Cleaning up municipal waterways
Whether you live on the East Coast, in the South, the Midwest or on the West Coast, if there are municipal ponds, lakes or beaches within city limits, at some point, you’re faced with how to clean or maintain those resources. Invasive plants, waterfowl or careless acts by residents or visitors all can turn a beautiful water feature into a smelly swamp if not maintained.
The Municipal spoke to officials in several cities about the steps they’ve taken or plan to take to protect their water resources.
In Sebastian, Fla., officials worked on an integrated pest management plan adopted at the end of August. Sebastian has several stormwater ponds, stormwater conveyance canals and ponds in city parks.
City Manager Paul Carlisle said, “With every body of water in Florida, the problem is overgrowth of vegetation, and trying to manage that is always a challenge.”
The city’s completed integrated pest management plan for the stormwater system employs manual or organic methods, with the use of chemicals, herbicides and fertilizers being only as needed and in the least invasive way.
In Garden Club Park, the city put in probiotics and upgraded aeration. Carlisle said three tests of soil and sediment on the bottom of the pond were conducted so the city will have control data moving forward, and it is expecting results soon. The city plans to launch another round of testing.
Carlisle said workers also spent hours and hours manually removing 30,000 cubic feet of vegetation from canals and redoing the water features to better channelize the water. All the outfalls have nutrient-reducing baffle boxes installed to filter the water before going into the Indian River Lagoon.
Stormwater Treatment Park in Sebastian is a series of interconnected ponds, dams and weirs that provide stormwater surge and treatment while also serving as a wetland habitat. The integrated pest management plan was developed by a subcommittee of members from the natural resources board, three local scientists from the Florida Department of Agriculture and city staff members. Carlisle said the committee held public meetings.
“It was a collaborative effort with a lot of input,” he said, adding the IPM “stresses more organic and more manual mitigation other than chemicals as a first resort to control vegetation.”
For example, the city uses aphids to attack potato vine and released alligator weed flea beetles in the system to control alligator weed.
Carlisle said Sebastian is the only city in Florida to create an integrated pest management program.
“The council wants to make sure our waterways are taken care of. Flood control is the main benefit, and we want to maintain (them) in a smart, educated, balanced approach.”
He noted Park Department Leisure Services Director Brian Benton is working with the city’s environmental specialist on these plans.
In addition, Sebastian has implemented programs for businesses, which offer stormwater credits to add rain barrels, swales, additional retention ponds and impervious parking lots.
Carlisle said he looks forward to continuing to clean up and maintain local waters. “We’ve been pretty proactive.”
In Plano, Texas, having clean water sources to keep wildlife healthy is a priority. Kym Hughes, natural resources district superintendent for the city of Plano, said the city hasn’t experienced a lot of invasive plants in its ponds, but it has been dredging a few because the sediment gets so deep it creates algae blooms and makes the water unfriendly to aquatic life.
The city contracted with American Undercover Services for hydraulic restoration (dredging) of the ponds. The company sent a certified scuba diver to the pond’s bottom with a hose that basically “vacuums” the water, muck and sediment into large geo bags that are 30 feet wide and 100 feet long. The muck and organic matter stay in the bags and are hauled away, while clean water is filtered through and returned to the pond. There are 12 ponds in the Plano park system.
Haggard and Prairie Meadow ponds were restored in 2019, while Shawnee followed in 2020. Hughes said staff monitor sediment levels every three to four years. If necessary, the ponds are put in a rotation to be restored.
Plano also has sediment studies conducted so officials know how much muck there is and how deep it is. Hughes said the city wants some plants to grow for wildlife, but when the sediment gets too deep, it creates an aquatic environment that is not good for wildlife.
According to Hughes, dredging the pond in this manner “doesn’t affect the wildlife as much as other types of dredging.”
Removing all that sediment on the pond bottom “turned out to be helpful — there’s a lot more distance between the surface and the bottom, making it harder for sunlight to penetrate to the bottom where some invasive plants use it to grow.”
She said the city also uses a blue or black aquatic dye to block some sun waves from reaching the bottom. They’ve started documenting the silt levels.
The ponds’ maintenance is contracted out, and they pick up trash in the pond and the surrounding buffer zones, test ph levels and measure the dissolved oxygen levels. They measure the DO levels to ensure the oxygen level is good, which is necessary for the fish. The city also has fountains and aerators in the ponds to help with that.
Signs have been posted stating “don’t mess with wildlife” and “don’t feed ducks and geese,” according to Hughes.
“People are more concerned about the wildlife,” she said, to the point that the city had to build a rock ramp in one pond so turtles could get out since it had concrete sides.
Plano established “conservation buffer zones” around each of the natural edges of ponds and creeks and in naturally occurring wooded areas to prevent soil erosion caused by heavy rains, severe floods and severe compaction from heavy machinery.
According to the conservation buffer zones document Hughes provided, “This zone slows down erosion because the turf and indigenous foliage are allowed to grow and spread, thus increasing their ability to make food and establish a more extensive and substantial root system. This increases plants’ ability to hold on more tightly to soil particles when flood waters come through.”
Other benefits include trapping sediments, enhancing water infiltration rates, filtering fertilizers and pesticides, promoting fish and wildlife habitat and protecting biodiversity. The plan also states vegetation should not exceed 18 inches at any time, and that ragweed be controlled with frequent inspections. Access lanes may be made where deemed necessary and appropriate for patrons to access the ponds or creeks and signage be placed in those areas.
Hughes said she’s been with the city for 20 years, and the city has “come a long way — we try to be as environmentally friendly as we can.”
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