Water Treatment

Water Treatment Plant Facility Plan

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The City of Ann Arbor is beginning a project to create a plan for rehabilitating the City's Water Treatment Plant (WTP). To ensure reliable, high-quality water into the future, the city must invest in significant infrastructure investments. The name of the project is the Water Treatment Plant Facility Plan, and its purpose is to evaluate the operational, maintenance and regulatory needs of the plant both now and into the future. The project includes strategic planning, an alternatives analysis, a small pilot plant used to evaluate new technology, and community engagement throughout. 

For further information, please see the project website at https://a2wtpfacilityplan.com/.

Background​

The city provides drinking water to approximately 125,000 people residing in the City of Ann Arbor in addition to Scio and Ann Arbor Townships. The city's drinking water is drawn from both surface and groundwater sources.  The original WTP was constructed in 1938 with expansions in 1949, 1965, and 1975, and treatment improvements in 1996, 2000, 2007, 2013 and 2020. 

To continue to provide reliable, high-quality services, the city evaluated a range of alternatives. The city commissioned a Water Treatment Plant Alternatives Evaluation Study in 2015 to look at various alternatives related to source water supply and treatment processes, including a wholesale customer connection to the Great Lakes Water Authority. That study recommended that the city continue with the existing sources of raw water and rehabilitate portions of the city's WTP in lieu of other options.  On September 13, 2021, the City staff held a work session with Council to provide a summary of the 2015 study. The City Council reaffirmed its commitment to investing in local infrastructure.

The Work Session included:

Recent and On-Going WTP Improvements

​There has been significant activity at the WTP in recent years. Some of the projects include: 

  • Condition Assessment, Softening and Lime Feed: The 2006 WTP Master Plan included a condition assessment of all the major plant components. Among other things, the plan recommended replacement of the 1938 softening basins with more efficient treatment technology. As recommended by the Master Plan, a new lime feed was completed in 2013, but no basins were replaced.
  • Per- and Polyfluoroalkyl Substances (PFAS): In recent years, the chemical PFAS has been detected in the Huron River. PFAS are widely used, long-lasting chemicals that break down slowly over time, and cause harmful effects in humans and animals. In 2018 and 2019, the City took steps to address this problem by installing new granular activated carbon (GAC) in its filters and replacing it on a more frequent cycle. The new carbon is designed to be more effective at PFAS removal, and since its installation PFOA and PFOS levels in the City's drinking water have not been detected.
  • In June 2017, the State of Michigan Department of Environment, Great Lakes & Energy (EGLE) notified the City that their drinking water supply contained levels of a microbial pathogen called Cryptosporidium that requires additional treatment to meet the EPA standards. The WTP decided to install an Ultraviolet light Disinfection System to be an additional barrier to protect public health and meet regulations. Construction of the UV system was completed in 2020.
  • In July 2022, there was a spill of  a liquid containing 5% hexavalent chromium into the Wixom sewer system. The Ann Arbor Water Treatment Plant continues to sample its water intake, and has not detected  the pollutant in its water source.  Safety is our number one priority and the City's water remains safe for all uses.  For more information, please visit the City's information page for more on the chromium spill.

Project Overview

The city has contracted the firm AECOM to develop a strategic plan, evaluate technical alternatives, and administer design, construction, and operation of a pilot plant. Community engagement throughout this project will be led by the Huron River Group.

The development of the Facility Plan will conclude in approximately two years, with most of the public participation concluding within the first year. Public engagement efforts will include focus groups, a YouTube video, social media updates, press releases, attendance at community events, a community survey, and more.

The strategic plan will lay out a vision for Ann Arbor's water supply, with input from the community and WTP experts.

The pilot plant is a smaller scale water production system used to physically test and validate the proposed treatment changes before detailed design and construction of a full-scale system. The pilot plant will specifically demonstrate whether the proposed treatment changes will reliably meet the city's finished water quality goals.

This project will be followed by separate contractor selection processes for design and construction.

Project Objectives

The WTP Facility Plan will consider the needs of the city's WTP to ensure reliable, high-quality water into the future. More specifically, it will consider the operational, maintenance and regulatory needs and consider the physical layout in a site whose footprint cannot be physically expanded.

The WTP Facility Plan will address regulatory requirements, emerging contaminants, cost, and maintenance of plant operations. The plan will also include a roadmap, including phasing of project components, and a master schedule.