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12.0 - Introduction

Investigations at several low, medium, and high priority SWMUs at CSSA are currently taking place as described in Sections 1 through 6 of this work plan.  This addendum is added as Section 12 to the work plan.  The work proposed at the twelve Areas of Concern (AOCs) and one Solid Waste Management Unit (SWMU) are similar investigative activities that have been performed routinely at CSSA.  The same methodologies and project controls established during previous work (Sections 1 through 4) are still valid for this addendum.

This addendum (Section 12 only) describes investigations and closure activities to be carried out at twelve AOCs (35, 36, 37, 38, 39, 40, 41, 42, 43, 50, 65, 66), and investigations/closure activities at one additional medium priority SWMU (B-9).  The locations of these sites are shown in Figure 12.1.  A brief description of each of the sites addressed in this addendum is provided in Table 12.1:

Table 12.1 - Sites included in this Addendum

This document was prepared by Parsons Engineering Science (Parsons ES) for CSSA under the U.S. Air Force AETC Contract F41689-96-D-0710, delivery order 5068, dated September 30, 1999.  This section is an addendum to the RL17 work plan (Sections 1 through 4).  It describes the scope of investigation and closure activities at the additional AOCs and SWMU.

The original version of this work plan was approved in December 1999.  This modification is a result of a change in the Statement of Work (SOW) approved on August 2, 2000.  For this modification, the work scope at AOCs 35, 42, and 43 were modified based on the geophysical work conducted in November 1999.  The scope of work at AOC 50 was expanded due to the discovery of potential UXO and other areas of disturbance.

12.1 - Description of DO 5068 Study

12.1.1   Purpose (Updated February 2001)

The objectives of the work at the twelve AOCs (35, 36, 37, 38, 39, 40, 41, 42, 43, 50, 65, 66) and the SWMU B-9, are similar to the objectives listed in Section 1.  In short, the overall objectives are to collect sufficient data to determine if each of these sites can be closed; and if possible, to close them.  If the AOCs and the SWMU meet RRS1 closure requirements, an effort will be made to obtain certified closure from the TNRCC.  Initially, RRS1 for all closures will be used.  If closure to RRS1 is not viable, then the data will be compared to TRRPS for an acceptable closure.  Clean closures using RRS1 standards will be obtained whenever technically and economically possible.  A detailed description of the closure standards and their associated requirements is provided in Section 2.2.

12.1.2   Scope of DO5068 Work (Updated February 2001)

This addendum describes the following tasks, and included the August 2000 SOW revisions:

12.2 - Rationale and Methodology

The following sections describe the rationale and methodology of the additional field actions at sites.  Sections 2.3.1 through 2.3.10 include a general description of the field investigation.

12.2.1   Field Efforts (Updated February 2001)

The field efforts to be conducted at the thirteen sites addressed in this addendum are summarized in below.  The procedures for field sampling will follow those described in Section 2 of the work plan, the FSP (Parsons ES, 1996a), and the DO5068 FSP addendum.

Table 12.2 - Summary of Field Sampling, DO 5068 Work Plan Addendum

The number of samples to be collected at each site is described in the site-by-site descriptions.  Sample collection and handling techniques will follow the Sampling Analysis Plan (SAP) for SWMU Closures at Camp Stanley Storage Activity (Parsons ES, 1996a) and the DO5068 FSP addendum.  Analytical techniques will follow procedures described in Test Methods for Evaluating Solid Waste, U.S. Environmental Protection Agency, SW-846 and Version 3.0 of the HQ AFCEE QAPP (AFCEE, 1998).

Four types of field quality control (QC) samples will be collected during the investigative effort.  QC samples to be collected include equipment blanks, field duplicate samples, trip blanks, and matrix spike/matrix spike duplicate (MS/MSD) samples.  Sample descriptions, identifications, and frequencies required are described in detail in the SAP (Parsons ES, 1996a). 

12.2.23  Geophysical Surveys (Updated February 2001)

For AOCs 35, 42, 43, 50, and SWMU B-9, Parsons ES will perform geophysical surveys to locate and delineate potential buried wastes.  The geophysical surveys will include both EM and GPR survey tools.  The electromagnetic survey will utilize a Geonics EM31 instrument with datalogger capability to measure both in-phase and quadrature signals.  The GPR instrument is an SIR-2 equipped with a 300 megahertz (mHz) antenna.

Prior to the survey, each site will be gridded and staked to establish survey lines.  The EM31 survey will range from 20 to 50-foot grids, dependent upon the survey size and terrain.  The GPR survey will be conducted along grid spacings ranging from 10 to 20 feet.  The corners of each site grid will be surveyed with the CSSA global positioning system (GPS) receiver.  The size of each survey area is as follows:

12.2.3  Subsurface Soil Borings (Updated February 2001)

If geophysical anomalies are identified during those surveys discussed in Section 12.2.3, soils borings will be drilled at AOCs 35, 42, and 43 to a maximum depth of 15 feet each.  Since the performance of these surveys in November 1999, geophysical anomalies have only been detected at AOC 42.  Therefore, soil borings at AOCs 35 and 43 have been de-scoped.  UXO avoidance support will be provided at AOC 42.

Three samples will be collected from each boring in accordance with the sampling and analysis plan addenda.  Anticipated sampling depths are surface samples, at the depth of the detected anomaly, and the total depth of the boring.  The following table lists the number of borings, samples, and analytical parameters for each site:

Table 12.3 - Summary of Soil Borings, DO 5068 Work Plan Addendum

At sites were no subsurface anomalies are detected by the geophysical surveys, soil borings and subsurface sampling may be replaced by surface sampling as the closure activity.  With the August 2000 SOW amendment, surface samples only will be collected at AOCs 35 and 43.

12.2.4   Surface Soil Sampling (Updated February 2001)

For AOCs 35, 36, 38, 39, 40, and 43, Parsons ES will collect a maximum total of 88 surface samples (not including QA/QC) from a maximum depth of 2 feet below grade.  Five sites are adjacent to each other at the northern end of the inner cantonment area, and one site is located south of B-24 as shown in Figure 12.1.  The following table lists the approximate size of each AOC:

Table 12.4 - Summary of Surface Samples, DO 5068 Work Plan Addendum

For AOCs 35, 36, 39, and 40, the sampling areas are predominantly long and rectangular, therefore samples will be spaced dependent upon prior soil gas or geophysical survey work . However, AOC 38 is large (35 acres), and will require a grid coordinate system for an accurate dispersion of the sampling locations.  Samples will also be collected from “hot spots” identified during prior soil gas work at the AOCs.  It is expected that approximately three to four days will be required to establish the sampling locations.  Samples will be collected using stainless steel hand trowels or hand augers in accordance to the SAP addenda.  Each sampling location will be surveyed using the CSSA GPS receiver.  At AOC 65, the concrete floor will be cored and two soil samples will be collected from the area beneath the former PCE vat.

Field activities will include collection and analyzing of surface soil samples for trichloroethene (TCE), dichloroethene (DCE) isomers, and tetrachloroethene (PCE) at AOCs 35, 36, 38, 39, and 40.  The DCE isomers are 1,1-DCE, cis-1,2-DCE, and trans-1,2-DCE.  Explosives and metals are the contaminant of concern at AOC 43. Upon conclusion of the field activities, the data will be validated and reported, and followed by updates to the Environmental Encyclopedia hard copy, hyperlinks and GIS database.

12.2.5   Soil Gas Sampling

Soil gas surveys will be performed at three adjacent AOCs (37, 41, and 66) located just north of Well 16 and the inner cantonment fenceline as show in Figure 12.1.  The size of each AOC is as follows:

The soil gas survey will be established as one contiguous grid of sampling points over the three sites (25.5 acres).  The sampling effort established on a 100-foot grid is expected to yield no more than 140 individual sample locations.  Only one soil gas sample will be collected per grid node.  The effort will consist of approximately three to four days of establishing the sampling grid, followed by ten days of sample collection and analysis.

Past soil gas work has demonstrated that the bedrock is relatively shallow, and that the probes typically cannot be driven beyond four to six feet below grade.  Samples will be obtained in Tedlar bags under a vacuum, and analyzed by a portable field GC for benzene, toluene, ethylbenzene, xylenes, PCE, TCE, and cis-1,2-DCE.  The corners of the soil gas survey will be surveyed with CSSA’s GPS receiver.

12.2.6   Interim Measures (Updated February 2001)

Interim measures (IM) that include the removal of nickel penetrate at AOC 50 will be completed as part of DO5068.  Up to 175 cubic yards of soil and waste will be removed from an area approximately 0.47 acres in size.  On average, up to three inches of soil/waste may be excavated from the site.  More or less soil will be excavated (up to 175 cubic yards) based upon the judgement of the supervising Parsons ES staff.  A UXO avoidance team will provide the necessary screening and clearance to perform the work safely.

A total of ten confirmation samples will be collected from the site upon completion of the IM activities.  Samples will be analyzed for VOCs, explosives, and metals.  An additional nine samples have been allocated for waste profiling, characterization, and confirmation by TCLP analyses (VOCs and metals).  All wastes have been assumed to be non-hazardous, and can be disposed of at a permitted, offsite landfill.  No fill material will be returned back to the site once the IM activities are complete.  Depending on the landfill requirements, there may be sample quantities that will be remaining.  It is the intention of Parsons ES to apply those funds associated with surplus samples to either the post-excavation sampling effort or from areas that may be discovered during the course of work.

12.3 - Reporting Requirements

This section provides the reporting requirements for the AOC and SWMU closure activities provided for in this work plan.  All reports will be submitted to the appropriate agencies as well as the appropriate contracting authorities.

An Informal Technical Information Report (ITIR) will be prepared and submitted to CSSA and AFCEE.  The ITIR will include all analytical data, including QC results and cross-reference table.

Technical/closure reports will be prepared in accordance with state closure requirements and upon completion of activities for the investigated sites.  These technical reports will discuss field activities, investigative and analytical results, and conclusions and recommendations for each SWMU listed for investigation.

In order to close an AOC or SWMU, a final report will be submitted to the TNRCC demonstrating compliance under the appropriate risk reduction standards.  The report shall include, but is not limited to, the following documentation:

1. Descriptions of procedures and conclusions of the investigation to characterize the nature, extent, direction, rate of movement, volume, composition and concentration of constituents in the environmental media.

2. Basis for selecting environmental media of concern.

3. Documentation supporting selection of exposure factors.

4. Descriptions of removal or decontamination procedures performed in closure, if applicable.

5. Summaries of sampling methodology and analytical results which demonstrate that constituents have been removed or decontaminated to applicable levels.

6. If necessary, a document that the person proposes to use to fulfill the requirements of deed certification for Risk Reduction Standard 2.

7. QA/QC analytical results.

8. Certification by an independent engineer, registered in the State of Texas, that the closure plan procedures were followed and compliance of the appropriate closure standard was met.

If investigative activities conclude that a site cannot be closed under RRS1 standards, a technical summary report will be prepared in lieu of a closure report.  The technical summary report will present the investigation findings and analytical results.  The report will identify which closure criteria were not met, as well as outline viable options and recommendations for future closure work.  Additionally, remedial alternatives which may mitigate or isolate those constituents that exceed closure criteria will be identified.

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