Managing Drinking Water in Park City, UT
Park City is one of Utah’s most famous cities due to its ski resorts and the Sundance Film Festival. It was named “The Best Town in America” by Outside magazine in 2013. Park City also faces some interesting challenges related to drinking water quality.
Park City, UT (Summit Co.)
Rahel Beyene, Jason Blankenagel
In 2007 and 2010, Park City experienced adverse water quality events with discolored water and high levels of arsenic, thallium, manganese, iron, and mercury in their water distribution system. Park City has an incredibly complex water system, with various sources (including groundwater, surface water, and water passing through old mine tunnels), several treatment plants, unique water demand patterns, and a complicated water distribution system with more than 50 pressure zones. .
The town is very proactive about maintaining water quality, and partnered with the Utah Water Research Laboratory and Confluence Engineering to assess the causes of these adverse water quality events, evaluate monitoring techniques that can be used to predict future events, and recommend strategies to prevent contaminant release. Tasks include the following:
- Evaluate historic water quality data as a preliminary assessment of causes of water quality events.
- Evaluate techniques to minimize deposition and/or subsequent release of corrosion scale, sediments, and biofilms in the distribution system. This included sampling at water sources and in the distribution system, as well as bench-scale experiments.
- Develop a monitoring strategy for the Park City water system, along with tools to manage and interpret collected data. The ultimate goal is to produce a guidance document to help the water utility respond to changes in their distribution system and avoid adverse water quality events.
Monitoring data from 14 sites within the Park City water distribution system were integrated into a UWRL-developed database for easy access and analysis by the utility and project team.
Analysis of more than 1,000 monitoring samples showed that despite PCMC’s known inventory of legacy pipe deposits, the distribution system is under good control. Only 22 metal releases (defined as measured bulk water metal concentration ³ 100% of background concentration) were identified during the year-long monitoring program. Of the 22 metal releases, 15 were in suspended form while seven were soluble.
Eleven of the suspended releases were associated with Fe and/or Mn release, indicating metal co-occurrence with these substrate metals. Of the seven soluble releases, all were associated with one or more shifts in water chemistry. Soluble thallium release was correlated with a drop in chlorine residual below 0.2 mg/L. Thallium was also shown to be highly mobile in laboratory-scale desorption and biofilm experiments, and significant suspended thallium was observed during a hydrant flushing trial.
This project was the focus of an entire special session at the American Water Works Association’s Water Quality Technology Conference in Salt Lake City in Nov 2015. A report is available from the Water Research Foundation.
Results will also be published in multiple peer-reviewed journal articles.
Benefits to Utah
This project helped Park City manage their complex water system to provide high quality water to their citizens and visitors.
The understanding gained about chemical and biological processes in the water distribution system, as well as strategies developed for real-time monitoring and assessment of these systems, are applicable to many other water utilities in Utah and across the US.
MLF funds were leveraged into a $495,000 project sponsored by the Water Research Foundaion and led by Confluence Engineering to assess and mitigate accumulation and release of inorganics into the Park City water system.