The former Big Tex Grain Site is located on a 7.5-acre lot in San Antonio, Bexar County, Texas, at 328 Blue Star Road. The geographic center of the site is located at Latitude 29.405° North Longitude -98.492° West.
The Big Tex Grain Site has historically been associated with industrial activity, including operating a vermiculite exfoliation plant, grain production, and sawdust warehousing. The EPA Region 6 office performed an assessment of the subject property to determine potential impact to human health and the environment based on the transporting of vermiculite from Libby, Montana, to the W. R. Grace vermiculite exfoliation plant in San Antonio, Texas. The property has been listed in the EPA CERCLIS database since 2000.
The site consists of approximately 31 structures including the Big Tex grain elevators and warehouses on the eastern portion of the property. To the north-northwest of the site, there are numerous grain silos that were converted into office spaces. The site is bounded to the south and west by Union Pacific railroad tracks and to the north and east by the San Antonio River. The site is secured by a chain link and barbwire fence extending around the entire perimeter of the facility. Within the facility exposed soil areas are heavily vegetated, but still accessible. The Big Tex Grain Site is scheduled to be developed into a “Mixed Use” facility.
USEPA/START began Activity Based Sampling operations on 04/16/2008, setting up Backgrounds Samplers at the high school across the San Antonio River from the Bog Tex Site. Due high winds, Activity Based Sampling was postponed. USEPA/START began AHERA closure sampling in the 8 silos located on the site. In addition to AHERA closure sampling, AHERA Reference Sampling was also conducted adjacent to the silo sampling locations. A leaf blower was utilized to stir up the dust within the silos followed by 5 hours of air sampling.
On 04/17/2008 the site Microscopist determined that all the AHERA indoor air sampling cassettes were too overloaded with dust to be analyzed. UEPA decided that due to the dusty conditions of the site buildings, AHERA closure sampling would be postponed until the facility building could be cleaned. START continued Activity Based Sampling utilizing the “raking scenario”. Upon inspection, the samples collected during the Activity Based Sampling were also overloaded. EPA ERT member suggested that sample times be reduced to 50 minutes rather than 100 minutes, as well as a less aggressive raking approach in hopes of reducing the amount of dust generated during the raking scenario. Due to rain in the forecast, 20x20 foot tarps were placed over the Activity Based Sampling location in an attempt to keep those areas dry.
Despite covering the Activity Based Sampling grids, rainfall up to 1 inch saturated the Activity Based Sampling locations. Per the Activity Based Sampling SOP, those impacted grids would need to dry for 72 hours. The OSC decided that all sampling operations would be postponed until the morning of 04/21/2008. USEPA/START demobilized the site until 04/21/2008.
On 04/21/2008, USEPA/START will continue Activity Based Sampling. USEPA/START will continue to run the raking scenarios for 50 minutes rather than 100. If samples appear to be in good condition to send to the lab for analysis USEPA/START may increase the amount of sample time from 50 minutes to closer to 100 minutes as it is stated in the SOP.
USEPA/START will continue Activity Based Sampling operations.
1. USEPA/START will continue to modify the Activity Based Sampling to attempt to reduce the chance of over loading the sample cassettes.
2. The Background sampling location at the adjacent high school had to be relocated because the sample pump batteries were stolen (but recovered). The new background sampling location will be across the San Antonio River directly across from the USEPA MCP.
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