Using recycled water in Denver city parks is part of conserving water, but it also may be behind an unexpected problem.

KUSA- It’s called Evergreen Hill — a landscape design added on to Washington Park about 100 years ago.

“We normally would’ve been in the dark here, almost, you know in the middle of the day. It was so shady in here,” said Sonia John, with Friends and Neighbors of Washington Park.

A 2010 report done for Denver Water by landscape consultants found high concentrations of sodium around trees in Denver Parks, which is irrigated with recycled water.

“They recommended that there is a reduction in the sodium content of the water because they say that the current sodium content of the water, you will see the conifers decline and eventually die,” said Cindy Johnstone of Friends and Neighbors of Washington Park.

In Washington Park, which first began using recycled water about ten years ago, the parks and recreation committee for the neighborhood group Denver, Inc. found 1/3 of the mature conifers – about 134 of them– had died in the park during that same time period.

However, Scott Gilmore, executive director of Denver Parks and Recreation, said that doesn’t necessarily mean recycled water is the problem.

“We have some challenges,” he said. “There’s weather factors and bugs and bees and pathogens and then we do have to work with reuse water.”

Over at Denver Water, officials said they’ve been working to reduce the amount of lye used to treat recycled water, which they say has helped lower salt levels.

“It’s been gradually decreasing, as treatment needs have changed based on the source water from metro,” said Russell Plakke, Water Treatment Plant Supervisor for Denver Water.

In the meantime, Denver Parks and Rec planted more trees on Evergreen Hill – though not all of the replacements will live up to the name “Evergreen Hill.”

“We are trying to look at what other species might not be negatively impacted as much,” Gilmore said.

Denver Parks and Rec said a new report out in December will look at the health of trees in the parks. They also said they will be starting a working group with Denver Water and community members to take a closer look at the use of recycled water and its effects on trees and park landscaping.

TREE EVALUATION