Former manufactured gas plant remediated for more than $600K

Remediation of the former manufactured gas plant is going to cost the City of Newton more than $670,000, but assuming nothing odd is found and the Iowa Department of Natural Resources sees nothing wrong with the water quality tests in the next two to three years, the long overdue project will finally be completed.

Council member Craig Trotter asked, “So we’re done with this then?”

Newton Mayor Mike Hansen responded, “Well, hopefully.”

Brian Laube, director of community services for the City of Newton, thinks so. Plus, the followup inspections will cost a fraction of what it would take to remediate the manufactured gas plant site, which had been operated by the city from 1911 to 1948 near West Third Street North and Sixth Avenue West.

The city received three bids. Arrowhead Contracting, of Indianola, provided the winning low bid of $679,880. The Bondurant-based contractor, J. Petticord, submitted a $710,360 bid, while the Des Moines-based Earth Services gave a $1,667,505 bid, which was nearly $1 million more than Arrowhead Contracting.

Engineers originally estimated the project would cost $520,000. Council member Steve Mullan asked the city to explain the increase in price compared to the winning bid. Laube said a typical public improvement project, like a street paving or bike trail, is easy to figure out the quantities and the amount of expenses.

“We know what they’re going to be — so many square yards of paving, so many acres of seeding, so many feet of pipe,” Laube said, noting the plant had not operated for 73 years and that engineers used soil borings, samplings, old records and drawings for estimates. “They’re using their best judgement.”

But because of the uncertainty with that city went ahead and asked for unit prices for any overruns. The city didn’t want to get in a situation where contractors were remediating and found excess product to handle, Laube said. The city also didn’t want the project to drag into a standstill due to change order negotiating price.

Why the remediation? When the plant was operating it used gasometer, which is a large underground vault measuring about 30,000 cubic feet. A byproduct of the manufactured gas process was a coal tar material, city documents state. Records show a small percentage of this material was disposed on site.

Portions of the gas plant were removed in the 1950s. The relief holder and gasometer remain underground on the site to this day.

Ever since 1991, on-site tests and reports had been sent to the IDNR, which suggested the need for two main remediation projects. Terracon submitted a proposal to the IDNR in 2019 to remediate both structures under on contract, which the city said would save it several hundred thousand dollars in costs.

The proposal was approved by the IDNR.

Both structures resemble brick silos, Laube said, that are 20 to 30 feet below the ground and measure about 25 feet wide. In the 1950s they were filled with demolition debris and capped with dirt and brick. Laube said the city will know more when contractors “pop the tops” off them.

The Newton City Council unanimously voted in favor of awarding contract to Arrowhead Contracting.

Contact Christopher Braunschweig at 641-792-3121 ext. 6560 or cbraunschweig@newtondailynews.com