Mandan Street homes

This illustration shows the Mandan Street homes’ proximity to the South Mountain Preserve.

It wasn’t quite a round of Middle East peace talks, but the negotiations that have led to a solution to perennial flooding on Mandan Street in Ahwatukee weren’t easy.

With at least seven different entities that each had their own concerns, Maricopa County Flood Control District officials weren’t even sure if they could achieve an agreement on a project to divert South Mountain runoff from pouring down into 17 homes during heavy rains.

But last month, Flood Control District officials told residents they had finally settled on a solution.

As a result, a permanent fix to a problem that has bedeviled homeowners during big storms for years is at hand for the neighborhood just off Elliott Road near 44th Street.

The county will solicit bids from contractors to build a concrete trapezoidal structure to divert runoff. The $1.2-million project is expected to begin early next year and last about nine months.

The structure consists of an 18-foot-wide concrete channel running parallel to the homes that will be about 3 feet below grade. There will be a 3-foot-wide walkway for cyclists and pedestrians between the backyards and the edge of the channel.

To the dismay of some homeowners, a chain link fence also will be installed along the channel rim. 

Officials say city law requires the fence near any drop that’s at least 18 inches to prevent people, particularly children, from falling into the channel. 

Those homeowners complained that the fence will mar their views of the preserve when they sit in their backyards.

But others were unmoved by their neighbors’ complaints, recalling how their first floor living rooms, kitchens and bedrooms have been flooded in past years by runoff.

The concerns for the view also failed to change the minds of officials who worked through four years of negotiations to solve the flooding problem.

Though the damage was particularly severe after a heavy storm in fall of 2014, landscape architect and consultant John Griffin noted flooding is a perennial problem on  Mandan whenever there was a heavy rain.

City and county officials began studying the problem in 2015 and originally came up with 10 different alternatives.

“It turned out all 10 of those alternatives had problems,” Griffin said.

One involved buying a couple homes, razing them and creating a path for the water to flow into the rest of the neighborhood. The homeowners didn’t think that was a good idea.

Another involved a wall above grade – but that ran afoul of homeowners.

“This option was rejected due to cost and the undesirable impact of impeding the views from the residential backyards facing the South Mountain Preserve,” said the city declared when it applied for a grant from the Federal Emergency Management Agency, which will cover 75 percent of the project cost.

“The mountain views from these lots is a significant factor in their economic value,” it added.

Another issue involved a wider concrete channel with a wall near the high-voltage lines running behind the homes.

But that raised major concerns for Arizona Public Service, the city Parks and Recreation Department and the Phoenix Parks and Recreation Board.

APS had indicated it has a particularly important interest in any construction that would infringe on its 120-foot-wide right-of-way. 

“Within that 120-foot right-of-way, AP at any given day for any reason whatsoever, has to bring this big truck out,” Griffin said. 

That truck is a monster, so heavy that it requires four stabilizing pads when its 120-foot-high crane is in operation. Each pad bears 180,000 pounds.

To build the channel too close to that right of way not only threatened APS’ access to their powerlines, but also risked a collapse of the channel walls under the pressure of the soil dislodged by the heavy stabilizing pads.

City parks and Preserve Commission officials had their own concerns: they didn’t want any structure encroaching too far into the preserve.

“We all love that park so much,” one city parks department official told residents. “We’re trying to make this thing happen in as narrow a space as possible.” 

“Part of that consensus meeting was generating enough support from everybody involved in a way they’re seeing the value of the project and everybody is getting something,” he added, stressing that no agreement “was a very real possibility.”

There also was a matter of cost – a concern for city, county and federal officials and one that was significantly affected by the APS truck’s weight.

If a wall was built too close to the APS right-of- way, Griffin said, it would have to be so thick that the cost would be well beyond what any of the government agencies could afford.

“What that ended up doing was raising the budget of our pricing by a factor of almost 2.5 so instead of, say, $1 million, it was closer to $2.5 million, which is way beyond the limit of the FEMA grants that we’ve applied for,” he said.

City parks officials and homeowners also were concerned about how the area will look after the structure is completed.

The construction work will obliterate some vegetation, so officials plan to revegetate with hydroseeding and that Griffin said “is typically not the norm.”

“That also includes using a temporary irrigation system to get that hydroseeding established as quickly as possible to be able to get that rolling again. We get it more quickly back to natural desert,” he said, stressing:

 “We wanted to make sure that we make this come back quickly and reestablish that vegetation.”

Additionally, some trees will be moved out of the work area, though Griffin said the project has been designed to keep that to a minimum. New trees also will be planted along the channel while cactuses were recovered and will be replanted.

 The Ahwatukee Board of Management will provide water for the project and is working with the agencies on maintenance issues.

The structure itself will not be gray concrete either and have a surface application that would create “a minimal footprint,” Griffin said, adding it its “visual mitigation color” will blend in with the Preserve’s “desert soils” – as will the fence’s color.

Some residents complained that the channel will force them to walk or drive to nearby Lomas Elementary School to access the Preserve’s trails behind their homes.

But Griffin said, “The Preserve isn’t intended to be accessed from the back of the residences. I know those that have lived out there a long time are used to the idea that you can walk out and walk into the in the reserve from your own home.”

“The idea is when this project is done to limit that access,” he added.

Ultimately, Griffin indicated, for a situation where there was “never a guarantee we’d arrive at a consensus,” the Mandan Street project represents a kind of bureaucratic miracle in which multiple parties with strong views gave in a bit for a long-needed solution.

Pointing to the Preserve area behind their homes, Griffin told the homeowners, “We want to make that look as pristine as possible so that when you’re looking out in the back of your homes...its look will be more natural, like native desert.”

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