Scottsdale approves $5M adjustment to Thomas Groundwater Treatment Facility construction contract

A graphic rendering showcases the outside view of the planned Thomas Groundwater Treatment Facility in south Scottsdale. (Submitted graphic)

Scottsdale City Council has approved a cost increase modification of more than $5 million for a former contract addressing the complete construction services of a project titled: the Thomas Groundwater Treatment Facility.

On July 1, the City Council approved on consent a resolution to authorize a contract with Archer Western Construction, LLC for a guaranteed maximum price from $20.8 million to a revised contract price of $26,096,287 for complete construction phase services to construct the complete Thomas Groundwater Treatment Facility.

The purpose of the action is to authorize the modification of the contract to provide complete Construction Manager at Risk — known as CMAR — construction services for the city’s project.

In 2015, Scottsdale acquired approximately five acres of property east of Pima Park, according to a city staff report; two of the five acres were purchased by Scottsdale Water for the purposes of building a treatment facility capable of controlling scale formation in the local water distribution system.

A view of perspective of how the groundwater treatment facility might look against a community backdrop. (Submitted graphic)

The location is northwest of Pima and Thomas roads.

The Thomas Groundwater Treatment Facility will be a new Reverse Osmosis water treatment facility on Thomas Road, adjacent to the existing Central Groundwater Treatment Facility at Pima Park. In addition to the new treatment plant, the CGTF will be undergoing operational improvements that will include the construction of a new building within the walls of the existing plant.

The CGTF treats water pumped from groundwater aquifers in south Scottsdale that contain trichloroethylene. The aquifers collectively make up the EPA-designated superfund site known as the North Indian Bend Wash.

Through airstripping technology, the CGTF removes the trichloroethylene from the groundwater to provide both a clean-up remedy for the aquifers and to allow the water to be used for the community, the staff report states.

Scale formation due to water hardness in this portion of the service area has resulted in costly water meter replacements, the city staff report stated. Failed water meters not only trigger meter replacement costs because of shortened service life, but they also lead to under-reporting of customer water usage, the report claims.

On April 5, 2016, the City Council approved an engineering services contract with Water Works Engineers to provide the engineering services for the Thomas Groundwater Treatment Facility. On Oct. 17, 2017, the City Council approved a municipal use master site plan amendment and a conditional use permit amendment to accommodate the future expansion of the existing Pima Park to include the stormwater detention basin as part of future Granite Reef Watershed improvements, and the Thomas Groundwater Treatment Facility.

The seal of the city of Scottsdale. (File photo)

Then, on Feb. 19, the council approved the CMAR contract between the city and Archer Western Construction for pre-construction services for the groundwater treatment facility. On April 15, the council approved a second CMAR contract with Archer Western Construction for GMP construction services.

Since the approval of GMP 1 on April 15, Archer Western has started construction of the first phase, which is limited to the site grading and drainage, underground piping including installation of electrical conduits, the underground portion of the elevator tower, floor slap and more.

The contractor, under GMP 2, will provide the remainder of the work items necessary to complete the construction of the treatment facility.

With council’s approval of the GMP 2 modification, the CMAR will continue construction with an anticipated completion of winter 2021, the staff report stated.

The finished treatment facility is designed to receive and treat a side stream of product water discharged from the adjacent Central Groundwater Treatment Facility. The treated side stream will be blended with the remaining CGTF product water in Reservoir 80 to achieve the desired finished water quality, the staff report stated.

Northeast Valley News Editor Melissa Rosequist can be e-mailed at or can be followed on Twitter at

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