GARY | Officials at U.S. Steel Gary Works say they are designing a plan to stem groundwater that has been leaking benzene into Lake Michigan for months.

By the end of this month, the steelmaker is expected to submit a treatment plan to state and federal environmental regulators for a $1 million treatment system to stop the chemical leak.

This past summer, as part of the steel plant's federal order to analyze soil and groundwater for contamination, officials discovered benzene-laden groundwater had been trickling into the lake.

Neither U.S. Steel nor U.S. Environmental Protection Agency officials know how much benzene has gone into the lake.

The company found benzene levels of one to three parts per million in groundwater monitoring wells near the affected water, EPA project manager Tamara Ohl said.

"It's not a level that's showing any immediate risk," Ohl said. "But it's high enough."

The EPA's threshold for the amount of benzene allowed in drinking water is five parts per billion.

"When benzene enters the lake, it's going to become diluted," Ohl said. "The concentrations we're seeing in the well are higher. Clearly we don't want a situation where benzene is going into the lake."

Neither U.S. Steel nor EPA officials have tested lake water to see if, or how, the benzene has been diluted. Ohl said she expects it will be sampled in the future.

Based on inspection of the vast plant, officials suspect the benzene stems from an old tank farm at the coke plant that was removed years ago. The flow of contaminated groundwater sped up, in part, because of a crack in a lake breakwall circling the plant.

Before the breach, which occurred seven years ago, groundwater flow to the lake was slowed by water accumulated behind the wall, U.S. Steel spokesman Charles Rice said.

Repairing the wall, which would require a U.S. Army Corps of Engineers permit, would not fix the tainted groundwater problem, Rice said.

In its $1.4 million remediation plan, U.S. Steel would build 11 wells lining the lake that would capture tarnished water and treat it to remove benzene. Plant officials said they hope to have the system operational by the summer or fall.

"Hopefully it'll go faster," Ohl said. "This is the right thing to do, and we're confident that it will work."

No additional measures have been taken to impede the groundwater flow to the lake, which now is stabilized, Ohl said.

Longtime local environmental activist Charlotte Read attended a public meeting recently at which the benzene issue was discussed. She called the issue, "A big deal. You don't want to drink it, and you don't want to breathe it."

But Ohl said the situation is not an emergency.