Detention Ponds vs. Retention Ponds: Whats the difference in Washington State

Detention Ponds vs. Retention Ponds: What’s the difference in Washington State.

In Washington State developers are being required to put in storm water management systems. The intent is to minimize the impact on the storm water drainage system while trying to return the rainfall to the qualifiers. The terms “detention pond” and “retention pond” are often used interchangeably. However, there are subtle differences between these two types of storm water management features. Basically a detention is normally dry exceed during heavy rains and a retention pond is wet year round. Here is a more detailed explanation:

A detention pond is designed to temporarily hold storm water runoff during and after a rainfall event. This allows the storm water to gradually infiltrate into the ground or be released slowly into the natural watercourse, reducing the peak flow rate and mitigating the risk of flooding. Detention ponds are commonly used in urban areas to manage storm water from impervious surfaces like roads, parking lots, and buildings.

On the other hand, a retention pond is designed to permanently hold storm water, creating a small wetland or lake. These ponds can provide various ecological benefits, such as habitat for wildlife, improved water quality, and flood control. Retention ponds are often used in areas with natural depressions or where storm water runoff is significant.

While both detention and retention ponds serve important roles in storm water management, their specific functions and design requirements can vary depending on local regulations and site conditions. In Washington State, the Department of Ecology has established guidelines and standards for storm water management, including the design and construction of detention and retention ponds. These guidelines ensure that these features are effective in protecting water quality and preventing flooding while also providing ecological benefits.

These systems do require maintenance and cleaning/ maintaining them can be a significant expense. If your association has one make sure it is included in the reserve study. Whatcom county has a great site that talks about stormwater management