[Home]

[Closure Plan]

Partial Facility Closure Plan for
B-20 Detonation Area
March 1994

Section 2
Site History and Background

2.1  Installation Description and History

CSSA is located in northwestern Bexar County, about 19 miles northwest of downtown San Antonio (Figure 2.1).  The land on which CSSA is located was used for ranching and agriculture until the 1900s (Army, 1990).  During 1906 and 1907, six tracts of land were purchased by the U.S. Government and designated the Leon Springs Military Reservation.  The lands included campgrounds and calvary shelters.

In October 1917, the installation was redesignated Camp Stanley.  U.S. involvement in World War I spurred extensive construction to provide housing for temporary cantonments and installation support facilities.  In 1931, Camp Stanley was selected as an ammunition depot, and construction of standard magazines and igloo magazines began in 1938 (Army, 1990).  Camp Stanley was transferred to the jurisdiction of the Red River Army Depot (RRAD) in 1947.  In addition to ammunition storage, CSSA lands were used to test, fire, and overhaul ammunition components.

CSSA currently occupies about 4,000 acres and is a restricted-access installation with inner cantonment lands to the southwest and outer cantonment areas to the east and north.  The primary mission of CSSA is receipt, storage, issue, and maintenance of ordnance materiels (Army, 1971).  CSSA also has an agreement for cattle grazing with the USDA Agricultural Research Service, and limited wildlife hunting is allowed.  No changes to the CSSA mission and military activities are expected in the future.

2.2  B-20 Unit Description

The B-20 unit is a 27.5-acre field surrounded by wooded areas in the northeastern portion of CSSA (Figure 2.2).  The area is vegetated with grasses and cedar shrubs.  Gravel roads are adjacent to the unit to the south, west, and north.  Site boundaries and other features are shown in Figure 2.3, with quadrants drawn by CSSA and RRAD to help delineate areas of interest.

Physiography of the site is influenced by native topography, the underlying geology, and explosive demolition activities at the site.  Site topography is cratered as a result of demolition operations.  In general, elevations on the U.S. 7.5-minute Camp Bullis topographic quadrangle map range from 1,360 feet aove mean sea level (MSL) at the western boundary (a gravel road), to about 1,300 feet MSL at the eastern boundary (Figure 2.2).  The individual craters vary in depth from 1 to 6 feet below the tops of crater walls.

Drainage is generally to the northeast in two runoff channels (Figure 2.3).  The larger channel begins in quadrant H just north of the gravel road at the southern site border, drains into a tiny pond, and continues northeast to the livestock pond.  The smaller channel begins at the east boundary of quadrant H near the north end of the cedar trees and runs northeast along the eastern site boundary until it branches into the larger channel.  A map symbol for the smaller channel is marked by the eastern site boundary on the site figures.  Both channels are ephemeral, and the ponds tend to dry during periods of little to no precipitation.  Due to areal topography with higher elevations north, west, and south of the site, these two channels receive all site runoff.

The B-20 site and surrounding area are situated on the upper member of the Cretaceous-age Glen Rose Formation (ES, 1993a).  The Upper Glen Rose consists of alternating beds of blue shale, limestone, and marly limestone with occasional gypsum beds (Hammond, 1984).  Based on well logs of the area, thickness of the limestone is up to 300 feet in Bexar County, but may be only 20 to 50 feet thick in the area of the site.  The upper member is underlain by the lower member of the Glen Rose, which is a massive, fossiliferous limestone grading upward into thin beds of limestone, marl, and shale (Ashworth, 1983).  Erosion of the alternating resistant and nonresistant beds causes the "stairstep" topography of the region.  Structurally, the site is about 6 miles north and west of the Balcones fault zone.  Based on topographic delineation of lineaments, a possible fault or fracture may trend northeast-southwest about 200 to 300 feet southeast of B-20 (Watterus, 1992), but field investigation has not confirmed this fracture.

Soil types at B-20 and the surrounding area are Brackett-Tarrant association, Crawford and Bexar stony, and Krum Complex (USDA, 1966).  Brackett-Tarrant association soils are formed on hills in the west-central and northern portions of the site and are grayish-brown, gravelly clay loam.  Crawford and Bexar stony soils occur in the north-central and central portions on broad, level to gently undulating areas.  The Crawford type soils are dark gray to reddish brown, noncalcareous stony clay, while the Bexar soils range from cherty clay loam to gravelly loam.  The Krum Complex soils are in infrequently flooded streambeds such as those in the eastern and northeastern areas of B-20.  The soil is dark grayish-brown, calcareous, and is found on "foot" slopes below Tarrant and Brackett soils.  Further delineation of these soil types can be found in the "Environmental Assessment Report for Camp Stanley Storage Activity" (ES, 1993b).

The depth to groundwater  below B-20 is unknown.  However, depth to water in CSSA well I, located about 500 feet northeast of the northern site boundary, was 206 feet BGL in October 1992 (ES, 1993a).  Hydrogeologically, the upper Glen Rose can yield small amounts of mineralized water from lateral flow along bedding planes between limestone and marl, and the lower Glen Rose normally yields small to moderate amounts of drinkable water from solution-enhanced permeable fractures (Ashworth, 1983).

B-20 site features include an inactive bunker west of the western gravel raod, a standpipe used once for static firing of a rocket motor and a junction box in quadrant B.  Broken aboveground conduit to the southeast (quadrants B, G, H and I) are currently visible at the site (Figure 2.3).  Fifteen craters have been identified, as well as five soil mounds in quadrant H.  The mounds are soil from the B-20 site that was piled for ready use

2.3  Unit History

Detonation operations at the B-20 area were recorded form 1981 to 1987.  The initiation date of detonation activities was not recorded, but may have been in the 1950s or 1960s.  The exact date of the first demolition operation was not recorded in CSSA records, and interviews with CSSA personnel indicated that no one at CSSA in the 1950s or 1960s still works there.  The operations included detonation of conventional explosive ordnance and other arms, static firing of one rocket motor nose down using the existing standpipe, disposal of scrap metal from detonation activities, and disposal of small arms ammuntion.

Table 2.1 indicates the type of explosives destroyed at B-20 and the size ranges.  As CSSA records do not indicate items disposed of, CSSA compiled this list from their explosive experts.  Includes are small arms ammunition, cannon and mortar ammunition, grenades, rockets from 2.75 to 5 inches, mines, and simulators.  Detonation material includes charges of trinitrotoluene (TNT), tetryl, and plastic composition compounds, pentaerthyrite tetranitrate (PETN) detonating cord, blasting caps, fuzes, and firing devices.

Table 2.1
Munition Items Disposed of at B-20
Camp Stanley Storage Activity, Texas

mm = millimeter

NA = Not available

*  = TNT blocks, tetryl block, compositions C-3 and C-4

PETN = pentaerythrite tetranitrate

Reference:  List compiled by CSSA, December 1993.

CSSA also compiled a list of exploisve weights detonated per year since November 1980 (Table 2.2).  This list was compiled by CSSA explosive experts from existing records and calculations.  No records or personnel interviews indicate the amount or type of explosives destroyed at B-20 prior to 1980.  From November 1980 through 1983, and in 1985, no explosives were detonated.  In 1984, 24,022 pounds of explosives were detonated, with a maximum single weight of 185 pounds.  In 1986 and 1987, 9,867 and 4,320 pounds of explosives, respectively, were destroyed.  During each of those years, the maximum weight per explosive device was less than 150 pounds.

Table 2.2
Yearly Weight of Explosives Destroyed at B-20
Camp Stanley Storage Activity, Texas

Reference:  List compiled by CSSA, January 1994.

2.4  Standard Operating Procedures

CSSA standard operating procedures (SOPs) for explosive demolition were established by explosive experts working at CSSA.  To provide the SOP summary, ES interviewed Mr. Howard J. Sampson on January 26, 1994, and reviewed the B-20 SOPs of March 28, 1986 (Appendix A).  Mr. Sampson was supervisor of B-20 demolition operations from 1982 to 1987.  Procedures for demolition prior to 1980 are not documented.

The detonation procedures were broken into five SOPs:

1. Receiving and unloading;

2. Charging demolition pits or pads;

3. Destruction by detonation;

4. Site inspection and destruction of duds; and

5. Locating lost or broken detonating cord, lead lines, or demolition shots.

These operations are described in detail in the B-20 SOPs (Appendix A).  Each operation had specific safety, operational, and inspection instructions, as well as general safety procedures for all CSSA demolition activities.  Necessary equipment and tools were listed for each operation.  All demolition activities took place at the B-20 site.

An overview of general operations used during the 1980s follows.  Up to seven pits were used for each demolition job.  As shown by existing crater locations at B-20 (Figure 2.3), different pits were used at different times but were not documented as to specific use or dates.  The crew usually consisted of 16 persons, including heavy equipment operators, firemen, and emergency medical personnel.  For each job, the pits were carefully excavated by backhoe.  Roughly 1,000 pounds of explosives were unloaded, or about 150 pounds per shot in up to seven shot areas.  Material to be destroyed was placed in each pit with detonating cord or timers, then covered with 6 to 8 feet of soil kept at the site for this purpose.  The explosives were usually laid nose to fin to ensure that contact was kept between them.  Each pit filled with materials and soil was a "shot."  Airspace was cleared prior to firing of each shot.  When all personnel left the site and other safety factors were checked by the supervisor, each shot was individually detonated.  After an appropriate waiting period, the shots were checked for duds.  If present, the duds were destroyed in a similar manner.

During the interview, Mr. Sampson indicated that most of the destroyed material, including ammunition and grenades, were from the Korean War era.  Only one rocket motor was destroyed at the B-20 site.  The engine motor was placed in the standpipe in quadrant A (Figure 2.3) and test fired nose down.  Mr. Sampson also indicated that aboveground conduits observed in the southeast quadrants G, H, and I were used prior to his employment at CSSA.

2.5  Preliminary Sampling and Results

As analytical data was never required at the B-20 site previous to the EPA compliance order, no chemical parameters were available for the site.  In preparation for this closure plan, CSSA and RRAD, with the agreement of EPA Region IV RCRA Enforcement, Texas Section, prepared a "Phase I sampling plan" (appendix B).  This plan outlined the following actions by CSSA and RRAD personnel:

As it is unknown and unlikely that unexploded ordnance (UXO) is at the site, the field screening team consisted of U.S.> Army personnel knowledgeable in field identification of UXO.  Standard Army health and safety precautions for UXO sites were followed by the team members.

2.5.1  Preliminary Mapping

Preliminary field actions took place at the B-20 site on January 24 through 28, 1994.  On January 24 and 25, Mike Lockard and Ron Williams of RRAD identified craters and kickout zones, separated the site into quadrants for better identification of site features, and selected sample locations.  Gene Giles, the facility engineer at CSSA, aided the RRAD personnel with field and CADD mapping.  The first day of sampling, January 26, was observed by Matt Andrus of EPA Region IV RCRA Enforcement, Texas Section, and Susan Roberts of ES.  Sampling was completed on January 27, 1994, by RRAD field team and the samples were sent by overnight Federal Express to the Inchcape/DNDRC laboratories, Inc., of Richardson, Texas.

General observations by the field team were as follows.  Site features were marked on a base map generated in CADD by CSSA using a 1990 aerial photograph as reference for roads, fences, and ponds.  Fifteen craters were noted in the field and, when identifiable, on the aerial photograph.  The field team identified the primary areas of 1980s demolition activity by the lack of shrub and tree growth in quadrants A, B, D, E, F, G, H, and I (Figure 2.3).  Quadrant D contained a large stand of cedar tree growth and six craters.  These six craters were not recognized as part of the 1980s demolition actions by Howard Sampson of CSSA, supervisor of 1982-1987 B-20 demolition actions before 1980.  Surface runoff in an ephemeral stream that led to two ponds was identified, though the stream was not running at that time.  Five soil mounds were observed in quadrant H.  Mr. Sampson recognized these mounds as soil used to cover pits prior to demolition of munitions.  Native soil is only a few inches deep or less at the site.

Other features emplaced by CSSA through the years include a bunker west of the site (Figure 2.3) where the personnel stayed during firing of demolition shots.  Subsurface wiring led to the junction box which still stands in quadrant B, and one rocket motor standpipe is in the same area.  Broken aboveground metal conduit was observed in quadrants G, H, and I.  Mr. Sampson noted that this conduit was not used during his time as supervisor and must have been emplaced for use prior to the 1980s.  Inert scrap metal was noted across the entire site and also found at least 100 feet outside of the site boundaries.  CSSA demolition experts observed that such inert metal projectiles are not uncommon for the type of shallow pit demolition procedures followed at B-20.

2.5.2  Sample Collection

Based on the preliminary field observations, sample locations were selected for discussion between CSSA, RRAD, EPA, and ES representatives.  It was agreed that surface soil, surface water, and sediment samples would be collected, as well as an appropriate number of QA/QC samples.  The sample locations are shown in Figure 2.4.  Four of the craters were selected for sampling to represent quadrants C, D, G, and I. Other sample locations were the soil mounds in quadrant H, pond sediments and surface water in quadrant F, sediments of runoff into the livestock pond, and livestock pond surface water.  Four background soil samples were collected about 700 feet west of the site (Figure 2.4).

A total of seventeen samples were collected at B-20 during January 1994.  These samples included eight surface soil samples, five surface water samples, and four sediment samples.  Surface soil samples were collected  from the three different soil types at B-20 (section 2.2).  Surface soil samples CS-12-94, CS-13-94, the samples from crater 8, and the four background samples were collected in the Brackett-Tarrant soils; CS-14-94 from crater 5 was collected from Crawford and Bexar soils; sediment samples CS-7-94 and CS-9-94 were collected within the Krum Complex soils.

Sampling was performed in accordance with the RRAD Phase I sampling plan (Appendix B).  Surface soil samples were collected with a stainless steel trowel, as a hand auger was not able to penetrate through the limy gravelly soils.  Surface water samples were collected as grab samples in amber 1-liter glass bottles prior to sediment sample collection so that disturbed sediments would not interfere in the water sampling.  Sediment samples were collected with a hand auger from approximately 6 inches below each pond's bottom.  All samples were placed in laboratory grade glass jars, labeled, packed in foam shipping containers, and preserved on ice in coolers.  The sampling tools were decontaminated before and after use.

The laboratory informed ES on February 4, 1994, that they had exceeded holding times for semivolatile organics, nitroaromatics and nitroamines (explosives), and pH in the three surface water samples CS-01-94 9crater 8), CS-03-94 (QA/QC samples), and CS-06-94 (livestock pond).  To obtain analytical results as soon as possible, the three water samples were recollected on Friday, February 4, and shipped to the laboratory for a Saturday delivery.  Crater 8 and the livestock pond were resampled, and a field blank was collected as the corresponding QA/QC sample.  It was later determined that the original QA/QC sample (CS-03-94) was a duplicate of CS-01-94 rather than a field blank.  Therefore, there are two different QA/QC samples, the CS-03-94 duplicate of CS-01-94 analyzed for volatile organics and metals, and the CS-03-94R field blank analyzed for nitroaromatics and nitramines, semivolatile organics, and pH.

2.5.3  Analytical Results

Analytical results of the preliminary samples are listed in a table for each media.  The laboratory analytical reports are presented in appendix D (volume II).

    Surface Soil

Surface soils and background samples were analyzed for nitroaromatics, nitramines, and metals.  Surface soil sampling analytical results are in Table 2.3.  Percent total solids of soil samples are included in the reported soil sample results.  For comparison purposes, 31 Texas Administrative Code (TAC) 335 Subchapter S, standard 2 medium specific concentrations (MSCs) for industrial sites are included in the table.  CSSA has chosen standard 3 for closure, however the plan may be amended if later investigation results indicate that standard 2 may be achieved (section 3).

No explosives were detected in the surface soil samples.  Of eight metals analyzed mercury, selenium, and silver were not detected in any of the surface soil samples.  All soil sample results are below the MSCs with the exception of arsenic levels detected in CS-10-94, the soil mound sample, and in CS-11-94, the sample from crater 5.

    Surface Water

Surface waters were analyzed for nitroarmoatics, nitramines, volatile organics, semivolatile organics, and metals; the results are listed in Table 2.4.  Three of the samples were also analyzed for pH.  No explosives, volatile organics, or semivolatile organics were identified in the surface water samples (Table 2.4).  The laboratory noted four semivolatile organics as tentatively identified compounds (TICs), or unknowns.  As these were found in samples from the crater water and the ponds, it is probable that the TICs are from humic acid or other organic compounds.  The TICs were not found in any of the QA/QC samples.

Of the metals analyzed in the surface water samples, chromium, mercury, selenium, and silver were not detected in any of the samples.  Low levels of arsenic, barium, cadmium, and lead were detected in one or more samples.  Table 2.4 lists the Texas concentration criteria in freshwaters for human health protection.  The concentrations listed are specified under the category of freshwaters which are designated public drinking water supplies and fisheries (30 TAC Chapter 307).  The ephemeral stream and ponds at the B-20 site are neither public drinking water supplies nor fisheries.  However, for freshwaters which are incidental fisheries, only lead and mercury have been assigned a concentration standard (0.250 milligrams per liter (mg/L) and 0.122 micrograms per liter (ug/L), respectively).  Therefore, the more conservative concentration criteria have been presented for comparison to surface waters at B-20.  It should also be noted that the surface water standards for metals are based on dissolved concentrations and the samples collected during the preliminary investigations were analyzed for total metals.  Only cadmium and lead were detected in samples at concentrations above the freshwater standards.

     Sediment

The sediment samples were analyzed for nitroaromatics, nitramines, volatile organics, semivolatile organics, metals and total solids.  The results are presented in Table 2.5.

Sediment samples did not contain nitroaromatic or nitramine explosives.  Methylene chloride was detected in three of the four samples at concentrations ranging from 31 to 172 micrograms per kilogram (ug/kg).  Also, the semivolatile organic compound bis(2-ethylehexyl)phthalate was detected in one of the four sediment samples at 10 milligrams per kilogram (mg/kg).  As these two compounds are common laboratory contaminants and were not detected in the duplicate sample CS-04-94, it is probable that they are anomalous to the sampling locations or due to laboratory contamination.  Neither chemical is a contaminant associated with the list of explosives at B-20 (Table 2.6).  Up to nineteen TICs were noted by the laboratory in the livestock pond sample.  The TICs are most likely due to the presence of organics such as humic acid or microscopic plants in the sediments.  Crater 8 sediments contained 3.9 mg/kg of arsenic.  Selenium and silver were not detected in any of the samples.

None of the metal analytical results for seventeen samples indicate the need for a TCLP testing, with the possible exception of cadmium in the quadrant F pond sediment sample (CS-09-94).  As cadmium is not expected to be one of the hazardous waste components resulting from demolition activities at B-20, the TCLP test for cadmium was not applied during the preliminary analyses.  Cadmium concentrations will be verified during the remedial investigation at B-20 prior to performing any TCLP tests.

2.6  Inventory of Wastes

Wastes at the B-20 site, including explosives noted in CSSA records, are listed in Table 2.6.  The list of explosives was compiled by CSSA demolition experts.  This table indicates all potential contaminants known or thought to be disposed of in the B-20 area.  The list includes scrap metals, composition explosives, TNT and its derivatives, lead azide and lead styphnate as fuzes, nitroglycerin, and RDX (cyclonite) and its biodegradation components.