Remediation Status: In active remediation

Why the technology was selected:
In situ bioremediation was chosen as the groundwater remedy because groundwater analytical and geochemical data indicated that reductive dechlorination was occurring at the site. Conditions were amenable to injection of HRC as a passive low-cost enhancement to naturally occurring biodegradation of contaminants. EOS was subsequently selected for injection under the facility floor slab. The bay that formerly housed the drycleaning operation had been vacated and was accessible for injection. It was not known when there woule be another opportunity for injection in the main source area. EOS was selected to as a long-lived carbon source. Aquifer or groundwater buffering was attempted in the intermediate surficial aquifer to raise the groundwater pH from approximatley 4.5 standard units to a higher pH (near neutral) to facilitate biodegradation.

Date implemented:
1st HRC injection: June 2000; 2nd HRC: April 2002 HRC-X injection; May 2003; Bioaugmentation: Injection of Bio-Dechlor Inoculum: May 2004. Biostimulation using EOS & Vitamin B12: September 6-9. 2005. Buffering: magnesium hydroxide pilot test: Februar

Final remediation design:
During the first bioremediation injection event Approximately 22,000 lbs. of HRC were injected via 175 direct push borings located behind the drycleaning facility on 10-foot centers, points were shifted 5 ft on every other north south transect. the HRC was injected at from 25-30 feet bls (or 5 lbs of HRC/foot). The second bioremediation injection event utilized 3,000 lbs of HRC injected in 48 direct push borings located on 10 foot centers. The HRC was injected at depths ranging from 20-30 ft bls. This amounted to from 3-7 lbs of HRC/foot During the third injection event approximatley 3,200 lbs of HRC-X was utilized. There were two separate injection areas. Area 1 (20 feet by 100 feet with 20 injection points Depth: 2 to 25 feet bgs Volume: 4lbs/ft) Area 2 (40 feet by 70 feet with 28 injection points, Depth 2 to 22 feet bgs, Volume: 2bls/ft) A bioaugmentation pilot study was conducted also in May 2003 using Bio-Dechlor INOCULUM (BDI). BDI was injected into 7 injection points near a source area well at from 10 to 20 feet bls. Injection volume was was 0.1 Liter/ft (1 Liter/point). The fourth bioremediation injection event was conducted from September 6-9, 2005. A total of 29 drums (1,595 gallons of emulsified oil substrate (EOS) mixed with 4,700 gallons of water and 64 ounces of EOS B12 supplement was injected into the eight wells installed beneath the facility floor slab (screened 5-25 ft bls). Magnesium hydroxide buffering pilot test consisted of the injection of the a 110 lbs. of magnesium hydroxide mixed with 200 gallons of water into a singe injection well (screened 15-25 ft BLS). The second buffering event was from April 3-5, 2006 when a solution of 100 kilograms of ammonium carbonate mixed with 150 gallons of water was injected into each of 7 intermediate surficial aquifer injeciton wells.

Other technologies used:
Bioaugmentation: using Bio-Dechlor Inoculum. Groundwater buffering: using magnesium hydroxide and ammonium bicarbonate.

Results to date:
The latest groundwater monitoring event conducted at the site was from March 19-20, 2009. This is over three and one-half years after the EOS injection event. Only two monitor wells, a shallow (5-15 ft BLS) and an intermediate zone (15-25 ft BLS) well produced detectable concentrations of PCE (1,000 and 2,800 ug/l, respectively. Both of these wells are installed under the floor slab of the former drycleaning facility. The primary contaminants in the shallow and intermediate zones are cis 1,2-DCE (up to 31,000 ug/l) and viny chloride (to 14,000 ug/l). In the deep zone (25-30 ft BLS) the only contaminant detected in groundwater samples in concentrations exceeding an MCL was vinyl chloride (to 3.0 ug/l). Chloride has been a good indicator of biodegradation activity. Background chloride is 6-20 mg/l). Chloride has been detected in concentrations ranging to 5,900 mg/l. Chloride concentrations during this monitor event have been as high as 400 mg/l.

Next Steps:
An additional injection of a long-lived carbon amendment under the facility floor slab is planned.

Cost to Design and Implement:
Well Installation & Baseline Sampling: $32,000
HRC Product (1st injection): $150,000
1st Injection Implementation: $80,000
HRC Product (2nd injection): $25,000
2nd Injection Implementation: $25,000
Monitoring, Reporting (both events): $42,000
HRC-X Product (3rd injection): $29,000
3rd Injection Implementation: $36,000

Why the technology was selected:
Source removal was selected because of the shallow water table (2-3 feet bls) that precluded SVE as a soil remedial technology and there was an oppotunity to excavate below the building floor slab where the primary contaminant source area was located. Piping was installed in the open excavation for a passive venting system.

Date implemented:
Interim Source Removal & installation of passive venting system: August 2005

Final remediation design:
From August 4-8 an interim source removal was conducted. An area of the facility floor slab approximatley 70 ft x 30 ft was removed and approximatley 110 cubic yards of contaminated soil was removed to a depth of 3 feet using a mini-trackhoe. The excavation was back-filled with pea gravel to a depth of 18 inches and then seven (7)4-inch diameter PVC laterals with 0.01-inch slot screens were installed on top the pea gravel. The lateral vapor recovery wells were piped out through a wall of the builidng and then extended upward along the exterior wall to the roof. Each pipe was capped with a neck turbine ventilator. Eight 2-inch diameter vertical injection wells, screened 5-25 feet were installed inside the facility. The remainng excvation was backfilled and the floor slab was poured.

Next Steps:
An additional injection of a long-lived carbon amendment under the facility floor slab is planned.

Why the technology was selected:
Piping was installed in the open excavation for a passive venting system.

Date implemented:
Interim Source Removal & installation of passive venting system: August 2005

Final remediation design:
From August 4-8 an interim source removal was conducted. An area of the facility floor slab approximatley 70 ft x 30 ft was removed and approximatley 110 cubic yards of contaminated soil was removed to a depth of 3 feet using a mini-trackhoe. The excavation was back-filled with pea gravel to a depth of 18 inches and then seven (7)4-inch diameter PVC laterals with 0.01-inch slot screens were installed on top the pea gravel. The lateral vapor recovery wells were piped out through a wall of the builidng and then extended upward along the exterior wall to the roof. Each pipe was capped with a neck turbine ventilator. Eight 2-inch diameter vertical injection wells, screened 5-25 feet were installed inside the facility. The remainng excvation was backfilled and the floor slab was poured.

Other technologies used:
passive venting

Next Steps:
An additional injection of a long-lived carbon amendment under the facility floor slab is planned.