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Final SWMU B-20 and B-21 RCRA Facility Investigation Report

Section 2 - Field Investigation

2.1 - Field Actions

As outlined in the Environmental Encyclopedia site-specific work plan (Volume 1-2, SWMU B-20/21), several activities were performed at SWMU B-20/21. The work performed under the current investigation includes conducting soil borings and additional UXO clearance activities. The UXO removal activities included removing the UXO and scrap metal from the soil via soil sifting. The sifted soil was then stockpiled and sampled at a rate of at least one sample per 500 yd³. Each sifted sample was analyzed for metals (arsenic, barium, cadmium, chromium, copper, lead, mercury, nickel, and zinc) and explosives. As part of the rework required due to ITS’ questionable practices, two soil samples from each of the 8 borings were submitted to a laboratory for analytical testing of explosives. All field activities conducted were in accordance with the field sampling and analysis plan (Volume 1-5, Field Sampling Plan, Quality Assurance Project Plan, and RL33 Addendum). Sample chain-of-custody documentation is provided in Appendix C.

The scope of the current investigation included:

All samples were obtained using a decontaminated trowel, split spoon, or core barrel. All decontamination, sample preparation and handling followed those protocols established in the Field Sampling and Analysis Plan (Volume 1-5, Field Sampling Plan, Quality Assurance Project Plan, and RL33 Addendum). Environmental sampling also included the collection and submittal of QA and QC at those frequencies outlined in the AFCEE QAPP (Volume 1-4, Quality Assurance Project Plan).

In addition to the RFI, interim measures are also being taken at the site, in accordance with the Consent Order, to address stockpiled sifted soil at the site. Results of sampling associated with the interim measures are also described in this RFI report because they are important for site characterization. However, plans for treatability studies associated with these soils are discussed in the Soil Pile Disposition Assessment Report.

2.1.1   UXO Clearance

In January 1997, UXO identification and removal activities were continued at the site. Soils from the northern portion of the site, shown as the grid area in Figure B20/B21-5, were excavated and sifted to remove remaining UXO and scrap metal. As described in Section 1.3.3.1, initially these items were removed during a "mag and flag" UXO identification operation. However, the large amount of buried metallic debris in this portion of the sites made this effort extremely labor intensive. Each individual metallic item identified by a magnetometer had to be flagged and hand-dug. Many of these items were found to be nails and other non-UXO debris. Therefore, sifting was identified as a cost-effective method for removing UXO from the subsurface.

UXO identification and removal activities were conducted between January 27 and May 19, 1997. UXO specialists from UXB International in Chantilly, Virginia conducted the UXO identification and removal, with oversight from Parsons ES. Schonstedt magnetometers were used to aid in locating UXO and metal scrap. A trailer-mounted electromagnet was also pulled over the site to remove metal debris and UXO. Photographs of the UXO removal activities are provided in Appendix F.

The sifting equipment was mobilized to the site on April 7, 1997, and the sifting operation commenced on the following day. Material in the northern six-acre area, with focus on the two grids that had not been previously cleared, was excavated with a backhoe. Excavation was generally to a depth of only 6 inches to one foot, unless waste indicated that further excavation was necessary. The excavated material was loaded into a hopper that encased breaker bars that broke the soil into small particles. The soil then moved up a conveyor belt to a shaker screening plant equipped with a ¾-inch mesh screen. The fine soil size fell through the shaker screen onto a conveyor “stacker,” which stockpiled the sifted soil.

UXO specialists examined all waste as it was excavated, as it was loaded into the hopper, and as it was discharged from the sifter. Most UXO was identified during excavation activities. Material left over in the screen after being sifted included metal scrap, limestone cobbles, clumps of hard clay, and UXO. This material was spread out on the ground surface and metal scrap and UXO were removed by hand-picking or with a trailer-mounted electromagnet. A final inspection of the remaining material was conducted to ensure it was UXO-free.

As material was sifted, discharged soil was stockpiled on site. At the conclusion of sifting operations at the site on May 19, 1997, a total of approximately 2,700 cubic yards of soil were stockpiled in five piles. The piles were situated in the northern portion of the site; however, in early June 2001, one pile was removed for a Phosphate-Induced Metals Stabilization (PIMS) treatability study. The remaining piles (except for 10 cubic yards) will also be addressed as part of the PIMS treatability study. Results will be reported in a PIMS Final Report due in September 2002. The remaining 10 cubic yards will be used for a treatability study planned as part of the Soil Pile Disposition Assessment.

On June 3, 1997 and between September 11 and 16, 1997, UXB personnel returned to the B-20 site to conduct final site restoration activities. Per CSSA’s request, each of the soil mounds on the east side of the site and each of the former detonation craters were graded level with the surrounding ground surface. Several additional UXO items were identified on the ground surface at this time.

All metal scrap found at the site was placed into roll-off containers and later transported to Newell Recycling in San Antonio, Texas. All UXO found at the site was segregated and later detonated at SWMU B-20 on September 25, 1997. TNRCC approved the detonations associated with the UXO investigations by letter dated April 4, 1997.

2.1.2   Soil Stockpile Disposition Samples

On May 9, 1997, one soil sample was collected from each of the five soil stockpiles to assess treatment/disposal options. These samples were identified as B20-SIFT1 through B20-SIFT5. The sifted soils were submitted to ITS Laboratories in Richardson, Texas for lead analysis (SW-7421). Results of the samples indicated that lead in the sifted soils exceeded background criteria. However, due to unacceptable practices by ITS Laboratories, in 1999 the EPA determined that these samples were not suitable to document soil conditions and could only be used for screening purposes.

On March 28, 2000, 13 additional sifted soil samples were collected as part of the soil pile disposition assessment and five sifted soil samples were collected as part of rework activities. All eighteen samples were analyzed for metals, including barium, chromium, copper, nickel, and zinc (SW-6010A); arsenic (SW-7062); cadmium (SW-7131); lead (SW-7421); and mercury (SW-7471). All of the metals analyses, except those for the five rework samples, were conducted by APPL Laboratory in Fresno, California. The five rework samples were analyzed by O’Brien & Gere Laboratory in Syracuse, New York. Eight of the 18 samples were analyzed for explosives by DataChem Laboratory in Salt Lake City, Utah using EPA method SW-8330. Sample analysis is summarized in Table B20/21-1. Three samples were analyzed for VOCs (SW-8260B) and SVOCs (SW-8270C) by APPL Laboratory. The samples for VOC analysis were recollected on April 21, 2000 due to problems with the trip blank. Samples were collected at random depths and locations in each pile, using a USEPA-approved random sampling methodology for stockpiles described in 40 CFR 761.

Table 1 - Summary of Sifted Soil Analytical Program

2.1.3   Waste Removal

In July 1999, a total of 402,680 pounds (approximately 120 cubic yards, including about 100 cubic yards from SWMU B-20 and 20 cubic yards from SWMU B-21) of sand containing shot material were disposed of as hazardous waste (due to elevated lead levels). This material was suspected of being generated at the Building 90 firing range and had been disposed of at an unknown date in the northern portion of the B-20 and the B-21 site. The three locations that the material was removed from are shown in Figure B20/21-5. Prior to disposal, the material was carefully inspected for any possible UXO by USA Environmental, Inc. No UXO was found.

These soils were stabilized with an approximate 14% (by weight) Portland cement mixture and transported by Eagle Construction & Environmental Services, Inc. The material was stabilized and disposed of at Texas Ecologists Landfill in Robstown, Texas in accordance with applicable regulations. The procedures included in the Waste Analysis Plan (Parsons ES, 1998) were followed during the waste removal and disposal activities.

2.1.4   Soil Borings

In March 2000, eight soil borings were drilled and sampled at the site. UXO personnel cleared driving paths and drilling locations before site work was begun. The borings were conducted to duplicate the soil boring sampling activities previously conducted in November and December 1994. Boring locations are shown in Figure B20/21-4. This re-sampling effort was necessary because the 1994 explosive analyses (discussed in Section 1.3 of this report) performed by ITS Laboratories, Inc., were deemed invalid by the EPA in 1999 due to unacceptable practices by ITS.

The eight borings were advanced at the approximate locations of the 1995 sampling event. With the exception of borings RW-B20-SB01 and RW-B20-SB02, two samples were collected from each boring at depths of 12-15 feet and boring terminus at 20 feet. At boring RW-B20-SB01, samples were collected at depths of 0 to 0.5 feet, 5.0 to 5.5 feet and 15.0 to 15.5 feet bgs. At boring RW-B20-SB02, samples were collected at 5.0 to 5.5 feet and 15.0 to 15.5 feet bgs. A total of 17 environmental samples were submitted to DataChem Laboratory in Salt Lake City, Utah for explosive analysis (SW-8330). Eight samples, ranging in depth from 5 to 17 feet bgs were submitted to Southwest Research Institute in San Antonio, Texas for perchlorate analyses using EPA Method 314M. At the time of sampling, no discernable evidence of contamination was noted. Soil boring logs are located as an appendix to the Remedial Investigation Report for B-20 Former Open Burn/Open Detonation Area.

2.1.5   Groundwater Samples

Groundwater samples were not collected during the current investigation at SWMU B-20/21. A sample of groundwater was collected from soil boring SB1 conducted in 1995. Discussion of the 1995 sample is presented in Section 1.3.2.4 and the Remedial Investigation Report for B-20 Former Open Burn/Open Detonation Area.

2.1.6   Bench-Scale Treatability Studies

Three bench-scale treatability studies have been completed to test potential methods for remediating contaminated soils at SWMU B-20. Treatability studies testing phytoremediation, soil washing, and stabilization and off-site disposal were conducted. The results of each study are summarized in the following documents which are all included in Volume 4 of the Environmental Encyclopedia:

2.1.7   Phosphate-Induced Metals Stabilization Pilot Study

A Phosphate-Induced Metals Stabilization (PIMS) pilot study is ongoing at CSSA to demonstrate the efficacy of the technology for soil remediation of lead-contaminated soils and, potentially, for other firing and ordnance range applications. The demonstration is conducted under unsaturated conditions primarily at SWMU B-20. Refer to Figure B20/21-4 for the location of the PIMS study area within SWMU B-20. Portions of contaminated soils from SWMU B-20 were transported to SWMU B-10 for a similar PIMS demonstration. Once completed, the treated soils were delivered back to SWMU B-20.

The PIMS technology is designed to stabilize metals, particularly lead, using the natural additive Apatite II. Excavated soils from the site are mixed with 5 percent Apatite II to induce precipitation of the soluble lead. Results of this PIMS demonstration are to be provided in the PIMS Pilot Study Final Report.

2.1.8   Geophysical Survey

A geophysical survey was not conducted during the current investigation at SWMU B-20/21.

2.1.9   Soil Gas Survey

A soil gas survey was not conducted during the current investigation at SWMU B-20/21.

2.1.10   Surface Soil Samples

Surface soil samples were not collected during the current investigation activities at SWMU B-20/21.

2.2 - Results and Comparisons

2.2.1   UXO Clearance

A total of 507 UXO items were recovered and destroyed. An itemized list is included in Appendix A. Only items that were thought to be live or contain explosives are included in the list. Over half of the items (254 of the 507) were 20mm projectiles, and a large number (91 of the 507) were fuses or fuse components. The remaining items found included 20-pond fragmentation bombs, 3-inch projectiles, 75mm projectiles, 3-inch Stokes mortars, grenades, and various other items listed in Appendix A. All 20mm projectiles found were considered live ordnance because they potentially contained high explosives in the nose of the projectile. The UXO items recovered were destroyed by detonation on September 25, 1997 at SWMU B-20.

All items that were not live or did not resemble live ordnance were taken offsite for recycling as scrap metal. In the B-20 area approximately 2,700 cubic yards of material were sifted. A total of 100,280 pounds of metal debris were removed and recycled. The sifted soils were stockpiled into five stockpiles between approximately 450 and 590 cubic yards each.

2.2.2   Soil Stockpile Disposition Samples

A total of 18 samples were collected from the sifted soil material for VOCs, SVOCs, explosives, and metals analysis. Analytical results of the samples indicate that VOCs and metal constituents are present in the stockpiled soils. SVOCs and explosives were not detected in the samples. Sifted soil sample results are summarized in Table B20/21-2, and a complete tabulation of all results is provided in Appendix B.

Methylene chloride, toluene, and TCE were detected at very low concentrations in the three sifted soil samples that were analyzed for VOCs. All VOC results were below RLs. Methylene chloride was detected in B20-SIFT11, toluene was detected in B20-SIFT16, and TCE was detected in B20-SIFT06 and B20-SIFT16. However, concentrations of all these analytes were below RLs and therefore, below RRS1 criteria.

No explosives or SVOCs were detected in the samples.

One or more metals concentrations in every sifted soil sample exceeded CSSA background levels. As shown in Table B20/21-3, barium, copper, lead, and zinc concentrations most often exceeded background. Concentrations as high as 314 mg/kg barium, 1,267.6 mg/kg copper, 40,509.44 mg/kg lead, and 478.5 mg/kg zinc were detected.

2.2.3   Waste Removal

As described in Section 2.1.3, in July 1999, a total of 402,680 pounds (approximately 120 cubic yards) of contaminated soil and spent ammunition were excavated, stabilized, and disposed as hazardous waste at Texas Ecologists Landfill in accordance with applicable regulations.

Table 3 - Summary of Metals Levels Above Background in Sifted Soil

2.2.4   Soil Borings

Results of the seventeen soil boring samples analyzed for explosives in March 2000 indicated that no explosives were detected in any of the samples. Therefore, all results were below the RRS1 and site closure with respect to explosive compounds is complete. Results of the current explosives analyses are provided in Table B20/21-4 and Appendix B. Results of the previous soil borings, with analyses by Terra Laboratory, are presented in Volume 1-2, SWMU B-20/21 tab.

One sample was also collected from each boring for perchlorate analyses. Results of the eight samples analyzed in April 2000 indicated that no perchlorates were detected above the minimum reporting limit of 20 μg/kg in any of the samples. Results of the perchlorate analyses are provided in Appendix C.

2.2.5   Groundwater Samples

Results of the groundwater sample collected in 1994 from boring SB01 at SWMU B-20/21 indicated that all analytes were below RRS1 standards. Additional information can be found in the Remedial Investigation Report for B-20 Former Open Burn/Open Detonation Area. No other groundwater sampling has been conducted.

2.2.6   Bench-Scale Treatability Studies

As described in Section 2.1.6, three treatability studies were conducted using sifted soils from the B-20 site. At the time that the treatability studies were conducted, lead was identified as the primary contaminant. The results of the studies are provided in Volume 4 of the Environmental Encyclopedia. A summary of the findings is provided in the following paragraphs. None of the technologies were found to be able to achieve RRS1 cleanup levels alone. Instead, consideration of a treatment process was recommended.

The results of the soil washing treatability study indicate that the physical treatment step of the soil washing process produces significant reductions in the lead concentrations in the soil composite samples. However, the treatment technique results only in recovery of the larger particulate lead fractions within the soil matrix. Therefore, this remediation process must be used in conjunction with another technique in order to recover small particulate and ionic fractions to reach cleanup standards.

In the stabilization treatability study report, it was recommended that use of phosphate-based stabilization be evaluated in order to treat soils with high levels of metallic lead concentrations.

Finally, in the phytoremediation treatability study report, additional study regarding several issues was recommended. These issues included establishment of a site-specific risk-based cleanup level, potential for movement of metals within the soil matrix, suitability of phytoremediation in the central Texas climate, likelihood of deer and other animals to eat the Indian mustard plant used in the treatability study, additional evaluation of costs for full-scale implementation, and additional information to optimize the time of harvest.

2.2.7   Phosphate-Induced Metals Stabilization Pilot Study

As discussed in Section 2.1.7, there is an ongoing PIMS pilot study at SWMU B-20. Results of this demonstration will be presented in the PIMS Study Final Report.

2.2.8   Geophysical Survey

A geophysical survey was not conducted during the current investigation at SWMU B-20/21.

2.2.9   Soil Gas Survey

A soil gas survey was not conducted during the current investigation at SWMU B-20/21.

2.2.10   Surface Soil Samples

As discussed in Section 1.3, surface soil samples were collected at SWMU B-20/21 in 1994. Results can be found in the Remedial Investigation Report for B-20 Former Open Burn/Open Detonation Area. No new surface samples were collected at SWMU B-20/21.

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