LAWRENCE - The city is "unable to adequately maintain" its new water treatment plant, jeopardizing its ability to provide clean drinking water, the state Department of Environmental Protection has said.

Now, in an effort to fix plant problems and stave off fines from the state, the city has hired private engineers to run the plant at a cost of about $400,000, Mayor Michael Sullivan said.

An October order from the DEP demanded the outside oversight, after the city failed to meet 12 improvement deadlines set by the state in May. Of the dozen deadlines, the city met three.

The new managers, from Camp, Dresser and McKee Inc., took over the plant last week. Sullivan said he plans to make the private oversight of the 7-month-old, $30 million facility a long-term arrangement by putting a contract out for bid.

"We've got some serious issues ahead of us as far as how much this is going to cost and how we're going to pay for it," the mayor said.

In a biting administrative order last month, the state DEP declared that the city "is unable to adequately maintain operation of its drinking water treatment facility in a manner to ensure the delivery of a safe water supply to its consumers."

And in some cases, the DEP found gates unlocked and key doors open between buildings at the facility, said Eric Worrall, the department's deputy director of the Northeast Region.

In recent weeks, the DEP has found high turbidity - a water cloudiness that opens the door to unwanted bacteria - at the plant, Worrall said.

"This is an issue, because Lawrence draws from the Merrimack River and surface water supplies are filled with all kinds of things," he said.

By improving security and bringing in new oversight, the city has temporarily skirted a series of fines for failure to fix problems at the plant. But Sullivan said the DEP wants to see a long-range plan to make sure those problems don't happen again. He said he wants to hire outside managers to run the plant full time, a move he hopes to make within six months. It will require City Council approval.

What that means for city jobs at the plant is unclear. Sullivan said it is too early to tell how many jobs, if any, would be replaced by outside workers.

As for discipline resulting from the failure to keep up with the state's demand, Sullivan said he is awaiting a report, expected by year's end, from private workers running the plant.

"I'll take the lead from the team that's in place now," he said.

Problems flagged by the DEP reach back to March, when workers at the old water treatment plant failed to notice a drop in chlorine levels that are necessary to keep bacteria and harmful organisms out of drinking water, according to an administrative order agreed to by Sullivan earlier this year.

Later, the new plant operated for its first two weeks without proper chlorine testing equipment and was not taking necessary water samples. The city then attempted to run the plant at maximum capacity. A chlorine pump failed, dropping chlorine levels and allowing giardia to remain in the water.

Those issues constitute a violation of the Federal Safe Drinking Water Act and the state Drinking Water Regulations, according to the DEP.