Efforts to improve water quality at the Newark Reservoir by installing a new aeration and mixing system will begin on Tuesday, Nov. 15, and the work could result in a “rotten egg” odor, according to city of Newark officials.

While the upgrades will not impact access to or the quality of drinking water supplied by the city, residents and businesses in the area may notice a strong odor during the installation process.

"Because the reservoir is supplied by a pipeline and not via a stream, the water is relatively static and can experience varying levels in temperature, increased algae growth, unpleasant odors and color," said Tom Coleman, director of the Public Works and Water Resources (PWWR) department. "By installing a fine bubble aeration and mixing system, we'll address these issues and ensure a greater supply of the water is consistently available for use."

Biannually, the 317-million-gallon reservoir experiences "seasonal turnover" where the cooler, denser water displaces the deeper, warmer water. The turnover results in low dissolved oxygen and elevated hydrogen sulfide (i.e. "rotten egg" odor) levels throughout the water column and, at times, renders a significant portion of the water unable to be treated.

The installation of multiple aeration disks at predetermined areas along the bottom of the reservoir will result in:

• Improved dissolved oxygen levels throughout the entire water column;

• Improved water quality and clarity;

• Improved settling of iron, manganese, and other minerals;

• Reduction/elimination of spring and fall turnover;

• Reduction/elimination of algae growth;

• Reduction/elimination of chemical treatments; and

• Reduction/elimination of odors including hydrogen sulfide.

This will be the first time the reservoir has been fully mixed since its inception, increasing the likelihood of unpleasant "rotten egg" odors being emitted during the mixing process.

The PWWR department expects any potential odors to last no longer than 3-5 days.

City personnel will actively monitor the air quality to ensure all levels of hydrogen sulfide are safe.