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SWMU B-9
Final RCRA Facility Investigation/Closure 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 and Recovery Act (RCRA), and further
amended by Hazardous and Solid Waste Act (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 and site closure requirements of Solid Waste
Management Unit (SWMU) B-9 and to recommend further investigation, if
necessary, or to provide documentation necessary for site closure.
The primary objective of the SWMU B-9 investigation is to determine if
the site meets Texas Commission on Environmental Quality (TCEQ, formerly Texas
Natural Resource Conservation Commission [TNRCC]) requirements for closure, as
described in Section 1.4, and to meet the requirements of the 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 Orders (DOs) RL17
and RL53, and Air Education and Training Command (AETC) Contract F41689-96-D-0710,
DO 5068. Air Force Center for
Environmental Excellence (AFCEE) provided technical oversight for the DOs.
Based upon the project Statement of Work (SOW), a set of work plans was
established to govern the fieldwork.
These
include:
For this report, Section 1 provides the site-specific
background, environmental setting, description of previous site
investigations, and closure standard.
Section
2 describes field actions and the closure evaluations.
Section 3 summarizes the findings, evaluates 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, 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.
Based on historical records, SWMU B-9 was used to dispose of miscellaneous
solid waste material. SWMU B-9
covers approximately 0.25-acres and is approximately 150 feet long
(northeast-southwest) by 50 feet wide (northwest-southeast).
The site is covered with rocks and native vegetation.
The only evidence of contamination observed during the investigation
was a minor amount of small metal fragments found on the ground surface at the
site. No activities are currently
conducted at SWMU B-9. Background
information regarding the location, size, and known historical use of the site
is also included in the Environmental Encyclopedia
(Volume 1-2, SWMU B-9).
Volume 1-2
includes a
Chronology of Actions
and a Site-Specific Work Plan Addendum
for SWMU B-9.
Historical records review indicates that SWMU B-9 was used as a disposal area
for miscellaneous solid waste (metal debris) (Parsons ES, 1993b).
Exact dates of this use of the site are unknown.
Possible contamination includes metal debris from the solid metal waste
(metals), explosive residue from unexploded ordnance (UXO), and volatile and
semivolatile organic compounds (VOCs and SVOCs) contamination from the
possibility of solvent disposal and trash burning.
SWMU B-9 is a 0.25-acre tract that is located in the southern portion of the
east pasture (Volume 1-2, Site Location
Map). The SWMU is
approximately 900 feet from the nearest facility boundary to the south.
The site is located within Area of Concern (AOC)-51 and immediately
south of AOC-44. SWMU B-9 and the
land immediately surrounding it are undeveloped
(Figure
B9-1).
Soils present at SWMU B-9 are classified as Brackett Soils. Brackett Soils occur on over 12.8 percent of CSSA lands.
The soils cover a large portion of the East Pasture and the Inner
Cantonment at CSSA. These soils
occur on slopes of 12 to 30 percent, such as those found on Steele, McFarland,
and Schasse Hills, as well as Taylor Ridge.
These loamy and clayey soils are very shallow (about four inches
thick), grayish-brown, and strongly calcareous.
Lying within and on the surface layer are gravel and cobblestones up to
six inches in diameter. The soils develop over soft limestone and are underlain by
hard limestone. The hills
associated with Brackett soils are steep, cone-shaped hills with saddles
between them. The soils are
nonarable and best suited to native grasses (United States Department of
Agriculture [USDA], 1991). Detailed
descriptions of the CSSA soil types are provided in the CSSA Environmental
Encyclopedia (Volume 1-1, Background
Information Report, Soils and Geology).
Bedrock outcrops at the surface throughout SWMU B-9 and the remainder
of the surface is covered by a very thin soil profile (approximately 0.5
feet).
SWMU B-9 lies just northwest of an area with steep topographic relief in the
extreme southeastern portion of CSSA (Figure
B9-2). The elevation of the
site is approximately 1,220 feet above sea level, sloping (eight percent
grade) to the northwest. The site
is approximately 250 feet southwest of a small valley that dissects the
steeper relief.
The Upper Glen Rose is the uppermost geologic stratum in the area of SWMU B-9
and the East Pasture (Figure B9-3).
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.
Where present at CSSA, the thickness of the Upper Glen Rose varies up
to 150 feet in thickness. 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
upward into thin beds of limestone, marl, and shale.
The Lower Glen Rose is underlain by the Bexar Shale facies of the
Hensell Sand, which is estimated to be approximately 60 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 two known major fault
(shatter) zones at CSSA: the North Fault Zone and the South Fault Zone.
SWMU B-9 is located south of both the North and South Fault Zones.
Additional information on structural geology at CSSA can be found in
the Environmental Encyclopedia (Volume 1-1, Background Information Report, Soils and
Geology). Boring
logs from the soil borings drilled in March 2000 indicate that limestone was
encountered at shallow depths below SWMU B-9, averaging 0.5 foot below ground
surface (bgs).
In general, the uppermost hydrologic layer at CSSA 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. Transmissivity
values are not available for the Upper Glen Rose. Regionally, 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 of differing
static water levels in adjacent wells completed in different beds.
Principle development of solution channels is limited to evaporite
layers in the Upper Glen Rose Limestone.
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 Middle
Trinity aquifer is separated from the lower Trinity Aquifer by the Hammett
Shale, which is an aquitard and is not considered to be part of either the
Middle or Lower Trinity Aquifer. The
Lower Glen Rose Limestone outcrops north of CSSA along Cibolo Creek and within
drainage ways located in the central and southwest portions of CSSA.
As such, principle 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. 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 gallons per
day per foot (gpd/ft) (Ashworth, 1983). In general, groundwater at CSSA flows in a north to south
direction. However, local flow
gradients may vary depending on rainfall, recharge, and possibly well pumping.
No
site–specific information regarding groundwater is available. However, the nearest well, Well CS-1, which is an active
drinking water supply well, is located approximately 2,300 feet southeast of
SWMU B-9. Between January 1997
and March 2000, static water levels have ranged from approximately 101 to 262
feet below top of casing.
The nearest surface water feature, located 550 feet to the northwest, is a
man-made intermittent tributary of Salado Creek.
The tributary trends northwest-southwest along the southern flank of
East Pasture firing range berm and intersects the main stream of Salado Creek
approximately 2,500 feet southwest of the site (Figure B9-1).
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. Cultural
resources are located within the site area of SWMU B-9.
The cultural resource consists of World War I trenches and foxholes.
The trenches surround the site on the north and northeast side.
The foxholes are located along the ridgeline just to the
south-southeast of the site.
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 on December 15 and 16, 1999.
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 is presented in
Section
3 of the
Technical
Approach Document for Risk Evaluation (Volume 1-6).
A small herd of cattle is maintained on CSSA by the USDA-ARC. The cattle roam freely in selected areas of the North
Pasture. CSSA also manages wild
game species for the purpose of hunting.
White-tailed deer, axis deer, and wild turkey all roam freely
throughout CSSA. A map of deer
hunting stands, which overlook mechanical feeders and planted food plots, is
located in
Figure 5.2 of the
Technical Approach Document for
Risk Evaluation (Volume 1-6).
In addition to managed wild game species, migratory birds, fowl, and
indigenous small game are also hunted in designated areas.
SWMU B-9 is located approximately 200 feet south of hunting stand
number 45. Four water tanks are
maintained at CSSA for the purpose of sport fishing.
Two of the tanks are located in the northwestern and northeastern
portions of the North Pasture while the other two tanks are located near the
western boundary of the Inner Cantonment.
Within CSSA, there is a full-time work force of approximately 100 persons
working in shops and office buildings. Personnel
also work outdoors throughout the facility to perform activities such as road
and fence maintenance, brush clearing, and security patrols. Approximately 25 people, including children, occupy seven
residences on the CSSA facility.
SWMU B-9 is located within the local endangered species habitat of the
Golden-cheeked Warbler. Another
potential habitat for the local endangered species of the Black-capped Vireo
is located approximately 600 feet north-northwest of the site
(Volume
1-1, Background Information Report, Figure 11). The vegetation at the site consists of native grasses and
scattered oak trees.
No previous investigations have been performed at SWMU B-9.
The site was identified during the 1993 Environmental Assessment.
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-9 under the Risk
Reduction Rule (RRR) (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 meet background
concentrations, then the site will be closed under Texas Risk Reduction
Program (TRRP). A notification of
intent to close sites identified to date (including B-9) in accordance with
the former RRR was sent to the TNRCC on July 12, 1999.
TNRCC 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 contaminants of concern (COCs) for SWMU B-9 are VOCs, SVOCs, metals,
and explosives the RRS1 standards should be the reporting limits (RLs) for
VOCs, SVOCs, and explosives, and the soil or rock background values for
metals. Background metals levels were statistically calculated for
CSSA soils and the Glen Rose Limestone, and are reported in the
Second Revision to the
Evaluation
of Background Metals Concentrations in Soil Types (Parsons, February
2002). TNRCC approved the
background evaluation on April 23, 2002.
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