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Restoring Kent Park Lake

Anticipating completion next spring
A view from the Morning Glory spillway of Kent Park Lake. The lake is undergoing an ambitious two-year reconstruction to overcome pollutant runoff, anticipated for completion in spring 2019. (photo by Cale Stelken)

OXFORD– Those who haven’t been out to Kent Park Lake in some time would certainly find it unrecognizable. Overlooking the dried-out lake bed, overgrown with vegetation and scattered with park remnants like uprooted tree stumps, it’s almost hard to imagine it was once the aquatic centerpiece to the Johnson County park. But the park’s most ambitious restoration project, which began in spring 2017, is moving at a persistent pace. Outdoor enthusiasts can rest assured, if all goes to plan, the lake with return to its previous glory by spring 2019.

A necessary measure

So what led Kent Park to need such an expansive project? Bacteria and phosphorous runoff, as a result of nutrient-rich soil erosion.
The lake, which first opened in 1970, is tested once a month through a state water-monitoring program, in which the University of Iowa also takes part, examining clarity, bacteria levels and phosphorus levels as they change with the seasons. The park studied for two years leading up to the current lake restoration project and realized the silt retention basins, designed to capture sediments, nutrients and pollutants, were actually part the problem as they reached their 20-year lifespan and became full.
“When we’d get a big rain event, those trapped nutrients, sediments, pollutions were moving from there into the lake,” explained Park Ranger Charles Bray of the Johnson County Conservation Department.
Those nutrients and pollutants settled to the bottom before slowly releasing throughout the lake. Such runoff typically comes from natural areas such as timbers and prairies, but it’s also the result of urban pollution from parking lots at the bottom of hills, which bypasses the natural component of filtration.
“It’d be the equivalent of in-town, right here at Kent Park,” Bray noted, citing an angler’s parking lot as an example.
“Phosphorus is a naturally occurring component in soil. And when that gets into the water, you add a little sunlight and that’s how an algae bloom starts,” he explained. These algae release microtoxins, polluting the water and sometimes releasing a foul odor.
While a cattle farm resides to the north of the park and may have contributed bacteria to some degree, Kent Park owns and maintains the majority of the watershed within the park. Goose droppings, however, have been cited as a major contributor.
Inefficient land management practices also added to the runoff, with a canopy effect developing in forested segments of the park. The lack of sunlight reaching the forest floor, combined with the spread of invasive plants like honeysuckle, can make the ground vulnerable to erosion in the face of a heavy rain. Gullies form as deep as 15 feet, to funnel runoff straight into the lake.

Construction & improvements

The current restoration project is in its second phase. Started in early spring last year, the first phase addressed the watershed. This involved rehabilitating existing catch basins as well building 11 new ones.
“The plan is to monitor those real heavily and not let those get to the state they were in when this project started,” Bray noted.
Phase two focuses on deepening the lake with excavators and removing all the silt. This is not the first time Kent Park Lake has needed a deep cleaning, but it marks first time the lake has been emptied. The 1990s saw the lake undergo a vacuum dredging, where a crew used a barge to pull silt off the bottom of the lake.
The Morning Glory cement spillway, located at the southern edge of the lake, uses a mechanical valve to empty the entire lake. This took about a month, with only about a foot draining per day initially, before speeding up for the majority of drainage. In its previous state, the average depth of the lake was about 6 feet, with one spot as deep as 20 feet at the dam. The park plans to increase the average depth to about 10 feet. This, Bray said, will also help with its phosphorus issues.
Fish habitat structures, spawning reefs and vegetation beds will also need to be reestablished in the improved lake. The park works closely with Johnson County Conservation, the Iowa Department of Natural Resources (DNR), fisheries and biologists to create such features.
Over the decades, as the once 200-acre park acquired more land, it also expanded its lake. Doing so required raising the dam and making its back slope steeper than it should have been. “It caused vegetation issues over the past 40 years, a lot of problems with the back side sloughing and things like that,” Bray said. The current project has allowed the park to move the dam slightly to the north. Doing so will generalize the slope, solving an issue not previously thought possible to fix.
Most notably from a user-experience standpoint, the project will also include the installation of a catwalk extending from the road dam to the spillway. “The idea is two-fold,” Bray explained. “One is to give people a neat chance to see the water overflow into a unique overflow tool here. But that will also give us real easy access to the valve to open and close.”
Opening the valve previously required going out by boat and even using a ladder from the boat, a more trepidatious procedure that will be now overcome via the catwalk.
An eco-friendly design feature known as a bioswale will also be installed in parking lots. Rather that being crowned, the lots will be concave to allow water to run in the middle. This will contain a filtration system made of wetland plants and sand.
Land management changes will also be implemented to clear some trees and let sunlight re-vegetate the ground of canopied areas prone to heavy erosion.
A completion date for the entire project is set for March 2019; however, the ranger noted this could change depending on weather.
“If we go into a drought cycle, it could sit like it is now for a whole ‘nother year,” the park ranger remarked. “If we get a good wet spring right after that, we could have this thing filled up and have a nice lake all summer long, but Mother Nature’s gonna decide that.”
When all is finished, the lake restoration will cost approximately $3 million, with half of that to be paid by the DNR’s Lake Restoration Program.

Business as usual

Having the centerpiece of Kent Park out of commission has certainly hampered attendance, even causing some potential campers to question whether the park is open for business. Last year saw an approximately 30 percent decrease, and 2018 is expected to yield slightly fewer visitors.
“There’s a lot of activities that were based just around that 27-acre piece of this park, so use is definitely down,” Bray said.
Nevertheless, he assured the park still provides an adequate outdoor experience for those interested in a large, quiet campsite tucked away in seclusion.
“All the things that you can do out on that main lake are actually still available here,” Bray said, citing the various small ponds and shelters, the over nine miles of hiking trails, the playground and bird blind features. The park also features the county’s Conservation Education Center, which offers education programs and workshops year-round, including include prairie hikes, fishing clinics and a youth group camp.
And to those who visit Kent Park solely for the lake, the park ranger encourages taking this rare opportunity to see the park in its current state.
“You would not recognize it right now,” he remarked. “We probably won’t see that lake bed dry again in our lifetime.”