subscribe to ENR magazine subscribe
contact us
careers industry jobs
events events
Dodge Data & Analytics
ENR Logo
Web access will be provided
as part of your subscription.

Nitrogen Diet Reduces Arizona County's Drinking Water Threat

Text size: A A
[ Page 1 of 3 ]
Photo Courtesy of MHW Constructors
The new Roger Road Water Reclamation Facility project includes several design improvements over the nearby facility it is replacing.
By Pam Hunter
Wastewater treatment spends $720-million to improve quality of effluent.
----- Advertising -----

A decade ago, Pima County's Regional Wastewater Reclamation Dept., or RWRD, was facing a problem: The Arizona Dept. of Environmental Quality had ruled that the levels of nitrogen coming from RWRD's network of 10 wastewater-stripping and treatment plants were too high. At that point, the 41- million-gallons-a-day Roger Road plant was releasing wastewater with nitrogen levels between 30 milligrams and 57 mg per liter, well above the 10 mg/l requirement, say county officials.

While nitrogen is known to be harmful to aquatic life, experts say that, when its levels are higher than would occur naturally, it also can be harmful to children and babies. Two of the system's plants—the facilities at Roger Road and Ina Road—discharge directly into the Santa Cruz River and thus presented a potential threat to health.

Although the county regularly monitors the quality of water and no local water providers draw from the groundwater near the Roger Road and Ina Road facilities, the county and Arizona Dept. of Environmental Quality (DEQ) officials were concerned that effluent discharged into the river could percolate into local groundwater and increase nitrogen and ammonia levels in the aquifer.

The Arizona DEQ, in accordance with federal requirements, had set permissible nitrogen and ammonia limits to a range of 8 mg/l to 10 mg/l. By 2006, the DEQ told Pima County officials they would need to meet the new requirements at the Ina Road facility by Jan. 1, 2014, and at the Roger Road facility by Jan. 1, 2015.

As a result, RWRD embarked on a $720-million Regional Optimization Plan (ROMP) to improve the quality of its effluent. The program is using innovative techniques as it expands and upgrades the 37.5-million-gallons-a-day Ina Road plant to 50 mgd and replaces an aging, outdated 41-mgd wastewater stripping plant with a new, state-of-the-art 32-mgd water reclamation plant at Roger Road. The plan also includes an interceptor sewer that reroutes flows from the Roger Road plant to the Ina Road facility, which was completed in December 2010.

New Way of Doing Business

For ROMP, the county opted to use alternative delivery methods on the projects, says Jackson Jenkins, utility director for the Pima County RWRD. With $720 million at stake in the ROMP program—the largest such undertaking in the county's history—officials decided "the time was ripe to take a look at some other methods," Jenkins says.

For the Pima County Water Reclamation Facility (WRF) at Roger Road, "we decided that a DBO [a design-build-operate contract] was the best value to the ratepayer and to the region. Based on how things have come out in the building and completion of this project, I think we made the right choice," Jenkins adds.

CH2M Hill won a $164-million portion of the design-build-operate contract in December 2010. The project's total cost for the capital phase is $172 million. The Englewood, Colo.-based firm will operate the facility for 20 years, using primarily local labor.

MWH Constructors Inc., Broomfield, Colo., is the construction manager-at-risk on the project's $227-million Ina Road upgrade and expansion, CH2M Hill is the designer, and Jacobs Field Services of North America is the program manager.


[ Page 1 of 3 ]
----- Advertising -----
  Blogs: ENR Staff   Blogs: Other Voices  
Critical Path: ENR's editors and bloggers deliver their insights, opinions, cool-headed analysis and hot-headed rantings
Project Leads/Pulse

Gives readers a glimpse of who is planning and constructing some of the largest projects throughout the U.S. Much information for pulse is derived from McGraw-Hill Construction Dodge.

For more information on a project in Pulse that has a DR#, or for general information on Dodge products and services, please visit our Website at

Information is provided on construction projects in following stages in each issue of ENR: Planning, Contracts/Bids/Proposals and Bid/Proposal Dates.

View all Project Leads/Pulse »

 Reader Comments:

Sign in to Comment

To write a comment about this story, please sign in. If this is your first time commenting on this site, you will be required to fill out a brief registration form. Your public username will be the beginning of the email address that you enter into the form (everything before the @ symbol). Other than that, none of the information that you enter will be publically displayed.

We welcome comments from all points of view. Off-topic or abusive comments, however, will be removed at the editors’ discretion.