A Jackson engineering company already involved with work at the city’s Wastewater Treatment Plant on Rifle Range Road will prepare the engineering and design to replace a primary clarifier that popped out of the ground at the plant earlier this year.

The Board of Mayor and Aldermen Monday amended its contract with Engineering Services, a division of Jackson-based M&G Enterprises, to begin the work for the new clarifier. The amendment, which will cost the city an additional $80,820, calls for the company to handle the design of installing the new clarifier. The project is estimated to cost the city at least $1.9 million.

The clarifier, which is used in the wastewater treatment process, was forced out of the ground Feb. 12 by water from an unknown source that pushed the 20-foot deep, 100-foot diameter pool from its pilings and burst several pipes under it, including a 30-inch water line.

The board Feb. 25 authorized contractor JS Haren, which was upgrading the clarifier when it popped up, to plug a ruptured 30-inch water line and repair other lines broken when the clarifier popped out the ground at a cost of $31,990 to remove water under the clarifier so it could be examined by engineers.

City Public Works Director Garnet Van Norman said the current plan calls for using the existing pilings that supported the original clarifier.

“I’m sure once they get into it, they’ll look at the pilings and see if they’re good,” he said. “If they’re not, they’ll have to drive pilings in.” Driving new pilings, he said, is estimated to cost an additional $65,000.

In another matter, the board amended the contract of CDM Smith of Jackson by $15,000 to serve as a consultant in negotiations with ESG Operations, a Georgia-based company, for a contract to operate and manage the city’s water treatment plant on Haining Road.

CDM Smith, which specializes in environmental issues, helped the city prepare specifications for requests for proposals to hire a private company to manage and operate the plant.