Why would I even think about installing a permeable parking lot?
- Permeable parking is one technique from a set known as "low impact development". Many of these techniques attempt to infiltrate precipitation rather than sending it to storm sewers. This has a number of advantages: 1) cities may be able to avoid expensive upgrades of storm sewer systems, 2) we can avoid sending hot stormwater to local streams (like McLoud Run), 3) infiltrating water results in cleaning the water up, and 4) we can recharge local groundwater. In our situation, we were able to gain additional parking spaces relative to a conventional lot, which would have required a detention area to handle runoff. And, from the Iowa Stormwater Manual, "when compared to most traditional parking lot construction (pavement placed directly on a compacted subgrade) an increased durability and life span of a properly constructed permeable pavement with an open-graded subbase layer will be attained."
- Yes! Permeable pavers in streets, alleys, parking lots, patios, and driveways are becoming more and more popular. They hold up well in the winter, are easy to repair, and reduce the buildup of ice on the surface. There are significant installations of city streets in West Union and Charles City, parking lots at Marion City Hall, alleys in Dubuque, and a patio over by Hickok Hall here at Coe.
During the same rainstorm on September 22, 2016, the conventional parking lot behind Brandt and Spivey Houses was holding water and sending it down the storm sewers. The new permeable lot was doing its job - infiltrating water with no visible puddles or surface water. The two pictures were taken within 5 minutes of each other.
How much does it cost?
- Well, it depends. The actual material costs are comparable to the cost of "regular" parking lot, but site preparation (digging a rock chamber underneath to store the water) is more expensive. The parking lot at Coe (240' by150", 80 spaces) would have cost approximately $150,000 to build using conventional techniques, and was about $220,000 to build using permable pavers. The difference was supplied by grants from the Iowa Department of Agriculture and Land Stewardship and the Linn County Soil and Water Conservation District. The permeable lot will also reduce our stormwater fees from the city of Cedar Rapids.
- The key is try to keep it clean. You can plow snow off of it (a rubber strip on the bottom of the plow is recommended, but not always used) and you can salt it, but you don't want to sand it. Regular vacuuming is recommended.
- More and more contractors have the expertise and equipment needed to construct permeable parking, patios, and driveways. In Cedar Rapids, Hardscape Solutions and Culvers both have significant experience with this type of construction. In the Iowa City area, check out Sustainable Landscape Solutions - owned and run by Kohawks! JPW Driveways, and CJS Concrete also list permeable pavers on their websites.
- Jason Santee (Hall and Hall Engineers) designed the lot, Matt Olmstead of Olmstead Construction was the general contractor, Curt Richey of Hardscape Solutions and his crew built the rock chamber and installed the pavers. Amy Bouska of IDALS and Jon Gallagher of Linn County SWCD supplied advice and oversight, while Marty St. Clair of Coe College wrote the proposal.