Environmental Engineering Reference
In-Depth Information
conducted in addition to and in support of the pilot test of the SERB tech-
nology. The subobjectives of the effort were as follows:
•
Identification and development of molecular probes for the detection
of known PCE-dechlorinating organisms
•
Molecular analysis of PCE-dechlorinating communities and isolates
•
Enrichment of PCE-dechlorinating bacteria in materials from con-
taminated field sites
•
Testing of molecular probes for detection of chloroethene-dehaloge-
nating communities in site materials
•
Testing of molecular probes for detection of chloroethene-dehaloge-
nating communities in Sages/Jacksonville site material
•
Evaluating potential for ethanol for toxicity to native microorganisms
5.3.2 Field process and site evaluation
5.3.2.1 Site description
The study was conducted at a former dry cleaner site in Jacksonville, FL,
that was operational from 1968 to 1973 and from 1979 to 1989 and is currently
abandoned. Prior to this, a gasoline service station was operated on the site
from 1953 until the mid- to late-1960s. Although the PCE release history is
unknown, dry-cleaning fluids were not stored on site and were replenished
by a delivery truck where occasional releases occurred. A former floor drain
sump was also used to collect drainage from the floor near the dry-cleaning
machine, and high subsurface PCE concentrations were found in this area.
Suspected sources of PCE contamination included the sump area, the area
outside the back door of the building, where filter tubes were washed with
PCE, and the area where a waste oil tank was removed that may have been
used for both service station activities (parts cleaning) and dry-cleaning
waste. The sump area was targeted for the cosolvent flushing pilot test
(Figure 5.4).
5.3.2.2 Site/source zone characterization
The subsurface site materials consisted primarily of fine-grained sands with
a discontinuous clay layer at approximately 10.7 m below ground surface
(bgs). The water table ranged from 2 to 2.6 m bgs during the 2
1
/
2
years of
groundwater monitoring. The natural hydraulic gradient during this time
ranged from 0.0025 to 0.006.
High PCE concentrations were measured at locations in the sump area
over a vertical interval of 7.9 to 9.6 m bgs. A high-frequency subsampling
technique determined the PCE in this area to be in thin layers (5 to 8 cm
thick) that were not necessarily continuous over the extent of the source area
(Jawitz et al., 2000).
Initial concentrations of PCE in groundwater from wells in the targeted
area ranged from 42 to 90 mg/l. More detailed characterization data can be
