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-ft² excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft², 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

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-ft² excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft², 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

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-ft² excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft², 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

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-ft² excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft², 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

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-ft² excavations within the chlorinated solvent source area and a 14-ft-deep area, approximately 1435 ft², 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