The Environmental Protection Agency is starting its work in digging three new test wells to help map whether contaminants have spread from a former coal gas site in northeast Le Mars.
This work follows ongoing study and cleanup by the EPA of the site where -- about a century ago -- a plant burned coal to produce gas for heating and lighting, leaving behind chemicals that could be harmful if they seeped into local drinking water sources.
Dan Garvey, of the EPA, was on-site Tuesday and said the community is not drinking contaminated groundwater.
"The groundwater study we're doing is in a different aquifer than the one with the municipal wells that the city gets their drinking water from," he said. "There's no impact to that aquifer."
The test wells allow the EPA to monitor the plume of contaminants from the original site, making sure it doesn't impact residents, and to measure whether their levels are diminishing, he said.
Drilling is a step-by-step process. The EPA is contracting with a drilling crew from Minnesota to dig the 200-to-220-foot-deep wells, which happens one segment at a time.
An EPA geologist is also on-site with the crew, looking at each coring -- a tube of earth dug up with each segment of drilling.
"The geologist is looking at the corings to determine the different aquifers they're passing through with their drill rig," Garvey explained.
That information helps the crew make sure they're drilling properly and containing each aquifer within itself, he said.
The EPA will send a crew back next month to take a routine water sampling of the new wells along with its 12 existing wells throughout Le Mars, which test groundwater in three different aquifers.
Garvey explained that for years the EPA has been monitoring and mapping the contaminated groundwater plume that emanated from the Le Mars coal gas plant. The site includes 1.5 acres on First Street Northeast, land now owned by the City of Le Mars.
The three new wells are to the south and southeast of the site.
Garvey explained the decision behind putting the wells there.
"In monitor well 1, which is about three blocks to the east, we measured benzene at 41 parts per billion recently," he said. "We looked at that number and we looked at this gap we have on the south side, and it drove us to put these three wells in."
These new wells provide "a complete coverage for the wells from the site area," he said.
The first well is on the boulevard at 41 Fourth Ave. N.E., which is city right of way, according to Public Works Superintendent Steve Hansen. That well is about one-half block from the original coal gas site.
The second two wells will be dug in the first alley south of Plymouth Street in a sort of triangle from the first location, Garvey said.
The drilling process for the three will take seven to eight days total, he said.
Monitoring will continue for years.
"We're seeing some levels go down and some stabilize," Garvey said. "It takes a long time for these things to disperse."
The Le Mars Coal Gas plant was built in 1884.
As part of the plant's production in the late 1800s and early 1900s, coal was burned to produce gas, a process which also produced a variety of hazardous substances, many of which were simply dumped on the ground, according to information from the EPA.
Some of the chemicals are cancer-causing but only if people are in direct contact with them -- such as drinking contaminated water, according to the Iowa Department of Public Health.
The EPA's study of the site has been ongoing for more than a decade.
The agency led an extensive cleanup project in 2004.
"We removed a significant amount of the chemicals at that time," Garvey said.