The Purpose of Retention Ponds

OnFocus Staff Photo.

MARSHFIELD, WI (OnFocus) – The little ponds you might see in and around municipalities like Marshfield serve a bigger purpose than just beautifying the landscape.

These ponds are retention ponds and they help municipalities drain and effectively store storm water. The City of Marshfield takes over 13 square miles of land and contains over 111 miles of storm sewer infrastructure. Sometimes, it makes more financial sense to put in a retention pond instead of digging up and upgrading a storm sewer system.

As more and more buildings parking lots, sidewalks and structure in general is built, there is less and less area for rain water to soak into the ground. Therefore, retention ponds create an outlet where rain water can be stored and flooding prevented.

The newest example of a retention pond in Marshfield is the new Starbucks building located on Central Ave. From Central Ave. you may not notice it but there is a pond located on the back side of the building that is used as a runoff site for rainwater.

According to City of Marshfield Engineer Tom Turchi, this specific pond has two main functions. The first was to help with the erosion control of the construction site and the second will help with storm water management now that the building is finished.

Turchi said this specific pond helped the lot meet a requirement in terms of the storm sewer system.

“There was an additional restriction placed on this development due to the overall capacity of the downstream storm sewer system,” Turchi said. “The pond was designed to not exceed the capacity of the receiving downstream system as it is already at maximum capacity. Therefore, this pond was enlarged to meet this specific requirement.”

He also mentioned that the ponds help so that the city doesn’t have to go through a massive storm sewer system upgrade and it helps the environment as well.

“The downstream stormwater infrastructure does not have to be upsized as the new development has increased impervious area which in turn increases stormwater runoff,” Turchi said. “The stormwater is given the opportunity to settle out solids and phosphorus with the end result of cleaner stormwater leaving our community.”

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News Desk
Author: News Desk