SAN ANTONIO – Dirt hauled from the construction site of the Henry B. Gonzalez Convention Center to a field near Highway 90 & 151 is safe despite reports, city engineer Mike Frisbe said Tuesday.
In 2013, Geo Strata Environmental tested the soil and found that "heavy metal concentrations in soil, primarily consisting of arsenic, barium, lead, mercury and selenium, exceeded state regulatory levels."
Geo Strata Environmental was contracted to conduct the study by the project's developers, Hunt-Zachary.
The study recommended the contaminated dirt be disposed of at an approved landfill, an option that would have cost the city $6 million.
Instead, the city sought a second opinion.
"We had a consultant review the first study and they said it needs to be more comprehensive," said Frisbe.
Frisbe said it is common to see a peer review or second opinion on a project the size of the Convention Center expansion.
The $325 million plan is the largest capital project in city history.
The secondary study was conducted by Raba Kistner Environmental, which was hired by the city and also conducted the review of the first study.
The supplemental testing found the same heavy metal concentrations but said the soil was safe for reuse.
"The minerals that were found are in earth all over Texas and beyond," Frisbe said. "These are metals that are inherent to the ground."
Frisbe contends the two studies aren't equal comparisons.
The Geo Strata study tested dirt throughout the Convention Center footprint, while the Raba Kistner study only tested the dirt that needed to be moved from the site because it was not sufficient enough to support the future structure, according to Frisbe.
Raba Kistner took more samples of the soil that was tested in the first study, he added.
Frisbe said the contaminant levels found in the first study did exceed normal ground levels, but the second study found they were within the limits for a commercial space.
"The result was we saved significant dollars. The result was we saved a landfill from being filled up with good material. And we also prepared another site for development," Frisbe added.
The dirt dumped near Highway 90 and 151 is designated for future business park development.
Frisbe said the dirt will be tested a third time in a few months this time by consultants overseen by the City Health Department.