Field Trial of Powdered Limestone Sediment Capping

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District of West Kelowna

Project Description:

This project was a field trial of limestone capping in Westside Cays, a man-made waterway connected to Okanagan Lake in West Kelowna. 90 tons of powdered limestone was applied to 1707 m2 at the remote end of Westside Cays. The application took a 3-man crew 5 days and involved making a low-solids slurry that was immediately sprayed onto the canal surface behind a geotextile barrier. The application was successful, producing a cap with a minimum thickness of 1 cm and a maximum thickness of 8 cm. During the application, pH increased by 0.8 and turbidity was raised to 190 NTU but both parameters dropped to normal within 10 days. The Westside Cays limestone cap hindered algae growth and delayed aquatic macrophyte growth throughout its first summer. Phosphorus in the water column was not measurably altered by the limestone application. Alkalinity decreased after the powdered limestone application - an unexpected result that merits further investigation. Monitoring was continued through summer 2011 and 2012 to determine the long-term benefits of powered limestone capping.

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