Matt Jobin, AIA, is a Project Manager with Rich and Associates. Based in Southfield, Michigan, Rich and Associates is the oldest firm in North America dedicated solely to parking design and planning. The firm can be found online at www.richassoc.com.
For years, U.S. school districts have put their best "green" foot forward by making facilities more ecologically friendly. While schools have reduced operating costs and created healthier, more comfortable indoor environments through lighting sensors, solar water heating arrays and other technologies, "going green" has become more than just an interior concept.
Many school districts are embracing the idea of sustainability when constructing surface parking lots, which not only saves thousands of dollars each year, but helps protect area water supplies while visually enhancing a site.
Detailed below are some of the more popular "green" design elements being applied in surface parking lots across the U.S.
Surface parking lots and their negative impacts
For all their usefulness, surface parking lots can negatively impact the environment in many ways. For starters, surface parking lots help contribute to heat island effect, a phenomenon in which built-up areas are warmer than more rural areas. Heat island effect can have a negative impact on communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, and heat-related illnesses.
Surface parking lots can also negatively impact underground aquifers, which are the geologic formations beneath the Earth’s surface that store and yield usable amounts of groundwater. Aquifers can be replenished by the infiltration of precipitation and surface water runoff through soil. They are an important source of water for residential, commercial and industrial uses.
Impervious surfaces like the asphalt and concrete used in a parking lot hamper the infiltration of precipitation and surface water, which is how aquifers are typically replenished. Also, any contaminant that accumulates in the surface parking lot (i.e., oil, grease, heavy metals and sediments) can harm the aquifer.
To properly combat these issues, school districts are constructing surface parking lots with "green" elements such as porous pavement, rain gardens and bio-swales.
The benefits of porous pavement
Porous pavement is a permeable surface that allows stormwater to pass through it, filtering out contaminants such as automobile oil, grease and sediment that frequently accumulate in parking lots. The runoff collects in a stone reservoir located underneath the surface parking lot. When climate and soil conditions are right, this "treated" runoff is absorbed into the ground.
In colder climates, pipes can be added beneath the stone reservoir to collect the runoff and discharge it into the municipal sewer system. This particular process allows runoff to be released to a sewer system at a much slower rate than in a typical drainage infrastructure system, ensuring the municipality’s sewer system is not overwhelmed. The end result is less water needs to be treated. In addition, smaller pipers are typically needed, meaning lower costs and less space necessary for the drainage infrastructure.
School districts are choosing from several pavement options, including porous asphalt, pervious concrete, and grass pavers. Porous asphalt and pervious concrete appear the same as traditional pavement, but are manufactured without "fine" materials and incorporate void spaces to allow infiltration. Grass pavers are concrete interlocking blocks or synthetic fibrous grid systems with open areas. These areas are designed to allow grass to grow within the void areas.
Rain gardens also popular
Rain gardens are another popular "green" design element. Outfitted with engineered soils and plants, as well as specially designed shallow depressions, rain gardens incorporate many of the pollutant removal mechanisms featured in ecosystems. They help lower nitrogen and phosphorus levels in the runoff before the water is collected in an underground stone reservoir and then discharged into a municipality’s system (similar to porous pavements).
Rain gardens are typically located in parking lot islands. This location means they can also have aesthetic value. Rain gardens can be an attractive way to showcase native plants and attract area wildlife (i.e., birds and butterflies). Also, the shallow depressions are engineered so that runoff is rapidly infiltrated. This ensures that water is not standing for long periods of time, a situation that can serve as a breeding ground for mosquitoes.
Bio-swales’ positive impacts
In terms of form and function, bio-swales are similar to rain gardens. Implemented in a linear fashion, bio-swales are typically planted on gentle slopes. Surface runoff flows along the length of the swale, allowing the bio-swale’s vegetation to slow and filter the water as it enters the soil. Suspended solids from are removed through the process of settling and filtration; dissolved pollutants are removed and/or transformed as runoff infiltrates into the ground.
Sloping bio-swales may also feature check dams, which help slow and detain the flow of runoff.
For larger surface parking lots, underdrains and infiltration trenches can be installed for better flow regulation and increased infiltration.
Another positive impact bio-swales can have is through the reduction of thermal pollution, which is the harmful increase of water temperatures in rivers, streams and lakes. When surface runoff washes across impervious surfaces, it can increase in temperature. This heated runoff can then enter a natural water source, and negatively affect fish and other wildlife that need cold water to live and breed.
Other "green" considerations
Schools are also reconsidering the size of their surface parking lots, as large lots use a significant amount of natural resources to construct and maintain. The size of parking spaces is also being reexamined. Many surface lots feature unnecessarily large space dimensions, which only contributes to the overall size of a surface lot, thus making its ecological footprint more significant.
Finally, many schools are utilizing lighter pavements, such as white concrete, which do not absorb the heat of the sun at nearly the same rate as dark pavements. Lighter pavements do not contribute to urban heat island effect.
Setting an example
By incorporating "green" design elements into their surface parking lots, schools districts are positioning themselves as proper environmental stewards. These districts are not only educating students in their classrooms on the importance of sustainability, but educating other districts through their examples.