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Addendum to Remedial Investigation Report for B-20 Former Open Burn/Open Detonation Area
Section 1 - Introduction
This document summarizes the results of the remedial investigation of the B-20 former open burn/open detonation (OB/OD) area at Camp Stanley Storage Activity (CSSA) in Boerne, Texas (Figure 1.1). This work was performed by Parsons Engineering Science (Parsons ES), previously Engineering-Science, Inc., under contract to Armstrong Laboratory/OEB (AL/OEB) at Brooks Air Force Base (AFB), Texas.
The remedial investigation (RI) of the B-20 site has been divided into two phases. The first phase was conducted in November 1994 through March 1995, and the results are documented in the B-20 RI Report (Parsons ES, 1995a) and summarized in this report. The second phase was conducted in September 1995 through March 1996 and is described in depth in this addendum report.
Closure of the B-20 former OB/OD area is being conducted under a Compliance Order sent to CSSA on June 30, 1993. The U.S. Environmental Protection Agency (EPA), Region VI, Resource Conservation and Recovery Act (RCRA) Enforcement, Texas Section, issued this compliance order which requires that CSSA immediately cease operation of the unit and prepare a closure plan for the unit in accordance with the applicable regulations. The compliance order requires that the B-20 closure plan comply with federal and state regulations (40 Code of Federal Regulations (CFR) 265 Subpart G and Title 30 Texas Administrative Code (TAC) Chapter 335 Subchapter S, respectively) for closure of hazardous waste management units.
Parsons ES was contracted by AL/OEB to perform investigation at waste management units (WMUs) at CSSA, including the B-20 former OB/OD site, under contract number F33615-89-D-4003, delivery order 126. Work performed under delivery order 126 is defined in the statement of work (SOW) dated September 30, 1993, and the SOW modification dated June 22, 1994.
The B-20 unit is a 33.5-acre field (acreage determined during investigation surveys) surrounded by wooded areas in the northeastern portion of CSSA (Figure 1.2). The area is vegetated with grasses and cedar shrubs. Gravel roads form the south, west, and north boundaries of the site. Site boundaries and other features are shown in Figure 1.3.
B-20 site features include an inactive bunker west of the western gravel road, a standpipe used one for static firing of a rocket motor and a junction box in the central portion of the site (Figure 1.3). Broken aboveground conduit is currently visible in the central-southeast area of the site. Fifteen craters (1 through 15) have been identified in the northern and central portions of the site. Five mounds in the eastern portion of the site are soil from the B-20 site that was piled ready for use in covering explosives prior to detonation (verbal communication, CSSA employee Mr. Howard Sampson, supervisor of B-20 activities from 1982 to 1987).
According to a 1950 memorandum on file at CSSA, the B-20 area was first used for demolition activities on March 4, 1946 (CSSA, 1950). The B-20 operations included detonation of conventional explosive ordnance and other ordnance items, static firing of one rocket motor nose down using the existing standpipe, disposal of scrap metal from detonation activities, and disposal of small arms ammunition. There are no known records describing use of the B-20 site between 1946 and 1980. However, review of aerial photographs from this period suggest that the site was periodically in use. Record and personnel employed at CSSA indicate that the site was used intermittently from 1980 through 1987. As described in Section 1.1.1, CSSA received a Compliance Order from the EPA for the site in June 1993. A chronology of events at the site, including environmental investigation activities, is listed below.
The following chronology lists relevant activities at the B-20 unit since the first known use of the site in 1946. Activities since September 1995 are part of the second phase of work at the site, and are reported in this document. Previous activities are only summarized in this addendum.
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1946-1987 |
CSSA periodically used the B-20 area for ordnance OB/OD activities. |
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June 1993 |
EPA issued a Compliance Order for the B-20 site for unpermitted treatment of hazardous waste and for failure to have a closure plan. |
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January 1994 |
Red River Army Depot (RRAD) collected preliminary samples at the site to provide an estimation of the nature and extent of contamination for environmental investigation planning purposes. |
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March 1994 |
Work plan for B-20 closure/remedial investigation (ES, 1994) submitted to EPA Region VI and TNRCC. |
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Nov. - Dec. 1994 |
First phase of closure/remedial investigation conducted. Investigation consisted of sampling and UXO clearing activities. |
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June 1995 |
Final RI report submitted. Report recommended additional sampling and UXO clearing activities. |
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September 1995 |
Second phase of RI initiated. Activities included subsurface soil sampling near three RI borings and surface soil sampling in south-central portion of the site. |
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October 1995 |
CSSA received concurrence letter from U.S. Fish and Wildlife Service (USFWS) for planned vegetation clearing activities at the site. |
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December 1995 |
Conducted field activities to locate UXO on site and in surrounding areas. Activities included vegetation clearing to facilitate UXO identification and systematic sweep of surface with metal detectors. Subsurface magnetic anomalies in craters and the northern portion of the site were excavated and removed. The UXO identification activities continued until March 1996. |
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January 31, 1996 |
All UXO found on site to date (365 items) were detonated after receiving approval from TNRCC on January 29, 1996. |
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February 1, 1996 |
Brush piles resulting from vegetation clearing activities at the site were ignited under controlled conditions. Intended to conduct controlled burn of entire site the following day, but weather did not permit. |
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February 20, 1996 |
CSSA sent metal scrap collected at the site to a metal recycling facility. |
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March 15, 1996 |
Field work ended. |
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May 8, 1996 |
UXO items identified since January 31 (447 items) were detonated on site. |
A second phase of field work (September 1995 through March 1996) was conducted at the B-20 former OB/OD area in response to recommendations made in the B-20 RI Report (Parsons ES, 1995a). Additional sampling and UXO clearing were recommended in the RI report to prepare the site for future closure under either risk reduction standard 1 (RRS1) or standard 2 (RRS2).
Th primary objectives of the additional field work conducted at B-20 were to further assess the nature and extent of subsurface and surface soil contamination, and to determine the extent and type of UXO at the site, including the craters. Other objectives included disposal (by onsite detonation) of UXO and collection of surface scrap metal.
The scope of this investigation, as presented in two amendments to the project plans (Parsons ES, 1995b and 1995c), consists of the following tasks:
Collect surface soil samples from specific areas of the site to help accurately delineate contaminant extent and determine the volume of material to be removed to comply with the RRS1 cleanup criteria, as outlined in 30 TAC 335.554(d).
Drill three soil borings adjacent to previously drilled locations exhibiting elevated arsenic and mercury concentrations and collect samples for leachate analysis. The results were used to determine if metal concentrations in the soil/rock could potentially release contaminants to groundwater via leachate.
Conduct surface sweep of entire site and some surrounding areas (based on blast patterns).
Identify, excavate, and remove subsurface magnetic anomalies in craters.
Identify, excavate, and remove subsurface magnetic anomalies identified in northern portion of the site.
The amendments to the project plans, which describe the scope of the second phase of work at the B-20 site, were submitted in September 1995 and December 1995.
Sampling procedures followed during this additional investigation are outlined in the Quality Assurance Project Plan (QAPP) (Parsons ES, 1994). All data collected was subjected to the quality assurance/quality control (QA/QC) procedures outlined in the QAPP.
As described in Section 1.1, this report is meant to serve as both a summary of results of previous investigations at the B-20 site and a record of findings of the second phase of the RI conducted from September 1995 through March 1996. Section 1 is this introduction, Section 2 summarizes the results of previous investigations, and findings of the second phase of the RI are reported in Section 3. Section 4 presents conclusions, and Section 5 describes closure options and the activities that must be conducted at the site to prepare it for closure, using two closure scenarios (RRS1 and RRS2). Section 6 lists references.