Owasso Basin

A large treatment pond provides flood protection to nearby properties.

The project was identified by the District’s Phalen Chain of Lakes Watershed Management Plan to address existing and future flooding problems. This area experienced significant flooding during a July 1987 storm event. Hydrologic modeling also showed that, under ultimate development conditions, the mobile home park, several businesses and local roadways would be impacted by al 100-year storm event. The plan identified the need for approximately 70 acre feet of flood storage in this area.

The project plans maximized the storage potential of the only available land in the area. The property was purchased from existing property owners and excavated to provide needed storage. Stormwater was diverted from the existing drainage ditch into the basin, and the ditch was maintained for overflow purposes. The basin was excavated to a depth four feet to provide water quality benefits.

Improving the basin

In 2005, a project was designed to improve the water quality treatment effectiveness of Owasso Basin. Past monitoring and modeling indicated that its water quality treatment was not meeting our goals, and the flow from other several smaller drainage areas were short-circuiting the basin.

A two-phase improvement plan was necessary, based on the MnDOT “Unweave the Weave” project being implemented in the same period. The Phase I improvements focused on improving water quality and the phase II improvements focused on water quantity. This project included the installation of four pretreatment manholes and one flow diversion structure that now treat and disperse incoming runoff.

A secondary purpose of the project was to test the effectiveness of the pretreatment manholes (also known as proprietary treatment devices). The devices provided treatment of stormwater in underground large concrete manhole structures and are designed to remove sediment particles and litter. Four different manufactures donated their products for our use. The District established a monitoring protocol and monitored the devices for a number of years.