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The Spokesman-Review Newspaper
Spokane, Washington  Est. May 19, 1883

Goodbye, green water: Manito’s Mirror Pond to get makeover

Gil Key walks his dogs Toby, left and Willow around Mirror Pond at Manito Park on Wednesday. (Colin Mulvany / The Spokesman-Review)

Mirror Pond will soon be more reflective of the beautiful park that surrounds it.

Spokane Parks and Recreation has announced plans to dredge and replace the murky, pea soup waters of the Manito Park pond and implement new measures to keep it clearer for years to come.

“Manito Park is a jewel in Spokane, so we want this pond to be looking as good as possible,” said Spokane Parks landscape architect Nick Hamad, who is spearheading the project.

The city received bids on the estimated $375,000 project this week and hopes to complete the pond’s rehabilitation next spring. Park officials have been pursuing a solution for almost a decade.

Enemy No. 1 is planktonic algae, which has spread throughout the 1 million gallon pond, clouding its waters for years.

“They float around in the water and that’s what makes the water look so murky,” Hamad explained.

Algae is naturally occurring in ponds, Hamad said, but it has grown out of control in Mirror Pond due in part to an abundance of organic phosphorus and nitrogen.

The nitrogen and phosphorus are prevalent in the pond due to leaf debris, excrement from fish and waterfowl, and even fertilizer that is no longer used in the park.

“All of those things have combined over the years to add a lot of extra phosphorus to the water,” Hamad said.

Mirror Pond – which is also called Manito Pond and the Duck Pond, depending on whom you ask – has long been a headache for parks officials, who have installed signs asking visitors to refrain from feeding the fish, turtles and waterfowl, which creates “excess duck waste.”

“This is a project we’ve been talking about for a number of years,” said Nick Sumner, president of the Spokane Park Board. “It’s just a highly used park and the pond is a signature part of that park, so people are interested in making sure it’s kept up and in good condition.”

The newest cleanup plan, which is funded through the Parks Department’s capital budget and received $45,000 of support from the Friends of Manito, is multifaceted and set to begin this fall.

First, the Parks Department will remove wildlife from the pond before a contractor pumps out the water.

Then the phosphorus and nitrogen-rich soil at the bottom of the pond will be removed and stored for reuse elsewhere. That process will not only remove a food source for plankton, but also deepen the pond.

The cleanup plan will increase the pond’s depth from about 2 feet deep to about 5 feet, allowing less light to reach the bottom and hindering future algae growth. The increased volume will also have the benefit of diluting the nitrogen and phosphorus that does make its way into the water.

Though it will have the appearance of a water feature, a system will be installed to recirculate the pond water through a treatment wetland that will be home to plants that suck up extra phosphorus.

Once that system is in place, water and wildlife will be reintroduced to the pond.

The Parks Department is careful to manage expectations. Though the water will be significantly clearer, park visitors shouldn’t expect it to look like a backyard swimming pool – it will still be a natural body of water.

“It’s a really high priority for us to not be using toxic chemicals in this water,” Hamad said.

The upcoming work is actually yet another phase in a yearslong effort to clean up nitrogen and phosphorus from Mirror Pond, which began with the replacement of sod around its edges with wetland-style plants.

The Parks Department has also completed a pathway project around the pond to concentrate where people are walking, in hopes of limiting the amount of mud that makes its way into the pond.

Editor’s note: A photo caption appearing with this story was changed on Sept. 19, 2019. Incorrect information about a park board meeting was removed from the caption.