FLINT, MI -- The city's decision to no longer use hydro excavation when digging up water service lines will add an estimated $14.6 million in unnecessary expenses to the program, and the state is warning Flint it has no plan to foot the bill.

Assistant Michigan Attorney General Richard S. Kuhl told attorneys for the city in a letter Wednesday, Aug. 1, that the decision to end the practice of excavation by using high-pressure water rather than traditional backhoe is "unreasonable" and urged officials to reconsider.

Kuhl warned that the decision by Mayor Karen Weaver will drive costs for the program higher than allowed for in a settlement agreement between the city, state, Concerned Pastors for Social Action and others.

On June 22, the city advised the state Department of Environmental Quality that it was stopping all hydro excavations because the practice may have missed water service lines that were thought to have been all copper but were later found to also contain galvanized steel or lead.

Instead of hydro excavating holes around the service line to identify its composition, the city began ordering contractors to dig 10-foot-long excavations to determine what lines are made of, raising the estimated cost of excavations from $77 per residence to $1,703.

Kuhl's letter says Flint cannot be reimbursed more than $5,000 for each excavation and replacement its contractors carry out without DEQ approval -- something it should not expect because "there is no measurable public health benefit to excavation versus hydro excavation.

"(There is) no valid justification" for "incurring the roughly $14.6 million in additional costs," the letter says.

MLive-The Flint Journal could not immediately reach Weaver, who previously compared the process of hydro excavation to Russian roulette, for comment immediately Thursday, Aug. 2.

Weaver told members of the Flint Water Interagency Coordinating Committee in June that hydro excavation was causing some service lines that appeared to be copper to be misidentified because other materials were still hidden underground.

City officials have never claimed publicly that its hydro excavation contractor did anything but carrying out the terms of its contract in performing its work.

Before June, roughly 8,500 excavations had been performed as part of the service line replacement program -- nearly all by using high-pressure water and vacuums to expose lines in Flint.

The state has been a booster of the efficiency of the practice and officials have said they expect it to be used across the state as water systems begin the process of replacing lead service lines in their own communities.

In the weeks since Flint ended the practice, the DEQ has questioned Weaver about her concerns, and Kuhl's letter says state officials have concluded the city's changed policy does nothing to protect residents.

"Any splice (with non-copper materials) outside the 10-foot excavation will be undetected," the letter says, and procedures requiring contractors to inspect service lines where it enters the home should already allow for identifying lead or galvanized material."

Flint is using state and federal funds to excavate all non-copper water service lines in the city, infrastructure that was damaged during the Flint water crisis.

As a part of the Concerned Pastors' settlement, the city is required to conduct 18,000 excavations and to replace any lead or galvanized service line by Jan. 1, 2020.

The same settlement requires the state to provide $87 million to reimburse the city for costs associated with the work, and an additional $10 million is available if Flint's costs exceed $87 million.

Under specified circumstances, the state could also be required to seek additional funds from the Legislature, but Kuhl warned, "If there is a perception that cost effective approaches were available to reach the same result but were not utilized by Flint, it will make any attempts to secure additional funds more difficult."