August 01, 2012 at 10:13 AM

Nitrogen Diet Reduces Arizona County’s Drinking Water Threat

Pima County and MWH Global are highlighted in the July 30 issue of ENR, click here to read the article. Pima, Ariz., has embarked on a $720-million Regional Optimization Plan to improve water quality. The program is using innovative techniques to cut nitrogen levels in the water. The plan includes expanding and upgrading the 37.5-mgd Ina Road plant and replacing an aging, outdated wastewater stripping plant with a new, state-of-the-art water reclamation plant. MWH is the construction manager-at-risk on the project's $227-million Ina Road upgrade and expansion.

During the design phase in 2009, the county discovered that parts of the plant were sitting on an irrigation and canal system dating back to the San Pedro period, between 1250 B.C. and 750 B.C. It is the earliest, most complicated and sophisticated agricultural irrigation system discovered in North America so far. Due to the design phase discovery, construction did not see any delays.

“The project is expected to be complete by October 2013, well ahead of the January 1, 2014, deadline,” says John Cevaal, vice president and director of operations for the western U.S.