Tusayan, Coconino County officials outline drainage master plan to reduce flood risk

Tusayan council members and Coconino County and engineering officials reviewed preliminary options for a drainage master plan at a town workshop, focusing on a mix of upstream watershed measures and in-town conveyance projects intended to reduce flood risk to the wastewater treatment plant, Highway 64 and town businesses.

Lucinda Andriani, flood control district administrator for Coconino County, said the project grew out of a planning grant secured through the State Transportation Board and that the team is still in a conceptual phase: “We started off with a whole lot of ideas. . . . We're at a still at a preliminary conceptual phase,” Andriani said. She noted the grant that funded the planning work was about $2,400,000 and that the district and town will need to pursue additional federal and state funding for construction.

The plan addresses a watershed of roughly 60 square miles above the Tusayan sewer treatment plant and models a 100-year storm with peak discharges in Coconino Wash on the order of 10,000 cubic feet per second (cfs), figures project hydrologist Joe Levrich presented to the council. “The watershed itself is about 60 square miles at the sewer treatment plant,” Levrich said. He described the watershed’s main tributaries—Long Jim, Bridal Wash, Coconino Wash and Water Tank tributary—and said recent study work used data from the August 2022 storm to calibrate hydrologic models.

Why it matters: project leads said the wastewater treatment plant and the highway…