is adding a permeable paver parking lot and entrance to .
Permeable pavers are like interlocking stones built on a bed of blocks and sand. The sand holds the pavers in place, restrained by the lot's outside perimeter.
The permeability of the new parking lot allows water to filter through the pavers and blocks to the soil below.
Along with environmental benefits, the permeable pavers also offer savings in the long-run. Asphalt requires about $20,000 in mainentance every two years and has a life expectancy of 20 years. The pavers require little maintenance and have a life expectancy of 100 years.
With assistance from a DuPage County Green Initiatives Water Quality Improvement Grant and due to the increased cost of petroleum, the permeable pavers cost the district $12,000 more than asphalt for the project.
Because the pavers allow water to filter to the soil, they eliminate drainage problems and standing water next to buildings. They also signifcantly reduce storm water runoff, decrease downstream flood risk and prevent pollution from entering nearby streams and rivers.
The district installed a permeable paver parking lot at last summer. Staff said the county was excited about the district's use of permeable pavers due to District 68's "environmental stewardship."
provided the additional information about permeable pavers below.
Asphalt pavements require extensive maintenance, which over the life of the system is quite expensive. Freeze and thaw cycles, which occur several times during a typical winter, accelerate the degradation of asphalt and result in expensive needed repairs. The school district seal coats, crack seals and stripes the parking lots on average about once every two years. After about 10 years, the asphalt parking lots need to be resurfaced. Usually between the 15th and 20th year of service an asphalt parking lot needs full replacement, including remediation to the underlayment.
Permeable paver systems require much less maintenance than asphalt systems. Permeable pavers require striping once every five years, and sometime between the fifth and tenth year the permeable paver lot will need to be vacuumed with a vacuum truck to remove contaminants that may be clogging the pores and new void filler respread over the parking lot. Although some pavers may fail, a wholesale replacement of the pavement will never be required as long as the vacuuming is performed when needed. Removing and replacing small sections of pavers is relatively simple and quick if a localized problem occurs. Due to the porous nature of the underlayment of the permeable paver system, freeze and thaw cycles have little to no negative impact on the system.
In all storm events, 95 percent of rainwater that falls on the surface of an asphalt parking lot becomes runoff. The runoff causes problems downstream such as flooding, riverbank scour, river degradation and pollutes aquatic resources.
In small to mid-sized rain events, permeable pavers only allow about 10 percent of rainwater to runoff. Storm water that does runoff is slowed down, which helps to reduce flooding and pressure on the municipal storm sewer systems. The water will disappear into the pavers, relieving surface water and flooding problems experienced at many of the schools in the district.
Asphalt pavements for parking lots generally consist of about 4” of asphalt sitting on top of 10” of stone base. If the ground beneath the stone base is too soft, a foot of soil will be removed and replaced with 3” stone (or stones about the size of a baseball).
Permeable pavers are 3 1/8” thick and sit on top of a 2” setting bed consisting of stones about the size of raisins. Below that is a 4” base course consisting of stones about the size of a grape, and below that is a 15” sub-base course consisting of stones about the size of baseballs. Added up, the total pavement section is 24” deep where asphalt is generally about 12-14”. In an asphalt system, certain areas are generally designated as heavy duty where heavy traffic is anticipated such as garbage trucks, fire trucks or school buses. The entire permeable paver system is heavy duty.
Asphalt is a major contributor in polluting water ways. Water falls on the surface, picks up oil, grit and heavy metals and runs directly into a storm sewer which discharges into a stream or river. The water is warmer than that of the receiving waters and helps promote algae growth, which adversely affects the river ecosystem.
Permeable pavement systems have been shown to remove up to 80 percent of pollutants, reduce runoff and cool the storm water prior to releasing it into the river or streams.
Asphalt is a major contributor to urban heat island effect, which along with automobile emissions causes air quality action days. By using pavements that are lighter in color, the temperature around the school can be decreased by a few degrees during the day and several degrees at night. This can reduce the risk of heat exhaustion, improve air quality and reduce the use of cooling systems in the building.
The United States Geological Survey performed a study on coal tar sealants, which are commonly used in Illinois. Below is an excerpt taken from an MSNBC article:
“Chemicals in a cancer-causing substance used to seal pavement, parking lots and driveways across the U.S. are showing up at alarming levels in dust in homes, prompting concerns about the potential health effects of long-term exposure, a new study shows.
The substance is coal tar sealant, a waste product of steel manufacturing that is used to protect pavement and asphalt against cracking and water damage, and to impart a nice dark sheen. It is applied most heavily east of the Rockies but is used in all 50 states.
But scientists with the U.S. Geological Survey say the sealant — one of two types commonly used in the U.S. — doesn’t stay put. It slowly wears off and is tracked into homes on the shoes of residents.
The USGS study, which found high levels of chemicals used in the sealant in house dust, marks the first time researchers have raised alarms about potential health effects for humans — especially young children — from the parking-lot coatings.”
The Chicago Tribune also published an article on January 15, 2011, by Michael Hawthorne titled, “Extremely High Levels of Toxic Chemical in Coal Tar Found in Booming Suburb” cautions against the harmful side effects of coal tar dust exposure.
The district will continue to investigate future opportunities of using permeable pavers to address these issues, provided the price differential between permeable pavers and asphalt remains low.