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MSOE's Pervious Parking Lot

Please park on our experiment!
MSOE installs environmentally friendly parking lot

Key terms to this project
Combined sewer system = a sewer system that collects both sanitary (bathroom) waste and rainwater from streets and parking lots, etc.
Pervious, permeable = porous, something that allows water to pass through it
Sewer overflow = when untreated water from the sewer system is forced into basements, streets, rivers, streams or lakes during storms
Standard parking lot = Parking lots made of traditional materials, such as asphalt, that contribute to stormwater runoff. (These are impervious, non-porous surfaces.)
Stormwater runoff = rainwater that has collected oil, dirt and debris from parking lots and other impervious surfaces
Like most people, you probably don't think much about parking lots.They're a place to park your car and not much more. But standardparking lots, considered a modern necessity, can have dire waterquality consequences. When rain hits parking lots, it
Oil and rainwater on asphalt
picksup the oil, dirt, and debris that has collected there and carries theminto the storm sewer-and directly into our rivers and lakes. In naturalareas, water is filtered by such items as grass and gravel on its wayto waterways. Parking lots, since they do not absorb water, speed upthis process and send water and all the junk in it directly into ourdrinking supply. The water and debris together are known as stormwaterrunoff.

Even worse, runoff takes up space needed to move sewage to thetreatment plants. When runoff fills up the sewers, no room is left for,well, the other stuff. Too much rainwater causes sewers to overflow –maybe into your basement.

 

What MSOE is doing to help

Students in the Master of Science in Environmental Engineering program are looking at ways to solve this problem. The MSOE Pervious Parking Lot (located on North Broadway,next to the APC Building) slows and removes pollutants in overlandrunoff from a large parking lot. A pervious, or porous, parking lotallows water to flow through it into the ground below. Before theproject was constructed, the runoff flowed directly into a combinedsewer. By holding back runoff, MSOE is helping to reduce the amount andfrequency of sewer overflows.

 

Diagram of pervious pavement layersOnpervious pavement, there is no runoff, because rainwater passes throughthe pavement, entering an 18 inch thick layer of crushed stone. It thensoaks into native soils, mostly sand and gravel, or seeps slowly into adrain tile that runs along the lower edge of the parking lot.

 

This parking lot contains two different types of pervious pavement.Pervious asphalt tops the south two-thirds. Pervious concrete tops thenorth one-third. Driveways for accessing the parking lots have standardasphalt. Pervious pavements are created by eliminating much of the finematerial from the mixes and applying special admixtures. Perviouspavements have a much rougher texture than standard pavements.Pervious vs. standard pavement during rainstormThis project is testing the pervious pavements performance includingpermeability, durability, maintenance needs, installation and winterperformance.

 

In fall 2004, the Milwaukee Metropolitan Sewerage District selectedMSOE's Pervious Parking Lot for funding as a stormwater Best ManagementPractices demonstration project. Best Management projects are thosethat use innovative ways to solve environmental problems. The projectdevelopment team included TEI Corp., a local environmental engineeringfirm that designed and constructed the project. MSOE is documenting theproject's environmental effectiveness. Professor Willie Gonwa, P.E. is the principal investigator.