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SWMU B-28 RCRA Facility Investigation Report

Section 2 - Field Investigation

As outlined in the Environmental Encyclopedia site-specific work plan (Volume 1-2, SWMU B-28), the scope of the current RCRA facility investigation included UXO identification and removal activities.

In addition to the RFI, interim measures are also being taken to address stockpiled soil at the site in accordance with the consent order. 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. All decontamination, sample preparation, and sample handling followed the protocols established in the Field Sampling and Analysis Plan (Volume 1-4, Field Sampling Plan, Quality Assurance Project Pan, and RL33 Addendum).

2.1.1   Geophysical Survey

The findings of the EM and GPR geophysical surveys performed at the site in 1995 are described in Section 1.3. The results of the 1995 surveys are also included in the Groundwater Investigation and Associated Source Characterization Report (Parsons ES, 1996).

As part of the current investigation, magnetometers were used during UXO identification and removal activities. On February 24 and 25, 1997, Schonstadt magnetometers were used to sweep the entire site, and areas bordering the site to aid in locating buried metal debris and/or UXO. After the trenches were located and excavated, the trench bottoms were surveyed again with the magnetometers to ensure that no additional metal debris was present at a greater depth.

2.1.2   Soil Gas Survey

The soil gas survey conducted at the site in 1995 is described in Section 1.3. No additional soil gas surveys were conducted at the site during the current investigation.

2.1.3   Surface Soil Sampling

The surface soil sampling conducted during the soil boring activities in 1995 is described in Section 1.3. No additional surface soil sampling was conducted at the site during the current investigation.

2.1.4   Subsurface Soil Sampling

The subsurface soil/rock sampling conducted during the soil boring activities in 1995 are described in Section 1.3. No additional subsurface soil/rock sampling was conducted at the site during the current investigation.

2.1.5   Groundwater Sampling

The groundwater sample collected from the soil boring in 1995 is described in Section 1.3. No additional groundwater samples were collected during the current investigation at the site.

2.1.6   UXO Clearance

UXO identification and removal activities were conducted between February 24 and July 25, 1997. UXO specialists from UXB International in Chantilly, Virginia conducted the UXO identification and removal, with oversight from Parsons ES. The intent of the work was to excavate waste in trenches identified by the 1995 geophysical survey to remove any UXO.

Due to the amount of buried metal debris at the site, sifting was identified as a cost-effective method for removing UXO from disposal trenches. After decontamination, the sifting equipment was mobilized to the site upon completion of sifting at SWMU DD. The sifting operation commenced on June 1, 1997. Due to inclement weather, all sifting activities were suspended between June 5 and July 18, 1997. They resumed on July 21 and were completed at SWMU B-28 on July 25, 1997. Material in each of the trenches was excavated with a backhoe and 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 size soil fell through the shaker screen onto a conveyor “stacker”, which stockpiled the sifted soil. Photographs of the sifting operation are included in Appendix E.

UXO specialist examined all waste as it was excavated from the trenches, 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 a trailer-mounted electromagnet or handpicked. A final inspection of the remaining material was conducted to ensure that it was UXO-free.

Each trench was excavated until no additional waste material was encountered on the bottom or in each of the walls of each trench. The northern trench was approximately 300 feet long by 15 feet wide and the southern trench was approximately 100 feet long by 15 feet wide. Both trenches were less than five feet deep. Small arms ammunition and metal ammunition parts were disposed of in both trenches. Some scrap metal appeared to have melted and cooled, indicating that waste material may have been burned in the trenches.

As material was sifted, discharged soil was stockpiled on site. At the conclusion of sifting operations at the site on July 25, 1997, a total of 730 cubic yards of soil were stockpiled in one pile.

On July 14 and 25, 1997, additional UXO surface clearance was conducted by UXB International. Schonstadt magnetometers were used to aid in locating UXO and metal scrap. A trailer-mounted electromagnet was also pulled over the site to remove remaining metal debris and UXO. All metal scrap found on 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.

2.1.7   Soil Stockpile Disposition Samples

Two preliminary samples of sifted soil from the stockpile were collected on June 19, 1997 to identify potential contaminants. The samples were submitted to ITS Laboratories in Richardson, Texas for analysis. The samples were obtained by those methods previously described in Section 1.3, and analyzed for VOCs, explosives, and metals.

The results indicated that the metals in the sifted soils exceeded background criteria. VOCs and explosives were not detected in the soils, but barium, copper, mercury, and zinc exceeded background (above RRS1) concentrations for CSSA soils. Arsenic, cadmium, chromium, lead, and nickel were all detected at levels below background levels. However, in an April 1999 memo from EPA, these analytical results were deemed unsuitable for closure verification due to questionable activities by ITS Laboratories.

On April 21, 2000, four sifted soil samples (SIFT03- SIFT05, and RW-SIFT06) were collected to assess the treatment disposal options and to determine a viable method for disposition. Three of the samples were analyzed by APPL Laboratory for barium, chromium, copper, nickel and zinc (SW-6010A); arsenic (SW-7062); cadmium (SW-7131); lead (SW-7421); and, mercury (SW-7471). One sample was also analyzed for explosives (SW-8330) by Data Chem. Metals analyses on the rework sample were conducted by O’Brien and Gere Laboratory in Syracuse, New York. Samples were collected at random depths and locations in each pile, using a EPA approved random sampling methodology for stockpiles described in 40 CFR 761.

2.2 - Results and Comparisons

2.2.1   Geophysical Survey

EM and GPR geophysical surveys were conducted at SWMU B-28 in 1995. Results of these 1995 surveys identified two anomalies associated with two waste disposal trenches (north and south trench). These anomalies are shown on Figure B28-4.

In 1997, during UXO removal activities, UXO specialists used Schonstadt magnetometers to assist in locating metal debris or other magnetic anomalies, which were immediately removed or flagged for later removal. The magnetometers were also used at the completion of UXO removal activities to confirm that all metal debris had been removed from the site.

2.2.2   Soil Gas Survey

A soil gas survey was not performed during the current RFI. A soil gas survey was conducted at the site between June 29 and July 19, 1995. Results indicate that PCE concentrations were less than 1 μg/L in the collected samples. Soil gas sampling locations from the 1995 survey are included on Figure B28-4.

2.2.3   Surface Soil Samples

Surface soil sampling was not conducted during the current RFI activities. As discussed in Section 1.3, samples collected from the soil borings indicate that the surface soil at boring location SB03 slightly exceeds RRS1, or background levels. Additionally, the surface soil samples from boring locations SB03 and SB05 contained detectable levels of phthalate compounds. The presence of phthalates in these samples is believed to be laboratory or field sampling artifacts and not representative of soils conditions at CSSA.

2.2.4   Subsurface Soil Samples

Subsurface soil sampling was not conducted during the current RFI activities. As discussed in Section 1.3, samples collected from previous soil borings indicate that di-n-butylphthalate was detected above the RLs in borings SB03 and SB04. The presence of phthalates in these samples is believed to be associated with laboratory or field sampling equipment and not representative of site conditions. Di-n-butylphthalate is not known to have been used at CSSA and therefore is not a contaminant of concern at the site. The cadmium concentration in one sample collected at 29 feet bgs at SB01 also exceeded the background concentration.

2.2.5   Groundwater Samples

Groundwater sampling was not conducted during the current RFI activities. VOCs were not detected in the groundwater sample collected from boring SB01R in 1995. No other groundwater sampling was conducted at this unit.

2.2.6   UXO Clearance

During the UXO clearance at B-28, a total of only 9 UXO items were recovered, identified and destroyed. Items identified included one 4.50 cal round, one 20mm projectile, one 60mm mortar, one 75mm projectile, and five 37mm projectiles. A list of items is provided in Appendix A. No mustard gas related items were located during the UXO clearance activities.

Approximately 1,300 cubic yards of material from the two trenches were sifted and 86,700 pounds of metal debris were removed and recycled. Approximately 730 cubic yards of sifted soil have been stockpiled at the site pending evaluation of remedial options. Follow-up magnetometer screening conducted at the end of UXO excavation activities indicated that all potential UXO material/metal objects have been excavated from the site. The trenches were too shallow to leave in place; therefore, the site was regraded with native soil at the conclusion of the UXO removal activities.

2.2.7   Soil Stockpile Disposition Samples

Results of the preliminary sifted soil samples indicate that barium, copper, mercury, and zinc are present above background (RRS1) levels. No VOCs or explosives were detected. However, these results are not suitable for verification of closure because the EPA determined that ITS Laboratories practiced questionable laboratory activities. Therefore, these data were used only as screening data to determine if additional investigations were needed at the site.

Results of the four sifted soil samples collected in April 2000 (SIFT03, SIFT04, SIFT05, and RW-SIFT06) revealed the presence of barium, copper, and zinc at concentrations above the background concentrations for CSSA soils. As noted in Section 1.4, background levels are the RRS1 criteria for metals concentrations, and laboratory RLs are the RRS1 criteria for VOCs and explosives. Results of the sifted soil samples are summarized in Table B28-3 and complete results are provided in Appendix B.

As shown in Table B28-4, barium, copper, and zinc concentrations exceeded CSSA soils background levels in every sifted soil sample. Barium was present above the CSSA soils background concentration (186.0 mg/kg) in samples SIFT03 (4,406.83 mg/kg), SIFT04 (7,885.85 mg/kg), SIFT05 (6,927.93 mg/kg), and SIFT06 (4,644.1 mg/kg). Copper was detected above the CSSA soils background concentration (23.2 mg/kg) in samples SIFT03 (59.08 mg/kg), SIFT04 (410.75 mg/kg), SIFT05 (76.72 mg/kg), SIFT06 (44.2 mg/kg), and SIFT06 FD1 (599.1 mg/kg). Zinc was detected at concentration above the CSSA soils background concentration (73.2 mg/kg) in samples SIFT03 (186.23 mg/kg), SIFT04 (188.76 mg/kg), SIFT05 (515.77 mg/kg), SIFT06 (199.7 mg/kg), and SIFT06 FD1 (707.5 mg/kg).

Table B28-4 - Summary of Metals Levels above Background in Sifted Soil

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