A wet pond, also called a stormwater retention pond, is a permanent pool of water designed to treat stormwater runoff through natural sedimentation and biological processes. Unlike a dry pond, which drains completely between storms, a wet pond maintains a standing pool of water at all times, with additional storage volume above the permanent pool to detain runoff during storm events.

Wet ponds resemble small lakes or ponds. During rainfall, stormwater runoff from surrounding areas enters the wet pond. This can be water from streets, parking lots, or other impervious surfaces that might otherwise contribute to flooding or pollution.

Once inside the wet pond, the stormwater begins to slow down. The reduction in velocity allows sediment to settle at the bottom of the pond. This natural sedimentation process helps trap pollutants, preventing them from reaching downstream water bodies.

Wet ponds act as storage and detention facilities. They're designed to temporarily hold and detain stormwater, allowing for the gradual release of water into the downstream environment. This helps control the flow and reduce the risk of downstream flooding.

The vegetation in and around wet ponds don't just look nice. They provide habitat, stabilize the pond's banks, and contribute to the biological processes that naturally filter and purify the water.

When it's time to release the stored water, wet ponds are equipped with outlet structures. These structures control the flow and ensure that water is released at a controlled rate. This gradual release helps prevent downstream erosion and flooding.

Wet ponds are crucial for managing stormwater, and regular inspections help ensure they're doing their job effectively.

Start with a visual inspection. Check the health of the vegetation. Healthy aquatic plants play a vital role in the pond's natural processes. Look for signs of stress, discoloration, or overgrowth. Also, look for signs of erosion or slumping on the slopes. Sediment can accumulate in wet ponds over time, which affects the pond’s capacity. Check for sediment buildup, especially near the bottom.

Inspect the inlet and outlet structures. These are crucial for controlling the flow of stormwater in and out of the pond. Ensure they're clear of debris, functioning properly, and not showing signs of damage or wear. Also check the maintenance access points for signs of erosion, woody growth, or other damage. Ensure valves, manholes, and locks can be opened & operated. Look for clogging, leakage, or debris in any trash tracks, pipes, or risers.

Consider water quality testing. While this may require specialized equipment, monitoring parameters like water clarity and nutrient levels can also give an idea of the pond's overall health and effectiveness.

If you notice damage, wear, excess sediment, unhealthy vegetation, or any other potential issues, consider contacting stormwater professionals to inspect and maintain your facility.

Proper maintenance by professionals ensures wet ponds continue to function optimally.

If you haven’t done an inspection, our team of licensed professionals can get that done for you. If you’ve already had an inspection on your system and noticed damage to the system, erosion, scouring or any other issues, we can help resolve any issues that have been documented.

Vegetation, sediment buildup, clogging or leakage, erosion control, and much more, we can help make sure your Wet Pond is functioning as it should be and will continue to into the future.

Exact is your go-to partner for your stormwater management needs. With our innovation & expertise in stormwater management, let's work together to make a lasting impact.

Wet pond maintenance includes vegetation management along the banks and shoreline, sediment removal from the forebay and main basin, inspection and maintenance of the outlet control structure, and management of aquatic vegetation and algae growth. For wet ponds with embankment erosion, HydroTurf turf reinforcement mats provide slope stabilization that supports vegetation growth while preventing further erosion.

Building a wet pond can be as simple as excavating a large depression into the landscape, but is often far more involved. Most wet ponds include special features like forebays, aquatic or safety benches, primary and emergency spillways, a low-flow orifice with a trash rack, aerators to keep the water fresh, and a way to drain the pond when necessary. All of these features work together to create a best management practice that’s both safe for you and the folks downstream, and effective at removing pollutants from the runoff that enters the pond.

Wet ponds are usually constructed with mild side slopes (4-5 feet of horizontal distance for every 1 foot of vertical change), and getting good vegetation established quickly will prevent those slopes from eroding into the pond. As for water depth, wet ponds are generally built with at least a 24” permanent reservoir to prevent nuisance conditions. If the local soils are highly permeable, a liner may be needed to prevent the permanent pool of water from draining out through the soil.

If you or your contractor are in the process of building a wet pond, be sure to ask them about what features are being included so that you can make sure the finished product looks great and performs as expected.

A wet pond maintains a permanent pool of water year-round and provides water quality treatment through sedimentation in the permanent pool. A dry pond fills only during storm events and drains completely between storms, providing primarily flood control and peak flow reduction. Both types require regular inspection and maintenance, and both use outlet control devices to regulate discharge rates. You can learn more about dry ponds on our dry pond guide page.

Algae growth in wet ponds is typically caused by excess nutrients (nitrogen and phosphorus) entering the pond through stormwater runoff. Management strategies include reducing nutrient inputs from the contributing drainage area, maintaining a healthy buffer of native vegetation along the shoreline, installing aeration systems, and in some cases using approved biological or chemical treatments. Exact Stormwater's Aquatics Group provides pond management services including algae assessment and treatment planning.

Wet ponds should be inspected at least annually, with additional inspections after significant storm events. Key inspection items include the condition of the embankment and emergency spillway, sediment levels in the forebay, the function of the outlet control structure, and the health of shoreline vegetation. In Virginia, DEQ requires annual inspections with records retained for three years. Exact Stormwater provides certified inspections across 12+ states. Call (804) 302-5151 to schedule.