Dense Nonaqueous Phase Liquids (DNAPLs)

Soil Vapor Extraction and Air Sparging

Halogenated Alkenes

Case Studies: Chlorinated Solvent Mixtures

Air Sparging and Soil Vapor Extraction at Landfill 4, Fort Lewis, Washington
Federal Remediation Technologies Roundtable Cost & Performance Database, 1998

Site investigations beginning in 1988 identified chlorinated hydrocarbon (TCE, DCE, and VC) and metal contamination in the groundwater beneath the landfill. The 1993 ROD prescribed a remedy consisting of SVE and AS and monitoring of groundwater for manganese. An SVE/AS pilot test was conducted at the site in December 1994 and the full-scale SVE/AS system was put on line in October 1996. By the end of October 1997, the system had removed approximately 60 pounds of TCE (in soil gas) from the subsurface, and currently continues to operate.

Air Sparging and Soil Vapor Extraction at the Mound Plant OU 1 Site, Miamisburg, Ohio
Federal Remediation Technologies Roundtable Cost & Performance Database, 2001

OU-1 is characterized by VOC contamination of a 15- to 20-ft-thick saturated zone composed of glacial outwash materials, primarily gravel and sandy gravel, and an unsaturated zone, ranging from 24 to 31 ft thick, composed of glacial till and artificial fill. The VOC contamination (DCE, TCE, toluene, PCE, ethylbenzene, and xylenes) in the vadose zone was primarily restricted to depths less than 20 ft bgs. Dissolved trichloromethane, DCE, TCE, VC, and PCE contaminated the groundwater at levels above the established regulatory limits. A study was conducted to evaluate the effectiveness of the combined application of AS/SVE technologies to remove the VOCs from water and soil matrices simultaneously, and to obtain operating and performance data to evaluate the design, operation, and cost of a full-scale system. Extracted vapors were treated with carbon prior to release to the atmosphere. The AS system was shut down after 7 weeks of operation due to fouling of the well screens. From start-up on December 16, 1997, through May 30, 2000, the SVE system removed 3,433 lbs of VOCs from the OU-1 site, and the total VOC concentration in the unsaturated zone decreased from 618.1 µL/L (ppmv) to 4.54 µL/L (ppmv).

Air Sparging/ High Vacuum Extraction to Remove Chlorinated Solvents in Groundwater and Soil
J.M. Phelan and M.D. Gilliat.
SAND-98-2016C, 12 pp, 1998

At the DOE Mound facility in Miamisburg, OH, an AS and high-vacuum SVE system was installed as an alternative to a containment pump-and-treat system. Technical data are presented on the operating characteristics of the system for removal of TCE, DCE, PCE, chloroform, Freon 113, and trichlorofluoromethane.

Innovative Technologies and Vadose Zone Treatment of Chlorinated Volatile Organic Compounds: Case Study
J.V. Noonkester, R.L. Nichols, and K.L. Dixon.
Environmental Geosciences, Vol 12 No 4, p 219-289, 2005

Shallow soils and groundwater beneath the TNX facility at Savannah River are contaminated with chlorinated VOCs like TCE, PCE, carbon tetrachloride, and chloroform. An interim pump-and-treat (P&T) remediation system was placed in operation in 1996 to provide hydraulic containment of groundwater affected by dissolved-phase TCE at levels above 500 µg/L. In 2001, SVE was selected to remove the chlorinated compounds. Cone penetrometer testing with soil vapor sampling provided the detailed understanding of the subsurface geology and contaminant distribution essential for proper well design and placement. Twelve SVE wells were installed using direct push technology and tested to determine specific capacity and VOC concentrations. This information was then used to develop a strategy for operating the SVE system. Based on the results of the baseline testing and previous studies, SVE will be implemented in sets of 2 to 3 extraction wells at one-month intervals. This approach will allow continuous operation of the SVE system and give individual wells up to 3 months for rebound between treatments. This mode of operation is intended to maximize contaminant recovery from individual wells and reduce the overall capital investment and operating cost of the SVE system.

Cometabolic Air Sparging at McClellan Air Force Base, OU A, Sacramento, CA
Federal Remediation Technologies Roundtable Cost & Performance Database, 2003

A demonstration of cometabolic air sparging was conducted to evaluate the effectiveness and costs of cometabolic AS to remove chlorinated aliphatic hydrocarbons (CAHs) (TCE, DCE, VC, TCA, and lower ethene isomers) from the groundwater. In the demonstration, air only was injected into the control plot, and both air and propane were injected into the active test plot. After 200 days of operation, CAHs in the saturated zone were reduced to near or below the MCLs, but after 500 days of operation, propane degradation had not been observed in the vadose zone and there was no evidence of CAH cometabolism. Methane was substituted for the propane and was rapidly degraded, along with the propane, and levels of CAHs decreased further. Possibly a lack of nitrogen in the vadose zone limited propane degradation and the addition of methane either stimulated direct propane degradation or propane was degraded cometabolically by methanotrophs. At this site, cometabolic air sparging using propane as the growth substrate was effective in the saturated zone but did not meet expectations on the vadose zone.

Evaluation of Enhanced VOC Removal with Soil Fracturing in the SRS Upland Unit
B.D. Riha, K. Dixon, W.K. Hyde, L. Murdoch, and R. Hall.
WSRC-TR-2005-00415, 53 pp, 2005

Solvent removal by SVE in zones of low permeability can be severely limited due to low flow rates, mass transfer resistance of the hydrophobic compounds by trapped interparticle water, and diffusion resistance. Introducing sand-filled fractures into these tight zones improves the performance of SVE by (1) increasing the overall permeability of the formation and thereby increasing SVE flow rates, (2) shortening diffusion pathways, and (3) increasing air permeability by improving pore water removal. The synergistic effect of the fracture well completion methods, fracture and flow geometry, and pore water removal appears to increase the rate of solvent mass removal over that of increasing flow rate alone. A field study was conducted where a conventional well in the Savannah River site Upland Unit was tested before and after hydraulic fracturing. The SVE well, monitoring point arrays, and 4 fracturing wells were installed, and 4 fractures were successfully created in July 2005. The fractures were created in an open area at the bottom of the steel well casing by using a water jet to create a notch in the soil and then injecting a guar/sand slurry into the formation. The sand-filled fractures increased the effective air permeability of the subsurface formation diffusion path lengths for contaminant removal. The primary metrics for evaluation were an increase in SVE flow rates in the zone of contamination and an increase in the zone of influence. The tests showed that fracturing in the Upland Unit accelerates SVE solvent (TCE, PCE, TCA) remediation and increases flow rates in the Upland Unit by at least one order of magnitude.

Final Removal Action Closeout Report: Non-Time-Critical Removal Action for Volatile Organic Compounds at Installation Restoration Site 9, Area 3, Naval Air Station North Island, Coronado, California
U.S. Department of the Navy, 34 pp, 2000

The removal action for Area 3 involved an SVE system using horizontal extraction wells to extract PCE, TCE, and cis-1,2-DCE from the vadose zone, as well as vertical passive air injection points to enhance airflow through the vadose zone and increase the volatilization of VOCs from the soil.

Groundwater Pump and Treat, Air Sparging, and Soil Vapor Extraction at the Cascade Corporation Site, Troutdale Gravel Aquifer, East Multnomah County Groundwater Contamination Site, OU 2, Gresham, Oregon
Federal Remediation Technologies Roundtable Cost & Performance Database, 2004

Soil and groundwater at the Cascade site are contaminated with chlorinated solvents, primarily PCE, TCE and cis-1,2-DCE, as well as LNAPL. The 1996 ROD specified the use of multiple technologies, including SVE with destruction of VOCs by catalytic oxidation or equivalent; continued operation of on- and off-site interim remedial action measures (using P&T); expansion of the off-site groundwater extraction trench; extraction of LNAPL by co-pumping LNAPL and groundwater; additional on-site groundwater extraction using existing and new wells; and AS using approximately 25 on-site wells. Performance data available through 2003 showed that a total of 958 lbs of VOCs was removed over a 13-year operating period, 561 lbs from groundwater, 377 lbs from soil, and 20 lbs as LNAPL. While contaminant concentrations and plume sizes have decreased, concentrations remain above cleanup levels. Operation of the control trench and groundwater extraction are continuing. A pilot test of bioaugmentation is planned for the source area. In addition, 850 poplar trees were planted in 2000 for future use in treating VOCs in groundwater north of the control trench.

Horizontal Wells Demonstrated at U.S. DOE's Savannah River Site and Sandia National Laboratory
Federal Remediation Technologies Roundtable Cost & Performance Database, 2000

To address chlorinated solvents contamination, horizontal wells were installed at several DOE facilities, including Savannah River Site (SRS) and Sandia National Laboratories. At SRS, 7 wells were installed at depths of 35 to 175 ft bgs, with horizontal screen sections ranging from 150 to 400 ft, and constructed of steel, stainless steel, PVC, HDPE, and fiberglass. The wells were used to demonstrate in situ air stripping, in situ bioremediation, and thermally enhanced soil vapor extraction; four of the wells were later integrated into a vapor extraction correction action. The SRS demonstration identified two important factors for consideration during design of horizontal wells: (1) trips in and out of the well bore should be minimized; and (2) well materials should be adequately flexible to negotiate curves.

In Situ Treatment at Three Dry Cleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2004

In situ treatment (ISCO and heat-enhanced SVE) was conducted at three dry cleaner sites: Former Market Place Shopping Center Site, Hilton Head, SC; Denver Colorado Dry Cleaner, Denver, CO; and United Cleaners Site #1973, Lemont, IL. PCE and TCE are the primary contaminants in groundwater. Concentrations varied by site, with levels of PCE in groundwater as high as 27,000 µg/L and TCE in groundwater as high as 12,600 µg/L. Levels of PCE and TCE in soil were as high as 4,300,000 µg/kg and 170,000 µg/kg, respectively. Full- and demonstration-scale remedial approaches involved the subsurface injection of ozone and ISOTEC's Modified Fenton's Reagent and the use of in-ground coils to transfer heat and remove volatile contaminants. At the Former Market Place, PCE concentrations were reduced substantially, but still remained above the cleanup goal of 5 µg/L. At the Denver site, PCE concentrations across the site decreased by 99%, and TCE concentrations fell by 90%. At the #1973 site, PCE soil concentrations were reduced by approximately 50%, and in one of the two areas where remediation equipment was installed, complete cleanup was achieved. At the Denver site, the cost of implementing ISCO was approximately $39/cubic yard of saturated soil treated. At the United Cleaners #1973 site, remote access capability allowed personnel to check the system regularly during operation.

Multi-Site Air Sparging
Environmental Security Technology Certification Program (ESTCP), 115, 2002

Of the 9 AS case studies presented in this report, 3 discuss remediation of dissolved-phase chlorinated solvents: TCE and daughter products at Landfill 4, Fort Lewis, WA; PCE and daughter products at McClellan AFB, CA; and TCE at OU-6, Hill AFB, UT.

Multi-Site In Situ Air Sparging, Multiple Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2003

Provides AS cost and performance data for 9 sites, 3 of which had chlorinated solvent contamination in the groundwater.

Photolytic Destruction Technology Demonstration at NAS North Island, Site 9, San Diego, California
Federal Remediation Technologies Roundtable Cost & Performance Database, 1998

As part of a non-time-critical removal action, an SVE system has been installed at the site in Areas 1 and 3 to remove and treat VOCs. PTI's Photolytic Destruction Technology for SVE offgas was selected for demonstration to allow comparisons with other commercially-available treatment technologies. The PTI system used for the demonstration was designed to treat 500 scfm of vapor from the SVE system (which was rated at 3,000 scfm) and to remove a minimum of 3.6 lbs/hr of VOCs. The maximum flow rate during the demonstration was 440 scfm, and the average amount of VOCs removed was 1.22 lbs/hr. The PTI system was relatively quick to install and was operational 89% of the time. A report presents detailed information on secondary wastes and residuals generated during the demonstration as well as a detailed discussion of operational problems encountered during the demonstration. The total demonstration cost was $93,726, including work plan, mobilization/ demobilization, site work, liquids collection and containment, treatment, monitoring, sampling and analysis, and residuals disposal. The estimated unit cost for a full-scale system was $3.77 per lb of VOC treated.

Pump and Treat and Air Sparging of Contaminated Groundwater at the Gold Coast Superfund Site, Miami, Florida
Federal Remediation Technologies Roundtable Cost & Performance Database, 1998

Solvent recovery operations at the 2-acre site included distillation of lacquer thinner and mineral spirits; blowdown from these operations was discharged directly onto the soil. In 1980, soil and groundwater contamination was detected in on-site soil (heavy metals and organics) and an off-site groundwater well (VOCs). Maximum initial concentrations were methylene chloride (100 µg/L), 1,1-DCA (2,000 µg/L), trans-1,2-DCE (3,000 µg/L), TCE (48,000 µg/L), PCE (100,000 µg/L), and toluene (545 µg/L)The site was placed on the NPL in 1983 and a ROD was signed in 1987. Five extraction wells were constructed in the Biscayne Aquifer at the site. Three wells were installed to a depth of 15 ft, with a design yield of 10 gpm; two wells were installed to a depth of 30 ft, with a design yield of 35 gpm. Extracted groundwater was treated using two air stripping towers in series, with each tower 36 ft high, 3 ft diameter, and packed to 26 ft with IMPAC, a material that enhances stripping of VOCs from water. Treated groundwater was re-injected into the aquifer through three injection wells. The P&T system created an inward gradient toward the site for plume containment. Cleanup was achieved after excavation of soil suspected to contain DNAPLs and performance of groundwater sparging. The cleanup standards were met at this site within 4 years of operation.

Pump and Treat and Soil Vapor Extraction at the Commencement Bay South Tacoma Channel Superfund Site, Tacoma, WA
Federal Remediation Technologies Roundtable Cost & Performance Database, 2001

Both shallow soil, subsurface soil, and groundwater at the site were contaminated with VOCs, including chlorinated solvents (PCA, PCE, TCE, DCE). SVE was used from 1993 to 1997 to treat soil at the site. A P&T system for groundwater was installed and began operating in 1988. The SVE system removed another 54,100 pounds of VOCs during its operation. Through December 2000, the P&T system removed about 15,000 pounds of VOCs; however, LNAPL and DNAPL present in the soil provide continuing sources of dissolved-phase contaminants, and remedial goals for the aquifer are not expected to be met using P&T. Future plans for the site are being evaluated to determine the optimal approach to address site-related contamination.

Remedial Action Report for Operable Unit 2
NASA, Jet Propulsion Laboratory, Pasadena, CA. 126 pp, 2007

The successful removal of VOCs (carbon tetrachloride, Freon 113, TCE, and 1,1-DCE) from the vadose zone during an SVE pilot test at the Jet Propulsion Laboratory in 1998 led NASA to proceed with this alternative using a trailer-mounted unit that was moved among 4 locations from April 1998 until September 2005. The system achieved all of its specified performance objectives.

Remediation System Evaluation: Savage Municipal Water Supply Superfund Site, Milford, New Hampshire
U.S. EPA, Technology Innovation Office, 38 pp, 2001

Contamination in OU1 stems mostly from the former OK Tool Company, which discharged VOCs (PCE, TCE, 1,1,1-TCA) and various trade-name oils and solvents into the subsurface. The source material in OU1 consists of dissolved-phase and possible free-phase VOCs. Remediation in OU1 began in 1998 with the installation of an extraction and treatment system and construction of a slurry wall that completely surrounds the source area. Treatment incorporates air sparging wells, an SVE system, 4 extraction wells (2 located inside the wall and 2 outside), and a treatment plant that consists of 2 equalization tanks, 2 air-stripping units, and a vapor-phase carbon unit for treating the offgas of the air stripper and the air recovered from the SVE system.

Soil Vapor Extraction of PCE/TCE Contaminated Soil
J.R. Bradley and M.R. Morgenstern.
WSRC-MS-98-00272, 8 pp, 1998

SVE units have been installed to remediate PCE and TCE contamination in the A/M Area of the Savannah River Site soil and groundwater. Lessons learned and optimization of the SVE units are discussed.

Soil Vapor Extraction (SVE) and Air Sparging at Three Drycleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2003

AS and SVE were conducted at 3 drycleaners in Michigan: Hooker's Cleaners, Charlevoix; Sunny Village Cleaners, Livonia; and Vicksburg Laundry & Dry Cleaners, Vicksburg. The sites were all contaminated with PCE, TCE, and their breakdown products from leaks, spills, or dumping of drycleaning solvents or wastewaters. Cleanup goals for groundwater were based on state regulatory cleanup levels, and ranged from 5.0 µg/L to 34 µg/L for PCE. The cleanup goal for TCE was 5.0 µg/L. Although all of the AS/SVE treatment systems removed contaminants from the subsurface, only the system at Vicksburg Cleaners was reported to have achieved groundwater treatment goals of 5.0 µg/L for PCE and TCE in a portion of the site.

Soil Vapor Extraction (SVE) and SVE Used with Other Technologies at Four Dry Cleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2004

SVE was implemented together with other technologies at four dry cleaner sites in Minnesota: Shorty Cleaners, Stillwater; Colonial Square Mall; Long Prairie, Long Prairie; and Midway Plaza, St. Paul. These sites were contaminated primarily with PCE, TCE, and BTEX. At Shorty, the cleanup approach involved SVE, ISCO, and MNA; PCE concentrations in the groundwater continue to remain high even though the concentration of degradation products has increased steadily over time. Colonial Square used SVE and MNA; the groundwater plume was stable and the SVE system was shut down after operating for 36 months. Long Prairie used SVE, P&T, and MNA. Midway implemented AS/SVE and multiphase extraction in different parts of the site. At the Long Prairie and Midway sites, soil cleanup goals were met and the SVE system was shut down.

Soil Vapor Extraction at Camp LeJeune Military Reservation, Site 82, Area A, Onslow County, North Carolina
Federal Remediation Technologies Roundtable Cost & Performance Database, 1998

Soil at Area A was contaminated primarily with TCE, PCE, and benzene. The ROD specified SVE for remediation of contaminated soil. The SVE system used at Area A had 8 vertical vapor extraction wells (installed to a depth of 15 to 16 feet bgs), one horizontal air injection well (horizontal displacement of 330 feet and total depth of 15 feet bgs), 32 soil probe clusters (for measurement of subsurface vapors; each cluster consisted of one shallow and one deep probe at approximately 6 feet and 12 feet bgs, respectively), a vapor-phase separator, a vapor-phase carbon vessel (granular activated carbon), and a vacuum extraction unit that included a positive displacement blower used to apply vacuum to the extraction wells. Confirmation sampling results showed that TCE and benzene met the cleanup goals in all soil boring samples. For 23 of 24 soil boring samples, PCE was reported at levels below the cleanup goal of 10.5 µg/kg. For one soil boring sample, PCE was reported at 29 µg/kg compared to the cleanup goal of 10.5 µg/kg. EPA approved shutdown of the system because the single exception was only slightly above the soil remedial goals and the contaminated groundwater under the area of concern was being addressed by P&T. The SVE system at Area A was reported to be cost effective. An on-site laboratory was being used for other analytical work on the base, and the shared cost of the use of that facility helped to keep the cost of the SVE application low.

Soil Vapor Extraction at Defense Supply Center Richmond, OU 5, Chesterfield County, Virginia
Federal Remediation Technologies Roundtable Cost & Performance Database.

A pilot study of SVE was conducted at OU-5 from December 1 to December 11, 1992, to identify additional design parameters for a full-scale system. A hydraulic influence test was conducted over a 24-hour period, followed by a 10-day hydrocarbon removal test. For the hydrocarbon removal test, one extraction well was used along with a carbon adsorption unit for the treatment of the offgas. Subsequently, soil sample results showed that the study had achieved the soil action levels. The maximum concentration reported for PCE was 0.18 mg/kg and 0.11 mg/kg for TCE. An explanation of significant differences (ESD) was signed in March 1996, indicating that a full-scale system would not be required. Covers were installed on the pits. According to the ESD, several factors contributed to the success of the pilot test: the actual area of contamination was smaller than originally estimated; natural attenuation may have contributed to decreased contaminant levels; and PCE concentrations in the untreated soil were only slightly higher than the cleanup goals.

Soil Vapor Extraction at the Basket Creek Surface Impoundment Site, Douglasville, Georgia
Federal Remediation Technologies Roundtable Cost & Performance Database, 1997

An action memorandum for Basket Creek signed on April 11, 1991, specified soil treatment targets for TCE, PCE, benzene, MEK, lead, mercury, and total halogenated organic compounds. Ex situ SVE was selected for the site after in situ SVE was ruled out because of the low permeability of the contaminated soil. Excavation of soil was performed within an enclosure to control emissions. Because of space constraints, the excavation took a much longer time (3 months) than the few days that would have been required had the excavation been done outside. The ex situ SVE system comprised a 7,200 sq ft containment building, a shaker (power) screen, 17 vapor extraction wells, vacuum pumps, a baghouse, an induced draft blower, and a thermal oxidizer. Excavation, screening, and vapor extraction all took place inside the containment building. The system was run from November 1992 to February 1993, and again from March to April 1993, for a total of 6 months of operation. Analytical data indicated that the soil treatment targets were met for all contaminants after a 6-month treatment period. Total VOCs in the treated soil ranged from 0.142 to 1570.7 mg/kg, and ~72,000 lbs of total VOCs were recovered from the soil. Toluene was the largest quantity VOC recovered, accounting for about 80% of the total VOCs recovered, and MIBK was the second largest quantity, accounting for 11%.

Soil Vapor Extraction Enhanced by Six-Phase Soil Heating at Poleline Road Disposal Area, Fort Richardson, Alaska
Federal Remediation Technologies Roundtable Cost & Performance Database, 2000

Four disposal areas were identified in an area encompassing approximately 1.5 acres. TCA and TCE were found in higher concentrations and over a larger area than any other chemicals detected. PCE also was detected above action levels. After a 1996 treatability study at the PRDA, it was concluded that using SVE alone to remove solvent vapors from the subsurface would require more than 10 years of treatment. In situ soil heating was recommended to complement SVE and achieve cleanup more rapidly. A treatability study was conducted between July and December 1997 to evaluate SVE enhanced by six-phase soil heating. Three arrays were constructed and operated. Two arrays were 27 ft in diameter and one array was 40 ft in diameter. Each array was operated for 6 weeks after a shakedown period. The smaller arrays demonstrated over 90% removal of soil contaminants; the larger array demonstrated over 80% removal of contaminants, indicating that there may be limitations to the size of the array that can treat soil effectively at a particular site. The size of the array is limited by the resistivity of the soil and power requirements.

Use of Cometabolic Air Sparging to Remediate Chloroethene-Contaminated Groundwater Aquifers
Environmental Security Technology Certification Program (ESTCP), 194 pp, 2001

Describes an 18-month field study to investigate the use of cometabolic AS using propane as a growth substrate to enhance bioremediation of TCE, DCE isomers, VC, TCA, and lower chlorinated ethane isomers at McClellan Air Force Base, CA. Each of 2 test plots contained one central sparge well, an SVE well, 6 multi-level monitoring points, and 2 groundwater monitoring wells. One air injection system and one SVE system were used for both test plots. A propane injection system was connected to the active test plot only. Phase 1 provided strong indications that propane degradation in the saturated zone stimulated TCE and c-DCE cometabolism, and that the onset of propane degradation and CAH cometabolism in the vadose zone began toward the end of the experimental operating period. Phase 2 was conducted for a total of 217 days between May and December 2000. Cometabolic AS was shown to be effective for treatment of groundwater but ineffective in the vadose zone, resulting in incomplete contaminant removal from the site.

Case Studies: PCE

Fracture Enhanced Soil Vapor Extraction Technology Demonstration at the A-014 Outfall
Riha, B.D. and W.K. Hyde (Savannah River National Lab); R. Hall (Clemson Univ.).
Report No: WSRC-STI-2008-00141, 45 pp, Mar 2008

Results of this study show that utilization of hydraulic fractures during soil vapor extraction of chlorinated solvent contamination (primarily tetrachloroethene) is an effective approach for increasing remediation efficiency at the A-014 Outfall field site and in the Upland Unit at DOE's Savannah River facility. Hydraulically fractured wells tend to produce greater flow rates and create larger zones of influence than do conventional wells. The ability to target source zones decreases diffusion pathways significantly, thus decreasing the time required to reach remediation goals.

Soil Vapor Extraction (SVE) and Air Sparging at Four Drycleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2001/2002

AS and SVE was conducted at four drycleaner sites: Alpine Cleaners, OR, Dry Clean USA #11401, Boca Raton, FL, Former American Uniform, Hutchinson, KS, and One Hour Dry Cleaners, Coral Springs, FL. Reported design and implementation costs ranged from $28,000 to $240,000. Reported annual O&M costs ranged from $16,000 to $200,000. All 4 sites were contaminated with chlorinated organic compounds (primarily PCE) from leaks, spills, or dumping of drycleaning solvents or wastewaters. Two sites reported that DNAPLs were present or likely to be present. Although all of the treatment systems removed contaminants from the subsurface, only one system achieved cleanup goals (Former American Uniform) in the source vadose zone after removing 221 lbs of PCE; however, rebounding PCE concentrations in groundwater were observed 6 months after the remediation was completed.

Soil Vapor Extraction (SVE) and Monitored Natural Attenuation (MNA) at Three Drycleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2003

SVE followed by MNA was implemented at three drycleaner sites: Aiea Laundry, Naval Station Pearl Harbor, HI; Dry Clean Inn, Lauderhill, FL; and Former Dollar Cleaners, Lake Worth, FL. All three sites reported that SVE reduced PCE concentrations in soil to below cleanup levels. Two sites (Dry Clean Inn and Former Dollar Cleaners) reported that natural attenuation had reduced contaminant concentrations in groundwater to below cleanup levels in the last two monitoring events. Both sites received Site Rehabilitation Completion Orders. Information on groundwater contaminant concentrations for the third site was not provided. Reported design and maintenance costs for SVE ranged from $109,000 to $135,000. Reported O&M costs for the SVE systems ranged from $28,000 to $30,000.

Soil Vapor Extraction (SVE) at Seven Drycleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2001/2002

To address chlorinated organic compound contamination resulting from drycleaning operations, SVE was conducted at 7 sites: Abe's Main Street Cleaners, Portland, OR; Donaldson's Drycleaners, WI; Dry Clean USA, Orlando, FL; One Price Drycleaners, Sunrise, FL; Sir Galloway Dry Cleaners, Miami, FL; Stuart Cleaners & Tailors, Stuart, FL; and The Dry Cleaner, Alamonte Springs, FL. Concentrations of PCE in soil varied among the sites and ranged from 1 to 1,000 mg/kg. Some sites reported other chlorinated organics in the soil, such as TCE, cis-1,2-DCE and VC. Groundwater concentrations of PCE ranged from 0.003 to 55 mg/L. All of the sites reported that SVE effectively removed PCE from soils, with the amount of VOCs removed ranging from 2 to 7 pounds. Reported design and implementation costs for the SVE systems ranged from $30,000 to $160,000 and reported annual O&M costs ranged from $26,000 to $67,000.

Soil Vapor Extraction (SVE) at Six Drycleaner Sites, Various Locations
Federal Remediation Technologies Roundtable Cost & Performance Database, 2003

SVE was conducted at six drycleaner sites: ABC Cleaners, Monroe, MI; Art's Dry Cleaners, Charlevoix, MI; Cox's One Hour Martinizing, Portland, OR; Crain Fabric Care Center, Traverse City, MI; Sunshine Laundry, St. Johns, MI; and Wash 'N Dry Cleaners, Spring Arbor, MI. Cleanup goals for soil were not provided for any of the sites. Cox's One Hour Martinizing and Art's Dry Cleaners reported that SVE reduced PCE concentrations in the soil from 25,000 to 5 mg/kg, and from 1,000 to 130 mg/kg, respectively. At two sites (ABC and Wash 'N Dry), SVE failed due to high water levels in the soil. No information on the results of SVE at the other two sites. Reported design and implementation costs for the SVE systems ranged from $18,000 to $52,000. O&M costs at one site was $3,500 for a period of 2 years.

Successful Remediation of Chlorinated Solvents Using Source Treatment and Natural Attenuation
J.W. Mercer, G.C. Frederickson, D. Burnell, S. Dublin, J.E. Donahue and R.M. Ferris.
Proceedings of the 5th International Conference on Remediation of Chlorinated and Recalcitrant Compounds, Monterey, California, May 2006, Battelle Press, Columbus, OH. 8 pp, 2006

Successful DNAPL source-area remediation combined with rapid biodegradation of an associated chlorinated solvent plume at a site in Palm Beach Gardens, FL, has reduced aquifer concentrations to near or below Florida's natural attenuation criteria. cis-1,2-DCE and VC were first detected in a municipal wellfield early in 1984. The contamination was traced to a small PCE source area ~40 ft x 80 ft x 30 ft deep in a recreational field. Source removal operations began in August 2001 and consisted of a downgradient, shallow, 2-well P&T system and an AS/SVE system. As of June 2005, P&T had removed approximately 158 lbs of PCE and the AS/SVE system had removed 1,325 lbs. Between 1999 and 2005, PCE concentrations at a monitoring well inside the source area decreased by almost 1,000 times, from 200,000 ppb in March 1999 to 340 ppb in June 2005. Site data indicate that this relatively small, shallow DNAPL source has been remediated to near the Florida natural attenuation cleanup goal of 300 ppb PCE in less than 5 years.

Case Studies: TCE

Effectiveness Monitoring of Soil Vapor Extraction with Rebound Testing and Formation of a Pathway to Closure
C. Switzer and D.S. Kosson.
Proceedings of Waste Management 2004, 29 February - 4 March, University of Arizona, Tucson. Paper WM-4268, 14 pp, 2004

A pilot study was designed and installed at a small waste site in DOE's Savannah River facility to examine the effectiveness of SVE for TCE contamination in a layered vadose zone. The challenges encountered at this site included subsurface heterogeneity and an unknown initial contaminant distribution. These challenges were addressed by the development of a comprehensive subsurface soil gas TCE-concentration rebound testing program that became the basis for site closure. Over the course of 4 years of SVE operation, 6 rebound tests were conducted at the site. The progression of rebound tests show declining soil gas TCE concentration rebound at nearly all of the SVE wells. Rebound has been observed at a few SVE wells and monitoring points, but the concentrations achieved at these locations have been substantially lower than concentrations observed initially. These observations indicate that a substantial portion of the available contaminant mass has been removed and that continued SVE operation would not recover much additional contaminant mass. Additional information from mass removal and diffusion modeling supported these observations, and the resulting decision was to transition the SVE system to passive operation.

First Five-Year Review Report for Watkins-Johnson Superfund Site, Scotts Valley, California
U.S. EPA Region 9, 22 pp, 2002

TCE concentrations of up to 5,500 ppb were found in the site's soil in 1987-88. One of the main conclusions of the RI was that the chlorinated hydrocarbons (primarily TCE and breakdown products) had entered both the perched zone and regional zone of the Santa Margarita Aquifer underlying the Site. During a 13-day pilot study of an SVE system in May 1989, a significant amount of TCE was removed. The remedy for the site specified prevention of off-site migration of contaminants within the perched zone by using infiltration leachfields (also referred to as perched zone recharge galleries), P&T with GAC treatment, SVE, and installation of a permeable cap to prevent mobilization of soil contamination into the groundwater. Completed in 1994, both the SVE system and the groundwater treatment system have been very effective in removing contamination at the site. The SVE system is close to meeting its ROD-defined goal of reducing soil contamination to a level that will not impact groundwater.

Photocatalytic Reactor for Treatment of SVE and MPE Off-Gas at the Stamina Mills Superfund Site, North Smithfield, RI
Federal Remediation Technologies Roundtable Cost & Performance Database, 2001

Spills of solvents used to clean fabrics manufactured at the plant resulted in contamination of soil and groundwater. SVE and multi-phase extraction (MPE) systems were installed to clean up the contamination, primarily TCE. A demonstration test of a photocatalytic oxidation system was conducted under EPA's Superfund Innovative Technology Evaluation (SITE) Program. Offgas from the SVE and MPE systems was treated using the photocatalytic oxidation system from August to October in 1999. Treatment goals for TCE were met. The vendor indicated that chloroform emissions from the scrubber could be reduced through the use of alternative photocatalysts or reactors.

Summary of Pilot Operation: Thermally-Enhanced Soil Vapor Extraction and Free Product Recovery
M.A. Coons and W.E. Collins.
2001 International Containment & Remediation Technology Conference & Exhibition, 10-13 June 2001, Orlando, Florida. 3 pp, 2001

About 32,000,000 gallons of liquid waste were disposed of at the former Chemical Waste Disposal Area at Naval Air Station North Island, CA. An SVE system installed in 1997 removed approximately 80,000 pounds of mixed VOCs, primarily TCE. Additional investigations in 1998 identified free product (mostly jet fuel and commingled TCE) underlying the site. Four steam injection wells and 10 combination SVE/product recovery wells were added to the system in 1999 to enhance product and TCE removal on a pilot scale. The pilot area was approximately one-tenth the area of the original non-enhanced SVE area. During 9 months of operation, the pilot-scale system removed over 28,600 pounds of fuel hydrocarbons and VOCs from the subsurface; the original non-enhanced SVE system removed only 25,000 pounds during the first 9 months of its operation from an area 10 times larger. Data comparison on a pound/month/foot of well screen basis shows that the thermal enhancement and free product recovery system increased the overall mass removal rate of the SVE system by over 2,400%. The removal rate of the vapor extraction portion alone was increased by over 1,200%.

Twin Cities Army Ammunition Plant Soil Vapor Extraction System: A Post-Audit Modeling Study
G.P. Williams, D. Tomasko, and Z. Jiang.
ANL/EAD/TM-97, 108 pp, 2000

Demonstrates the use of the T2VOC model for simulating the progress of vapor extraction to remove TCE from silty sand at the Twin Cities site.