YAO addressing aging Main Outlet Drain infrastructure in Gila Valley

Written by: Yuma Area Office

Upstream side of the permanent bypass prior to the tie-in of the MOD. <em>LCR photo by David Janda</em>
Upstream side of the permanent bypass prior to the tie-in of the MOD. LCR photo by David Janda
Addressing aging infrastructure is an ongoing commitment of Yuma Area Office (YAO) staff members. The most recent example of this commitment is the replacement of its aging water delivery/drainage system infrastructure at the Main Drain Outlet (MOD) siphon crossing, located at Avenue 7E in the Gila Valley east of Yuma.

The work, performed by Lillard and Clark, included the installation of a permanent bypass around the existing siphon structure, demolition and removal of the existing upstream and downstream headwalls and cutting the existing siphon pipe to install additional reinforced concrete pipe to extend the siphon. It also involved moving the headwalls and outlet and inlet transition structures away from the Avenue 7E road right-of-way.

“This project has many interesting challenges that needed to be taken into consideration during the initial design phase,” said Principal Design Engineer Steve Messinger.

He described and listed these challenges as a 20-foot deep excavation that was required to install the bypass under Avenue 7E, overhead electrical lines, a buried jet fuel line that supplies the Yuma Marine Corps Air Station, two buried phone lines, and the need to maintain traffic through the construction area at all times.

“This required the development of an approved traffic control plan for detouring traffic through the construction zone during the installation of the permanent bypass,” he added.

Additionally, the project also called for extending the existing double-barrel siphon by approximately 40 feet on both sides of Avenue 7E.

Significantly, in order to uphold treaty obligations and control salinity in the Colorado River, the design had to include a bypass around the construction area in order to maintain flows during the construction period, team members said. Flows in the MOD cannot be diverted into the Colorado River for extended periods without affecting YAO’s ability to meet Colorado River salinity requirements. The maximum amount of time generally allowed for diverting flows into the Colorado River and totally drying up the canal is 10 to 14 days.

The estimated project duration for removing and replacing the headwalls and extending the siphon was 120 days without the installation of the permanent bypass. However, with installing the permanent bypass, it added an additional 60 days, extending the entire project to a total of 180 days (six months).

Team members added that the contractor has completed demolition of the old headwalls and is now proceeding with extending the length of the siphon on both sides of the road. Subsequent to this, the contractor will begin construction of the downstream headwall structure and they are currently working on the downstream siphon. After the project is completed, this will address an old Category 2 aged Review of Operation & Maintenance (RO&M) recommendation.

Published on May 09, 2016