December 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 (CSSA). These modifications were developed and agreed upon by the Texas Natural Resource Conservation Commission (TNRCC), U.S. Environmental Protection Agency (EPA) Region 6 RCRA Enforcement, and CSSA, and prepared by Parsons ES, as appropriate and relevant to the closure of B-20, during the October 19, 1995 meeting concerning the B-20 project status. The October 26, 1995 plan of action resulting from this meeting is included as Attachment 1. Project work is performed for CSSA by Parsons Engineering Science (Parsons ES) under Armstrong Laboratory OEB contract F33615-89-D-4003, order 126.

Plans for site clearance and UXO screening were covered by the Amendment to Project Plans for the Remedial Investigation Report for B-20 Former Open Burn/Open Detonation Area (Parsons ES, 1995a); however, the October 26, 1995 plans of action will also be covered fully in this amendment.

CSSA is currently considering closure of the site under either 30 TAC 335 Subchapter S risk reduction standard 1 (RRS1) or standard 2 (RRS2). Several tasks must be completed at the site towards closure under either standard. Work must be completed at the site to address possible remaining unexploded ordnance (UXO), as well as to address scrap metal and metals contamination. For funding reasons, this additional work will be accomplished in phases. Since the possible remaining UXO poses a greater threat to human health and the environment, UXO-related tasks will be completed first. Therefore, this work plan amendment only addresses these tasks. The plan of actions for the modifications covered by this amendment includes:

Field work is tentatively scheduled to begin on December 11, 1995, and will continue through January 1996.

Modifications

1.0 - UXO Removal and Destruction

1.1   Initial UXO Destruction

During the initial sweep of the B-20 site performed as part of the Remedial Investigation (Parsons ES, 1995b), a non-movable bomblet was found on site. This UXO will be destroyed by blow-in-place (BIP) prior to the initiation of the controlled burn and site clearance procedures. BIP will be performed by Army 137th Explosive Ordnance Detachment (EOD) or by UXB International, Inc. (UXB), the UXO subcontracotr, as an Emergency Response action.

1.2   Additional UXO Destruction

The additional 192 UXO items identified during the initial UXO sweep are currently being temporarily stored on site. Prior to clearing vegetation from the site, these items will be moved to a temporary location (at least 500 feet from the site) for the duration of the controlled burn activities. After the controlled burn, the UXO will be moved back on site, and all additional UXO found will also be temporarily stored there, unless the professional judgment of UXO experts dictates that the item(s) cannot be moved. All moving of UXO will be conducted by UXB International. Items which cannot be moved will be destroyed by BIP by Army 137th EOD or by UXB as an Emergency Response action.

2.0 - UXO Sweep and Identification

2.1   Site Preparation

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 initial UXO sweep. UXB International, Inc. will clear the site under the supervision of Parsons ES. Vegetation at the site and within 300 feet from the site, where conflagration patterns dictate, will be cleared using a combination of burning and physical removal. The area to be cleared and swept for UXO is shown in Figure 1.

Due to previous identification of an endangered species (black capped vireo) in the vicinity of the site, efforts will be made to follow measures recommended by the U.S. Fish and Wildlife Service (USFWS), while still ensuring human safety. These measures are presented in correspondence included as Attachment 2.

2.2   Sweep Procedures

Additional sweeping for UXO is required to address possible remaining UXO outside of the original site boundary, and possible remaining UXO within the site (which may have been previously obstructed from view by vegetation). Specialists from UXB will sweep and identify UXO materials within 300 feet from the site where conflagration patterns dictate, and the site itself. Figure 1 shows the area which will be cleared and swept. The total area to be screened, including the 33.5-acre site, is approximately 50 acres. If UXO are identified during the additional sweeping activities, an additional 50 feet (as agreed at the October 19-20, 1995 meeting) will be swept for UXO. UXO screening will be conducted in accordance with the guidelines outlined in the closure plan (ES, 1994).

2.3   Magnetometer Survey and Magnetic Anomaly Excavation

UXB will perform magnetometers surveys after vegetation and surface UXO clearing to locate possible buried UXO at the craters in which magnetic anomalies were previously identified and to locate any possible UXO in the northern portion of the site. Equipment and techniques will remain the same as described in the closure plan.

a. Northern Portion of B-20

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 in the northern portion (approximately 6 acres) of the site. This area includes small ammunition disposal areas and detonation craters ten (10) through fifteen (15). All magnetic anomalies which UXO professionals feel can be safely moved will be excavated. UXO found will be detonated with other UXO items after all site clearing tasks have been completed.

b. Craters in B-20

Two types of magnetometers have been employed by UXB. 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 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 ten craters (1, 3, 4, 5, 6, 7, 8, 9, 14, and 15) during the RI. However, this information was only used to determine appropriate drilling locations. These anomalies will be re-identified for removal purposes using the equipment described above. Magnetic anomalies which can be safely moved will be excavated.

3.0 - Sampling

Field test explosives analyses will be performed on up to twenty surface soil samples near SS19 and SS20 to semi-quantitatively identify possible explosives contamination. Locations SS19 and SS20 are two locations at which raw explosive pieces were found during the remedial investigation (Parsons ES, 1995a). Other locations at which raw explosives pieces are found will also be sampled. Two confirmation samples will be collected for laboratory analysis (SW-8330). QA/QC for laboratory analysis is described in the Partial Facility Closure Plan (ES, 1994).

4.0 - Reporting

The UXO-related tasks described in this project plan amendment are only some of the tasks which need to be completed before closing under either RRS1 or RRS2 can be attained. Therefore, the closure plan will not be amended until the other tasks are completed. In the interim, results of the additional work described in this plan amendment and the September 1995 Plan Amendment (Parsons ES, 1995b) will be reported in an Addendum to the Remedial Investigation Report (Parsons ES, 1995a).