Seven years after a major underground leak of gasoline was discovered at a central Lawrence gas station, it is creating new concerns for the surrounding neighborhood.

Officials with the Kansas Department of Health and Environment gave details Friday about a plan to contain a spreading plume of gasoline left from a 2006 leak that still contaminates groundwater in the Old West Lawrence neighborhood near Ninth and Ohio streets.

KDHE officials are confident the gasoline is not putting any properties at risk, but officials said they want to ensure that the vapors from the gasoline aren’t sucked into homes through sump pumps or leaky foundations. The fumes, once inside the house, could become a combustion threat.

“That has not happened, and we want to make sure it doesn’t happen,” said Randy Carlson, the KDHE section chief that oversees underground gasoline storage tanks.

The gasoline is left from a leak that was discovered in 2006 at the underground tanks of the Presto Convenience Store, 602 W. Ninth Street. The tanks, which likely had been slowly leaking for years, allowed more than 1,000 gallons of gasoline to seep into the soil and the groundwater in the neighborhood.

KDHE in 2006 installed monitoring wells and a trench to capture the contaminated ground water just east of the gasoline station. But on Friday, KDHE said they want to soon begin work to install three more trenches, after receiving tests this summer that showed the gasoline plume had begun spreading to the east.

“It is surprising,” Carlson said. “No one really thought it was going to show up in that area. But that is why we have the monitoring wells, and why we’ll continue to monitor the area.”

Carlson said KDHE officials talked with residents in the area this summer, and installed vapor detectors in any home thought to be in the potential path of the plume of contaminated water. He said there haven’t been any sign of vapors entering the homes.

The 2006 leak was discovered after an apartment house caught fire, and investigators discovered signs that gasoline fumes may have been sucked into the building via a sump pump and then ignited by a spark.

Lawrence Fire Chief Mark Bradford said he’s aware of the latest findings by KDHE in the area. He said he believes the levels are still relatively low, but supports the state’s decision to install the additional trenches.

“If people do smell gasoline or a gasoline odor in or around their home, they should call us,” Bradford said.

Carlson said one of the trenches will be installed underneath Ohio Street in the section between Eighth and Ninth streets. A second will be installed beneath the parking lot of the Ninth Street Baptist Church. A third trench will be installed across Ohio Street and into the front yards of 825 and 829 Ohio.

Carlson said KDHE officials are optimistic the newest trenches will stop the gasoline plume from spreading any farther east. He said the existing trench is working fine, but the gasoline plume likely already had spread farther than they had expected when the trench was built in 2006.

“Usually when you cut off the head of it, it doesn’t have any more push,” Carlson. “Once you cut off the head it stops. That is what we thought we did.”

Carlson, though, said the trenches, a series of monitoring wells, and a special blower house that sucks the fumes out of the trench, will be a part of the neighborhood for many years to come.

“It already has been seven years,” Carlson said of the state’s mitigation efforts. “I would say it probably will be in the tens of years before we’re done. It is really not close to being done.”

Money from a state trust fund designed to address clean-up projects from storage tank leaks will pay for the installation of the trenches. Carlson said the trenches are expected to cost about $250,000 to install. He estimated the total clean-up costs dating back to 2006 will be about $850,000, once the latest project is completed.

City officials are estimating that the 800 block of Ohio Street will be closed to traffic for about two weeks once construction work begins on the trenches, which likely will be this month.