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SWMU B-8
RCRA Facility Investigation
Report
Section 1 -
Introduction On
May 5, 1999 an Administrative consent order was issued to CSSA pursuant to §3008(h)
of the SWDA, as amended by RCRA, and further amended by HSWA of 1984.
In accordance with the RFI requirements of the consent order, this report
has been prepared to document the environmental condition of SWMU B-8 and to
recommend further investigation, if necessary, or to provide documentation
necessary for site closure. The
main objectives of the SWMU B-8 investigation are to determine if the site meets
TNRCC requirements for closure, as described in
Section
1.4, and to meet requirements of the consent order. This
specific RFI was performed by Parsons under the U.S. Air Force AMC Contract
F11623-94-D-0024, Delivery Orders RL17 and RL33.
AFCEE provided technical oversight for the delivery order.
Based on the project SOW, a set of work plans to govern the fieldwork
were established. These include: Work Plan Overview Site-Specific Work Plan Field Sampling Plan Health and Safety Plan . For
this RFI report, Section 1 provides the site-specific background and closure
standard. Section
2 describes field actions and closure evaluation.
Section 3 summarizes the findings,
evaluates the attainment of data quality objectives, provides recommendations,
and certifies the site closure, if applicable.
References cited in this report can be found in the CSSA Environmental
Encyclopedia (Volume
1-1, Bibliography). In
addition to the consent order requirement to conduct an RFI, interim measures
are also required to address SWMU B-8 soil that has been inspected to remove UXO.
The UXO removal activities are described in this report, but activities
related to the interim measures are addressed in the Soil Pile Disposition
Report, being prepared under a separate delivery order. General
information regarding the history and environmental setting of CSSA is provided
in the CSSA Environmental Encyclopedia
(Volume
1-1, Background Information Report).
In that report, data regarding the geology, hydrology, and physiography
are also available for reference.
SWMU B-8 is a former burn area and suspected disposal
trench located within the outer cantonment of CSSA (Figure B8-1) where fire bricks and
ammunition were reportedly disposed. An
approximately 0.5-acre area appeared to be disturbed in a 1966 aerial
photograph. The 1973 and 1986 aerial
photographs do not show disturbance in this area.
As described in Section 1.3,
a geophysical survey conducted at the site in 1995 indicated an electromagnetic
anomaly in the area.
The site is mostly level and covered with sparse vegetation
and a thin soil profile. Except for cattle and wildlife grazing, no other activities currently
take place at SWMU B-8. There are no
utilities at SWMU B-8; however, an overhead utility line trending
northeast-southwest and an abandoned underground 4-inch diameter pipe are
located just south of the site.
Figure 3.1
of the Technical Memorandum on
Geophysical Surveys shows the locations of these utility lines.
A gravel road leading into the western portion of the outer cantonment
from Gate 6 passes just to the northeast of SWMU B-8.
Background information regarding the location, size, and known historical
use of SWMU B-8 is also included in the Environmental Encyclopedia (Volume 1-2,
SWMU B-8).
Volume 1-2 also
includes a
Chronology of Actions and a
Site-Specific Work Plan Addendum
for SWMU B-8.
1.1.2.2 Potential Sources of Contamination
The
potential source of contamination at SWMU B-8 was considered to be residue of
burned waste at the ground surface and potentially buried waste, suspected of
consisting of fire bricks and ammunition. There
are no records available confirming possible waste disposed at the site.
Many types of waste potentially were disposed there.
Upon excavation, waste in other trenches at CSSA has been found to
consist chiefly of metallic debris; therefore, this was considered to be the
most likely waste type at SWMU B-8. Although
liquid chemical wastes were known to be disposed at the SWMU O-1, it is possible
that some paints, solvents, or fuels may also have been disposed at SWMU B-8.
Fuels may also have been used to ignite fires at the site.
SWMU
B-8 is located within the North Pasture area of the outer cantonment (Figure B8-1).
The SWMU is approximately one mile west of the nearest facility boundary.
Well CS-16, the nearest well to the site, is located about 1,000 feet to
the southwest. AOC 41 is located
approximately 100 feet south of the site, and a gravel road forms the northeast
boundary of the site.
1.2.1 Site Topography and Soils The
elevation of the site is approximately 1,260 feet above sea level (Figure
B8-2), and the ground surface slopes gently to the southwest.
Surface runoff from the site drains to the southwest via an unnamed
intermittent creek, which eventually drains to Salado Creek.
The site is relatively flat, and vegetated with native grasses. SWMU
B-8 lies entirely within the Krum Complex soils.
Detailed descriptions of the CSSA soil types are provided in the CSSA
Environmental Encyclopedia (Volume
1-1,
Background Information Report, Soils and
Geology). Most CSSA soils are
typically calcareous clay, ranging in depth from 4 to 60 inches and are
underlain by limestone. SWMU B-8
appears to be fairly typical, with silty clay observed to a depth of
approximately 6 feet bgs. The
Upper Glen Rose formation is the uppermost geologic strata in the area of SWMU
B-8 and in the north pasture (Figure
B8-3).
The Upper Glen Rose consists of beds of blue shale, limestone, and marly
limestone, with occasional gypsum beds. Generally,
it outcrops in stream valleys and at the ground surface where soils are poorly
developed or eroded. The thickness
of the Upper Glen Rose is estimated to be up to 150 feet at CSSA.
It is underlain by the Lower Glen Rose, which is estimated to be 300 feet
thick beneath CSSA. The Lower Glen Rose is a massive, fossiliferous, vuggy
limestone that grades upwards into thin beds of limestone, marl, and shale.
The Lower Glen Rose is underlain by the Bexar shale (regionally known as
the Hensell shale), which is estimated to be from 60 to 150 feet thick under the
CSSA area. The Bexar shale consists
of silty dolomite, marl, calcareous shale, and shaley limestone.
The geologic strata dip approximately 10 to 12 degrees to the
south-southeast at CSSA. Based
on current published information, there are known to be two major fault
(shatter) zones at CSSA: the North
Fault Zone and the South Fault Zone. SWMU B-8 is located north of both of these zones
(Figure
B8-3). Additional
information on structural geology at CSSA can be found in the Environmental
Encyclopedia (Volume
1-1,
Background Information Report, Soils and
Geology).
At
SWMU B-8, the near-surface site geology consists of 1.5 to 6 feet of surface
soils composed chiefly of silt and clay. Upper
Glen Rose Limestone was encountered at depths as shallow as 1.5 feet bgs.
At SWMU B-8, this limestone was pale yellow to pale brown, weathered near
the surface and marly. The
limestone was dry, hard, and for the most part, massive.
Allochemical constituents included pelecypods and bivalves, as well as
assorted shell fragments. Boring
logs are provided in Appendix A.
At
CSSA, the uppermost hydrogeologic layer is the unconfined Upper Trinity aquifer,
which consists of the Upper Glen Rose limestone.
Locally at CSSA, low-yielding perched zones of groundwater can exist in
the Upper Glen Rose; however, no perched groundwater was encountered in the SWMU
B-8 borings. Transmissivity values
are not available for the Upper Glen Rose.
Groundwater flow is thought to be enhanced along the bedding contacts
between marl and limestone; however, the hydraulic conductivity between beds is
thought to be poor. This
interpretation is based on the observation that static well levels are
discordant in adjacent wells completed at approximately the same elevation.
Principal development of solution channels is limited to evaporite layers
in the Upper Glen Rose limestone. Groundwater
discharge occurs predominantly via natural springs, seeps, and pumping.
Regional groundwater flow appears to be to the southeast. The
Middle Trinity aquifer is unconfined and functions as the primary source of
groundwater at CSSA. It consists of
the Lower Glen Rose limestone, the Bexar Shale, and the Cow Creek Limestone.
The Lower Glen Rose Limestone outcrops at CSSA along Cibolo Creek and
within the central and southwest portions of CSSA.
Principal recharge into the Middle Trinity aquifer is via precipitation
infiltration at outcrops. At CSSA,
the Bexar Shale is interpreted as a confining layer, except where it is
fractured and faulted, therefore allowing vertical flow from the up-dip Cow
Creek limestone into the overlying, but down-dip Lower Glen Rose.
Fractures and faults within the Bexar Shale may allow hydraulic
communication between the Lower Glen Rose and Cow Creek Limestones.
Groundwater flow within
the Middle Trinity aquifer is toward the south and southeast, and the average
transmissivity coefficient is 1,700 gpd/ft (Ashworth, 1983).
In general, groundwater at CSSA flows in a north to south direction.
However, local flow gradient may vary depending on rainfall, recharge,
and possibly well pumping. No
site-specific information regarding groundwater is available. Groundwater was not encountered at any borings drilled at
SWMU B-8, nor did any water accumulate in the open boreholes
prior to their abandonment. The
nearest well (Well CS-16), which is an inactive drinking water well, is located
approximately 1,000 feet southwest of SWMU B-8.
Water levels measured in Well CS-16 have ranged from 78.58 (November
1998) and 316.88 (April 1995) feet below top of casing (Volume
5, Introduction to Quarterly Monitoring Program, Table 3).
No
creeks, streams, or ponds are
located within SWMU B-8; however, a drainage channel that leads to Salado Creek
is located approximately 90 feet to the northwest of the site.
More information regarding surface water hydrology at CSSA is in the
Environmental Encyclopedia (Volume
1-1,
Background Information Report, Surface Water Resources).
Cultural
resources are prehistoric and historic sites, structures, districts, artifacts,
or any other physical evidence of human activity considered important to a
culture, subculture, or community for scientific, traditional, or religious
purposes. The nearest site of potential archeological significance is a
Salado Creek drainage channel, approximately 90 feet to the northwest of SWMU
B-8. This drainage channel has the
potential to be an area of high prehistoric archaeological potential.
A
land use survey discussing local and possible future uses of groundwater and
surface water, a water well survey, and sensitive environmental areas at CSSA
was completed during December 15 and 16, 1999 in accordance with the TNRCC TRRP.
The results of this survey, along with results from a more in-depth
survey to identify potential receptors, points of human exposure, and possible
constituent pathways are presented in Section
3 of
the Technical Approach Document for Risk Evaluation (Volume 1-6). Land
within 0.25 mile of SWMU B-8 is classified as “Evergreen Forest Land” in Figure
1.1 of
the Technical Approach Document for Risk Evaluation.
There are no buildings within 0.25 mile of the site, but there are two
inactive water supply wells (Wells 16 and D).
The nearest residential area is approximately 4,000 feet to the west of
SWMU B-8, and Fair Oaks Elementary School is over one mile from the site.
A
small herd of cattle maintained on CSSA by the USDA-ARC roam freely throughout
selected areas of the North Pasture. In
addition, wild game species, including white-tailed deer, axis deer, and wild
turkey, roam freely throughout CSSA. A
map of deer hunting stands which overlook mechanical feeders and planted food
plots is shown in Figure 5.2 of the Technical Approach Document for Risk Evaluation.
SWMU B-8 is located within an area where shotgun hunting is allowed, and
other hunting is allowed in the surrounding area.
The closest deer blind (#34) is approximately 1,500 feet northeast of
SWMU B-8. The
nearest potential habitats for local endangered species
(Volume
1-1, Background Information Report, Figure 11) are 600 feet to the
northwest (Black-Capped Vireo) and 1,800 feet to the north (Golden-Cheeked
Warbler). On
February 27 and 28, 1995, an EM survey was performed using a Geonics EM-31
instrument along north-south transects spaced at 25-foot intervals at SWMU B-8.
The dimensions of the surveyed area were 350 feet long by 250 feet wide.
The EM conductivity and in-phase contour maps are shown on
Figure
3.2 and
Figure 3.3 of the Technical Memorandum on Geophysical Surveys (Parsons
ES, 1995c).
An EM anomaly was detected to the southwest of the site.
However, this anomaly is associated with an abandoned underground 4-inch
diameter pipe trending northeast-southwest.
This metal pipe continues southwest of the site toward Well 16.
The pipe is broken and exposed in certain places outside the surveyed
area. One
anomaly suspected of being associated with past waste management activities was
identified at the site. This anomaly, identified as “A” on
Figure
3.4 of the Technical
Memorandum on Geophysical Surveys, is more pronounced on the in-phase
contour map, and therefore, is suspected of being associated with buried metal
debris. At the time of the survey,
there was no metal debris at the burn area's ground surface that may have caused
electromagnetic interference.
No
other previous environmental investigations have been performed at this site. As
described in Section
4.3 of
the Risk Assessment Technical Approach
Document (Volume 1-6), CSSA
has opted to pursue closure of SWMU B-8 under the Risk Reduction Rule (30 TAC §335).
If the site concentrations do not exceed background, then the site will
be closed using RRS1. If the site
exceeds background, then a determination will be made regarding the feasibility
of cleaning the site to meet background concentrations.
If the decision is made to clean the site to background, closure under
RRS1 will be sought. However, if it
is determined that the site cannot be closed to meet background concentrations,
then the site will be closed under TRRP. A
notification of intent to close sites identified to date (including SWMU B-8) in
accordance with the former RRR was sent to the TNRCC on July 12, 1999.
Acceptance of this notification was received on October 5, 1999. RRS1
requires that the site be closed following removal or decontamination of waste,
waste residues, and contaminated operation system components; and demonstration
of attainment of cleanup levels (30 TAC §335.554).
If closure requirements under RRS1 are attained and approved by the TNRCC
Executive Director, then the owner is released from the deed recordation
requirement.
Since
the COPCs for SWMU B-8 are VOCs, explosives, and metals, the cleanup levels
should be the RLs for VOCs and explosives, and the background levels for metals.
Chlorinated VOCs and explosives are man-made chemicals, and rarely occur
naturally. Background metals levels
were statistically calculated for soil and the Glen Rose Limestone, and are
reported in the Second
Revision to the Evaluation of Background Metals Concentrations in Soils and
Bedrock (Parsons ES, February 2002).
1.2 -
Site Environmental Setting