City officials are taking a closer look at the possible decommissioning of Highland Park Reservoir.
And that is necessitating that they simultaneously look at changes to Cobbs Hill Reservoir, as well.
“It might be a second reservoir. It might be somehow partitioning the existing reservoir,” said David Rowley, water production manager for the city. “We don't know yet.”
But something needs to change for the city to be in compliance with tightening federal water safety regulations for open top water storage facilities. Specifically, the rules aim to mitigate the risk of contamination from a pathogen called cryptosporidium.
This is a discussion that has dragged on for years, as the reservoirs are integral parts of the city water system that — in the case of Highland and Cobbs Hill — double as park features.
Options include installing an ultraviolet light disinfection system or covering the reservoir, which the city already did with an upland reservoir at Rush.
Now it’s getting down to decision time for Highland and Cobbs Hill.
Highland must be compliant by 2029, and Cobbs Hill by 2035. That may seem like a long time but there are environmental reviews and studies to be done, cost comparisons and public outreach to be made, official signoffs to be gotten, and construction that needs to happen.
“It does not matter what solution we choose,” Rowley said, “the way things look now will not be the way they look in the future.”
The city hit pause during the pandemic then hired a consultant last year to focus on Highland.
“And one of the things that came up that we hadn't considered in a lot of detail before was the possibility of decommissioning Highland reservoir,” he said.
If that’s the decision, Highland would remain solely as a water feature in the county park.
But it’s more complicated than simply turning it off. The water in Highland looks clean and clear because it completely turns over every two and a half to three days.
“The minute we stop doing that,” Rowley said, “there will be challenges ... with regards to keeping it from becoming anoxic, which means, in essence, kind of a smelly pond, if you will.”
Maintenance is another concern.
The berm that holds the reservoir in place is considered a dam. Currently, city residents and property owners cover expenses as part of their water bills.
“You know, who's going to take care of it? Who's going to maintain it? Who's going to pay for all of it?” he said. “And then, do you fill (Highland) in, make it a shallower water feature? Well, you could. But who's going to pay for that? That's not cheap either. It's a lot of dirt.”
Also, the city still needs a second reservoir in the city – to balance water pressure at peak times and to serve as a backup if a reservoir is down for maintenance.
“The more we dig into it,” Rowley said, “the more complicated it becomes. ... There's just no end to the things that we need to consider.”
So, the consultant last month was asked to expand their study to include Cobbs Hill, more than doubling the size of the contract to a maximum of $1.5 million.
“As the city has progressed in the study of ... compliance options at Highland Reservoir, it has become evident that potential alternatives selected for Highland Reservoir could have impacts on the alternatives selected for Cobbs Hill Reservoir due to the interconnected nature of the water system,” Mayor Malik Evans wrote to City Council members.
Cobbs Hill is huge, with a capacity of 140 million gallons. Highland is 25 million gallons. The city needs 45 to 60 million gallons of storage.
The partitioning idea is just as it sounds and would split or divide Cobbs Hill reservoir into two separate ponds with separate machinery for both.
The city is working to schedule a public meeting to update residents on all the options. Cost estimates could be worked up by early fall.
