Engineers working on Tusayan’s flood-control system say design work is advancing, but the project will eventually require extensive excavation, new underground drainage pipes and reconstruction of RP Drive.

In an Oct. 13 presentation to the Town Council, engineers reported that the drainage master plan is complete and 60% design documents for improvements within town were finished in August. They hope to reach the 90% design stage by the end of October. Here is a link to the presentation.

The proposal would collect runoff from Middle Wash, Coconino Wash and Water Tank Wash in large storm drains running down RP Drive. The system would discharge near Long Jim Loop and the wastewater treatment plant into a new concrete channel. Engineers said the channel would be at least 40 feet wide and approximately 10 to 16 feet deep.

Because the underground pipes would occupy much of RP Drive, engineers anticipate removing and reconstructing the pavement. They said existing streetlights would remain and the plan would preserve a bicycle and pedestrian path along much of the road.

Other improvements include six box culverts at Long Jim Loop, detention facilities upstream of town and a new low-water crossing to improve access to the wastewater treatment plant.

Engineers have dropped an earlier proposal for a detention basin near Long Jim Loop and Highway 64, saying it would provide too little benefit. Instead, they propose boring a six-foot pipe under the highway to help handle runoff without tearing up the roadway.

For a separate flood-retarding structure on national forest land, engineers are still evaluating earthen and concrete alternatives, spillway designs, environmental considerations and costs. The work involves coordination with the Forest Service.