TolTest environmental remediation project featured in Jan/Feb 2010 issue of The Military Engineer magazine
Release Date: December 30, 2009
Source: The Military Engineer. January-February. 2010
Multiple Contaminant Removal at Tyndall AFB, FL
From 1981 to 1992, the Little Cedar Creek Fire Training Area at Tyndall Air Force Base, Fla., provided a training ground for firefighters on aircraft and fuel spill fires. Although such training is essential in military settings, an unfortunate side effect of such land usage is contamination of soil and groundwater caused by the use of fire accelerants. In the case of the Little Cedar Creek Fire Training Area, an August 1999 contamination assessment report of Site FT023 showed soil and groundwater contamination due to petroleum constituents with free product. January 2002 tests confirmed approximately 2,600-gal of petroleum free product in the area's shallow aquifer.
Toluene, ethylbenzene and total xylene levels exceeded the Florida Department of Environmental Protection (FDEP) soil cleanup target levels (SCTL) for leachability criteria. Benzene exceeded residential SCTL, and total petroleum hydrocarbons exceeded industrial criteria during sampling performed in 2002. Furthermore, well sampling in 2004 revealed benzene, toluene, ethylbenzene and total xylene (BTEX) levels exceededing FDEP groundwater target cleanup levels (GTCL). Benzene exceeded the Environmental Protection Agency's (EPA) maximum contaminant level and light non-aqueous phase liquid was detected at the site at a thickness of .5-ft.
Earlier cleanup efforts at Site FT023, including passive and manual removal methods and one attempted interim remedial action, had only minimally impacted free product levels. Clearly, a more aggressive technical approach was needed to bring Site FT023 into environmental compliance.
In 2005, TolTest Inc. was tasked to reassess the site under an Air Force environmental contract managed by the Air Force Center for Engineering and the Environment (AFCEE). The project team applied value engineering of several technical approaches, with the goal of optimizing volatile organic compound (VOC) contaminant removal.
A total of 7,632-yd3 of petroleum-contaminated soil was either transported and disposed off site or treated on site by aeration between July 2005 and August 2006. In-situ chemical oxidation (ISCO) injection events performed in 2007 reduced the remaining VOCs to within FDEP natural attenuation default concentrations (NADC).
Based on the successful implementation of the soil and groundwater remedies and the residual low levels of groundwater contamination remaining at the site, the closure strategy implemented was termination of active remediation and natural attenuation monitoring (NAM) . After four quarters of monitoring, the site's groundwater has reached EPA and FDEP cleanup criteria.
Engineering Considerations
During soil excavation activities to implement an approved Remedial Action Plan (RAP), the project tean1 observed a continuous black organic layer existing across the site at approximately 3-ft below grade that would have affected the ability of the soil vapor extraction (SVE) and dual-phase extraction systems to remediate the site. During hot spot soil removals, liquid containing hydrocarbon sheen was seen trapped above a pl astic liner beneath a concrete fire training pit.
The team performed an engineering and cost analysis to ascertain the best remedial approach to deal with the unforeseen site conditions. Options included modification of the SVE system to treat soils above and below the organic layer, on-site soil land farming and on-site soils ae ration . Based on costs and meeting the contract period of performance, soils aeration and ISCO was determined to be the best option to treat both soils and groundwater.
Based on an engineering analysis of site geology and hydrogeologic characteristics, additional RAPs for the site were prepared and submitted for approval to the client, AFCEE and FDEP. Remedial action alternatives consisted of on-site soils aeration and ISCO. The solution has been effective: On a pilot test, BTEX concentrations were reduced from 4,749-parts per billion (ppb) to less than 3-ppb, while tests on groundwater showed a 99 percent reduction ofVOCs follovving remedial activities. Aerated soils were then reused as backfill for the excavations.
For the full -scale soils treatment, TolTest excavated 7,632-yd3 of soil from depths of between 6.5- ft and 7.5 -ft and ran it through a trommel unit- a heavyduty power screen vvith a 9-yd3 hopper and a 5-ft by lO-ft rotary screen-at a rate of 150-yd3 per hour. Soils were processed two to five cycles until field screening data showed contaminant levels of less than 100 parts per million (ppm) measured vvith an organic vapor analyzer (OVA) . The maximum soil stockpile pretreatment OVA concentration was 40,553-ppm.
Two ISCO injection events were performed for remedi ation of the free product in the groundwater: In June 2007, approximately 8,820-gal of reagent was injected, and in August 2007, an additional 9,180-gal of reagent was injected. Due to lower-than- expected BTEX levels between the first and second injections, additional injections were not necessary, and active site remediation was terminated.
Regulatory Issues
TolTest worked in partnership with Tyndall AFB environmental officials and FDEP to ensure compliance with all regulatory guidelines.
As per Florida Administrative Code (FAC) Chapter 62-770, NAM commenced upon attainment of NADC concentrations in groundwater and no soil contamination. The NAM requhed a minimum of one year of quarterly groundwater monitoring. Because the contaminant plume was shown to be stable or shrinking, the project team pursued a No Further Action determination under Risk Managerrient Options Level II in accordance vvith Chapter 62-770.680(2) . After four quarters of monitoring, the site met cleanup standards.
Milestones
The Little Cedar Creek Fire Training Area project was a results based product delivery task order with six performance objectives or milestones to be met with in a year-yea r period of performance. Using an innovative approach, each of the milestones was achieved under the performance-based contract.
During the final stages of monitoring, Tyndall AFB was involved in a Resource Conservation and RecovelY Act (RCRA) order that transferred t11e regulatory oversight of Site FT023 from FDEP to EPA Region 4. Quarterly sampling and reporting took place from April 2008 to April 2009. Having met the performance objective of reaching FDEP cleanup standards, TolTest submitted the Site Rehabilitation and Completion Report (SRCR) to the Air Force on May 18, 2009.
The remediation activities succeeded where others failed. Thorough planning, knowledge of state regulations and communications vvith Tyndall AFB, AFCEE and FDEP enabled the project team to remove the free product and eliminate soil and groundwater contamination at Site FT023 within the period of performance. Free product was reduced from .5-ft to less than the GTCLs.
TolTest is an award-winning DoD contractor headquartered in Maumee, Ohio, employs 386 associates, and has CONUS locations in California, Colorado, Delaware, Florida, Georgia, Illinois, Indiana, Kansas, Maryland, Michigan, Nevada, New Jersey, New Mexico, North Carolina, South Carolina, Texas, Washington, Wyoming, and OCONUS locations in Afghanistan, the Azores, Guantanamo Bay (Cuba), Guam, Iraq, Japan, Kuwait, Qatar, South Korea, and Spain. Services include asbestos & lead abatement/demolition; bulk fuel services; construction; design/build; environmental consulting & remediation; general contracting; operations & maintenance (O&M); site engineering; telecommunications installations; transportation and disposal; underground/above-ground storage tank management, removal & installation; and value engineering.
