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Final Solid Waste Management Unit B-4 RCRA Facility Investigation Report
Section 2 - Field Investigation
As outlined in the Environmental Encyclopedia site-specific work plan (Volume 1-2, SWMU B-4), the project RFI requirements were to drill twelve soil borings and to collect soil samples for VOCs, SVOCs, explosives, and metals analyses. All field activities conducted were in accordance with the Field Sampling and Analysis Plan (Volume 1-4, Field Sampling Plan, Quality Assurance Project Plan, and RL83 Addendum).
2.1.1 Geophysical Survey
In accordance with the approved work plan, a geophysical survey was not performed in association with the investigation conducted for SWMU B-4. Figure B4-4 illustrates the locations of geophysical anomalies identified at SWMU B-4 during previous investigations.
A soil gas survey was performed in conjunction with soil gas surveys performed at other sites: SWMU B-3, AOC 55, AOC 57, AOC 63, AOC 65 and the WWTP from January 2, 2001 through February 23, 2001. Twenty soil gas survey sample points were collected. Soil gas sampling depths varied from 2 feet to 10 feet, and were usually determined by refusal. Additional information on the methodology and results for this soil gas survey is located in Volume 3-1 Solid Waste Management Units, behind the Soil Gas Survey and SWMU B-4 tabs.
Thirteen surface soil samples and one duplicate surface soil sample were submitted for analytical testing during this phase of the investigation. These samples were collected in conjunction with the subsurface soil sampling program; therefore, the analytical results obtained for the surface soil samples are included together with the discussion of the subsurface soil/rock sample results presented in Section 2.2.4.
Between April 3 and 6, 2000, twelve soil borings (B4-SB06 through B4-SB17) were drilled to characterize subsurface soils at SWMU B-4. The locations of the borings are shown in Figure B4-4. Initially, all borings were planned to be within the geophysical anomalies identified during previous investigations. However, before drilling began, additional information regarding the possible presence of UXO in the trenches became available. Therefore, drilling within the trenches was not possible. Borings were drilled as close as possible to the trenches.
Four samples were obtained from each boring (except B4-SB10); one soil sample was taken from the surface, one from a depth of approximately 5 feet bgs, one at a depth of approximately 10 feet bgs, and one at the total depth of the boring. Drilling at SB10 had to be terminated at 9.5 feet because metal waste, potentially including UXO, was encountered at that depth. Boring logs associated with boreholes conducted at SWMU B-4 are contained within Appendix B. Boring depths ranged from 9.5 to 19.7 feet bgs. Lithologic descriptions from the boring logs indicate silt and clay was encountered overlying limestone and marl, identified as the Upper Glen Rose Formation.
The analytes for the soil samples collected at SWMU B-4 were VOCs (SW-8260B), SVOCs (SW-8270C), arsenic (SW-7062), barium (SW-6010B), cadmium (SW-7131A), chromium (SW‑6010B), copper (SW6010B), lead (SW-7421), mercury (SW-7471), nickel (SW‑6010B), zinc (SW-6010B), and explosives (SW-8330). A total of 52 soil/rock samples (including three duplicates) were submitted for analysis. All samples were submitted to APPL Laboratories, Inc. of Fresno, California, except those for explosives analysis which were submitted to DataChem Laboratory in Salt Lake City, Utah.
Samples collected above the bedrock were obtained using a decontaminated hollow-stem auger and split-spoon sampler. Rock samples were obtained by air core using a decontaminated core barrel. All decontamination, sample preparation and handling followed those protocols established in the Field Sampling and Analysis Plan (Volume 1-4, Field Sampling Plan, Quality Assurance Project Plan). Environmental sampling also included the collection and submittal of QA and QC samples at those frequencies outlined in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan). All sampling points were surveyed by Parsons ES using a Trimble Asset-grade GPS. Surveying methodologies are described in the Amendment to the Field Sampling Plan (Parsons ES, 2001b). All sample location and analytical data will be incorporated into the CSSA GIS after it has been approved by AFCEE and CSSA.
2.1.5 Groundwater SamplesIn accordance with the approved work plan, groundwater samples were not collected in association with the current investigation conducted for SWMU B-4. No groundwater was encountered in the soil borings.
In accordance with the approved work plan, a geophysical survey was not performed in association with the current investigation conducted for SWMU B-4.
As described in Section 1.3.3, PCE was detected at a maximum concentration of 3.8 μg/L in a sample collected just northwest of the SWMU B-4 boundary, near SWMU O-1. Additionally, as described in Section 2.1.2, a soil gas survey consisting of twenty soil gas data points was conducted at SWMU B-4 from January to February 2001. Minor amounts of benzene were detected in one soil gas sample from the SWMU B-4 soil gas survey. The detection of this compound is attributed to contamination from the gas generator used to power the vacuum pump and/or the combustion engine of the geoprobe truck. Benzene was detected at sampling point B4-1 at a concentration of 0.02 mg/L. No figure is included in this report depicting a contaminant plume in this grid layout because the target compound benzene that was detected at a concentration of 0.02 mg/L is attributed to the geoprobe rig and gas generated exhaust. No other target VOC compounds were detected. Additional information on the methodology for this soil gas survey is located in Volume 3-1.1 Solid Waste Management Units, behind the SWMU B-4 tab.
Surface soil samples were obtained during soil boring drilling and sampling. The results of the surface soil sampling program are combined with the discussion presented in Section 2.2.4.
Several compounds exceeded RRS1 criteria, including the metals barium, cadmium, chromium, copper, nickel, mercury, and zinc, and organics toluene, methylene chloride, bis(2-ethylhexyl)phthalate, and dichlorofluoromethane. Table B4-3 lists all of the analytes detected at SWMU B-4. Appendix A contains all of the analytical results obtained from SWMU B-4 environmental samples. Metal debris was encountered in boring B4-SB10 at a depth of 6.5 feet bgs, and fill material was encountered in borings B4-SB08 and B4-SB09.
Barium concentrations were above the background level in thirteen of the samples: B4-SB07 (8.5-9 ft), B4-SB07 (14.5-15 ft), B4-SB08 (0-0.5 ft) and B4-SB08 (15-15.5 ft), B4-SB09 (14.5-15 ft), B4-SB12 (4.5-5 ft), B4-SB13 (10-10.5 ft), B4-SB14 (15-16 ft), B4-SB15 (9-9.5 ft), B4-SB15 (16.5-17 ft), B4-SB16 (9.5-10 ft), B4-SB16 (14.5-15 ft), and B4-SB17 (18.5-19 ft). Of these thirteen samples, only one (B4-SB08 (0-0.5 ft) is representative of soils, where a concentration of 776.45 mg/kg of barium was detected above the background level for barium in soils, 186 mg/kg. The remaining thirteen samples are representative of materials collected from the Glen Rose Formation. The highest concentration of barium in the Glen Rose was 30.19 mg/kg in B4-SB13 (10-10.5 ft). The background value for barium in Glen Rose Limestone is 10.0 mg/kg . The Texas-specific median background concentration for barium is 300 mg/kg (30 TAC 351.51(m)).
Three of the soil samples had cadmium concentrations that exceeded applicable RRS1 standards: B4-SB14 (15-16 ft), B4-SB16 (0-0.5 ft) and the duplicate of B4-SB16 (0-0.5 ft). Two of the samples, B4-SB16 (0-0.5 ft) and B4-SB16 (0-0.5 ft) are surface soil samples (Tarrant soils) and exceeded the background value for cadmium in soils of 3.0 mg/kg. Of the soil samples, the maximum concentration detected was 2.09 mg/kg cadmium. The maximum concentration detected in Glen Rose Limestone is 0.12 mg/kg in Sample B4-SB14 (15-16 ft), slightly above the Glen Rose background level of 0.1 mg/kg; however, cadmium was also detected in a laboratory blank associated with this sample.
Chromium concentrations were above the Glen Rose RRS1 background level of 8.1 mg/kg in fourteen samples: B4-SB07 (8.5-9 ft), B4-SB07 (14.5-15 ft), B4-SB07 (14.5-15 ft, field duplicate), B4-SB08 (15-15.5 ft), B4-SB09 (14.5-15 ft), B4-SB09 (14.5-15 ft, field duplicate), B4-SB11 (9.5-10 ft), B4-SB11 (15-15.5 ft), B4-SB14 (15-16 ft), B4-SB15 (9-9.5 ft), B4-SB15 (16.5-17 ft), B4-SB16 (9.5-10 ft), B4-SB17 (4-6 ft), and B4-SB17 (18.5-19 ft). These exceeding concentrations ranged from 10.4 mg/kg to 26.2 mg/kg. The Texas-specific median background concentration for chromium is 30 mg/kg.
Copper concentrations were above the RRS1 standards in three soil samples: B4-SB08 (0-0.5 ft), B4-SB09 (5-5.5 ft), and B4-SB10 (0-0.5 ft). Copper concentrations ranged from 26.66 mg/kg to 30.56 mg/kg in the soil samples, above the background value for soil of 23.2 mg/kg. All concentrations were above the Texas-specific median background concentration of 15 mg/kg.
The applicable RRS1 standard for mercury was exceeded in nine of the samples: B4-SB07 (0-0.5 ft), B4-SB08 (0-0.5 ft), B4-SB08 (15-15.5 ft), B4-SB09 (0.5 ft), B4-SB10 (0-0.5 ft) B4-SB10 (4.5-5 ft), B4-SB11 (0-0.5 ft), B4-SB16 (0-0.5 ft), and the duplicate of B4-SB16 (0-0.5 ft). Of these samples, SB08 (15-15.5) is representative of the Glen Rose Limestone, and the concentration was 0.13 mg/kg, slightly above the background value of 0.1 mg/kg. Mercury concentrations associated with soil samples that exceeded RRS1 standards ranged from 0.77 mg/kg to 16.99 mg/kg, above the background level in soils for mercury of 0.77 mg/kg.
Nickel concentrations exceeded the Glen Rose background level of 6.8 mg/kg in four samples: B4-SB07 (8.5-9.0 ft), B4-SB11 (9.5-10 ft), B4-SB14 (15-16 ft), and B4-SB15 (16.5-17 ft). The nickel concentrations in these four samples ranged from 9.18 to 15.44 mg/kg.
Zinc concentrations in Glen Rose Limestone slightly exceeded the Glen Rose background concentration of 11.3 mg/kg in six samples: B4-SB07 (8.5-9 ft), B4-SB09 (14.5-15 ft), B4-SB14 (4.5-5 ft), B4-SB14 (8-10 ft) FD, B4-SB14 (15-16 ft), B4-SB15 (9-9.5 ft) B4-SB15 (16.5-17 ft), and B4-SB16 (14.5-15 ft). These samples had zinc concentrations ranging from 11.64 mg/kg to 19.3 mg/kg. Zinc concentrations in soils exceeded the background level of 73.2 mg/kg in B4-SB08 (0-0.5 ft) at a concentration of 124.44 mg/kg. The soil concentration is the only detection above the Texas-specific median background concentration for zinc of 30 mg/kg.
2.2.4.2 VOC ResultsThree target VOC compounds, toluene, methylene chloride, and dichlorodifluoromethane, were detected above RRS1 levels in the subsurface soil samples.
Toluene was detected slightly above the RL in three samples: B4-SB06 (0-0.5 ft), B4-SB09 (0-0.5 ft), and a duplicate of B4-SB12 (0-0.5 ft). The detected toluene concentrations were 0.0066 mg/kg, 0.0103 mg/kg, and 0.0092 mg/kg, respectively. The RL for toluene is 0.005 mg/kg.
Methylene chloride concentrations exceeded the RL in samples B4-SB13 (0-0.5 ft), B4-SB14 (0-0.5 ft) and B4-SB14 (15-16 ft). The concentrations detected were 0.0118 mg/kg, 0.0093 mg/kg, and 0.0055 mg/kg, respectively. All three detections were flagged with a “B” indicating that the methylene chloride was found in an associated blank, as well as in the sample. The RL for methylene chloride is 0.005 mg/kg.
Two samples were identified with dichlorodifluoromethane concentrations that surpassed the RL of 0.005 mg/kg. Sample B4-SB16 (0-0.5 ft) had a dichlorodifluoromethane concentration of 0.0144 mg/kg and B4-SB16 (14.5-15 ft) contained a concentration of 0.0096 mg/kg.Other VOCs detected in SWMU B-4 samples included benzene and chloroform in nine samples, 1,2,4-trimethylbenzene in seven samples, sec-butylbenzene in six samples, trichlorofluoromethane in five samples, and ethylbenzene, TCE, and o-xylene in four samples. All of these detections were below RLs.
2.2.4.3 SVOC ResultsThe only SVOC detected in the subsurface soil samples submitted was bis(2-ethylhexyl)phthalate. It was found in fifteen of the samples but only four of those detections were above the RL of 0.7 mg/kg. The concentrations that exceeded the RL were found in samples B4-SB09 (14.5-15 ft) FD, B4-SB11 (5-5.5 ft), B4-SB11 (9.5-10 ft), and B4-SB11 (15-15.5 ft). The concentrations reported for these samples were 4.7 mg/kg, 14.0 mg/kg, 6.9 mg/kg, and 2.2 mg/kg, respectively.
One explosive compound, tetryl, was detected in one of the subsurface soil samples submitted. The sample B4-SB08 (10-10.5 ft) had a tetryl concentration of 0.19 mg/kg. This concentration is below the RL of 0.65 mg/kg for this compound.
In accordance with the approved work plan, groundwater samples were not collected in association with the investigation conducted for SWMU B-4. Groundwater was not encountered in any of the soil borings.