City, Alterra HOA working out erosion issues created by overpass construction

When the city built the overpass across the Union Pacific Railroad tracks, as part of the project it moved North Maricopa Road to align with the new structure.

That led to erosion in the Alterra community, which lies south of the overpass and west of State Route 347/Maricopa Road.

Now, after several years of working toward a solution, the city and Alterra’s homeowners association have agreed the city will fix the problem.

“This has been going on for about two years,” said Richard Mueller, Alterra HOA treasurer. “Now, the city is going to do something with it. The city will survey the area in February and we’re hoping construction can start in April or May.”

Maricopa spokesman Quinn Konold said representatives of the Public Works Department met with the HOA recently to view the site to understand the situation.

“The issue is that rainwater runoff from the old roadway area is entering the Alterra retention basins in various locations and that has caused erosion of the sloped areas,” Konold said. “We informed the HOA that the city will be surveying the area to determine an appropriate solution.”

Maricopa and Alterra Homeowners’ Association agree those issues were caused by raising the new roadway, which redirected water that previously flowed south into a retention basin at the north end of Alterra. The multi-acre basin sits south of Exceptional Community Hospital and north of First Baptist Church.

The problem was an unintended consequence of construction of the overpass.

“To accommodate the building of the bridge, part of SR 347 between Alterra and the First Baptist Church was removed and abandoned,” Mueller said. “The removed portion of the road was part of a drainage system that controlled water runoff in that area. The water would flow down the highway to a storm grate, which funneled the water in a controlled manner into a Alterra retention basin.”

Mueller said that system was removed, and the abandoned portion of SR 347 was filled with dirt and raised to a higher level than its original design. This caused water to flow uncontrolled into Alterra rather than entering the retention basin through a grate and flowing through an engineered channel into the retention basin.

“Alterra is now dealing with erosion damage in that area that never occurred in the 14 years that I have been an HOA board member,” Mueller said. “The only thing that has changed is the removal of the road.”

Damage in the community is limited to retention basin banks being eroded and washed down into Alterra drywells, and a concrete footing supporting a large masonry column on one of the banks being undercut by the water runoff, according to Mueller.

Konold said the city is offering a comprehensive solution that would create a drainage swale adjacent to the retention basin to collect the runoff water. It also will develop a couple of points along the basin with riprap to control how the water enters the basin from the swale to avoid erosion. Riprap is an aggregate designed for the harshest outdoor conditions. It withholds channel flow, slope stability and erosion, which protects the property and public safety. Because of riprap’s large size, it will not compact.

Konold added that the city expects to follow up with the HOA in the near future to present its plan and discuss proposed improvements.

Despite the drainage and erosion issues, Mueller said he and the HOA are pleased with discussions with the city.

“We are all thankful they are doing something, and we’re glad it’s being fixed without any cost to us here in Alterra,” Mueller said. “The overpass is the best thing that’s happened to this town and I wouldn’t want to see it go away. We’re just glad this is going to be resolved.”