Hip Hip Hooray – Mirror Pond at Manito Park is No Longer Green!
Locals of Spokane claim that “everyone has memories at Manito Park.” The 78-acre park features a robust set of walking trails, the Nishinomiya Tsutakawa Japanese Garden, a conservatory, and the Mirror Pond, among other park amenities.
For decades, Spokane Parks and Recreation has been working to manage the planktonic algae of Mirror Pond that created a signature “green” hue to the water with no lasting solution. To correct this problem, the Mirror Pond master plan was formed by the Friends of Manito along with city funds from the Spokane Parks and Recreation Department. These planning efforts helped prioritize a long-term solution for the pond’s appearance and overall water quality.
The Investigation
AHBL’s landscape architects and civil engineers assessed local ponds to better understand local ecology and what ideal levels of nutrients in a park pond setting were. After visiting park ponds in Liberty Lake and Qualchan Golf Course, the team had water quality data to cross-check Mirror Pond against. It was determined that Mirror Pond had too many nutrients and if organic matter contributing to the pond’s poor water quality was not removed, the planktonic algae would continue to be a significant and persistent factor. AHBL developed a detailed report articulating the pond’s existing conditions, potential solutions, and recommended a solution based on longevity and associated costs. The Parks Board and Department reviewed and approved AHBL’s pond restoration plan.
The Solution
AHBL's team of civil engineers and landscape architects were determined to design and implement a pond system that addressed the problem, not just the symptoms. Through AHBL’s research and report development, it was critical that the team develop a system that dealt with the uncontrollable factors (ducks, geese, feeding of park wildlife) that contribute to an offset of nutrients. It was determined that deepening the pond would help increase volume which would, in turn, decrease algae bloom.
AHBL’s civil engineers developed a tiered filtration system which is a treatment wetland. Plants were specifically selected for high nutrient uptake that could be harvested to remove nutrients. As detailed in Spokane Parks & Recreation’s 2020 Facebook post, “plants have been installed in and around the new treatment wetland at Manito Park’s Mirror Pond. Once the aquatic plants have established themselves, the water will be turned on to filter algae-causing phosphorus and nitrogen from the pond 24 hours a day!”
The Outcome
The positive effects of the Mirror Pond restoration project ripple throughout the park and the Spokane community. The new treatment wetland for the pond has created a natural, self-reliant system for water filtration into the pond, helping create ecological harmony among the newly introduced plants, park critters, and patrons. The pond sediment that was excavated to deepen the water feature was relocated and has been recycled by the Parks Department as fertilizer and compost. And most obvious of all, the pond is no longer green! The AHBL team has enjoyed reading the reaction from Manito Park supporters and frequenters on Facebook. Comments have included - “I was there today with a friend. It looks amazing. It will be great fun to watch the plants grow and do their work.” “What a beautiful and natural nature vibe you have created for us all to treasure and respect! Thank you all!”
“It’s just beautiful,” said a resident who takes a daily walk around the pond. “It’s really nice to see the water looking much clearer than it’s looked, ever.”
Our hats are off to Spokane Parks and Recreation, Friends of Manito, and AHBL’s landscape architects and civil engineers on a job well done!
Sources:
https://m.facebook.com/SpokaneParks/posts/10157759326454865?d=m