Objective 1: Meet TNRCC Requirements for Site Closure

Attainment of Risk Reduction Standard Number 1: Closure/Remediation to Background

Attainment of Risk Reduction Standard 1

Remove all hazardous and nonhazardous waste and waste residues and contaminated design and operating system components such as liners, leachate collection systems, and dikes from the unit or area of the unauthorized discharge. For remediation of media that have become contaminated by releases from a waste management unit or by other unauthorized discharge of hazardous or nonhazardous waste, the contaminated media must be removed or decontaminated to cleanup levels specified in this section (30 TAC 335.554(b) and (c)).

Geophysical survey, surface and subsurface sampling were conducted to identify potential areas with buried waste at the site, and to determine if contamination has migrated from waste trenches. Analytical results for subsurface samples collected from around the trenches indicate slight exceedances of RRS1 closure criteria.

No. Since there is evidence that waste is buried at the site, this objective has not been attained.

Excavate in areas of anomalies. Remove waste materials and recycle or properly dispose of them. Sample excavated soil and remediate or properly dispose.

Determine compliance with RRS1 closure requirements by comparing to background as represented by results of analyses of samples taken from media that are unaffected by waste management or industrial activities. If the practical quantitation limit (PQL) is greater than background, then the PQL rather than background shall be used as the cleanup level provided that the person satisfactorily demonstrates to the executive director that lower levels of quantitation of a contaminant are not possible (30 TAC 335.554(d)).

Contaminant concentrations were compared to revised background levels (Parsons, February 2002) or RLs, which are equivalent to PQLs.

No. Metal concentrations (barium, chromium, nickel, and zinc) exceeded RRS1 (background) levels.

Removal of soils exceeding RRS1 should be conducted during the removal of waste materials described above. Results are only slightly above RRS1 levels, so significant overexcavation of the trenches is not anticipated.

Attainment of Risk Reduction Standard 1 (cont.)

Attainment of cleanup levels shall be demonstrated by collection and analysis of samples from the media of concern (30 TAC 335.554(e)).

Soil gas, surface, and subsurface soil samples were collected at the site.

No. Metal concentrations (barium, chromium, nickel, and zinc) exceeded RRS1 (background) levels.

See above.

Objective 2: Meet Requirements of 3008(h) Order for RFI

RFI Workplan Requirements

Field Sampling (Detailed listing of methods and procedures are provided in project plans which are incorporated by reference).

Conduct field sampling in accordance with procedures defined in the project work plan, SAP, QAPP, and HSP.

All sampling was conducted in accordance with the procedures described in the project plans.

Yes.

None.

Facility Investigation

Characterization of Environmental Setting - Hydrogeology (B.3.A.1)

Evaluate hydrogeologic conditions at the site.

Shallow groundwater was not encountered during drilling at the site.

Groundwater of the Trinity Aquifer is being addressed through the Groundwater Investigation.

NA

NA

Characterization of Environmental Setting- Soils (B.3.A.2)

Characterize soils in accordance with USCS soil classification system (B.3.A.2(a)).

Soil types at the site are based on the SCS Bexar County Soil Survey (USDA, 1991) and are described in Section 1.2.1.

Yes.

None.

Determine soil pH (B.3.A.2(e)).

The pH of each of the soil types evaluated as part of the background metals concentration study was determined through laboratory analysis. According to those analyses, the pH of Trinity and Frio soils is 7.90.

Yes.

None.

Determine moisture content (B.3.A.2(g)).

The moisture content of each sample was analyzed. Moisture content values are provided in the laboratory analytical packages.

Yes.

None.

Characterization of Environmental Setting – Surface Water and Sediment (B.3.A.3)

Characterize marshes, creeks, wetland areas, or ditches at the site.

No marshes, creeks, wetland areas, or ditches are present at the site. Direction of runoff flow has been evaluated in Section 1.2.3.

Yes.

None.

Source Characterization (B.3.B)

Identify the source area (B.3.B.1).

A description of the source area is provided in Section 1.1.2. Sample collection was biased toward areas suspected of contamination as identified by the geophysical survey.

Yes. The source of contamination at SWMU B‑15/16 is the waste disposed of in the covered trenches. Target vehicles and weapon mounts were disposed at the site.

As waste material is removed from the known trenches at SWMU B-15/16, the types of waste disposed there can be verified.

Source Characterization (B.3.B) (cont.)

Identify the location of the unit/disposal area (B.3.B.2(a)).

In 1999, points along the boundary of each site were surveyed with a Rockwell Plugger GPS unit (estimated accuracy of ±25 feet). The measurement points were identified by the CSSA Environmental Coordinator.

Yes. Although the accuracy of the boundary survey of the site is estimated to have an approximate error of 25 feet, this accuracy is sufficient for closure under RRS1.

None.

Identify the type of unit/disposal area (B.3.B.2(b)).

Information regarding the type of site was obtained from the Environmental Assessment (ES 1992) and from field activities. Base records and aerial photographs were reviewed, and base personnel were interviewed.

Yes.

None.

Identify design features (B.3.A.2(c)).

Information regarding design features was obtained during the Environmental Assessment (ES, 1993) and through visual observation during the field investigation. All available information regarding the design of the disposal site is provided in Section 1.1.2.1.

Yes.

None.

Identification of past and present operating practices, period of operation, age of unit/disposal area, and method used to close the unit/disposal area (B.3.B.2(d), (e), (f), and (h)).

All known information regarding these items is provided in Section 1.1.2.1. This information is from the Environmental Assessment, records review, interviews, aerial photo review, and visual observations.

Yes. To the extent possible with data available.

None.

Determine general physical conditions of the site (B.3.B.2(g))

The general physical condition of the site was determined during the field investigation. This information is presented in Section 1.1.2.

Yes.

None.

Source Characterization (B.3.B) (cont.)

Identify waste characteristics, including type of waste placed in the unit, physical and chemical characteristics of the wastes, and migration and dispersal characteristics of the waste (B.3.B.3).

Records regarding historic waste disposal practices at CSSA are very limited. All known information, derived from the Environmental Assessment, records review, interviews, and visual observations at the site is provided in Section 1.1.2.2.

NA

NA

Contamination Characterization – Groundwater (B.3.C.1)

Characterize the vertical and horizontal extent of groundwater contamination.

Shallow groundwater was not encountered during drilling at the site.

Groundwater of the Trinity Aquifer is being addressed through the Groundwater Investigation.

NA

NA

Contamination Characterization – Soil (B.3.C.2)

Determine vertical and horizontal extent of contamination (B.3.C.2(a)).

Surface samples and borings were advanced as close as possible, but not within, the waste trenches.

Yes. Results indicate that contamination has not migrated significantly from the trenches.

During recommended removal action at this site, samples should be collected to verify that all contamination above RRS1 levels has been removed.

Describe soil properties (B.3.C.2(c)).

See “Characterization of Environmental Setting – Soils” above.

NA

NA

Identify the direction of contaminant movement (B.3.C.2(d)).

Samples collected adjacent to waste trenches did not indicate significant contamination migration.

NA

NA

Extrapolate future contaminant movement (B.3.C.2(e)).

Since only slight RRS1 exceedances were detected, no extrapolation of future movement of contamination was conducted.

NA

NA

Contamination Characterization – Soil (B.3.C.2) (cont.)

Implement a soil boring investigation to determine the extent of soil contamination. Soil gas monitoring will be performed during drilling of all borings. Laboratory analysis of borings for contaminants of potential concern will be performed on soils at depths where either visual contamination is evident, or soil gas concentrations indicate contamination. All boreholes shall be properly abandoned.

A phased approach is being taken for the investigation SWMU B-15/16. The first phase included a soil gas survey followed by a geophysical survey to determine if any potential contamination exists at the site and to determine the extent of past waste management activities. Surface and subsurface soil samples were then collected to determine if there is surface and subsurface contamination. Borings were properly abandoned.

Partially. Only very slight RRS1 exceedances were detected in a few of the samples. Therefore, the horizontal extent of contamination has been determined.

To verify that the vertical extent of contamination has been defined, samples should be collected from the trench bottoms after the waste material has been removed.

Prepare a map of all areas included in the investigation (B.3.C.2(i)).

Figures included in this report show all areas included in the investigation.

Yes.

None.

All reporting limits should be below regulatory criteria.

RLs were approved by TNRCC on October 5, 1999. RLs are considered RRS1 standards for all analytes except metals.

Yes.

None.

Perform all analyses in accordance with the AFCEE QAPP.

All analyses were performed in accordance with the AFCEE QAPP and approved variances.

Yes.

None.

All data flagged with “U,” “F,” “M,” and “J” are considered usable for site characterization purposes.

Yes. “M” flagged data are also considered usable. The matrix interference is minimal and does not significantly affect the sample results.

None.

Contamination Characterization – Soil (B.3.C.2) (cont.)

Perform all analyses in accordance with the AFCEE QAPP (cont.).

All “R” flagged data are considered unusable. Non-compliance of the relative percent difference (RPD) of the field duplicate collected on the same day lead to “R” flagged data for one metal. There were five sets of field duplicates collected on the same day at different sites. The non-compliant RPD was a field duplicate collected for surface soil samples. This non-compliance resulted in flagging one metal for two soil boring samples. In addition, two out of the five sets of field duplicates collected were for soil boring samples. Both these sets of quality control (QC) data were within QC criteria.

Yes.

None. As the field duplicates for the soil boring samples were compliant, it is evident that the sample collection procedures were not compromised. Since the non-compliant field duplicate was a surface soil sample and the rejected metal was from a soil boring sample, the data are considered usable for characterization and closure purposes.

Contaminant Characterization – Sediment and Surface Water (B.3.C.3)

Conduct a surface water and sediment investigation to characterize contamination resulting from releases at the Facility.

SWMU B-15/16 is located in the Salado Creek floodplain. In the vicinity of CSSA, Salado Creek only contains water during and shortly after heavy precipitation. Therefore, surface water was not sampled as part of the SWMU B-15/16 investigation. Sampling of sediments in association with the SWMU B-15/16 investigation is not warranted due to the very limited amount of contamination detected at SWMU B-15/16.

NA

NA

Potential Receptors (B.3.D).

Collect the information necessary to describe the human populations and environmental systems that are susceptible to contaminant exposure from the Facility

Information regarding receptors is provided in the Risk Assessment Technical Approach Document (Volume 1-6). In addition, the Well Research Report identifies private groundwater users within 0.25-mile and public water suppliers within 0.5-mile of CSSA. Potential receptors are discussed in Section 1.2.5.

Yes.

None.