New London — State environmental officials issued several violation notices to the city last month focused on its apparent failure to either remove or keep track of its underground heating oil storage tanks.

Facing a 30-day deadline to submit details on proposed corrective actions, the city has enlisted an environmental consultant to complete an inventory of underground tanks and develop a plan to remove at least two tanks no longer in use.

City Risk Manager Paul Gills said two violations issued by the state Department of Energy and Environmental Protection target two 10,000-gallon underground tanks at New London High School on Jefferson Avenue that DEEP records show were installed in 1970.

Gills said the city already has uncovered documentation to prove the tanks at the high school were removed and replaced with a newer tank in 1992 that still is in use. It is unclear why the documentation on the tank removal was not documented at the state level but it is clear, Gills said, the city has not kept up with annual tank inspections.

One of the violations that needs to be corrected involves the discovery of 3½ inches of water in the high school tank still in use. An environmental contractor is expected to be hired to remove the water.

A DEEP spokesman said the violation notices were issued following regular inspections, which are conducted statewide. Older tanks, which do not have the same kind of corrosion or spill protections as newer tanks, present an environmental hazard and are required to be removed. Gills said many newer tanks are installed above ground.

Of the approximately 45,000 commercial underground storage tanks currently registered in Connecticut, only about 12,000 still are in use, DEEP says.

Gills said the city must remove at least two existing underground tanks to remain compliant: a 5,000-gallon tank at Harbor School and another, much smaller tank at fire department headquarters on Bank Street. He said Harbor, which has a dual fuel heating system, now relies on natural gas rather than fuel oil but the tank inadvertently was filled with oil in 2014 and will need to be drained by a licensed company, with the contents disposed of as waste oil.

Gills said the cost of tank removal is between $10,000 and $15,000, not including the cost of environmental assessment to ensure there is no contamination of surrounding soil.

He said he expects the city, based on the work now underway, will avoid penalties and fines that potentially could cost as much as $25,000 per day per violation. DEEP has asked that the details of corrective action be submitted within 30 days of its Feb. 26 violation notice.

The city, which does not carry pollution insurance, hopes to avoid crippling costs associated with a tank spill. The town of Newington earlier this year discovered an underground diesel spill at a bus garage that is costing the town $4 million to $5 million for cleanup.

Gills said New London has kept ahead of the curve in some areas. Joseph Lanzafame, the director of public utilities, has been proactive in removing and updating tanks related to the wastewater treatment facility and pumping stations, he said.

“Our ultimate goal for this project is to get a handle on our inventory of underground tanks, assess their conditions and complete the appropriate paperwork,” Gills said.

The city has enlisted environmental consultant Paul Burgess to conduct the initial environmental assessment.

At the end of this project, Gills said the city will update DEEP, remove the tanks “and achieve compliance and get on track with our required reporting in order to minimize liability to taxpayers.”

g.smith@theday.com