Culvert upgrade recommended to city council

Submitted by wtip on Tue, 10/14/2008 - 1:55pm

According to the Grand Marais City Engineer, at least one street culvert should be replaced to handle future heavy rainstorms in the city. Jamison Mehle, told the council the current culvert at 2nd Street and 11th Avenue East is installed at considerably less of a slope than before construction took place approximately four years ago.

Mehle told the council that the culvert is carrying about half the original water flow it was designed to carry. This contributed to serious flooding during the June 6 rainstorm. Generally, a culvert in such a street location would be designed for a 24-hour 10-year storm. The current design is for less that a one-year event, he said.

The cost of upgrading to a ten-year storm event is estimated at $10,600. The Council, however, opted to go for a 50 to 100 year event design for $12, 200. According to mean rainfall frequency tables for the Grand Marais area, the chance of a storm meeting or exceeding a 100 year event in any given year is 1%. Statistics show this year’s storm actually exceeded the rainfall per hour total for a 100 year storm.