Drycleaner Site Profiles

Memphis City Schools, Memphis, Tennessee

Description
Historical activity that resulted in contamination.

The Memphis City Schools site consists of several tracts of land that are being redeveloped to accommodate a new school. For a period of more than 50 years (early 1900s to early 1970s), Loeb Laundry occupied property on the west side of the site. Drycleaning services were added around 1937. By the 1990s, the buildings associated with the Loeb facility were removed and an asphalt parking lot was constructed. The property was eventually sold to the City of Memphis. Based on the age of the Loeb Drycleaners and the typical operation of a drycleaning facility, stoddard solvent and tetrachloroethylene (PCE) were expected to be present at the site. Soil, groundwater, and free product samples collected at the site indicated the presence of PCE, stoddard solvent, total petroleum hydrocarbons (TPH), and other volatile organic compounds (VOCs).

Contaminants
Contaminants present and the highest amount detected in both soil and groundwater.


Contaminant Media Concentration (ppb) Nondetect
tert butylbenzene groundwater 1,400 ppb
tert butylbenzene soil 21,100 ppb
cis-1,2-Dichloroethene groundwater 50,640 ppb
cis-1,2-Dichloroethene soil 86,900 ppb
ethylbenzene groundwater 181,000 ppb
ethylbenzene soil 4,560 ppb
n-butylbenzene soil 31,000 ppb
n-propylbenzene groundwater 1,450,000 ppb
n-propylbenzene soil 38,400 ppb
Tetrachloroethene (PCE) groundwater 116,000 ppb
Tetrachloroethene (PCE) soil 3,040,000 ppb
p-isopropyltoluene groundwater 983,000 ppb
p-isopropyltoluene soil 21,200 ppb
1,1,1-Trichloroethane groundwater 1,490,000 ppb
1,2,4-trimethylbenzene groundwater 14,000,000 ppb
1,2,4-trimethylbenzene soil 368,000 ppb
1,3,5-trimethylbenzene groundwater 7,470,000 ppb
1,3,5-trimethylbenzene soil 196,000 ppb
naphthalene groundwater 260,000 ppb
naphthalene soil 11,300 ppb
Trichloroethene (TCE) groundwater 43,560 ppb
Trichloroethene (TCE) soil 78,200 ppb
trans-1,2-Dichloroethene groundwater 479 ppb
trans-1,2-Dichloroethene soil 12,600 ppb
Vinyl Chloride groundwater 2,345 ppb
Vinyl Chloride soil 3,930 ppb

Site Hydrology

Deepest Significant Groundwater Contamination:   16ft bgs
Plume Size:   Plume Length: 200ft
Plume Width: 45ft
Average Depth to Groundwater:   8ft

Lithology and Subsurface Geology

 
  chert fragments and construction debris
Depth: 0-4ft bgs
4ft thick
Conductivity: 0.0085ft/day
Gradient: 0.01ft/ft
 
  brown to yellow-brown or greenish gray silty clays with some sand, some mottling
Depth: 4-20ft bgs
16ft thick

Pathways and DNAPL Presence

checkGroundwater
Sediments
checkSoil
DNAPL Present

Vapor Intrusion Pathway

Has the potential for vapor intrusion (VI) been evaluated?
  Yes
How was the site evaluated?
  Indoor air sampling
Results of VI evaluation:
  The VI pathway was ruled out (or does not exist)
Has a vapor mitigation system been installed?
  No 

Remediation Scenario

Cleanup Goals:
  Goals are site-specific based on potential receptors, risk assessment and other factors. The State of Tennessee uses the EPA's Clean Water Act MCLs for groundwater and the EPA Region 9 PRG's for soil as clean-up guidelines. TN Division of Solid Waste Management Remedial Goal Levels (TPH: 500 ppm; PCE: 6.0 ppm; TCE: 60 ppm) were used as the remedial goal during the soil excavation.

Technologies

In Situ Biostimulation
 

Why the technology was selected:
Lateral extent of contamination was limited to fairly localized hot spots located within the footprint of the new building that was to be constructed. The highest contaminant concentrations were detected above and beneath the water table. Excavation was selected due to its effectiveness and the speed of remediation. Biostimulation and zero-valent iron was selected to biotically and abiotically stimulate reductive dechlorination at the site.

Date implemented:
Spring 1999 Summer 2007 Spring 2009

Final remediation design:
The final design consisted of two 16-ft-deep, 225-ft<sup>2</sup> excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft<sup>2</sup>, within the TPH/free product contaminated area. Waste was characterized based on depth and contaminant concentration profiles and disposed of as construction & debris waste, special waste, or hazardous waste. 12,710 gallons of water were recovered from the excavations and treated/disposed of offsite. An additional excavation covering the previously excavated area as well as the surrounding soils (approx. 300 ft x 320 ft) was conducted to establish a stable base grade for the new building. Water from this excavation contained low levels of TPH and VOCs and was discharged to the sanitary sewer.

A groundwater recovery system was installed between 2001 and 2003 (trench network in 2001, operation unit in 2003 after facility construction) to extract residual contaminants from groundwater up to 10 ft bgs. The recovery trench system is located 20 ft bgs and consists of horizontally placed 4 diameter Schedule 4-inch PVC slotted piping with bell-end joints. The joints are glued together and connected to a center cross-fitting with the ends of the piping finished with PVC caps. Filter fabric sock covers the slotted portion of the piping. The piping is entrenched with crushed limestone rock with the trench bed sloped to the northeast. The northeast end of the network is attached to a PVC sweep-fitting that connects the trench system to a 6-inch vertical PVC pipe recovery well. The well is secured within a lockable well vault. Effluent from the system is discharged to the sanitary sewer. The system pumps 30-50 gpm and, on average, has discharged 300,000 gallons/month to the sewer.

Innovative Environmental Technologies (IET) preformed the in-situ injections at the site using zero valent iron and various hydrogen donors and nutrients during two remedial events. The injections were conducted using a recovery well and monitoring well in the source area.

Other technologies used:
Passive gas samplers (EMFLUX®) and summa canisters were utilized as part of an air/soil gas monitoring program to determine if hotspots remained, if contaminants entered the new school via vapor intrusion, and if the vapor concentrations detected were a health hazard to the students.

Results to date:
The excavations were terminated when confirmation samples collected from the walls and floor of the excavation indicated contaminant concentrations below the established regulatory levels. The maximum PCE and TCE concentrations detected within the exposed soil surface post-excavation are 7.2 and 13.70 mg/kg, respectively. Five wells, including the recovery well (RW), are included in the groundwater recovery monitoring. The wells were sampled three times prior to starting the system and three times since operation began in June 2003. Two wells, MW-22 and MW-25, have shown no impact from site contaminants. Samples from the remaining wells, RW, MW-23, and MW-24, have indicated PCE and degradation products at elevated levels. Prior to system startup, elevated PCE (max 1210 µg/l), TCE (max 345), and cis 1,2 DCE (max 537 µg/l) were detected at RW. PCE and TCE concentrations at MW-23 and MW-24 were at or below the detection limit; elevated cis 1,2 DCE concentrations ranging from 70-106 µg/l were detected. VC concentrations were elevated in all three wells, with the maximum pre-startup concentration detected being 437 µg/l at MW-23. After system startup, VC concentrations in MW-23 and MW-24 have dropped to <1.00 µg/l and 1.88 µg/l, respectively. PCE and TCE at RW have declined overall (266 µg/l and 166 µg/l), with some fluctuation occurring with data from the last two sampling events. Vapor monitoring study indicated no apparent health risk. Four groundwater monitoring events have occurred since the injection event of 2007 and two groundwater monitoring events have occurred since the injection event of 2009. Five monitoring wells were sampled prior to the remedial events, as well as after to monitor the efficacy of the remedial design. MW-23 was used as an injection well for the 2007 remedial event and was not sampled during the two subsequent sampling events. During the four monitoring events in 2008 and 2009, CVOC concentrations were below the laboratory detection limit of 1 ug/L. The pre-injection contaminant concentrations included cis-1,2-DCE concentrations of 174 ug/L and vinyl chloride concentrations of 103 ug/L. MW-24 has been sampled six times since the initial remedial injection of 2007. During the October 2009 sampling event, all concentrations of CVOCs were below their EPA MCL values. cis-1,2-DCE was reported as 59.5 ug/L and trans-1,2-DCE was reported as 1.63 ug/L. All other concentrations were below the laboratory detection limit of 1 ug/L. Concentrations of the contaminants of concern decreased to below the EPA MCL and EPA Region9 PRGs from the pre-injection concentrations of 6.18 ug/L for 1,2-DCA and 92.8 ug/L for cis-1,2-DCE. The recovery well was not sampled during the 2009 sampling events because it was used as an injection well during the Spring 2009 injection event. The last sampling event was Winter 2008 in the recovery well. The concentration of PCE was 12.4 ug/L and the other CVOCs sampled were below the laboratory detection limit of 10 ug/L. The pre-injection concentrations for the first injection event in Summer 2007 were 3.65 ug/L for 1,2-DCA, 70.3 ug/L for cis-1,2-DCE, 43.1 ug/L for PCE, 17.9 ug/L for TCE, and 2.13 ug/L for vinyl chloride. MW-26 was sampled during the October 2009 sampling event and CVOC concentrations were reported as cis-1,2-DCE at 60.4 ug/L, trans-1,2-DCE at 2.42 ug/L, and vinyl chloride at 10.6 ug/L. The levels of cis-1,2-DCE and trans-1,2-DCE are not above the EPA MCL or the EPA Region 9 PRGs. The level of vinyl chloride is above the EPA MCLs, as well as the EPA Region 9 PRGs. The level however, indicates that reductive dechlorination is occurring at the site. The pre-injection concentrations for the 2009 injection event were 78.8 ug/L for cis-1,2-DCE, 1.99 ug/L TCE, and 2.3 ug/L vinyl chloride. MW-25 was not sampled during the Fall 2009 sampling event, but was sampled during the Summer 2009 sampling event. The concentrations of all but 1,2-DCA w

Next Steps:
Site closed December 20, 2011

Cost to Design and Implement:
$559,527 $42,361.62 - Two injection events during 2007 and 2009 conducted by IET

In Situ Zero Valent Iron
 

Why the technology was selected:
Lateral extent of contamination was limited to fairly localized hot spots located within the footprint of the new building that was to be constructed. The highest contaminant concentrations were detected above and beneath the water table. Excavation was selected due to its effectiveness and the speed of remediation. Biostimulation and zero-valent iron was selected to biotically and abiotically stimulate reductive dechlorination at the site.

Date implemented:
Spring 1999 Summer 2007 Spring 2009

Final remediation design:
The final design consisted of two 16-ft-deep, 225-ft<sup>2</sup> excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft<sup>2</sup>, within the TPH/free product contaminated area. Waste was characterized based on depth and contaminant concentration profiles and disposed of as construction & debris waste, special waste, or hazardous waste. 12,710 gallons of water were recovered from the excavations and treated/disposed of offsite. An additional excavation covering the previously excavated area as well as the surrounding soils (approx. 300 ft x 320 ft) was conducted to establish a stable base grade for the new building. Water from this excavation contained low levels of TPH and VOCs and was discharged to the sanitary sewer.

A groundwater recovery system was installed between 2001 and 2003 (trench network in 2001, operation unit in 2003 after facility construction) to extract residual contaminants from groundwater up to 10 ft bgs. The recovery trench system is located 20 ft bgs and consists of horizontally placed 4 diameter Schedule 4-inch PVC slotted piping with bell-end joints. The joints are glued together and connected to a center cross-fitting with the ends of the piping finished with PVC caps. Filter fabric sock covers the slotted portion of the piping. The piping is entrenched with crushed limestone rock with the trench bed sloped to the northeast. The northeast end of the network is attached to a PVC sweep-fitting that connects the trench system to a 6-inch vertical PVC pipe recovery well. The well is secured within a lockable well vault. Effluent from the system is discharged to the sanitary sewer. The system pumps 30-50 gpm and, on average, has discharged 300,000 gallons/month to the sewer.

Innovative Environmental Technologies (IET) preformed the in-situ injections at the site using zero valent iron and various hydrogen donors and nutrients during two remedial events. The injections were conducted using a recovery well and monitoring well in the source area.

Other technologies used:
Passive gas samplers (EMFLUX®) and summa canisters were utilized as part of an air/soil gas monitoring program to determine if hotspots remained, if contaminants entered the new school via vapor intrusion, and if the vapor concentrations detected were a health hazard to the students.

Results to date:
The excavations were terminated when confirmation samples collected from the walls and floor of the excavation indicated contaminant concentrations below the established regulatory levels. The maximum PCE and TCE concentrations detected within the exposed soil surface post-excavation are 7.2 and 13.70 mg/kg, respectively. Five wells, including the recovery well (RW), are included in the groundwater recovery monitoring. The wells were sampled three times prior to starting the system and three times since operation began in June 2003. Two wells, MW-22 and MW-25, have shown no impact from site contaminants. Samples from the remaining wells, RW, MW-23, and MW-24, have indicated PCE and degradation products at elevated levels. Prior to system startup, elevated PCE (max 1210 µg/l), TCE (max 345), and cis 1,2 DCE (max 537 µg/l) were detected at RW. PCE and TCE concentrations at MW-23 and MW-24 were at or below the detection limit; elevated cis 1,2 DCE concentrations ranging from 70-106 µg/l were detected. VC concentrations were elevated in all three wells, with the maximum pre-startup concentration detected being 437 µg/l at MW-23. After system startup, VC concentrations in MW-23 and MW-24 have dropped to <1.00 µg/l and 1.88 µg/l, respectively. PCE and TCE at RW have declined overall (266 µg/l and 166 µg/l), with some fluctuation occurring with data from the last two sampling events. Vapor monitoring study indicated no apparent health risk. Four groundwater monitoring events have occurred since the injection event of 2007 and two groundwater monitoring events have occurred since the injection event of 2009. Five monitoring wells were sampled prior to the remedial events, as well as after to monitor the efficacy of the remedial design. MW-23 was used as an injection well for the 2007 remedial event and was not sampled during the two subsequent sampling events. During the four monitoring events in 2008 and 2009, CVOC concentrations were below the laboratory detection limit of 1 ug/L. The pre-injection contaminant concentrations included cis-1,2-DCE concentrations of 174 ug/L and vinyl chloride concentrations of 103 ug/L. MW-24 has been sampled six times since the initial remedial injection of 2007. During the October 2009 sampling event, all concentrations of CVOCs were below their EPA MCL values. cis-1,2-DCE was reported as 59.5 ug/L and trans-1,2-DCE was reported as 1.63 ug/L. All other concentrations were below the laboratory detection limit of 1 ug/L. Concentrations of the contaminants of concern decreased to below the EPA MCL and EPA Region9 PRGs from the pre-injection concentrations of 6.18 ug/L for 1,2-DCA and 92.8 ug/L for cis-1,2-DCE. The recovery well was not sampled during the 2009 sampling events because it was used as an injection well during the Spring 2009 injection event. The last sampling event was Winter 2008 in the recovery well. The concentration of PCE was 12.4 ug/L and the other CVOCs sampled were below the laboratory detection limit of 10 ug/L. The pre-injection concentrations for the first injection event in Summer 2007 were 3.65 ug/L for 1,2-DCA, 70.3 ug/L for cis-1,2-DCE, 43.1 ug/L for PCE, 17.9 ug/L for TCE, and 2.13 ug/L for vinyl chloride. MW-26 was sampled during the October 2009 sampling event and CVOC concentrations were reported as cis-1,2-DCE at 60.4 ug/L, trans-1,2-DCE at 2.42 ug/L, and vinyl chloride at 10.6 ug/L. The levels of cis-1,2-DCE and trans-1,2-DCE are not above the EPA MCL or the EPA Region 9 PRGs. The level of vinyl chloride is above the EPA MCLs, as well as the EPA Region 9 PRGs. The level however, indicates that reductive dechlorination is occurring at the site. The pre-injection concentrations for the 2009 injection event were 78.8 ug/L for cis-1,2-DCE, 1.99 ug/L TCE, and 2.3 ug/L vinyl chloride. MW-25 was not sampled during the Fall 2009 sampling event, but was sampled during the Summer 2009 sampling event. The concentrations of all but 1,2-DCA w

Next Steps:
Site closed December 20, 2011

Cost to Design and Implement:
$559,527 $42,361.62 - Two injection events during 2007 and 2009 conducted by IET

Ex Situ Pump and Treat
 

Why the technology was selected:
Lateral extent of contamination was limited to fairly localized hot spots located within the footprint of the new building that was to be constructed. The highest contaminant concentrations were detected above and beneath the water table. Excavation was selected due to its effectiveness and the speed of remediation. Biostimulation and zero-valent iron was selected to biotically and abiotically stimulate reductive dechlorination at the site.

Date implemented:
Spring 1999, Summer 2007, Spring 2009

Final remediation design:
The final design consisted of two 16-ft-deep, 225-ft<sup>2</sup> excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft<sup>2</sup>, within the TPH/free product contaminated area. Waste was characterized based on depth and contaminant concentration profiles and disposed of as construction & debris waste, special waste, or hazardous waste. 12,710 gallons of water were recovered from the excavations and treated/disposed of offsite. An additional excavation covering the previously excavated area as well as the surrounding soils (approx. 300 ft x 320 ft) was conducted to establish a stable base grade for the new building. Water from this excavation contained low levels of TPH and VOCs and was discharged to the sanitary sewer.

A groundwater recovery system was installed between 2001 and 2003 (trench network in 2001, operation unit in 2003 after facility construction) to extract residual contaminants from groundwater up to 10 ft bgs. The recovery trench system is located 20 ft bgs and consists of horizontally placed 4 diameter Schedule 4-inch PVC slotted piping with bell-end joints. The joints are glued together and connected to a center cross-fitting with the ends of the piping finished with PVC caps. Filter fabric sock covers the slotted portion of the piping. The piping is entrenched with crushed limestone rock with the trench bed sloped to the northeast. The northeast end of the network is attached to a PVC sweep-fitting that connects the trench system to a 6-inch vertical PVC pipe recovery well. The well is secured within a lockable well vault. Effluent from the system is discharged to the sanitary sewer. The system pumps 30-50 gpm and, on average, has discharged 300,000 gallons/month to the sewer.

Innovative Environmental Technologies (IET) preformed the in-situ injections at the site using zero valent iron and various hydrogen donors and nutrients during two remedial events. The injections were conducted using a recovery well and monitoring well in the source area.

Other technologies used:
Passive gas samplers (EMFLUX®) and summa canisters were utilized as part of an air/soil gas monitoring program to determine if hotspots remained, if contaminants entered the new school via vapor intrusion, and if the vapor concentrations detected were a health hazard to the students.

Results to date:
The excavations were terminated when confirmation samples collected from the walls and floor of the excavation indicated contaminant concentrations below the established regulatory levels. The maximum PCE and TCE concentrations detected within the exposed soil surface post-excavation are 7.2 and 13.70 mg/kg, respectively. Five wells, including the recovery well (RW), are included in the groundwater recovery monitoring. The wells were sampled three times prior to starting the system and three times since operation began in June 2003. Two wells, MW-22 and MW-25, have shown no impact from site contaminants. Samples from the remaining wells, RW, MW-23, and MW-24, have indicated PCE and degradation products at elevated levels. Prior to system startup, elevated PCE (max 1210 µg/l), TCE (max 345), and cis 1,2 DCE (max 537 µg/l) were detected at RW. PCE and TCE concentrations at MW-23 and MW-24 were at or below the detection limit; elevated cis 1,2 DCE concentrations ranging from 70-106 µg/l were detected. VC concentrations were elevated in all three wells, with the maximum pre-startup concentration detected being 437 µg/l at MW-23. After system startup, VC concentrations in MW-23 and MW-24 have dropped to <1.00 µg/l and 1.88 µg/l, respectively. PCE and TCE at RW have declined overall (266 µg/l and 166 µg/l), with some fluctuation occurring with data from the last two sampling events. Vapor monitoring study indicated no apparent health risk. Four groundwater monitoring events have occurred since the injection event of 2007 and two groundwater monitoring events have occurred since the injection event of 2009. Five monitoring wells were sampled prior to the remedial events, as well as after to monitor the efficacy of the remedial design. MW-23 was used as an injection well for the 2007 remedial event and was not sampled during the two subsequent sampling events. During the four monitoring events in 2008 and 2009, CVOC concentrations were below the laboratory detection limit of 1 ug/L. The pre-injection contaminant concentrations included cis-1,2-DCE concentrations of 174 ug/L and vinyl chloride concentrations of 103 ug/L. MW-24 has been sampled six times since the initial remedial injection of 2007. During the October 2009 sampling event, all concentrations of CVOCs were below their EPA MCL values. cis-1,2-DCE was reported as 59.5 ug/L and trans-1,2-DCE was reported as 1.63 ug/L. All other concentrations were below the laboratory detection limit of 1 ug/L. Concentrations of the contaminants of concern decreased to below the EPA MCL and EPA Region9 PRGs from the pre-injection concentrations of 6.18 ug/L for 1,2-DCA and 92.8 ug/L for cis-1,2-DCE. The recovery well was not sampled during the 2009 sampling events because it was used as an injection well during the Spring 2009 injection event. The last sampling event was Winter 2008 in the recovery well. The concentration of PCE was 12.4 ug/L and the other CVOCs sampled were below the laboratory detection limit of 10 ug/L. The pre-injection concentrations for the first injection event in Summer 2007 were 3.65 ug/L for 1,2-DCA, 70.3 ug/L for cis-1,2-DCE, 43.1 ug/L for PCE, 17.9 ug/L for TCE, and 2.13 ug/L for vinyl chloride. MW-26 was sampled during the October 2009 sampling event and CVOC concentrations were reported as cis-1,2-DCE at 60.4 ug/L, trans-1,2-DCE at 2.42 ug/L, and vinyl chloride at 10.6 ug/L. The levels of cis-1,2-DCE and trans-1,2-DCE are not above the EPA MCL or the EPA Region 9 PRGs. The level of vinyl chloride is above the EPA MCLs, as well as the EPA Region 9 PRGs. The level however, indicates that reductive dechlorination is occurring at the site. The pre-injection concentrations for the 2009 injection event were 78.8 ug/L for cis-1,2-DCE, 1.99 ug/L TCE, and 2.3 ug/L vinyl chloride. MW-25 was not sampled during the Fall 2009 sampling event, but was sampled during the Summer 2009 sampling event. The concentrations of all but 1,2-DCA w

Next Steps:
Site closed December 20, 2011

Cost to Design and Implement:
$559,527 $42,361.62 - Two injection events during 2007 and 2009 conducted by IET

Ex Situ Recirculating Wells
 

Why the technology was selected:
Lateral extent of contamination was limited to fairly localized hot spots located within the footprint of the new building that was to be constructed. The highest contaminant concentrations were detected above and beneath the water table. Excavation was selected due to its effectiveness and the speed of remediation. Biostimulation and zero-valent iron was selected to biotically and abiotically stimulate reductive dechlorination at the site.

Date implemented:
Spring 1999 Summer 2007 Spring 2009

Final remediation design:
The final design consisted of two 16-ft-deep, 225-ft<sup>2</sup> excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft<sup>2</sup>, within the TPH/free product contaminated area. Waste was characterized based on depth and contaminant concentration profiles and disposed of as construction & debris waste, special waste, or hazardous waste. 12,710 gallons of water were recovered from the excavations and treated/disposed of offsite. An additional excavation covering the previously excavated area as well as the surrounding soils (approx. 300 ft x 320 ft) was conducted to establish a stable base grade for the new building. Water from this excavation contained low levels of TPH and VOCs and was discharged to the sanitary sewer.

A groundwater recovery system was installed between 2001 and 2003 (trench network in 2001, operation unit in 2003 after facility construction) to extract residual contaminants from groundwater up to 10 ft bgs. The recovery trench system is located 20 ft bgs and consists of horizontally placed 4 diameter Schedule 4-inch PVC slotted piping with bell-end joints. The joints are glued together and connected to a center cross-fitting with the ends of the piping finished with PVC caps. Filter fabric sock covers the slotted portion of the piping. The piping is entrenched with crushed limestone rock with the trench bed sloped to the northeast. The northeast end of the network is attached to a PVC sweep-fitting that connects the trench system to a 6-inch vertical PVC pipe recovery well. The well is secured within a lockable well vault. Effluent from the system is discharged to the sanitary sewer. The system pumps 30-50 gpm and, on average, has discharged 300,000 gallons/month to the sewer.

Innovative Environmental Technologies (IET) preformed the in-situ injections at the site using zero valent iron and various hydrogen donors and nutrients during two remedial events. The injections were conducted using a recovery well and monitoring well in the source area.

Other technologies used:
Passive gas samplers (EMFLUX®) and summa canisters were utilized as part of an air/soil gas monitoring program to determine if hotspots remained, if contaminants entered the new school via vapor intrusion, and if the vapor concentrations detected were a health hazard to the students.

Results to date:
The excavations were terminated when confirmation samples collected from the walls and floor of the excavation indicated contaminant concentrations below the established regulatory levels. The maximum PCE and TCE concentrations detected within the exposed soil surface post-excavation are 7.2 and 13.70 mg/kg, respectively. Five wells, including the recovery well (RW), are included in the groundwater recovery monitoring. The wells were sampled three times prior to starting the system and three times since operation began in June 2003. Two wells, MW-22 and MW-25, have shown no impact from site contaminants. Samples from the remaining wells, RW, MW-23, and MW-24, have indicated PCE and degradation products at elevated levels. Prior to system startup, elevated PCE (max 1210 µg/l), TCE (max 345), and cis 1,2 DCE (max 537 µg/l) were detected at RW. PCE and TCE concentrations at MW-23 and MW-24 were at or below the detection limit; elevated cis 1,2 DCE concentrations ranging from 70-106 µg/l were detected. VC concentrations were elevated in all three wells, with the maximum pre-startup concentration detected being 437 µg/l at MW-23. After system startup, VC concentrations in MW-23 and MW-24 have dropped to <1.00 µg/l and 1.88 µg/l, respectively. PCE and TCE at RW have declined overall (266 µg/l and 166 µg/l), with some fluctuation occurring with data from the last two sampling events. Vapor monitoring study indicated no apparent health risk. Four groundwater monitoring events have occurred since the injection event of 2007 and two groundwater monitoring events have occurred since the injection event of 2009. Five monitoring wells were sampled prior to the remedial events, as well as after to monitor the efficacy of the remedial design. MW-23 was used as an injection well for the 2007 remedial event and was not sampled during the two subsequent sampling events. During the four monitoring events in 2008 and 2009, CVOC concentrations were below the laboratory detection limit of 1 ug/L. The pre-injection contaminant concentrations included cis-1,2-DCE concentrations of 174 ug/L and vinyl chloride concentrations of 103 ug/L. MW-24 has been sampled six times since the initial remedial injection of 2007. During the October 2009 sampling event, all concentrations of CVOCs were below their EPA MCL values. cis-1,2-DCE was reported as 59.5 ug/L and trans-1,2-DCE was reported as 1.63 ug/L. All other concentrations were below the laboratory detection limit of 1 ug/L. Concentrations of the contaminants of concern decreased to below the EPA MCL and EPA Region9 PRGs from the pre-injection concentrations of 6.18 ug/L for 1,2-DCA and 92.8 ug/L for cis-1,2-DCE. The recovery well was not sampled during the 2009 sampling events because it was used as an injection well during the Spring 2009 injection event. The last sampling event was Winter 2008 in the recovery well. The concentration of PCE was 12.4 ug/L and the other CVOCs sampled were below the laboratory detection limit of 10 ug/L. The pre-injection concentrations for the first injection event in Summer 2007 were 3.65 ug/L for 1,2-DCA, 70.3 ug/L for cis-1,2-DCE, 43.1 ug/L for PCE, 17.9 ug/L for TCE, and 2.13 ug/L for vinyl chloride. MW-26 was sampled during the October 2009 sampling event and CVOC concentrations were reported as cis-1,2-DCE at 60.4 ug/L, trans-1,2-DCE at 2.42 ug/L, and vinyl chloride at 10.6 ug/L. The levels of cis-1,2-DCE and trans-1,2-DCE are not above the EPA MCL or the EPA Region 9 PRGs. The level of vinyl chloride is above the EPA MCLs, as well as the EPA Region 9 PRGs. The level however, indicates that reductive dechlorination is occurring at the site. The pre-injection concentrations for the 2009 injection event were 78.8 ug/L for cis-1,2-DCE, 1.99 ug/L TCE, and 2.3 ug/L vinyl chloride. MW-25 was not sampled during the Fall 2009 sampling event, but was sampled during the Summer 2009 sampling event. The concentrations of all but 1,2-DCA w

Next Steps:
Site closed December 20, 2011

Cost to Design and Implement:
$559,527 $42,361.62 - Two injection events during 2007 and 2009 conducted by IET

Ex Situ Other
 

Why the technology was selected:
Lateral extent of contamination was limited to fairly localized hot spots located within the footprint of the new building that was to be constructed. The highest contaminant concentrations were detected above and beneath the water table. Excavation was selected due to its effectiveness and the speed of remediation. Biostimulation and zero-valent iron was selected to biotically and abiotically stimulate reductive dechlorination at the site.

Date implemented:
Spring 1999 Summer 2007 Spring 2009

Final remediation design:
The final design consisted of two 16-ft-deep, 225-ft<sup>2</sup> excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft<sup>2</sup>, within the TPH/free product contaminated area. Waste was characterized based on depth and contaminant concentration profiles and disposed of as construction & debris waste, special waste, or hazardous waste. 12,710 gallons of water were recovered from the excavations and treated/disposed of offsite. An additional excavation covering the previously excavated area as well as the surrounding soils (approx. 300 ft x 320 ft) was conducted to establish a stable base grade for the new building. Water from this excavation contained low levels of TPH and VOCs and was discharged to the sanitary sewer.

A groundwater recovery system was installed between 2001 and 2003 (trench network in 2001, operation unit in 2003 after facility construction) to extract residual contaminants from groundwater up to 10 ft bgs. The recovery trench system is located 20 ft bgs and consists of horizontally placed 4 diameter Schedule 4-inch PVC slotted piping with bell-end joints. The joints are glued together and connected to a center cross-fitting with the ends of the piping finished with PVC caps. Filter fabric sock covers the slotted portion of the piping. The piping is entrenched with crushed limestone rock with the trench bed sloped to the northeast. The northeast end of the network is attached to a PVC sweep-fitting that connects the trench system to a 6-inch vertical PVC pipe recovery well. The well is secured within a lockable well vault. Effluent from the system is discharged to the sanitary sewer. The system pumps 30-50 gpm and, on average, has discharged 300,000 gallons/month to the sewer.

Innovative Environmental Technologies (IET) preformed the in-situ injections at the site using zero valent iron and various hydrogen donors and nutrients during two remedial events. The injections were conducted using a recovery well and monitoring well in the source area.

Other technologies used:
Passive gas samplers (EMFLUX®) and summa canisters were utilized as part of an air/soil gas monitoring program to determine if hotspots remained, if contaminants entered the new school via vapor intrusion, and if the vapor concentrations detected were a health hazard to the students.

Results to date:
The excavations were terminated when confirmation samples collected from the walls and floor of the excavation indicated contaminant concentrations below the established regulatory levels. The maximum PCE and TCE concentrations detected within the exposed soil surface post-excavation are 7.2 and 13.70 mg/kg, respectively. Five wells, including the recovery well (RW), are included in the groundwater recovery monitoring. The wells were sampled three times prior to starting the system and three times since operation began in June 2003. Two wells, MW-22 and MW-25, have shown no impact from site contaminants. Samples from the remaining wells, RW, MW-23, and MW-24, have indicated PCE and degradation products at elevated levels. Prior to system startup, elevated PCE (max 1210 µg/l), TCE (max 345), and cis 1,2 DCE (max 537 µg/l) were detected at RW. PCE and TCE concentrations at MW-23 and MW-24 were at or below the detection limit; elevated cis 1,2 DCE concentrations ranging from 70-106 µg/l were detected. VC concentrations were elevated in all three wells, with the maximum pre-startup concentration detected being 437 µg/l at MW-23. After system startup, VC concentrations in MW-23 and MW-24 have dropped to <1.00 µg/l and 1.88 µg/l, respectively. PCE and TCE at RW have declined overall (266 µg/l and 166 µg/l), with some fluctuation occurring with data from the last two sampling events. Vapor monitoring study indicated no apparent health risk. Four groundwater monitoring events have occurred since the injection event of 2007 and two groundwater monitoring events have occurred since the injection event of 2009. Five monitoring wells were sampled prior to the remedial events, as well as after to monitor the efficacy of the remedial design. MW-23 was used as an injection well for the 2007 remedial event and was not sampled during the two subsequent sampling events. During the four monitoring events in 2008 and 2009, CVOC concentrations were below the laboratory detection limit of 1 ug/L. The pre-injection contaminant concentrations included cis-1,2-DCE concentrations of 174 ug/L and vinyl chloride concentrations of 103 ug/L. MW-24 has been sampled six times since the initial remedial injection of 2007. During the October 2009 sampling event, all concentrations of CVOCs were below their EPA MCL values. cis-1,2-DCE was reported as 59.5 ug/L and trans-1,2-DCE was reported as 1.63 ug/L. All other concentrations were below the laboratory detection limit of 1 ug/L. Concentrations of the contaminants of concern decreased to below the EPA MCL and EPA Region9 PRGs from the pre-injection concentrations of 6.18 ug/L for 1,2-DCA and 92.8 ug/L for cis-1,2-DCE. The recovery well was not sampled during the 2009 sampling events because it was used as an injection well during the Spring 2009 injection event. The last sampling event was Winter 2008 in the recovery well. The concentration of PCE was 12.4 ug/L and the other CVOCs sampled were below the laboratory detection limit of 10 ug/L. The pre-injection concentrations for the first injection event in Summer 2007 were 3.65 ug/L for 1,2-DCA, 70.3 ug/L for cis-1,2-DCE, 43.1 ug/L for PCE, 17.9 ug/L for TCE, and 2.13 ug/L for vinyl chloride. MW-26 was sampled during the October 2009 sampling event and CVOC concentrations were reported as cis-1,2-DCE at 60.4 ug/L, trans-1,2-DCE at 2.42 ug/L, and vinyl chloride at 10.6 ug/L. The levels of cis-1,2-DCE and trans-1,2-DCE are not above the EPA MCL or the EPA Region 9 PRGs. The level of vinyl chloride is above the EPA MCLs, as well as the EPA Region 9 PRGs. The level however, indicates that reductive dechlorination is occurring at the site. The pre-injection concentrations for the 2009 injection event were 78.8 ug/L for cis-1,2-DCE, 1.99 ug/L TCE, and 2.3 ug/L vinyl chloride. MW-25 was not sampled during the Fall 2009 sampling event, but was sampled during the Summer 2009 sampling event. The concentrations of all but 1,2-DCA w

Next Steps:
Site closed December 20, 2011

Cost to Design and Implement:
$559,527 $42,361.62 - Two injection events during 2007 and 2009 conducted by IET

Costs

Cost for Assessment:
  $23,699
Cost for Operation and Maintenance:
  $34,832
Total Costs for Cleanup:
 

Contacts

TN Department of Environment and Conservation
Division of Remediation
Drycleaner Environmental Response Program
L&C Annex, 4th Floor
401 Church Street
Nashville, Tennessee 37243
615-532-0900

Site Specific References

1.Preliminary Solvent Impact Assessment (RI)
2. Soil Characterization Report - March 1999
3. Report of Soil Removal and Disposal - April 1999
4. Groundwater Monitoring Reports: 1st Quarter GWM Rpt - October 2003 through 3rd Quarter GWM Rpt - April 2004.
5. Remedial Alternatives Study (FS)- Dec. 11, 1998
6. Health Consultation Report, Downtown School Memphis City Schools - March 2003
7. Response Complete December 20, 2011