Cost of dredging a detention pond?12/7/2023 While pond dynamics are complex, low oxygen levels can result from many factors, including a lack of sunlight and wind, which causes water temperatures to vary by depth, or thermal stratification. Good water quality needed to support aquatic life includes dissolved oxygen, and when oxygen levels are too low, phosphorus can be released from the sediment. “This work resulted in a powerful tool with quantified benefits for cities and counties to manage retention ponds more cost-effectively and to better answer questions from the public about ponds in their communities,” said Patrick Sejkora, water resources engineer, City of Eden Prairie. Too much phosphorous results in eutrophication-excess nutrients that promote certain plant growth such as algae and starve water of oxygen. Instead, high concentrations are building up and overflowing into other bodies of water within the watershed. Some older or failing ponds, however, are not retaining pollutants in the sediment. The ponds act as sinks, keeping the phosphorus from overflowing into lakes and streams. Much of this material, which generally settles to the bottom of the ponds, contains phosphorus. Stormwater contains dirt, vegetation and other material from municipal lawns and streets, agriculture and industrial sources. ![]() Cities, counties and transportation agencies often each manage hundreds of these ponds. Rainwater runs over Minnesota’s roads and other impenetrable surfaces into more than 30,000 retention ponds that overflow into lakes and streams. New research sponsored by the Minnesota Local Road Research Board has identified cost-effective methods for ensuring pollutants remain in pond sediment and are not released into other bodies of water. Cities and counties depend on stormwater retention ponds to protect water quality in lakes and streams.
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