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[SWMU B-27 RFI Table of Contents]
Prepared for:
July 2002
On May 5, 1999, an Administrative Consent Order was issued to CSSA pursuant to §3008(h) of the SWDA, as amended by the RCRA, and further amended by the HSWA of 1984. In accordance with the RFI requirements of the Consent Order, this RFI report has been prepared to document the environmental condition and site closure requirements of SWMU B-27 and to recommend further investigation, if necessary, or to provide documentation necessary for site closure. The main objectives of the SWMU B-27 investigation are to determine if the site meets TNRCC requirements for closure, as described in Section 1.4, and to meet requirements of the Consent Order.
This specific RFI was performed by Parsons under the U.S. Air Force AMC Contract F11623-94-D-0024, Delivery Order RL17. AFCEE provided technical oversight for the delivery order. Based upon the project SOW, a set of work plans to govern the fieldwork was established. These include:
· Work Plan Overview (Volume 1-1, RL17 Addendum);
· Site-Specific Work Plan (Volume 1-2, SWMU B-27);
· Site-Specific Rework Plan (Volume 1-2, SWMU B-27);
· Field Sampling Plan (Volume 1-4, RL17 Addendum); and
· Health and Safety Plan (Volume 1-5, RL17 Addendum).
For this report, Section 1 provides the site-specific background and closure standard. Section 2 describes field actions and summarizes the findings. Section 3 presents the conclusions, evaluates attainment of data quality objectives, provides recommendations, and certifies the site closure. References cited in this report can be found in the Bibliography (Volume 1-1 of the Environmental Encyclopedia).
General information regarding the history and environmental setting of CSSA is provided in the CSSA Environmental Encyclopedia (Volume 1-1, Background Information Report). In that report, data regarding the geology, hydrology, and physiography are also available for reference.
SWMU B-27 is a medium priority site at CSSA that was previously used as a sanitary landfill. A review of aerial photographs dated 1934, 1957, 1966, 1973, 1985, 1991, 1996, and 1999 revealed only slight ground disturbance on the southern boundary of the site in 1957. All later photographs showed a grass-covered area.
SWMU B-27 is 550 feet long in the northwest direction and 200 feet wide in the southeast direction (Figure B27-1). A series of elongated one to two foot tall soil mounds and approximately one-foot deep trenches run the length of the site, giving SWMU B-27 the appearance of rolling topography. Seven narrow, shallow trenches and seven mounds run northwest-southeast on SWMU B-27, and range in length from 375 to 525 feet. The total volume of soil in the long, thin mounds is estimated at 975 cubic yards. The trenches are less than ten feet wide. Soil borings drilled at the site have shown evidence of waste burning. The crests of the soil mounds have a rounded shape suggestive of erosion since the time of their emplacement. The site is bounded on three sides by roads to the east, south, and west. A creek bed traverses the area just north of the site.
Background information regarding the location, size, and known historical use of SWMU B-27 is also included in the Environmental Encyclopedia (Volume 1-2, SWMU B-27). Volume 1-2 includes a Chronology of Actions and a Site-Specific Work Plan for SWMU B-27.
SWMU B-27 was reportedly used as a sanitary landfill. The contents of the landfill are not known. However, based on the typical types of wastes associated with CSSA waste disposal areas, the potential constituents of concern are metals, VOCs, and SVOCs.
SWMU B-27 is located in the western portion of CSSA, approximately 1,800 feet from the western facility boundary. It is a rectangular area oriented in the northwest direction, situated near the corner of Central Road and a gravel road (Figure B27-1). D-Tank is located across the gravel road, approximately 500 feet west of SWMU B-27, and AOC-53 is located approximately 300 feet southeast of SWMU B-27.
The soils at SWMU B-27 are representative of Krum Complex soils (Figure B27-2). Krum Complex soils cover approximately 20 percent of the land at CSSA and occur on slopes of two to five percent, occupying ‘foot’ slopes below Brackett and Tarrant soils. Generally, Krum Complex soils occur down-slope of prairie plains and receive sediments from higher elevations. Krum Complex soils are typically dark grayish-brown, calcareous clay dominant soils. At SWMU B-27, the Krum soils are 5.5 to 6.5 feet thick. Detailed descriptions of the CSSA soil types are provided in the CSSA Environmental Encyclopedia (Volume 1-1, Background Information Report, Soils and Geology).
SWMU B-27 is located on a northeast-trending slope that leads to a tributary of Salado Creek. This intermittent stream flows to the east. The elevation of the ground surface at SWMU B-27 is approximately 1,235 feet above sea level. The site was originally vegetated with juniper trees and grasses, with oak trees along the east and west boundaries. Prescribed burning activities were conducted by CSSA to clear the vegetation at the site prior to the investigation. SWMU B-27 is presently covered by grasses.
The lateral contact between the Upper Glen Rose and the Lower Glen Rose Formations traverses SWMU B-27 (Figure B27-3). The contact between these beds approximately follows an elevation contour of 1,233 feet at the site, with the Upper Glen Rose occupying the higher elevations in the southern portion of the site, and the Lower Glen Rose occupying the lower elevations in the northern third of the site.
The Upper Glen Rose consists of beds of blue shale, limestone, and marly limestone, with occasional gypsum beds. Generally, it outcrops in stream valleys and at the ground surface where soils are poorly developed or eroded. The thickness of the Upper Glen Rose Formation is about two feet at SWMU B-27. However, the Upper Glen Rose may be up to 150 feet thick within other areas at CSSA. It is underlain by the Lower Glen Rose, which is estimated to be 300 feet thick beneath CSSA. The Lower Glen Rose is a massive, fossiliferous, vuggy limestone that grades upwards into thin beds of limestone, marl, and shale. The Lower Glen Rose is underlain by the Bexar Shale facies of the Hensell Sand, which is estimated to be from 60 to 150 feet thick under the CSSA area. The Bexar Shale consists of silty dolomite, marl, calcareous shale, and shaley limestone. The geologic strata dip approximately ten to twelve degrees to the south-southeast at CSSA.
Based on current published information, there are two known major fault (shatter) zones at CSSA: the North Fault Zone and the South Fault Zone. SWMU B-27 is located just about 500 feet south of the North Fault Zone (Figure B27-3).
At CSSA, the uppermost hydrogeologic layer is the unconfined Upper Trinity aquifer, which consists of the Upper Glen Rose Limestone. Locally at CSSA, low-yielding perched zones of groundwater can exist in the Upper Glen Rose. Transmissivity values are not available for the Upper Glen Rose. Regionally, groundwater flow is thought to be enhanced along the bedding contacts between marl and limestone associated with the formation; however, the hydraulic conductivity across beds is thought to be low. This interpretation is based on the observation that static well levels are discordant in adjacent wells completed in different beds. Principle development of solution channels is limited to evaporite layers in the Upper Glen Rose Limestone.
The Middle Trinity aquifer is unconfined and functions as the primary source of groundwater at CSSA. It consists of the Lower Glen Rose Limestone, the Bexar Shale, and the Cow Creek Limestone. The Lower Glen Rose Limestone outcrops north of CSSA along Cibolo Creek and within the central and southwest portions of CSSA. As such, principle recharge into the middle Trinity aquifer is via precipitation infiltration at outcrops. At CSSA, the Bexar Shale is interpreted as a confining layer, except where it is fractured and faulted, therefore allowing vertical flow from the up-dip Cow Creek Limestone into the overlying, but down-dip Lower Glen Rose. Fractures and faults within the Bexar Shale may allow hydraulic communication between the Lower Glen Rose and Cow Creek Limestones. Groundwater flow within the middle Trinity aquifer is toward the south and southeast and the average transmissivity coefficient is 1,700 gpd/ft (Ashworth, 1983). In general, groundwater at CSSA flows in a north to south direction. However, local flow gradient may vary depending on rainfall, recharge, and possibly well pumping.
No site-specific information regarding groundwater is available. Two CSSA drinking water wells are located within ˝ mile of SWMU B-27. CSSA well number CS-10 is located approximately 1,600 feet southwest and well number CS-11, which is currently inactive, is located approximately 1,800 feet west-southwest of SWMU B-27. Between October 1992 and March 2000, water levels in Well CS-10 have ranged from 132.98 feet BTOC (December 1998) and 413.74 feet BTOC (April 1996), and in Well CS-11 they have ranged from 102.87 feet BTOC (October 1997) and 398.03 feet BTOC (February 1996) (Volume 5, Introduction to Groundwater Monitoring Program, Table 3). Several offsite water supply wells are also located within ˝ mile of SWMU B-27.
The nearest surface water body to SWMU B-27 is D-Tank. D-Tank is a reservoir located about 200 feet west of SWMU B-27 (Figure B27-1). An ephemeral tributary of the Salado Creek is approximately 15 feet north of SWMU B-27.
Cultural resources are prehistoric and historic sites, structures, districts, artifacts, or any other physical evidence of human activity considered important to a culture, subculture, or community for scientific, traditional, or religious purposes. The Quonset huts located approximately 800 feet northeast and 1,200 feet southeast of SWMU B-27 are considered cultural resources. There are no historical pits or trenches located near SWMU B-27.
A land use survey discussing local and possible future uses of groundwater and surface water, a water well survey, and a sensitive environmental areas survey at CSSA were completed during December 15 and 16, 1999. The results of this survey, along with results from a more in-depth survey to identify potential receptors, points of human exposure, and possible constituent pathways are presented in Section 3 of the Technical Approach Document for Risk Evaluation (Volume 1-6).
SWMU B-27 is located 1,800 feet east of the western boundary of CSSA. The nearest off-base residential housing is located approximately 2,000 feet west of SWMU B-27. Generally, CSSA is a controlled-access facility, so access is limited by a security guard and perimeter fence. No potential habitats for endangered species are located within a one-mile radius of SWMU B-27.
A small herd of cattle is maintained on CSSA by the USDA ARC. The cattle roam freely throughout the Inner Cantonment and in selected areas of the North Pasture. CSSA also manages wild game species for the purpose of hunting. White-tailed deer, axis deer, and wild turkey all roam freely throughout CSSA. A map of deer hunting stands which overlook mechanical feeders and planted food plots is located in Figure 5.2 of the Technical Approach Document for Risk Evaluation (Volume 1-6). SWMU B-27 is located approximately 1,300 feet northeast of hunting stand number 16.
Four water reservoirs are maintained at CSSA for the purpose of sport fishing. Two of the reservoirs are located in the northwestern and northeastern portions of the North Pasture while the other two reservoirs are located near the western boundary of the Inner Cantonment. One of the four site reservoirs (D-Tank) is located approximately 200 feet west of the site. This reservoir is not considered a potential receptor with respect to SWMU B-27 for several reasons. First, surface water runoff from SWMU B-27 is toward the north toward the adjacent ephemeral creek bed north of the site. The elevation of the base of the reservoir is reported to be 1,240 feet. Groundwater was not encountered within soil borings advanced to depths equivalent to the basal elevation of the reservoir. Therefore, the reservoir functions as a recharge feature for the area groundwater system thus negating the potential for impact to the reservoir from the site.
No previous investigations have been performed at SWMU B-27.
As described in Section 4.3 of the Risk Assessment Technical Approach Document (Volume 1-6), CSSA has opted to pursue closure of SWMU B-27 under the Risk Reduction Rule (30 TAC §335). If the site COC concentrations do not exceed background, then the site will be closed using RRS1. If the site exceeds background, then a determination will be made regarding the feasibility of cleaning the site to meet background concentrations. If the decision is made to clean the site to background, closure under RRS1 will be sought. However, if it is determined that the site cannot be closed to meet background concentrations, then the site will be closed under TRRP. A notification of intent to close sites identified to date (including SWMU B-27) in accordance with the former RRR was sent to the TNRCC on July 12, 1999. TNRCC acceptance of this notification was received on October 5, 1999.
RRS1 requires that the site be closed following removal or decontamination of waste, waste residues, and contaminated operation system components; and demonstration of attainment of cleanup levels (30 TAC §335.554). If closure requirements under RRS1 are attained and approved by the TNRCC Executive Director, then the owner is released from the deed recordation requirement.
Since the COCs for SWMU B-27 are metals, VOCs and SVOCs, the RRS1 standards should be the soil or rock background values for metals and the RLs for VOCs and SVOCs. Background metals levels were statistically calculated for CSSA soils and the Glen Rose Limestone, and are reported in the Second Revision to the Evaluation of Background Metals Concentrations in Soil Types (Parsons, February 2002). The values are used in this report as RRS1 comparison criteria, and were approved by TNRCC on April 23, 2002.
SWMU B-27 was reportedly used as a sanitary landfill. The dates of its usage are unknown, and it is presently inactive. In an effort to characterize the site and determine its readiness for RRS1 closure, a geophysical survey was conducted at the site in 1996. In addition, surface and subsurface sampling were performed in 1996. However, the analytical data associated with the surface and subsurface samples were rejected by the EPA in 1999 due to questionable practices by the laboratory, ITS Laboratory in Richardson, Texas. Surface and subsurface sampling were repeated in March 2000, as described in this section. Analytical data for samples collected in 2000 are presented in Appendix A.
An EM geophysical survey was conducted at SWMU B-27 in March 1996. Prior to collecting the EM data, a grid system was established at the site which encompassed the areas of suspected ground disturbance. This grid consisted of staked locations separated by intervals ranging from 20 to 100 feet, depending on the size of the area and the amount of obstructions, if any. The grid for the SWMU B-27 geophysical survey was 460 feet by 560 feet with a 20-foot interval.
EM data were collected at 2-foot intervals along transects that were separated by 20 feet using the established geophysical survey grid. EM measurements were taken using a Geonics EM31-DL ground conductivity meter, and recorded with a Polycorder data logger. The conductivity meter consists of transmitter and receiver coils that are separated by 12 feet. The instrument has a nominal depth of penetration of approximately 16 feet when operated in the vertical-dipole mode. The instrument measures both quadrature- and in-phase components of an induced magnetic field. The quadrature-phase component is a measure of apparent ground conductivity while the in-phase component is more sensitive to the presence of ferromagnetic metal. A lateral variation in apparent ground conductivity indicates a lateral change in subsurface physical properties (i.e., related to degree of disturbance). Apparent ground conductivity is measured with a precision of approximately ±2 percent of the full-scale meter reading which corresponds to approximately 2 milliSiemens per meter (mS/m). The in-phase component of the EM-31 is the response of the secondary to primary magnetic field measured in units of parts per thousand (ppt). The primary magnetic field is due to the current source from the EM-31. The secondary magnetic field is due to induced currents within conductive material in the subsurface.
Data were collected by setting the instrument to record in an automatic vertical dipole mode. Readings were taken at 0.5 second intervals which corresponded to a reading every 2 feet along a given transect. Both apparent ground conductivity (i.e., quadrature phase) and in-phase data were recorded. The operator aligned himself along a transect and, with the instrument parallel to the transect, paced between marked or staked stations separated by 10 feet.
The EM-31 survey was completed according to the procedures described in Volume 1-4, Sampling and Analysis Plan, Section 1.1.2. Prior to the survey, a site near the SWMU that was determined to be free of disturbances and anomalies was selected and marked to perform background checks and calibration. The background checks were also performed after the survey. All calibration and before- and after-background readings were recorded in the field logbook.
During each field day, data were transferred from the data logger to computer diskettes. The data were processed using DAT31 software (Geonics, LTD) and contoured using Surfer software.
In accordance with the approved work plan, a soil gas survey was not performed in association with the current investigation conducted for SWMU B-27.
Three surface soil samples (SS01, SS02, and SS03) were collected on March 8, 1996, and analyzed for metals, VOCs, and SVOCs by ITS Laboratories. Two samples were collected from trenches (SS02 and SS03), and one from a soil pile between two trenches (SS01). All samples were collected from the top foot of soil. The analytical data for the soil samples was determined to be unusable by the EPA in April of 1999. The Work Plan was then amended in November of 1999 to allow for re-sampling of the soils at SWMU B-27 (RL17 Work Plan Amendment for Data Quality Rework at SWMU B-27).
Three surface samples were then re-collected at SWMU B-27 on March 20 and March 21, 2000. Sample locations are shown in Figure B27-4. Sample RW-B27-SS01 was collected on March 20, 2000, and samples RW-B27-SS02 and RW-B27-SS03 were collected on March 21, 2000. Samples were collected from the top one-half foot of soil adjacent to the locations of surface samples collected in 1996. Equipment decontamination procedures, as well as sample collection, preparation, handling, and shipping, are described in the Field Sampling and Analysis Plan (Volume 1-4, Field Sampling Plan, Quality Assurance Project Plan). Sample chain-of-custody documentation is included in Appendix B. QA and QC samples were collected as described in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan). Sampling locations were recorded with a Trimble Asset-grade GPS by Parsons. Survey methodology is described in the Amendment to the Field Sampling Plan (Parsons ES, 2001b). The sample locations and analytical data will be incorporated into the CSSA GIS.
RW-B27-SS01 and a field duplicate were collected on March 20, 2000. A field duplicate, matrix spike, and spike duplicate of RW-B27-SS03 were also collected. In total, three environmental samples, two field duplicates, one equipment blank, two trip blanks, one matrix spike, and one matrix spike duplicate were submitted for analyses of metals to O’Brien and Gere Laboratory in Syracuse, New York. Metals analyses included barium, chromium, copper, nickel, and zinc (SW-6010B); arsenic (SW-7060A); cadmium (SW-7131A); lead (SW-7421); and mercury (SW-7471A). Samples were submitted to APPL Laboratory in Fresno, California for analysis of VOCs (SW-8260B) and SVOCs (SW-8270C).
The soils at SWMU B-27 are Krum Complex soils. Generally, the soils in the uppermost foot of the soil profile at SWMU B-27 were observed to be dark brown, silty clay, containing minor sub-angular limestone clasts and roots.
On August 26, 1996, three soil borings were advanced at SWMU B-27. SB01 and SB02 were drilled at the same location as SS01 and SS02, respectively. SB03 was drilled just past the outermost soil pile on the northeast side of the site. Samples were collected from SB01 at 5 and 11 feet, from SB02 at 5.5 and 10 feet, and from SB03 at 1, 4.5, and 12.5 feet. Due to a laboratory error, a soil boring was advanced adjacent to SB03 to re-collect a SVOC sample from a depth of 4.5 feet on May 15, 1997. The soil boring samples were sent to ITS Laboratories for analysis of metals, VOCs, and SVOCs.
During drilling in 1996, water was noted in SB02 after 48 hours had elapsed after drilling. However, this water is attributed to a heavy rainfall event that occurred six hours before drilling. Fill materials were identified at the surface of each boring location. The fill material was observed to contain glass, metallic debris, and a 1960’s copper penny. The bulk of fill material was observed at SB03, where buried waste material was observed in the borehole. Charred material was observed from two to six feet deep in SB03. As described previously, the analytical data for the soil samples collected in 1996 and 1997 from the site were determined to be unusable by the EPA.
Three soil borings (RW-B27-SB01, RW-B27-SB02, and RW-B27-SB03) were re-drilled on March 20 and 21, 2000, adjacent to the borings advanced in 1996. The borings ranged in depth from 10.5 to 13.7 feet bgs. Subsurface soil samples were collected with a split-spoon sampler and hollow-stem auger until advancement refusal was encountered. Once refusal was encountered, rock samples were collected with an air core and a core barrel.
On March 21, 2000, samples were retained from RW-B27-SB01 at 5 to 5.5 feet and 10.5 to 11 feet, and from RW-B27-SB03 at 0 to 0.5, 4 to 4.5, and 12.5 to 13 feet. A field duplicate was collected for RW-B27-SB01 (5 to 5.5 feet). Two samples were collected from RW-B27-SB02 at 5 to 5.5 feet and 9.5 to 10 feet on March 20, 2000. A field duplicate, matrix spike, and spike duplicate from RW-B27-SS03 were also retained. A total of six environmental samples, two field duplicates, two trip blanks, two matrix spikes, and two matrix spike duplicates were submitted for analyses to APPL for analysis of VOCs and SVOCs and to O’Brien and Gere for analysis of metals. Analytical methods used for surface soil samples were also used for subsurface samples.
The natural soils at SWMU B-27 are representative of Krum Complex soils. Fill materials were identified within the upper portions of the material profiles at each of the borings. Generally, soil and fill material comprised the topmost 5.5 to 6.5 feet at SWMU B-27. The soil observed in 1996 was dark brown silty clay, containing trash (wire, metal, glass, charred material) throughout the soil profile. No significant differences were noted in the materials encountered within the 2000 borings as compared to the 1996 borings.
In accordance with the approved work plan, groundwater was not investigated in association with the current investigation conducted for SWMU B-27. Groundwater was not encountered in any of the borings during drilling activities conducted at the site in March 2000.
The geophysical surveys revealed subsurface anomalies as described below, possibly related to past waste disposal activities. Both the in-phase component and the quadrature phase component of the EM survey revealed anomalies throughout portions of SWMU B-27. The in-phase portion revealed multiple anomalies oriented in northwest-southeast trending lines which may be related to waste management activities such as buried material containing metal (Figure B27-5). The quadrature phase component (apparent conductivity) also revealed an anomalous area throughout the central portion of the SWMU that is potentially related to subsurface disturbance (Figure B27-6). These anomalies could potentially be related to waste management activities because they are clearly visible in both components of the survey. In-phase readings during the EM survey ranged from a minimum of -1 parts per thousand (ppt), to a high of 1.0 ppt. Quadrature-phase readings ranged from a low of 30 milliSiemens per meter (mS/m), to a high of 55 mS/m.
In accordance with the approved work plan, a soil gas survey was not performed in association with the current investigation conducted for SWMU B-27.
All analyte concentrations in surface soil samples were below RRS1 comparison criteria. The detected constituents are summarized in Table B27-1, with the RRS1 standards applicable to the data. A complete list of results is provided in Appendix A.
Metals concentrations in samples collected from RW-B27-SB01 (10.5-11.0 feet bgs) and RW-B27-SB03 (4.0-4.5 feet bgs) exceeded RRS1 (background) concentrations. The only SVOC detected above the RL was a common laboratory contaminant, bis(2-ethylhexyl)phthalate, and no VOCs were detected above RLs. These data are presented in Appendix A and the detected constituents are summarized in Table B27-2, along with the appropriate RRS1 comparison concentrations.
Several VOCs and SVOCs were detected at concentrations below RLs. Benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(g,h,i)perylene, bis(2-ethylhexyl)phthalate, chrysene, fluoranthene, indeno(1,2,3-cd)pyrene, and pyrene were detected at low concentrations. These compounds are indicative of past burning activities.
The VOC concentrations associated with each of the samples collected for the investigation were below applicable RLs, therefore RRS1 criteria for VOCs have been met. VOCs and SVOCs detected below RLs were benzene, methylene chloride, toluene, naphthalene, 1,2,3-trichlorobenzene, and benzo.
Four out of six samples, RW-B27-SB01 (5 to 5.5 ft), RW-B27-SB01 FD (5 to 5.5 ft), RW-B27-SB02 (9.5 to 10.0 ft), and RW-B27-SB03 (12.5 to 13 ft) contained reported concentrations of bis(2-ethylhexyl)phthalate greater than the sample RLs. The reported exceedances ranged from 0.96 to 2.9 mg/kg, and the RL for all of these samples was 0.7 mg/kg. Bis(2-ethylhexyl)phthalate was also reported in sample numbers RW-B27-SB01 (10.5-11.0 ft) and RW-B27-SB02 (5.0-5.5 ft) at concentrations below the laboratory RLs.
Metals concentrations exceeded background in the sample collected from 4 to 4.5 feet bgs at RW-B27-SB03, and the sample collected from 10.5 to 11 feet bgs at RW-B27-SB01. At RW-B27-SB03 (4-4.5 ft), copper (47.8 mg/kg), lead (210 mg/kg), and zinc (128.4 mg/kg) concentrations exceeded background. The lead sample was diluted by a factor of 100. In the duplicate sample collected at RW-B27-SB01 (10.5-11 ft), barium (19.3 mg/kg), copper (16.6 mg/kg), and zinc (17.0 mg/kg) concentrations exceeded background. However, in the original sample collected at the same location, only barium (13.4 mg/kg) exceeded background.
Soil boring logs from the borings advanced in 1996 are presented in Appendix C. According to the Re-Work Plan (RL17 Work Plan Amendment for Data Quality Rework at SWMU B-27), new boring logs were not to be recorded, but the differences between the 1996 and 2000 borings were to be noted. The borings advanced in 2000 were advanced adjacent to the 1996 borings. Groundwater was not encountered in the borings collected in 2000, and no significant differences were observed in the materials encountered within the borings.
In accordance with the approved work plan, groundwater samples were not collected in association with the current investigation conducted for SWMU B-27. Groundwater was not encountered in any of the soil borings during drilling in March 2000.
SWMU B-27 was reportedly used, at an unknown time, as a sanitary landfill. The site consists of a series of elongated trenches and soil piles. A geophysical survey conducted in 1996 revealed an anomalous area associated with the trenches and soil piles present at the site.
Three soil borings were drilled at the site in March 2000. Waste material was encountered at a depth of 2 to 6 feet bgs in one of the borings, RW-B27-SB03. A sample collected at 4 to 4.5 feet in this boring showed copper, lead, and zinc concentrations above RRS1 criteria. In addition, at RW-B27-SB01 (10.5-11 ft), barium, copper, and zinc levels slightly exceeded background.
Bis(2-ethylhexyl)phthalate was detected above the RRS1 in four out of six subsurface samples, but none of the surface samples. However, in the absence of any other exceeding VOCs or SVOCs, bis(2-ethylhexyl)phthalate concentrations detected in exceedance of the RL are considered to be associated with laboratory or sampling equipment. The equipment blanks collected on March 20 and 21, 2000, which may be used for comparison to the SWMU B-27 samples with detected bis(2-ethylhexyl)phthalate, had a reported concentration of 1.71 mg/kg. No other VOCs or SVOCs were reported above laboratory RLs. Based on the results of the RFI sampling, VOCs and SVOCs can be removed from the list of soils contaminants of potential concern.
Overall data quality objectives (DQOs) for the investigations at CSSA are provided in Volume 1-1 behind the RFI Addendum tab (Section 11 of the Work Plan Overview). A detailed list of DQOs for SWMU B-27, along with an evaluation of whether each DQO has been attained, is provided in Appendix C. As described in Section 1, the main objectives of the SWMU B-27 investigation are to determine if the site meets TNRCC requirements for RRS1 closure and to meet requirements of the 3008(h) Administrative Consent Order.
All data generated during the SWMU B-27 investigation were reviewed to confirm conformance with the AFCEE QAPP; the data verification reports are included in Appendix D. All data are considered useable for site characterization purposes. Although several results are flagged with an “M”, these results are considered useable because the matrix interference is minimal and does not significantly affect the sample results. Results for one analyte, cadmium, were flagged with “R”. However, the data are still considered usable, as described in Appendix D. In addition, the duplicate of the “R” flagged sample was not rejected.
Geophysical anomalies and waste material encountered during drilling indicate that the site does not meet the TNRCC RRS1 requirement for removal of all waste. Some of the 3008(h) RFI requirements, such as determination of vertical extent of contamination, have also not yet been met. Because buried waste is known to exist on the site, comparison to Tier 1 levels was not conducted.
Geophysical anomalies and buried waste were detected beneath the surface at SWMU B-27 during the RFI. Therefore, it is recommended that remediation at SWMU B-27 be conducted. To meet RRS1 closure requirements, the buried waste at SWMU B-27 should be excavated and properly disposed of. Based on the results of the geophysical survey, it is estimated that there are three trenches containing approximately 17,800 cubic yards of material. Waste and waste residue within these trenches should be excavated and confirmation soils samples obtained. Samples of the excavated material should be collected for characterization purposes. Landfills typically require approximately one characterization sample per 250 cubic yards of material. The large estimated volume of waste from SWMU B-27 would require 72 samples.
It is recommended that confirmation samples be analyzed for barium, chromium, copper, and zinc (SW-6010B); lead (SW-7421); and mercury (SW-7471A). The resulting excavations should be backfilled with clean fill material, and the ground surface should be graded. If the soil in the long, thin mounds is not contaminated, it can be used to regrade the site. Following regrading, the site should be reseeded/revegetated with native drought-tolerant species.