January 16, 2025
Gustavo Rodriguez
Impervious Coverage & Run-off
One of the biggest challenges homeowners, schools, municipalities, and private clubs face when looking to construct a sports court is dealing with the effects of impervious coverage and restrictions imposed by municipalities. The use of concrete, asphalt, pavers, and compaction of soils in urban areas leads to an increase of water runoff rather than absorption by the soil underneath. This leads to flooding of the sport
court, low lying adjacent areas, and of
neighboring properties. The results of this can
range from annoyance to heavy fines along
with forced removal of the impervious surface
or added project costs due to stormwater
drainage dictated by local municipalities.
Effects
Water pollution occurs as run-off from
impervious surfaces picks up contaminants
such as oil, fertilizers, heavy metals, and
debris. This polluted water finds its way to storm drains, rivers, lakes, and oceans degrading
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water quality. Algae blooms, depleted oxygen levels, and contaminated aquifers lead to loss of aquatic life and increased water treatment costs.
Solution
Permeable surfaces allow for the development of an area for increased usage without compromising water drainage. Permeable sport courts are designed to allow water to pass through the surface, reducing water runoff and promoting sustainability. These courts are of considerable value in areas where rainwater management is important or where heavy rain can disrupt play. There are several types of permeable sport courts, each with unique features suited to specific sports and environmental needs.
Permeable Asphalt
A porous version of traditional asphalt, permeable asphalt is gaining traction as a solution for those looking for the structure and bounce associated with a hard asphalt court. Water drains through the court into the stone base significantly avoiding run off that is typically seen on traditional sport courts. In order to encourage active draining through the surface of the asphalt, larger aggregate, less fines, and less binder are used to create larger voids in the composition of the surface to allow water to pass through quickly.
The ability for water to infiltrate the surface reduces the need for stormwater infrastructure with the added benefit of water filtration as it passes through the stone base the asphalt was laid on on its way to replenish underground aquifers. It is particularly beneficial in urban areas where running additional drainage is difficult or cost prohibitive.
Permeable Concrete
Similar to permeable asphalt, this concrete is engineered to create voids that enable water to flow through, facilitating groundwater recharge and reducing the need for conventional drainage systems. Typically concrete is composed of sand, cement, and aggregate whereas permeable concrete significantly reduces fines such as sand. The cement added is formulated to coat the larger aggregates without filling in the voids in between them creating air voids that are crucial for water infiltration. Maintenance is key to ensure that the concrete sport court continues to
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perform as the voids can become clogged over time. Special consideration must be taken in areas with freezing temperatures to avoid cracking of the surface.
Hard Packed Gravel
Another solution which is typically more cost effective is a stone court composed of large aggregate stone or crushed concrete underneath a layer of sand or stone dust. In order to create a hard surface suitable for sports play, the stone or crushed concrete is compacted in lifts and is covered with a thin layer of fines to ensure a smooth and uniform surface. The surface is covered with a geotextile cloth that allows water infiltration, but prevents migration of the fines on the surface. There are various sport tile options that can be laid on top of the cloth which act as the playing surface. These courts offer a great alternative in areas where zoning or impervious surface quotas can not be exceeded. The court can also easily be converted into a paver patio area in the future or used as a base for laying asphalt or concrete. It is important to note that bounce on a hard packed gravel court will not be as robust nor as uniform as that on a traditional concrete, asphalt, or wooden sport court. Slight overinflation of balls requiring bounce helps mitigate this. Thorough compaction in lifts is key to ensuring the best playing surface as well as active drainage to divert run-off away from the court and avoid saturation during heavy rainfall especially if the hard packed gravel court is constructed in a low lying area.
Turf
Natural and artificial turf are the most natural looking ways to build a sports court.
Artificial turf, mostly suited for activities not dependent on bounce, is also seeing use in multisport courts that combine basketball and lawn sports. Utilizing turf that does not absorb as much energy as longer tufted material traditionally used ensures a better bounce while still offering the look and cushion of a natural sports surface. Outdoor turf counts on perforations to allow water to pass through in the stone subsurface below. In hotter environments, artificial turf requires irrigation in order to maintain surfaces cool, an added maintenance cost not always factored into a sports construction project.
Natural turf can be less costly to install, but typically requires more regular maintenance not needed by artificial turf. Depending on soil composition, natural turf can become saturated more
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quickly than artificial turf as it does not always count on a stone base with voids that allow water to stay off of the playing surface.
Benefits
Environmental sustainability and adherence to local impervious surface statutes are the key drivers in the installation of permeable sport courts.
Traditional asphalt and concrete absorb and retain heat, contributing to urban heat island effect. Permeable asphalt and concrete, by allowing water to pass through, help cool the surrounding environment, reducing the overall heat in urban areas and reducing this effect.
Permeable sports surfaces allow faster playability where traditional courts may become overwhelmed and require additional time, sunshine, and the use of squeegees and other mechanical means to move water from low areas on courts.
The various permeable sports court surfaces discussed provide efficient options that help manage water, reduce runoff, and provide quality playing surfaces for a variety of sports while adhering to local ordinances regarding impervious surfaces and keeping neighbors happy.