SVE and P&T:
-- A pilot test of SVE was conducted at the site on April 9, 1998, indicated that the permeability of the soil was adequate to implement the technology.
-- The full-scale SVE system consisted of two horizontal vapor extraction wells, a positive-displacement blower, a condensate tank, a vapor-phase granular activated carbon (GAC) treatment vessel, and an infiltration gallery.
-- The two horizontal vapor extraction wells were 130 to 200 feet deep with a screened interval of 80 to 100 feet, and were 40 feet apart. The wells were installed parallel to each other in a line extending from the west to the east side of the dry cleaning facility.
-- The radius of influence of each SVE extraction well was expected to be 24 feet.
-- The off gas from the SVE system was originally treated using a 1,000-pound vapor-phase GAC unit. The effluent from the GAC unit was vented to the atmosphere. The treated water was pumped to an on-site infiltration gallery.
-- The P&T system consisted of one groundwater recovery well, a submersible pump, an influent tank, a feed pump, an air stripper system, and an on-site infiltration gallery.
-- The recovery well was 6 inches in diameter and was screened at 5 to 25 feet bgs.
-- Air stripping was selected to treat the recovered groundwater.
-- The design pumping rate was 7 to 10 gallons per minute (gpm). Operating pumping rate was 10 to 12 gpm. The off gas from the air stripper was expected to meet air discharge requirements of 5.5 pounds per day and was not treated.
-- A targeted application of ISCO using 1 percent hydrogen peroxide was considered to treat the area near source area monitoring well MW005 in order to expedite closure of the site.
-- Existing monitoring well MW005 was used for injecting the oxidant and a new well (MW038) was installed (approximately 3 feet north of well MW005) for monitoring purposes using direct-push technology.
-- The treatment zone included the upper 5 feet of the surficial aquifer and extended a distance of 7.5 feet in a radial direction from well MW005. The total treatment area was177 ft² and the treatment volume was 708 cubic feet (based on an estimated treatment thickness of 4 feet).
-- On October 4, 2005, the first batch of hydrogen peroxide was transferred to injection well MW005 using an in-line pump at a rate of 9 gpm with no back pressure (as indicated by the pressure gauge). The injection rate was reduced and maintained at 2.7 gpm for the second batch of injection.
-- Overall, 1,057 gallons of 1 percent hydrogen peroxide was injected into the treatment zone over a 2-day period from October 4 to 5, 2005.
-- When the injection event was completed, dissolved oxygen and temperature were recorded in wells MW038 and MW005 each hour for a minimum of 8 hours. During the injection process, pH readings were continuously collected from well MW005 to monitor the effects of peroxide injection on groundwater.
-- After ISCO treatment, quarterly monitoring was conducted at the site during 2006 (January, May, July, and October 2006).
Bureau of Waste Cleanup (as part of FDEP's Dry Cleaning Solvent Cleanup Program)
Groundwater — Volatiles-halogenated: tetrachloroethene (PCE) DNAPL; cis-1,2-dichloroethene (DCE); trans-1,2-DCE; trichloroethene (TCE); vinyl chloride (VC).
Soil — PCE
Relatively large or long-term discharge of chlorinated solvents from the dry cleaning facility.
Type/Quantity of Media Treated:
Soil; Groundwater (quantity not documented)
Purpose/Significance of Application:
To minimize migration of the plume of volatile organic compounds (VOC) in groundwater by reducing the concentrations of PCE in the source area beneath the foundation of the dry cleaning facility, and remediation of the contaminated groundwater plume in the upper portion of the surficial aquifer, where PCE concentrations exceeded 100 µg/L. The goal for remediation system for PCE-contaminated soil was to achieve the Florida Department of Environmental Protection (FDEP)'s cleanup target levels (CTL).
Regulatory Requirements/Cleanup Goals:
The cleanup goals for the volatile organic compounds (VOCs) found at the site were the FDEP's CTL, which were the same as the Florida maximum contaminant levels (MCL). PCE was the only contaminant detected in soil at the Dry Clean USA site. The FDEP CTL for PCE in soil was 30 micrograms per kilogram (µg/kg).
SVE and P&T:
-- The SVE system met design performance specifications at the end of the first year of operation in March 2000. The mass recovery of the SVE system during the first year of operation was estimated at 5.1 pounds, nearly equal to the original design estimate of 5.2 pounds.
-- Detectable PCE concentrations were found in groundwater samples from some monitoring wells at the end of the first year of SVE system operation.
-- In its first year of operation, the P&T system recovered and treated a total of 2.56 million gallons of PCE-contaminated groundwater; the estimated mass recovery for PCE was 2.9 pounds.
-- In the second year of operation, both the SVE and P&T systems did not operate for most of the first quarter (between May and July 2000) so that equipment that was damaged in a power overload could be repaired.
-- The SVE system continued to operate into the third quarter of the second year (November 2000 to January 2001) until soil sampling results from November 2000 indicated that the PCE concentration in soil was below the cleanup goal of 30 µg/kg. FDEP approved a recommendation to discontinue soil remediation, and the SVE system was shut down and decommissioned on December 1, 2000.
-- In its second year of operation, the SVE system recovered an estimated 9.8 pounds of total VOCs.
-- Approximately 2.1 million gallons of contaminated groundwater were treated during the second year of P&T system operation. The P&T system was deactivated during the fourth quarter of the second year (on January 17, 2001) at the request of FDEP to assess contaminant concentrations under natural groundwater flow conditions. Quarterly groundwater monitoring was continued to assess the impact of deactivating the P&T system.
-- The CTL of 3 µg/L for PCE in groundwater had not been met in all monitoring wells when the SVE and P&T systems were shut down. The PCE concentration was higher than the CTL at a former source area well MW011 (4.9 µg/L) and at MW029 (6.1 µg/L) in the March 2002 sampling event. These results indicated a possible rebound of the PCE level in certain locations. Therefore, the P&T system was restarted in February 2002, before the March 2002 sampling event, and continued to operate until November 2002.
-- MNA groundwater monitoring was conducted on a quarterly basis from December 2003 until July 2004.
-- In July 2004, concentration of PCE in MW005, a source area well, exceeded the CTL (6.5 µg/L). Hence, a targeted application of ISCO using 1 percent hydrogen peroxide was considered to treat the area near well MW005 to expedite closure of the site.
-- On October 4 and 5, 2005, 1,057 gallons of 1 percent hydrogen peroxide was injected into former source area well MW005.
-- The initial pH at well MW005 was 7.32; the pH was reported to be 5.87 when the injection system was shut down.
-- A post-injection groundwater sample was collected from well MW005 on October 6, 2005. This groundwater sample indicated that the concentration of PCE in well MW005 was below detection limits
Cost for site characterization totaled $97,700. Cost for design and implementation totaled $249,850, which included $221,445 for the SVE and P&T systems, and $28,405 for the ISCO system. The operation and maintenance (O&M) costs for soil and groundwater were $121,143 per year. Monitoring costs totaled $26,614 and site restoration costs totaled $7,000.
Dry Clean USA No. 11502 is a former dry cleaning facility that operated from 1988 to 1998 in Orlando, Florida. The site is located in a shopping center in a mixed retail commercial/ residential setting. A second dry cleaning operation was located in the same shopping center 65 feet east of the Dry Clean USA facility and operated from 1957 to 1988. Early site investigations conducted in 1993 and 1994 indicated chlorinated solvents, particularly tetrachloroethene (PCE), to be the main contaminant at the site. The area of the plume was estimated to be 70,000 square feet (ft²). PCE was detected at a maximum concentration of 27,300 micrograms per liter (µg/L) in groundwater, indicating the possible presence of dense nonaqueous phase liquid (DNAPL). Site investigations conducted in 1997 accurately defined the source area at the facility and assessed the horizontal and vertical extent of chlorinated solvents in the subsurface. These investigations indicated that an area of elevated concentrations of chlorinated solvents existed in the soil and groundwater, extending approximately 300 feet east-southeast of the Dry Clean USA facility.
SVE was chosen to remediate the contaminated soil at the site after conducting a successful pilot test in April 1998. P&T using an aboveground air stripper was selected to contain the contaminant plume and remediate the groundwater. The SVE system operated from April 1999 to December 2000, and the P&T system operated until November 2002. Monitored natural attenuation (MNA) was the remedy at the site after the P&T system was deactivated. In July 2004, increased concentrations of PCE were detected in samples from one source area well MW005. In situ chemical oxidation (ISCO) using hydrogen peroxide was implemented to treat PCE in the vicinity of well MW005 to expedite remediation of this hot spot.