Olsson Associates


Olsson channels services for Sonoqui Wash Channelization project

Wednesday, July 15, 2015

Sarah Ferdico, Communications

The Sonoqui Wash in Phoenix’s Southeast Valley once gave eye-opening interpretation to “when it rains, it pours.”

With perennial flooding threatening hundreds of homes and costing the taxpayers millions of dollars in damages, the Flood Control District of Maricopa County (District) needed to find a solution to contain the destructive floodwaters that came with the heavy downpours from desert mountain watersheds that could not be contained by the flat, desert washes of the alluvial landscape. The Sonoqui Wash Channelization project began in 2003 with delineation studies, and it was broken into three phases. Olsson has been involved with the design of the current phase, Phase III, which is currently under construction and can be viewed here. A time-lapse video of more than 1,400 cubic yards of concrete being poured for the large inlet structure on the southeast corner of the basin can be found here. The videos are courtesy of Blucor Contracting, which is the project's prime contractor.

Phase III is a $15 million, regional drainage project that will benefit homeowners and landowners in the Southeast Phoenix Metropolitan Valley. This project phase is located in an existing 323-acre floodplain that consists of 182 properties. Once the project is completed, all of these properties will be out of the regulatory floodplain. The District completed construction for Phase IIIA1 and IIIA2 for the Sonoqui Wash Channelization in 2014, and it is constructing Phase IIIB in 2015.

During the design phase for Phase III, Olsson was a subconsultant and completed the landscape and multi-use design and structural design. In addition, Olsson provided civil engineering, specifications, special provisions, structural design, engineering cost estimates, and surveying services. Further, Olsson provided context-sensitive planning and design services that will take advantage of the project’s multi-use opportunities that will fit into the regional trail system in the area.

“There were multiple design challenges for this project,” said Dave Jensen, Olsson’s project manager. “Because drainage corridors were not well defined, many instances of ‘sheet flooding’ in the area needed to be addressed. This type of flooding caused the majority of the flooding damages. With the design of our channel and storm drain system, we were able to reduce future damages.”

During construction, Olsson has been supporting the District by reviewing contractor submittals, surveying drainage easements, providing operation and maintenance planning, completing the record as-built drawings, and completing permit applications with the county and state.

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