Remediation Status: In groundwater monitoring

Why the technology was selected:
Although soil sampling found minimal contamination during the site assessment work conducted in 2006, an active soil gas survey (Modified Active Gas Sampling - MAGS) was conducted and soil gas samples collected had PCE concentrations as high as 17.2 mg/cubic meter, indicating sufficient PCE was still present in the unsaturated zone to continue to act as an ongoing source for groundwater contamination. Since the soil was permeable (fine to fine-grained sand) and was capped by the asphalt parking lot and the water table was relatively deep for a Jacksonville site, the decision was made to install a soil vapor extraction system to address contaminated soil at the site. Biostimuation using ChitoRem was chosen as the groundwater remedy because anerobic conditions existed in groundwater and PCE daughter products were present. ChitoRem SC-20 is a chitin complex. It has been described as a food grade biopolymer. It is composed of crushed crab shell material (< 1 mm in nominal size). It has an approximate composition of 20% chitin, 40% chitin-bound calcium carbonate, 30% protein and less than 9% nitrogen.

Date implemented:
Soil Vapor Extraction: September 24, 2009.

Date completed:
October 27, 2011. SVE system operated for 25 months.

Final remediation design:
The soil vapor extraction system consists of eleven (11) vertical vapor extraction wells constructed of 4-inch Schedule 40 PVC. The wells were screened from 1-4 ft BLS. The system is powered by a 7.5 HP blower. Off gas is treated via a 170-lb. G.A.C. vessel. The system design flow rate is 196 scfm with an applied vacuum of 20 inches w.c.

Cost to Design and Implement:
All technologies: Design: $10,500
Implementation: $102,300

Why the technology was selected:
Biostimuation using ChitoRem was chosen as the groundwater remedy because anerobic conditions existed in groundwater and PCE daughter products were present. ChitoRem SC-20 is a chitin complex. It has been described as a food grade biopolymer. It is composed of crushed crab shell material (< 1 mm in nominal size). It has an approximate composition of 20% chitin, 40% chitin-bound calcium carbonate, 30% protein and less than 9% nitrogen.

Date implemented:
Biostimulation (ChitoRem): September 2009.

Final remediation design:
ChitoRem SC-20 was emplaced in four 3-foot diameter boreholes drilled with a large diameter hollow stem auger. Three of these boreholes were drilled to a depth of 8 ft BLS. Amendment distribution wells, 6-inches in diamter, with 3 feet of 0.01-inch slot screen (formed in an L-shaped joint in the bottom of the auger hole) were installed in the bottom of the boreholes. The boreholes were backfilled with a mixture of #57 limestone and ChitoRem to approximatley one foot above the water table. Approximatley 25 pounds of ChitoRem was emplaced in each of the three distribution wells. Another 3 foot diamter borehole was drilled to 11 ft BLS and two 6-inch diameter amendment distribution wells were installed in the borehole with 7 foot of 0.01-inch slot screens installed slanted in the borehole. Approximatley 25 pounds of ChitRem was emplaced in each of these amendment distribution wells. The bottom 5.5 feet of this borehole was backfilled with a mixture of #57 limestone and ChitoRem. A total of 250 pounds of ChitoRem was used at the site.

Results to date:
The latest groundwater monitoring event was conducted in March 2012. Two monitor wells produced groundwater samples with contaminant concentrations exceeding MCLs: MW001 - 5.8 ug/L PCE; MW002 - 14 ug/L PCE, 21 ug/l TCE, 27 ug/l cis 1,2-DCE.

Next Steps:
Continue monitored natural attenuation.

Cost to Design and Implement:
All technologies: Design: $10,500
Implementation: $102,300