By Naomi Hatch
“It started nine years ago through a series of litigation from flooding,” said engineer Rob Toy as he began a tour on Friday, Sept. 14, of Snowflake’s Southern Solution detention basin.
Toy showed the flow pattern of the water on a map given to each person noting that at the time, the Federal Emergency Management Agency (FEMA) was threatening to put Snowflake on probation, which would mean the town would not qualify for federal funds. There were 14 litigants who came together to find a solution to solve the flooding issues, although these private and public partners each had a way of looking at the problems.
The basins were designed to capture and temporarily hold large frequency floodwaters from approximately 4.33 square miles of upstream drainage area. The constrictions formed by the outlet works serve to govern the flows. This results in an attenuation of the peak flows that minimizes the impact of large surges of water.”
An agreement was made to build the basin on land owned by Langley Properties, LLC, but a post-Katrina FEMA policy change governing the definition of the design storm resulted in an increase in the size of the ba-sins, which required more land. They were able to work with Langley Properties to get the needed land. Toy explained that FEMA’s post-Katrina policy definitions went from a six-hour storm to a 24-hour storm.
The tour began with Toy showing town officials and others involved in the project the first detention basin been built on land owned by Langley.
Toy walked everyone through the features of the basin.
“FEMA has given a conditional letter of map revision,” said Toy, noting that their opinion is that if it is built according to the conditional letter, FEMA will do a map revision and remove Snowflake from the floodplain; however this will also require approval from FEMA of the Eurofresh Northern Solution flood control features.
Toy explained that this is a really good example having diverse entities come together to solve the problem even though they don’t always agree on what is needed.
“The basins are only designed to retain the water,” said Toy, pointing out a green strip of land that was left undisturbed. He explained that it was the traditional watercourse and federal law requires that, in order to receive funds, the project must minimize impact to the natural watercourses. He said that Show Low Construction did an exceptional job on the project, and because they realized and understood the traditional watercourse, they worked with it.
“We worked really closely with guys from Show Low Construction,” said Toy. “They took a pride in crafts-manship.”
He said that only one project in the state was awarded FEMA money, and that was this project.
Toy pointed out that the spillway is in the first basin, then took the group to that site. He said that they have done the rip rap work and the major inlet is coming back. He also noted that the seed mixture is starting back and pointed out that they had to make sure all the seeds were palatable to cattle because it is rangeland. “Nature is reasserting herself,” said Toy.
Reach 1 will handle the majority of the peak flows that go into the industrial park and golf course areas.
Information handed out on the tour stated, “When completed, the entire Southern Solution will reduce the peak flow from approximately 2,500 CFS to 5,600 CFS (cubic feet per second).”
“The project was completed on time and under budget,” said Toy. “We want to start the next phase as soon as possible.”
He explained that Reach 2 consists of basins in the golf course and two crossings along Highway 277. Reach 3 consists of a lined channel that runs between the railroad and highway, and will have entrance crossings.
“The next step is to sit down with ADOT (Arizona Department of Transportation) on the crossings,” said Snowflake Town Manager Paul Watson, noting they are also working on a way to divert traffic during the cross-ing construction.
Work stopped in phase 1 at the culvert crossing because there will be two crossings and they felt it would save money to have both crossings constructed at the same time.
By Naomi Hatch