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Soils: Trinity and Frio soils (frequently flooded).
Known: The site is located south of SWMU B-19, B-28,
and AOC 62, and west of SWMU B-4, near Salado Creek. The site is approximately 2 acres in size.
Previous
Investigations (Updated February 2001): Under Order 67, records were reviewed at CSSA
during a preliminary evaluation for groundwater investigation. A preliminary geophysical survey was
conducted in May 1995 at all the “open” areas within a 2,000-foot radius of
Well 16. The four anomalies were
discovered and labeled A through D.
Anomaly A may be associated with the trash pile present in the same area
and is designated as AOC 62. Anomaly B
is a trench designated as AOC 52.
Anomalies C and D may be additional trenches and are designated as AOC
42. The geophysical effort did not
delineate the southern extents of anomalies C and D.
In June and July 1995, fourteen soil
gas survey samples were collected, and an additional 19 follow-up samples were
collected and analyzed for chlorinated and aromatic volatile organics. PCE was detected in
this area (0.19 ug/L was the highest concentration
detected).
A November
1999 geophysical survey extended the original survey conducted
in May 1995 to fully delineate the geophysical anomalies detected. A total of six anomalies were
detected over the 3.7-acre survey area. Four anomalies were
consistent with trench-type disposal units, while the remaining two anomalies
were isolated occurrences.
Data
Needs
(Updated February 2001): Geophysical survey and analytical data (VOCs,
explosives, and metals) for subsurface soils.
Rationale
for Analytical Program (Updated
February 2001): Based on a prior geophysical survey at the
site and the proximity to several SWMUs, chemicals of potential concern include
VOCs,
explosives, and metals.
Metals (arsenic, barium, cadmium, chromium, copper, lead, mercury,
nickel and zinc) are included due to the potential metallic nature of waste
that may be buried there. VOCs analysis
is included in the analytical program to detect typical contaminants associated
with a disposal area. SVOCs and
explosives are not included at this site since no evidence of ammunition, UXO,
or waste burning has been found.Explosive analyses have been
included with the August 2000 SOW amendment because of the strong metallic
signature detected in the disposal units.
Original
Scope of Work (May 2000)Closure
Activities: The
following activities constitute an additional investigation of AOC 42. This work will be completed as part of the
requirements under the RCRA 3008(h) Order under AETC delivery order 5068.
1. Remove
any vegetation necessary to complete field activities listed below. If any potential UXO is observed during field
activities, work will cease until UXO specialists are brought on site to
identify and remove UXO.
3. 2.
Conduct a geophysical survey, as
described in Section 2.4.1 of the Work Plan Overview, of the mapped site to
identify and delineate known anomalies.
The scoped geophyscial survey will extend
south beyond the original May 1995 survey.
A ground penetrating radar (GPR) device and an
EM-31 instrument will be used to complete the geophysical survey. The approximate locations of the survey
points are shown on Figure AOC42-1. The
locations of four of the corners of the survey points will be recorded using a
GPS unit. Analysis of the EM data will
follow field activities.
5. 3.
If the survey information indicates
an anomaly is present, complete 5 soil borings to characterize the subsurface
surrounding the anomaly. Two soil
samples will be collected from each boring.
The total depth of each boring will be approximately 10 feet. Each sample will be analyzed for VOC and
metals. QA/QC samples will be collected
as described in Section 2.4 of the FSP.
6. 4.
If the geophysical survey does not
identify subsurface anomalies, the funding for the soil borings may be replaced
with surface samples to satisfy closure criteria with significant cost savings
to CSSA. A modification by the AETC
contracting officer will be required to change the basic statement of work
(SOW). Until such a modification is in
effect, no change to the pre-defined scope of work may be directed.
8. 5.
IDW will be handled as specified in
the FSP.
9. 6.
If the results of the above work
indicate that the site can be closed under RRS1 without any further
investigation and/or remediation, a technical/closure report will be prepared
and submitted in accordance with TNRCC closure requirements. If the site does
not meet RRS1 requirements, a technical report describing the results of the
investigation and recommended additional investigation and/or remediation will
be prepared.
Figure AOC 42-1 (Use Existing
Figure)
Revised Scope of Work: (August 2000): The November 1999 geophysical
survey detected six electromagnetic anomalies with a strong metallic
signature. Because there is a potential
for UXO, the remainder of the investigation will proceed with conservative
caution. The SOW was revised on August 2, 2000, and is
reflected in this version of the work plan.
1. Remove any
vegetation necessary to complete field activities listed below. A UXO subcontractor will assist in directing the
fieldwork, and will be responsible for clearing the work site as safe. If any potential UXO is observed during field
activities, work will cease until UXO specialists are brought on site to remove
the UXO.
2.
Since the geophysical
survey information indicates anomalies are present, complete 9 soil borings to characterize
the subsurface surrounding the anomalies as shown in Figure AOC42-2. Three soil samples will be collected from
each boring. The total depth of each
boring will be approximately 15 feet.
Each sample will be analyzed for VOC, explosives, and metals.
QA/QC samples will be collected as described in Section 2.4 of the FSP.
3.
IDW will be handled as specified in the FSP.
2.
A technical report to document the findings of the investigation will be prepared and submitted in accordance with
TNRCC closure requirements. If the site does not meet RRS1 requirements, a
technical report describing the results of the investigation and recommended
additional investigation and/or remediation will be prepared. (The overall objective is to collect
sufficient data to determine if the site can be closed; and if possible, to
close it. Initially, RRS1 for the
closure will be used. If closure to RRS1
is not viable, then the data will be compared to TRRPS for an acceptable
closure. Clean closures using RRS1
standards will be obtained whenever technically and economically possible.)
Figure AOC 42-2