A soil treating process may end up saving the city up to $1 million on the Brownfields cleanup project, even though contractors treated and removed nearly 50 percent more soil than was estimated.
Prudent Technologies Inc., hired to treat and remove contaminated soil under the oversight of Terracon Consultants Inc., is finished with field work except for some grading.
"What we did, in a nutshell," David Koch, Terracon senior consultant, told city officials last week, "is we went out and removed the material from the site, stabilize it, put it into landfills and remove that risk from the site."
The former shooting range is "an unusual and uncommon site in some aspects," Koch said.
Lead tended to leach and become highly mobile with changes in pH and water moving through it, he said.
Koch said he doesn't expect any long-term leaching issues, and geologist Michaela Brewster said they "weren't finding much lead in the groundwater; it was primarily in the soil."
Lead contamination on the land, which was farmed after serving as a shooting range, was more widespread and found at deeper depths than anticipated, Koch said.
Lead primarily was found in the top six inches, he said, "but we did see it down to 18 inches, and in the very end of the cleanup on the west side, unexplainably, it's down to 24 inches in some places."
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The base line used for contract bid specifications was treatment of about 14 acres down to 18 inches - roughly 18,000 cubic yards - Koch said. Ultimately, however, around 27,000 cubic yards over 15 acres was remediated.
The additional treated soil will likely add around $400,000 to Prudent's base bid of $844,641, estimated Michael Hagemeister, project engineer.
While the final cost has not yet been determined, it is still expected to be well below the $2.3 million estimate Terracon originally assigned to the project, in large part due to the phosphate treatment process Prudent used on the soil before removing it.
Excavation began in late November, Brewster said.
"Before it was removed," she explained, "Prudent used a treating agent ... basically a powdered phosphate reagent. When it mixes in with the soil, it changes the pH in the soil, and therefore it can change the soil from being hazardous material to a nonhazardous material.
"Nonhazardous material can be disposed of for about $44 a cubic yard, while hazardous material can cost up to $150 a cubic yard. This option was a great way for the city to really save some money, and it's a process that Prudent was very familiar with," she said.
"That saved the city several hundred thousand dollars by doing the treatment," Hagemeister said. "The original estimate we had was $2.3 million on this project, and that was for a lower volume than what ended up actually going through the system, so we probably dropped, I would say $800,000 to $1 million off the total project by adding treatment to the project."
The next step is completing a report to the Nebraska Department of Environmental Quality in hopes of receiving a "no further action" letter so the land can be developed.
That report, Terracon officials said, should be completed by late February or early March after data is received from third party testing at the site, and an NDEQ response is expected within 30 to 60 days of that.
"We should have that letter by the end of April based upon what we know today," Administrative Services Director Jan Rise said.
Natura Pet Products is set to purchase the land from the city pending receipt of NDEQ's final approval.