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Scope of Services Provided:
Role: Prime Contractor to Owner
Date Started: August 1993
Terra Vac was selected in June 1993 for the design, installation and
operation of a remediation system at this large former manufacturing
complex in Southern California. Soil at this site has been impacted
by methyl ethyl ketone and trichloroethane from the ground surface to
the water table, approximately 50 feet below grade. The impacted soil
consists of high plasticity clays from ground surface to approximately
30 feet below grade. Much of the impacted area lies under an existing
building and 25,000 volt substation.
Terra Vac's approach to these difficult site conditions includes the
use of slant vapor extraction wells, medium and high vacuum vapor extraction
systems, and low and high pressure pneumatic soil fracturing systems.
The system consists of 135 well casings, 210 pneumatic soil fracturing
points, four separate piping manifold systems, automatic solenoid valve
control of all pneumatic soil fracture points, a 100 horsepower (Hp)
vapor extraction unit, a 40 Hp vapor extraction unit, a 60 Hp low pressure
air compressor, a 15 Hp high pressure air compressor, two water/vapor
separators, and a thermal oxidizer for vapor stream treatment.
The operations phase of this project is anticipated to last between
12 and 18 months.
Scope of Services Provided:
Role: Prime Contractor to Army Corps of Engineers
Date Completed: May 1993
Tank No. 2, a former waste solvent tank at the Sacramento Army Depot,
was excavated in 1986. Residual contamination in the soil of volatile
and semi-volatile organic compounds, primarily ethylbenzene and xylenes,
was quantified in a remedial investigation. Vacuum extraction was the
favored technology suggested in the Record of Decision to remediate
the vadose zone soils at this Superfund (CERCLA) site.
The design phase was completed in July 1992 and included an eight well
system to remediate 2-butanone, methyl ethyl ketone, Freon 113, perchloroethylene,
ethylbenzene and xylene. Semi-volatile solvent contamination (naphthalene
and pesticides) were also present, and the biologic degradation, enhanced
through the use of vacuum extraction (BIOVAC), was continuously monitored
with on-line sensors.
After 24 weeks of operation four confirmatory borings were drilled.
Thirteen of 14 soil samples collected document residual contamination
in the parts per billion range, meeting all requirements for closure
of this Superfund site. The closure report was submitted to the Environmental
Protection Agency and closure was granted in May 1993.
Scope of Services Provided:
- Dual Vacuum Extraction
- On-Site Gas Chromatograph
- Entrainment Extraction
- Design/Construct Full-scale Remediation
- OSHA-trained Personnel Piezometer Well Installation
- RCRA Site Closure Underground Well Installation
- Design/Construct Pilot Test
Role: Subcontractor to Consultant
Pilot Test: October to November 1991 (seven days operation)
Date Started: October 1991
Date Completed: June 1992
Terra Vac successfully completed remediation of a RCRA listed industrial
waste landfill. The project was under the general oversight of Burns
and McDonnell Waste Consultants in Overland Park, Kansas. The pilot
study and full scale remediation took place at the Ground Operations
Center of a major airline at its Kansas City International Airport facility.
The landfill was composed of fill (soil, slidge and debris) of variable
thickness overlying glacial till consisting of unsorted silty clays
admixed with sand, pebbles, cobbles, and boulders. The volatile organic
compounds of concern included unspecified fuels, paints, and chlorinated
solvents. Due to the presence of perched water at the glacial till/fill
material interface, Dual Vacuum Extraction (DVE) was utilized to recover
both vaporous contaminants and groundwater (by vacuum extrainment).
Pilot Study
For the pilot test, four DVE wells were drilled into a unique waste/fill
material with piezometer probes set to monitor radius of influence.
A mobile gas chromatograph (GC) with flame ionization detector (FID)
was used to quantify the VOC extraction rate. The vacuum influence extended
40 feet, and VOC recovery for the seven days of operations totaled 2,400
pounds. The rate dropped from 312 to 214 pounds per day while flow increased
from 181 CFM to 216 CFM during the 7-day pilot test. Three thousand
gallons (3,000 gal) of groundwater were recovered and treated on-site.
Full Scale Study
For the full-scale project, Terra Vac completed installation of 20 DVE
wells, covering an area of 30,000 square feet. The cleanup objective
was to remove 90% of an estimated theoretical mass which was calculated
to be 15,500 pounds. A total of 14,400 pounds of VOCs were removed in
a 6-month operation. Eight target compounds were reported and they included
acetone, benzne, trichloroethene, toluene, tetrachloroethene, clhlorobenzene,
ethylbenzene and xylenes.
Total operating time, including pilot operations, was 155 days. Initial
extraction rates for total VOCs were 750 pounds per day (lb/d). Within
three days the VOC extraction rates had declined to 350 lb/d.
Terra Vac removed 14,400 lbs of VOCs including 2,700 pounds of methane,
and 11,700 pounds of other VOCs. At shutdown, after 155 days, the daily
VOC extraction rated was 28 lb/d. After 155 days, VOC extraction rates
had been reduced by nearly 99%. The theoretical total mass of contamination
was reduced by 93%. Tetrachloroethene was reduced by 83%. Cleanup criteria
were met, and the State of Kansas granted closure.
Scope of Services Provided:
Role: Prime to Owner
Date Completed: May 1993
Terra Vac was contracted by a heavy equipment manufacturer to design,
install, and operate a pilot-scale vacuum extraction system (VES) to
determine the effectiveness of vacuum extraction (VE) for remediation
of several existing soil piles contaminated with perchloroethylene (PCE),
trichloroethylene (TCE), and 1,2-dichloroethylene (DCE). This action
was to be taken as part of a RCRA closure. The pilot study was conducted
in two phases to evaluate both VE and VE with hot air injection.
The pilot system consisted of a 300 cubic yard treatment cell, a VE
blower, an air/water separator tank, activated carbon, and an air injection
system. Each phase of the test lasted seven days. Approximately 20 pounds
of volatile organic compounds were removed over the 14 days of operation,
reducing the soil concentration by over 99% from 285 ppm to 0.4 ppm.
The pilot test proved the effectiveness of VE to remediate the soil
piles. Negotiations to finalize the full-scale remedial action plan
are currently underway with the regulatory agency.
Scope of Services Provided:
Role: Subcontractor to Consultant
Date Completed: September 1991
After completing the successful pilot program, Terra Vac was authorized
to design, install and operate four separate vacuum extraction systems
(VES) to remediate gasoline-contaminated soils at the Tampa International
Airport. Site constraints required Terra Vac to install wells under
the basement of a parking garage, sidewalks and access roads. The necessity
for placements of the wells within the active car rental facility also
required the construction of overhead piping in the parking garage.
In addition to the parking garage area, another below grade well system
was required at an existing underground storage tank farm. Terra Vac
worked with the general contractor to coordinate the removal of eight
tanks prior to installation of the VES.
The third area to be managed by Terra Vac involved two ex situ treatment
cells, each designed to hold 20,000 cubic yards (15,000 m3) of contaminated
soil. Each of the treatment cells required a cover to manage rainwater
infiltration and runoff during the project.
The full-scale system consisted of 60 vacuum extraction (VE) wells,
seven VE units and two catalytic oxidation units. Terra Vac successfully
treated approximately 100,000 cubic yards (75,000 m3) of gasoline-contaminated
soils over a nine-month operating period ending in September 1991. All
soils treated were cleaned to below detectable limits for benzene, toluene,
ethylbenzene, and xylene (BTEX) compounds, and Terra Vac met the requirements
of its 12-month performance-based contract.
This page and contents © Copyright 2001 by Terra Vac Corporation. ALL
RIGHTS RESERVED
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