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Amendment to Project Plans for Remedial Investigation at B-20 Former Open Burn/Open Detonation Area
September 1995
Introduction
This amendment describes changes to the Partial Facility Closure Plan (ES, 1994) for the B-20 Former Open Burn/Open Detonation Area at Camp Stanley Storage Activity. These changes which are based on recommendations presented in the Remedial Investigation Report (Parsons ES, 1995), reflect additional closure investigation actions intended to aid in the decision to cost-effectively close the site under TNRCC risk reduction standard (RRS) 1 or 2. An estimated twenty-four (24) samples will be collected to further delineate the amount of soil that must be removed to meet RRS1. Six of the twenty-four samples will be taken from soil borings.
Initially, unexploded ordnance (UXO) was not considered to be a major concern. However, initial UXO sweeps conducted by UXB International, Inc. located and identified 193 UXO items (Parsons ES, 1995). Several magnetic anomalies discvoered in detonation craters may represent buried UXO. Extended site clearance of UXO comprise part of this amendment. The additional activities covered under this amendment are divided into the six categories below:
Modifications
Approximately twenty-four (24) samples will be collected to more accurately predict the amount of soil that must be removed to meet risk reduction standard 1 or 2. These samples will be distributed as follows:
Four (4) surface soil samples are to be taken in the vicinity of SS7 and SS28 and three (3) surface soil samples nearby SS35 and SS21. These samples will be analyzed for total mercury (Hg), lead (Pb), and cadmium (Cd). Six (6) surface soil samples will be taken in the vicinity of SS23 and SS33 and will undergo analysis for Hg, Pb, and barium (Ba). Mercury and lead analyses will also be run on three samples collected near SS6. Sample selection will be judgmentally based to aid in delineating extent of contaminant occurrence.
Field test explosive analyses will be performed on twenty (20) surface soil samples near SS19 and SS20 to semi-quantitatively identify possible explosive contamination. Two (2) confirmation samples will be taken for laboratory analysis. Three soil borings will be drilled near SB2, SB9, and SB10 to determine vertical contaminant extent. Two samples will be taken from each for a total of six (6) samples for synthetic precipitation leaching procedure (SPLP) and toxicity characteristic leaching procedure (TCLP) in metal analysis at depths of 4.0-6.0 feet and 13.0-15.0 feet. The above is summarized in Table 1.2. Tentative sample locations are shown on Figure 1.
Drilling and subsurface soil sampling procedures during these additional activities are the same as outlined in sections 4.3.3 of the Partial Facility Closure Plan for B-20 (ES, 1994). Surface sample procedures will be the same as discussed in the closure plan (section 4.2). Laboratory methodology and procedures and quality assurance/quality control and data validation procedures will follow the guidelines in the closure plan and the Quality Assurance Project Plan (QAPP) which is appended to the closure plan.
Three borings will be drilled near prior borings SB2, SB9, and SB10 to further delineate metals contamination. Drilling will follow the same procedures as described in the closure plan and the Health and Safety Plan (Parsons ES, 1994) regarding operations where UXO is a concern. Drilling will easily be completed within a week. Proposed drilling localities are shown in Figure 2.
The B-20 site will be cleared of vegetation to aid in the identification and removal of further UXO that may not have been detected during the inital UXO sweep. UXB International, Inc. will clear the site under the supervision of Parsons ES. Vegetation at the site and within 600 feet from the site will be cleared using a combination of burning and physical removal. Clearing techniques will be approved in advance by the U.S. Fish and Wildlife Service.
Specialists from UXB International, Inc. will sweep and identify UXO materials on, and within, 300 feet of the B-20 site perimeter. If UXO is found within the first 300 feet of the site, and additional 300 feet will be swept. The maximum expected area to be swept is shown in Figure 3. UXO screening will be conducted in accordance with the guidelines outlined in the closure plan.
UXB International, Inc. will perform magnetometer surveys after site clearing to locate buried UXO. Equipment and techniques will remain the same as described in the closure plan.
Due to the lack of records on historic activities in the northern portion of the site, a magnetometer survey will be conducted to identify any possible buried UXO. This area includes small ammunition disposal areas and detonation craters ten (10) through fifteen (15). All magnetic anomalies detected will be removed as described below in section F.
Two types of magnetometers have been employed by UXB International. A Foerster Ferex (Mk-26) Ordnance Locator was used at the craters. It provides an audio and metered signal and can detect large ferrous items up to a depth of 19 feet. A Schonstedt GA-52B Locator was used in areas where extensive metal scrap at the surface necessitated the use of a magnetometer less sensitive than the Foerster Ferex. The GA-52B has an audio signal only and can detect large ferrous items up to a depth of 10 feet. Magnetometers used at the B-20 site are discussed in greater detail in the Partial Facility Closure Plan (ES, 1994).
Magnetic anomalies were identified in several craters during the remedial investigation. However, this information was only used to determine appropriate drilling locations. There anomalies will be re-identified for removal purposes.
UXO discovered and exposed during visual and magnetometer sweeps will be removed for future disposal unless the professional judgment of UXO experts dictates that the item(s) cannot be moved. All removal activities will be conducted by UXB International. Buried UXO will be excavated and removed by a qualified UXO professional with a backhoe or other appropriate heavy equipment. UXB International recommends specific ordnance located during previous surveys not be moved and should be disposed of by the blow-in-place method (Parsons ES, 1995). this recommendation will likely pertain to any future UXO located during investigation pursuant this amendment.