Technology:
Phytoremediation
- In December 1996, 118 hybrid poplar trees were planted 9 ft bgs in a plot approximately one-third of an acre in size; in addition, some trees were planted along the boundary of the site at 3 ft bgs (shallow rooted) to minimize groundwater and rainwater infiltration from off-site
- The trees were planted 10 ft apart on the north to south axis and 12.5 ft apart on the east-west axis
- Site maintenance involves fertilization, and control of insects, deer and unwanted vegetation
- Over 40 direct push microwells were installed to monitor groundwater
|
Cleanup Authority:
Not identified
Contacts:
George Prince
U.S. EPA, ERT (MS101)
2890 Woodbridge Avenue
Edison, NJ 08837-3679
Tel: 732-321-6649
Fax: 732-321-6724
E-mail: prince.george@epa.gov |
Contaminants:
Chlorinated Solvents and Xylene
- Maximum concentrations in groundwater – dichloromethane (490,000 ppb), PCE (160 ppb), TCE (390 ppb),trimethylbenzene (TMB) – (2,000 ppb),xylenes (2,700 ppb) |
Waste Source:
Leaking drums and containers |
Type/Quantity of Media Treated:
Groundwater
- Highly permeable sand layer from 0 to 5 ft bgs, underlain by a much less permeable layer of sand, silt, and clay from 5 to 18 ft bgs
- Most of the contamination is confined from 5 to 18 ft bgs |
Purpose/Significance of Application:
Long-term field demonstration of phytoremediation for treatment of chlorinated solvents in groundwater |
Regulatory Requirements/Cleanup Goals:
Provide hydraulic containment and removal of contaminants; no quantitative cleanup goals identified |
Results:
- Dichloromethane was reduced over the first 3 years of monitoring, with concentrations at 4 locations decreasing from 490,000 down to 615 ppb, 12,000 ppb to ND, 680 ppb to ND, and 420 to 1.2 ppb
- PCE was reduced at 1 location from 100 to 56 ppb
- TCE increased at 1 location from 9 to 35 ppb, but decreased at another location from 99 to 42 ppb; at other locations TCE remained stable over the 3 year period
- Trimethylbenzene was reduced from 147 to 2 ppb, 246 to ND, 1900 to 50 ppb, and 8 to 1 ppb at four microwell points in the treated area; at another well point within the treated area, concentrations of TMB were relatively unaffected, 102 ppb in August 1997 compared to 128 in August 1999
- Xylenes were unaffected or slightly increased at 1 location, 26 ppb in August 1997 compared to 34 ppb in August 1999; at two other locations, xylene concentrations dropped from 590 to 17 ppb, and from 56 to 1.4 ppb |
Cost Factors:
The total cost for installation was $105,000, consisting of $24,000 for site preparation, $65,700 for planting; and $15,300 for maintenance |
Description:
From the mid-1960s to the early 1990s, the Edward Sears property was used for the repackaging and sale of paints, adhesives, paint thinners, and various military surplus materials. The soil and groundwater were contaminated with a variety of contaminants, including dichloromethane, PCE, TCE, TMB, and xylenes. A demonstration of phytoremediation to clean up shallow groundwater was performed at the site was performed by the U.S. Air Force (USAF) as part of the Department of Defense's (DOD's) Environmental Security Technology Certification Program (ESTCP), and the SITE Program.
At the Edward Sears site, a process called deep rooting was used to achieve hydraulic influence. Hybrid poplar trees were planted in late 1996 at 9 ft bgs in a plot of one-third acre, with performance measured for 3 years (a fourth year of monitoring is planned). There were substantial reductions in dichloromethane and TMB concentrations during the 1998 growing season. For example, dichloromethane was reduced to 615 parts per billion (ppb) from 490,000 ppb at one location and to a non-detect level from up to 12,000 ppb at another location; TMB was reduced to 50 ppb from 1,900 at one location. There is also indication of anaerobic dechlorination in the root zone as the level of PCE dropped and TCE increased. The total cost for installation was $105,000, consisting of $24,000 for site preparation, $65,700 for planting; and $15,300 for maintenance. Groundwater monitoring will continue into 2002. |
