Volatile organic compounds in passive soil-gas samples at the Highlands Acid Pit Superfund site, Highlands, Texas, April 2025

The Highlands Acid Pit Superfund site (hereinafter referred to as "the site") is located on a peninsula on the eastern bank of the San Jacinto River in the town of Highlands in Harris County, Texas. The site is bordered by Grennel Slough to the west, Clear Lake to the south, flooded former sand pits to the northeast and east, and private properties to the north. During the 1950s, industrial waste from refinery operations was disposed of in an excavated sand pit at the site, resulting in contamination of soil and shallow groundwater. Historical and ongoing groundwater monitoring at the site has revealed that arsenic and benzene are present and exceed protective concentration levels. It is unknown if vapor migration from contaminated groundwater is occurring or if the site poses a vapor intrusion concern for private properties adjacent to the site.

To evaluate the status of soil-gas quality, the U.S. Geological Survey (USGS), in cooperation with the U.S. Environmental Protection Agency (EPA), deployed and retrieved soil-gas samples from 43 discrete locations at the site in April 2025. This dataset includes soil-gas sample locations and environmental and quality-control soil-gas data sampling results for a suite of volatile organic compounds at the site.