Permeable Parking Lot

Luther College installed a Permeable Parking Lot during the summer of 2010. Construction started in early July and was completed and occupied by the end of August. To permeate means to pass into or through every part of. Luther’s new parking lot, located across from the Facilities Services building, lets precipitation slip right through its bricks into the rocks placed underneath.

Luther was awarded a $85,979 grant, later increased to an even $100,000, on February 2, 2010. The permeable surface paving has a design life of 50 years and is expected to function for at least 20 years with minimal maintenance. Because the lot is located within 100 yards of the Upper Iowa River basin, precipitation that collected on the asphalt flowed into the adjacent street and the city’s storm sewer system and quickly entered the river.

The run-off water can potentially carry oil or other contaminants into the river, and at times of heavy rainfall or snow melt, the large volume of run-off water can increase the risk of flooding. Facilities’ employees say they have not seen any water run into the drains from the parking lot since it was made permeable.

The new permeable surface of the lot will allow surface water and snow-melt water to seep through the paving and into the underlying soil, which significantly reduces the rate at which the water enters the river. The sandy soil underlying the permeable pavement lot also acts as a filter for the groundwater, removing particles of contaminant as the water percolates through the sand.

In June 2008, torrential rainfalls in eastern Iowa and southeast Minnesota raised the Upper Iowa River to record levels, causing a 20-foot breach in the dike on the west edge of the Luther campus. The lower campus, including some athletic facilities and fields, were covered with floodwater to a depth of nine feet in some areas.

The college sustained more than $2 million in damage and flood-related expenses. Although the most severe flooding in Decorah was confined to the campus, some residential and commercial areas also sustained damage.

The permeable surface parking lot pavement project will be the latest of a series of flood prevention and control projects the college has done since the 2008 floods.