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AOC-58
Final
RCRA Facility Investigation Report
Section 1 - Introduction
On May 5,
1999 an Administrative Consent Order was issued to Camp Stanley Storage
Activity (CSSA) pursuant to §3008(h) of the Safe Drinking Water Act (SDWA),
as amended by Resource Conservation Recovery Act (RCRA), and further amended
by the Hazardous and Solid Waste Amendments (HSWA) of 1984.
In accordance with the RCRA Facility Investigation (RFI) requirements
of the Consent Order, this report has been prepared to document the
environmental condition of Area of Concern-58 (AOC-58) and to recommend
further investigation, if necessary, or to provide documentation necessary for
site closure. The main objectives
of the AOC-58 investigation are to determine if the site meets Texas
Commission on Environmental Quality (TCEQ) requirements for closure, as
described in Section 1.4, and to meet requirements of the 3008(h)
Administrative Consent Order.
This
specific RFI was performed by Parsons under the U.S. Air Force Air Mobility
Command (AMC) Contract F11623-94-D-0024, Delivery Order RL83.
The Air Force Center for Environmental Excellence (AFCEE) provided
technical oversight for the delivery order.
Based upon the project statement of work (SOW), a set of work plans to
govern the fieldwork were established.
These
include:
For this RFI report, Section 1 provides the site-specific background and closure
standard. Section 2 describes
field actions and the closure evaluation.
Section 3 summarizes the findings, evaluates the attainment of data
quality objectives (DQOs), provides recommendations, and certifies the site
closure, if applicable. References
cited in this report can be found in the
Bibliography
(Volume 1-1 of the Environmental Encyclopedia).
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.
AOC-58 is
a suspected disposal trench located within the inner cantonment of CSSA (Figure
AOC58-1). An
approximately 0.2 acre area appeared to be disturbed in a 1973 aerial
photograph. The 1966 and 1986
aerial photographs do not show disturbance in this area.
The site is mostly level and covered with sparse vegetation and a thin
soil profile. Oak trees surround
the site. Except for cattle and
wildlife grazing, no other activities currently take place at AOC-58.
There are no utilities or roads at AOC-58.
Background information regarding the location, size, and known
historical use of the site is included in the Environmental Encyclopedia
(Volume
1-3, AOC-58). Volume 1-3
also includes a
Chronology
of Actions and the
Site-Specific
Work Plan Addendum for AOC-58.
The
potential source of contamination at AOC-58 is buried waste.
Unfortunately, there are no records available regarding 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 is considered to be the
most likely waste type at AOC 58, if indeed there is a landfill trench located
there. No unexploded ordnance has been found at AOC-58.
Although
liquid chemical wastes were known to be disposed at the oxidation pond (O-1),
it is possible that some paints, solvents, or fuels may also have been
disposed at AOC-58.
AOC-58 is
a 0.2-acre tract that is located near the approximate center of CSSA, in the
northeastern portion of the inner cantonment area
(Figure
AOC58-1). The general
shape of the site is approximately 250 feet long (north-south) by 100 feet
wide (east-west). The AOC is
approximately one mile west of the nearest facility boundary and is
immediately west and southwest of monitoring well CS-MW2.
The physical boundaries of AOC-58 are identified by AOC-42 to the west
and northwest, monitoring well CS-MW2 to the northeast, and trees to the
north, east, and south (Figure AOC58-1).
AOC-58
lies at the eastern edge of the Salado Creek valley
(Figure
AOC58-2). The elevation
of the site is approximately 1,210 to 1,220 feet above sea level, sloping
gently to the northwest. Surface
water runoff from the site drains to the west and into Salado Creek.
During heavy rain events, AOC-58 is frequently flooded by waters
flowing southeasterly within Salado Creek.
The site is vegetated with native grasses, with surrounding oak trees.
At
AOC-58, Trinity and Frio soils cover the northwest portion of the site and
Tarrant Association (gently undulating) soils are found in the southeast
portion
(Figure
AOC58-2). Detailed
descriptions of the CSSA soil types are provided in the CSSA Environmental
Encyclopedia (Volume
1-1, Background Information Report, Soils and Geology).
Both soil types are typically clayey and gravelly loam and calcareous
clay, ranging in depth from 30 inches to 5 feet and are underlain by
limestone. While no descriptions
of subsurface conditions have been gathered at this site, it is assumed that
bedrock occurs within approximately five feet of the land surface as it does
at most of CSSA.
AOC-58 is
situated over the contact between the Upper and Lower Glen Rose Formations
(Figure
AOC58-3). While very
little bedrock is present at site (except for possibly within ephemeral
streams which dissect the site), the limestone bedrock unit does crop out at
elevations slightly above AOC-58 to the east and at other nearby SWMUs
including B-19, O-1, B-4, AOC-64, and Building 43.
Limestone bedrock also outcrops in the shallow Salado Creek bed
approximately 100 feet west of the site.
AOC-58 is
located just south of what has been referred to as the northern fault zone,
which trends to the northeast, and transects the central portion of CSSA
(Figure
AOC58-3). This fault
(shatter) zone has been mapped with a width between 2,000 to 3,000 feet, and
consists of multiple normal faults with small throws of displacement.
Numerous faults with small displacements have been located near the
site using mapping, seismic, and ground penetrating radar (GPR) techniques.
Vertical displacement between 5 to 30 feet has been reported
(Volume
1-1, Background Information Report, Soils and Geology),
with the downthrown blocks typically occurring on the southeast side of
the fault.
No
site-specific information regarding groundwater is available.
However, at nearby well CS-MW2, groundwater of the Trinity aquifer
typically occurs at a depth of approximately 250 feet.
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.
While no
descriptions of hydraulic conditions have been gathered at this site, it is
reasonable to assume that direct precipitation upon AOC-58 recharges the Lower
Glen Rose Limestone, which lies directly beneath the site.
The
nearest cultural resources are Building 43 and various warehouses and bunkers,
all historical structures that pre-date World War II.
Building 43 is located approximately 1,000 feet north of AOC-58.
The warehouses and bunkers are located approximately 600 feet west of
AOC-58 and World War I training trenches are located approximately 3,500 feet
south of the site.
Much
of the land within 0.25-mile of AOC-58 is evergreen forest land.
To the west and south of the site, land use is classified as
“commercial and services,” and includes two storage buildings on the east
side of H and I section. No water
supply wells are within a 0.25-mile radius of the site.
A human and ecological sensitive receptor survey has been conducted at
CSSA, and the results are presented in Section 3 of
Volume
1-6, Risk Assessment Technical Approach Document.
AOC-58 is
located at the western edge of a potential habitat for the Black-Capped Vireo,
which is a local endangered species (Volume
1-1, Background Information Report,
Figure
11, Biological Receptors).
The
nearest potential habitat for the Golden-Cheeked Warbler is approximately
4,000 feet east of AOC-58.
No
investigations were previously conducted at AOC-58.
A chronology of known actions/investigations at AOC-58 is located
behind the “AOC-58”
tab in both Volumes 1-3 and 3-2 of
the CSSA Environmental Encyclopedia.
As
described in
Section
4.3 of the Risk Assessment Technical Approach Document
(Volume 1-6), CSSA has opted to pursue closure of most sites under
the Risk Reduction Rule (30 Texas Administrative Code [TAC] 335).
If the site concentrations do not exceed background, then the site will
be closed using Risk Reduction Standard 1 (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
background, then closure under the Texas Risk Reduction Program (TRRP) will be
conducted.
A
notification of intent to close sites identified to date (including AOC-58) in
accordance with the Risk Reduction Rule was sent to the TCEQ on July 12, 1999.
Acceptance of this notification was sent by TCEQ on October 5, 1999.
RRS1
requires that the site is 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
TCEQ Executive Director, then the owner is released from the deed recordation
requirement.
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