MILWAUKEE COUNTY, Wis. (CBS 58) -- Milwaukee County supervisors are calling for an audit of the Milwaukee Metropolitan Sewerage District (MMSD) and their water treatment facilities. 

It comes after the Common Ground group accused leaders of mismanagement. 

The alliance says workers told them breakdowns, mismanagement and reduced capacity have caused problems in Milwaukee sewers and the deep tunnel storage system. 

Leaders at the facilities defended the system, saying the city's threshold for waste in water is half of what the federal government allows. 

Now, county supervisors are calling for a third-party audit of MMSD operations before giving Veolia, the company that manages Milwaukee's wastewater plants, another 10-year contract.

The full statement released Monday by the Milwaukee County Board of Supervisors said:

“As County Supervisors concerned with the health, safety, and wellbeing of all residents of Milwaukee County, we are troubled by the serious concerns raised by two whistleblowers regarding Veolia and MMSD's management of our wastewater treatment facilities. We understand that 24 other sources have reached out to Common Ground, as well.

“These concerns should be taken with the utmost seriousness. It is in Milwaukee County's best interest to ensure our wastewater operations are conducted safely and transparently, and to maximize protection of our Lake, our water, and our basements.

“Furthermore, we believe that the management-side HR attorney-led ‘investigation’ proposed by MMSD leadership would be entirely insufficient to address the scope and nature of these concerns with the transparency and accountability that Milwaukee residents deserve.

“Concerns this severe and systemic require a more robust, third-party audit of Veolia’s management of Milwaukee’s wastewater plants, and luckily, the Wisconsin State Legislative Audit Bureau’s 2002 audit of MMSD can serve as a blueprint.

“That is why today we are calling for the Legislative Audit Bureau to conduct a similar audit and for MMSD leadership to fully cooperate prior to awarding Veolia another 10-year contract to manage those plants.

“In partnership with the LAB, MMSD has the power to address concerns that impact every resident of Southeastern Wisconsin. They must work immediately and transparently investigate what needs to change, and solutions that will lead to those changes.”