What is a retention pond?
Most neighborhoods in Naperville were designed to include a low-lying, open area or a pond that collects stormwater during a rainfall and helps prevent flooding. If there is a pond that was constructed to retain stormwater, it is called a retention pond.
Retention pond at May Watts Park
If the open area is typically dry ground, which can collect water and then drain it within a day or two, the area is called a detention basin.
Detention basin at Seager Park
Earlier in its history, Naperville Park District acquired parkland that included retention ponds, but no longer purchases or accepts land that includes retention ponds. The District currently manages 28 retention ponds. While some of the impacts on ponds are beyond the District’s control, the District seeks to maintain and improve the health and function of its retention ponds.
What are the benefits of a retention pond?
According to the Lower DuPage River Coalition, when a retention pond is working properly, it reduces the rate at which stormwater enters local waterways. By temporarily storing stormwater, a retention pond can prevent flooding. Since retention ponds capture stormwater runoff from surrounding landscapes and rooftops, stormwater collects in the pond instead of on homeowners’ properties.
Challenges to the Health and Function of a Retention Pond:
Sediment entering the pond in stormwater runoff:
Sediment from surrounding landscapes can be washed into the pond during a storm event and cause murky or cloudy water and a buildup of silt on the bottom of the pond, decreasing pond depth.
Stormwater runoff also carries nutrients from fertilizers, animal waste and other sources into the pond. An increase in available nutrients, along with summer heat, sunshine and a lack of rainfall allows algae to flourish. Additionally, shallow ponds warm up more quickly, which supports algae growth. Abundant algae impacts aquatic life by blocking sunlight and decreasing oxygen levels in the water.
If the pond’s shoreline does not have deeply rooted plants to stabilize the soil, shoreline erosion can occur. Tree roots along a shoreline cannot hold the soil, and are a common cause of erosion. The eroded soil builds up on the bottom of the pond and adds nutrients like nitrogen and phosphorus into the water, encouraging algae growth.
Trees causing erosion at the pond at Brook Crossings
Caring for our ponds
In a large suburban city like Naperville, one of the main challenges to the health of our ponds and streams is pollution, including lawn chemicals, oil and gasoline from automobiles, animal waste and sediment. All of these materials are swept into storm drains or washed over land and carried to our waterways during heavy rains. Another is the increase in hard surfaces, such as buildings and roads that allow rainwater to run easily off the surface and into storm drains, carrying the pollutants to our ponds and streams.
What is the Park District doing?
If a pond is deep enough, an aerator can help minimize algae growth. However, most ponds are too shallow to benefit from an aerator. The Park District installs aerators in selected ponds if depth allows.
Promoting growth of deep-rooted, native plants along the shoreline.
Park District staff controls invasive plants around ponds by mowing or by controlled burns. The beneficial native plants then can grow more freely.
Minimizing use of chemicals that can harm wildlife.
As part of its commitment to environmental stewardship, the Park District uses principles of Integrated Pest Management to maintain ponds and shorelines, which begins with assessing conditions and then, if needed, applying only chemicals that are safe for aquatic life.
Shoreline restoration projects...
begin with the removal of or treatment of invasive plant material, including invasive trees which have grown up along the shoreline and cannot hold the soil. Next, the shoreline is stabilized with coir rolls and/or regrading as needed, and then native plants are installed. Native plants have a deep network of roots that help clean stormwater and hold soil in place to prevent erosion. Other benefits include discouraging the presence of Canada geese, reducing maintenance costs, enhancing habitat for wildlife and adding the beauty of wildflowers. A more detailed explanation of the Naperville Park District’s shoreline projects can be found here.
Pond dredging projects...
include location-specific dredging to remove silt from the bottom of retention ponds. The silt is collected and stored in sediment drainage bags to dry on site. The leftover material can then be used wherever needed in Naperville Park District parks to build berms or fill in low areas.
The pond at Brook Crossings after dredging and shoreline restoration
How can you help maintain your local retention pond?
- Reduce lawn chemical usage: Reducing the amount of fertilizers and pesticides used on your lawn reduces the amount of chemicals that will be carried in runoff into the retention pond. Phosphorus feeds algae and weeds in the pond; therefore, use phosphorus-free products and apply as little as possible.
- Pick up your pet’s waste: Animal waste contains bacteria which will run off into the water and deteriorate water conditions.
- Do not litter: Make sure to dispose of trash and recyclables properly. Otherwise, stormwater can carry litter into the retention basin and block the basin’s water flow.
- Do not feed wildlife: Feeding ducks and geese can pollute the water and cause harm to the waterfowl.
Interpretive sign at Winding Creek Park explains the benefits of shoreline restoration at a pond
- Fishing is allowed; a list of fishing locations at the Naperville Park District can be found.
- Swimming, canoeing, boating and ice skating are NOT allowed at Naperville Park District ponds.
- Do not release fish or plants from home ponds or aquariums into Park District ponds.
For more background information about retention ponds, check out these references: