13.0 - Introduction

Investigations at several low, medium, and high priority SWMUs at CSSA are currently taking place under other delivery orders as described in Sections 1 through 6 of this work plan.  This addendum is added as Section 13 to the work plan.  The work proposed at the three Areas of Concern (AOCs)  and the groundwater monitoring are investigative activities that are similar to those performed routinely at CSSA.  The methodologies and project controls established during previous work (Sections 1 through 3) are valid for this addendum.

This document is a revised work plan addendum (Section 13 only) that describes investigations and closure activities to be carried out at three AOCs (57, 65, 67), and quarterly groundwater sampling planned at up to 28 on-post drinking water and monitoring wells and 20 off-post well locations. The locations of the AOCs are shown in Figure 13.1.  The on-post monitoring wells to be sampled as part of this delivery order (modification number two) are presented in Table 1 of the SAP Addendum for On-Post Groundwater Sampling Activities.  The off-post private wells will be selected by CSSA, and will be based on regional coverage and accessibility.  A brief description of these sites or activities addressed in this addendum is provided in Table 13.1.

Table 13.1 - Sites or Activities Addressed in this Addendum

This document was prepared by Parsons Engineering Science, Inc. (Parsons ES) for CSSA under the U.S. Air Force AETC Contract F41689-96-D-0710, delivery order 5084, dated September 20, 2000.  This section is an addendum to the RL17 work plan (Sections 1 through 3 of the work plan overview tab in this volume of the Environmental Encyclopedia).  It describes the scope of investigation and closure activities at the additional AOCs.

13.1 - Description of DO 5084 Study

13.1.1   Purpose

The objectives of the work at the three AOCs (57, 65, 67) are similar to the objectives listed in Section 1 of the work plan.  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.  Both soil gas and soil data will be collected as part of the phase II RFI at AOC 65.  Soil data, and possibly perched groundwater, are planned for the AOC 67 RFI (no soil gas sampling), and only a preliminary soil gas survey is planned for AOC 57.  If the AOCs and the SWMU meet Risk Reduction Rules, Standard 1 (RRRS1) closure requirements, an effort will be made to obtain certified closure from the TNRCC.  A detailed description of the closure standards and their associated requirements are provided in Section 2.2.

The AOC 65 soil borings will be left open over-night to see if perched water accumulates.  If perched water is found, CSSA will make arrangements for perched water sample collection and analysis before the borehole is plugged.  In the event CSSA is unable to collect this sample in a timely manner, borehole abandonment will proceed after the final soil boring is drilled and sampled.

The objective of the on-post groundwater monitoring of up to 28 monitoring wells is to determine the concentration of contaminants, if any, present in groundwater underlying the facility as part of a quarterly facility-wide evaluation.  The primary objective of the off-post groundwater monitoring is to determine concentrations of VOCs that may be present in off-post wells.  A secondary objective of the off-post sampling is to determine the potential extent of off-post contamination.  A subsidiary objective of both on-post and off-post quarterly sampling is to assess whether there are apparent trends (decreasing or increasing) in contaminant levels over time in the tested wells.

13.1.2   Scope of DO5084

This addendum describes the following tasks:

13.2 - Rationale and Methodology

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

13.2.1   Field Efforts

The field efforts to be conducted at the three AOCs addressed in this addendum are summarized in Table 13.2, and are described in this section.  Quarterly groundwater monitoring of off-post and on-post wells are also described in this section.  The procedures for field sampling will follow those described in Section 2 of the work plan, the sampling and analysis plan (Environmental Encyclopedia, Volume 1-4, Field Sampling Plan tab), and the AETC DO5084 Sampling and Analysis Plan addendum (Environmental Encyclopedia, Volume 1-4, DO 5084 tab).

Table 13.2 - Summary of Field Sampling, DO 5084 Work Plan Addendum

The number of samples to be collected at each site and the analytical testing planned for each sample are 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 and the AETC DO5084 SAP addendum for the RFI activities.  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 (Environmental Encyclopedia, Volume 1-4, Quality Assurance Project Plant tab).

Five types of field quality control (QC) samples will be collected during the soil investigative efforts at AOC 65 and at AOC 67 and the groundwater monitoring of off-post and on-post wells.  QC samples to be collected include equipment blanks, field duplicate samples, trip blanks, matrix spike/matrix spike duplicate (MS/MSD), and matrix duplicate (MD) samples.  Per the updated QAPP, ambient blanks may also be collected during each day of soil sampling efforts at AOC 65 and AOC 67.  Sample descriptions, identifications, and frequencies required are described in the applicable SAP addenda (Environmental Encyclopedia, Volume 1-4).

13.2.2   Subsurface Soil Borings

Ten soils borings will be drilled at AOC 65 to a maximum depth of 35 feet.  Locations of these borings will be biased toward ‘hot spot’ locations identified during the soil gas survey.  Since the performance of these surveys is scheduled for January through February 2001, no ‘hot spots’ have been identified.  Therefore, actual locations of soil borings at AOC 65 will not be determined until after the soil gas survey is complete.  An additional boring will be drilled at the outfall of the Building 90 drain line to a maximum depth of 35 feet.  A skid-mounted hollow stem auger rig will also be used to drill and sample three soil borings inside Building 90 in the vat area (one boring) and in the former drain line area (two borings) to a maximum depth of 20 feet.

Three soils borings will be drilled at AOC 67 to a maximum depth of 35 feet at the low-point of the concrete pad (one boring) and in the ditch located east of Building 90-1 (two borings).  Water is not expected to be encountered in any of these three borings, but if discovered, a grab sample of the perched water shall be collected and analyzed for the same parameters as the soil samples.  The borings outside Building 90 in AOC 65 and AOC 67 will be augered to refusal, and then air cored to 35 feet below grade.

The AOC 65 soil borings will be left open over-night to see if perched water accumulates.  If perched water is found, CSSA will make arrangements for perched water sample collection and analysis before the borehole is plugged.  In the event CSSA is unable to collect this sample in a timely manner, borehole abandonment will proceed after the final soil boring is drilled and sampled.

Two samples will be collected from each AOC 65 and AOC 67 boring in accordance with the SAP addendum for AETC DO 5084.  Sampling intervals will be selected based on observations and field screening results during the drilling process.  The following table lists the number of borings, samples, and analytical parameters for each site.

Table 13.3 - Summary of Soil Borings, AETC DO 5084 Work Plan Addendum

13.2.3 Soil Gas Sampling

Soil gas surveys will be performed at two AOCs (57 and 65) located in the vicinity of Building 90, including the wastewater treatment plant as shown in Figure 13.1.  The total area to be surveyed is approximately 70 acres. 

The soil gas survey will be established as one contiguous grid of sampling points over the two sites.  The sampling effort will be established on a 100-foot grid throughout AOC 57, tightened to a 25-foot grid within the limits of AOC 65.   The initial grid is expected to yield approximately 325 individual sample locations in AOC 57 and 75 sample locations in AOC 65.  Only one soil gas sample will be collected per grid node.  The effort will consist of establishing the initial sampling grid(s), followed by 25-30 days of sample collection and analysis.  Based on the findings of this initial grid, an additional 200 individual sample locations will be established by tightening the grid around ‘hot spot’ areas.  An additional 10-15 days are anticipated to complete the establishment of the tightened grid and the subsequent 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 4 to 6 feet below grade.  A geoprobe rig will be utilized to drive (hammer) the probes into the ground, and to retrieve the probes after sample collection is complete.  A pneumatic hammer and jack will be used to drive and retrieve rods in areas not accessible by the geoprobe rig.  Samples will be obtained in Tedlar^® bags under a vacuum, and analyzed by a mobile laboratory equipped with a gas chromatograph for benzene, toluene, ethylbenzene, xylenes, PCE, TCE, vinyl chloride, trans-1,2-DCE, and cis-1,2-DCE.  Each of the unique soil gas sample locations will be surveyed with CSSA’s GPS receiver (Section 4 of the Sampling and Analysis Plan Addendum for the soil gas survey, Environmental Encyclopedia, AETC DO5084 Addendum tab).  Relevant field parameters, such as depth, oxygen levels, lower explosive limit (LEL), date and time will be collected using the Trimble receiver.

13.2.4   On-Post Groundwater Monitoring

Three rounds of groundwater samples will be collected from up to 28 wells.  Sample quantities and analytical methodology for the groundwater sampling planned under this delivery order are summarized in Table 13.4.  Quality assurance and quality control (QA/QC) sampling and analysis will also be performed to meet the requirements of the AFCEE QAPP and the SAP (Environmental Encyclopedia, Volume 1-4).  Analytical results from the initial round of groundwater samples collected from the on-post wells will be evaluated to determine whether the analyte list can be reduced during succeeding rounds.  For all newly constructed wells, the groundwater samples will also be tested for cations and anions during the initial sampling event at each well.

Table 13.4 - Summary of Groundwater Sampling, AETC DO 5084 Work Plan Addendum

13.2.5   Off-Post Groundwater Monitoring

Four rounds of groundwater samples will be collected from twenty off-post privately or publicly owned supply wells.  The samples will be collected from the owner’s taps, with no purge required for currently active wells, and a 15-minute purge for inactive wells.  The specific wells to be sampled and the analytical methods to be performed are detailed in the SAP addendum for off-post groundwater sampling under this delivery order.  These samples will be tested for specific chlorinated hydrocarbons including: 1,1-dichloroethene, bromodichloroethene, chloroform, cis-1,2-dichloroethene, dibromochloromethane, methylene chloride, trans-1,2-dichloroethene, tetrachloroethene, trichloroethene, and vinyl chloride.  This list consists of the volatile organic hydrocarbons approved for testing in CSSA groundwater samples after January 1, 2000, and is subject to modification as appropriate (Environmental Encyclopedia, Volume 1-1, Correspondence with Regulatory Agencies/EPA tab).

Sample quantities and analytical methodology for the groundwater sampling planned under this delivery order are summarized in Table 13.4.  Quality assurance and quality control (QA/QC) sampling and analysis will also be performed to meet the requirements of the AFCEE QAPP and the Field Sampling Plan (Environmental Encyclopedia, Volume 1-4).

13.3 - Reporting Requirements

This section provides the reporting requirements for the AOC 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 for each sampling event and will be submitted to CSSA and AFCEE.  The ITIR will include the AFCEE forms, the case narrative, the approved variances, and the data verification and data validation summary report.

Technical/closure reports for each of the AOCs 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.  Reports for groundwater sampling events will be prepared in a manner consistent with the on-going quarterly monitoring reports.

In order to close an AOC or SWMU under the risk reduction rules, 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 which is required per 30 TAC §335.553:

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. QA/QC analytical results.

7. 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.  The technical report will also discuss whether data gaps exist and recommendations for filling those gaps.  Additionally, remedial alternatives which may mitigate or isolate those constituents that exceed closure criteria will be identified.

Technical reports for the quarterly groundwater monitoring events will be prepared in a manner consistent with previously submitted reports.  Data from each quarterly monitoring event will build upon data generated from previous rounds of data collection.  The format for the off-post groundwater technical report will be determined by CSSA.  The reports will become part of the administrative record in accordance with CSSA’s Community Relations Plan (located in Volume 1-6 of the Environmental Encyclopedia).

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