The Ralph Engelstad Arena in Thief River Falls is the premier high school hockey arena in the State of Minnesota. The Arena fills two city blocks and is covered by 85-90% impervious (hard) surface. Rainfall events completely inundate roads and sidewalks, overloading the stormsewer system. Larger events cause water to stand high enough to reach the front steps to the Arena. Roof runoff produces large amounts of water running from the downspouts. Runoff has made sod establishment on the grounds difficult. Washouts have developed carrying sediment to the stormsewer. During spring melt, runoff crosses the sidewalks and freezes at night causing a slippery and hazardous conditions.

By implementing multiple raingardens, runoff water will be stored on site to control a majority of the runoff. Not only will water quantity be reduced, but water quality of the stormwater will be improved coming off the site.

This project will have an immediate benefit, reducing pollutants associated with urban runoff such as phosphorus, sediment and nitrogen. The proposed raingardens will hold approximately 3.05 acre/ft of water during a one inch rainfall event. Runoff water will be slowly released either into soil or into the stormsewer through underground tile.