cadmium, and thallium in the UWBZ are below the ROD cleanup goals; therefore, no furtherroutine monitoring for these metals is planned. Post-injection monitoring will be performed toensure that the injections treat the plume source areas, and that natural attenuation is reducingplume concentrations outside the injection areas. The estimated cost avoidance byimplementing in situ abiotic treatment, rather than biological treatment, is $15 million.

V. SUPPORT AGENCY COMMENTS

The EPA and EPD have reviewed this ESD and the associated documentation that explain therationale and justification behind changing the remedy components for OU 6. The EPA andEPD concur with the basis for changing the extent of source controls, and the basis for changingthe groundwater treatment to in-situ abiotic chemical destruction. The EPA and EPD concurthat this work should proceed.

VI. STATUTORY DETERMINATIONS

Pursuant to the requirements of CERCLA Section 121, the modified remedy for OU 6 (basewidegroundwater) is adequately protective of human health and the environment, complies withapplicable or relevant and appropriate requirements, is cost-effective, and uses permanentsolutions and alternative treatment technologies or resource recovery technologies to themaximum extent practicable. The modified remedy includes chemical injections that destroythe contaminants in place, thus the remedy satisfies the preference for treatment as a principalelement. Source controls and natural attenuation within untreated areas of the OU 6 plumeswill reduce over time the toxicity and mobility of the contaminants.


VII. PUBLIC PARTICIPATION COMPLIANCE

This ESD and other supporting documentation will be placed in the Administrative Recordlocations referenced in Section I above for public review. Copies will also be available in theInformation Repository. A notice will be published in a local newspaper of general circulationto summarize the ESD and reasons supporting the modified remedy. Therefore, the publicparfch^jpation requirements set forth in NCP Section 300.435(c)(2)(i) have been met.

r, MCLB Albany

Winston A.DirectorWaste Management DivisionU.S. Environmental Protection Agency - Region IV

MCLB Albany ESD final 0070605 Page 16 of!6

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