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Playground Drainage Issues

by Curtis Stoddard, Playground Contractor

Playgrounds of course should not be designed as water collection points for the buildings or ground water surrounding a playground. However, here we see water from the roof of the school building draining onto the asphalt area, which then drains into the playground protective area.
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For playground safety surface systems to be durable and perform properly, good drainage is essential. Whether using loose fill products, such as engineered wood fiber or rubber chips, or using unitary surfaces, such as rubber tiles or poured-in-place rubber, the playground area needs proper water drainage.

Most people involved in playground design and construction know that water needs to drain away from the playground. However, it is important for designers to understand how a particular drainage system will affect the playground during and after construction.

A drainage sump pit should be placed away from playground equipment footings.

All drainage is not equal. Drainage for a playground in Las Vegas will have different drainage needs than a playground in Orlando, Fla. A local water expert can ascertain how much drainage is needed for a particular climate and how much water on average will enter your playground surfacing area at any given time. As a drainage system needs to adequately discharge water away from the surface area, a playground in Orlando may require the use of a drain field into the surrounding area's drainage systems, whereas a playground in Las Vegas may not need such an extensive system.

Water Collection Points
While it's inherently obvious that playgrounds should not be designed as water collection points for the buildings or ground water surrounding a playground, you will see just that scenario, as pictured on the opening photo on p. 20.

Water from the school roof is falling to the impervious asphalt area and flowing onto the playground. It appears that over half the water at this school is being discharged into the playground surfacing, rendering the playground unusable after a downpour. Additionally, it can cause displacement of wood fiber, premature rotting of the wood, and growth of insects and mold in the wood surfacing.

Heavy rains or flooding of a playground with loose fill materials, e.g., wood fiber, pea gravel, rubber mulch, and less than ideal drainage can wash away the loose fill. Keeping proper fill depth of surfacing materials is important for safety. Alternatives are a rubberized surface or artificial grass (BCI Burke's 'Burke Turf' pictured).

A sump pit inside the playground protective area is a common and economical way to address drainage concerns. A sump pit consists of a hole being dug a certain length, width, and depth. The hole is then covered with a geotextile fabric and filled with drainage rock. To avoid interference with the footing layout provided by the playground equipment manufacturer, designers should place sump pits to be installed in the fall zone area or other location with the footer placement in mind. (See Fig. 1, p. 20.)

While designers may add slope to the play area to aid in drainage, slope can lead to concerns for the installer.

Modular playgrounds are designed to be installed on level ground, so if the designer intentionally adds slope, care should be taken to make sure it will not create problems for the playground installer to meet equipment height requirements. For example, if there is two feet of slope in a 40-foot long play structure with slides at opposite ends, one slide exit will be on the ground, while the other will be too high, making both slide exits out of compliance. Be sure to design slope that takes equipment height requirements into consideration. Manufacturers can adjust for slope if it is discussed and incorporated into the play structure during the design stage.

A layer of drainage rock used throughout the play area can interfere with the structural integrity of the playground equipment footing.

In the late 1980s, a drainage design consisting of a layer of drainage rock throughout the entire playground protective area was widely used. Without regular surfacing maintenance, geotextile fabric was exposed and ripped in high traffic areas, causing the drainage rock to contaminate the loose fill safety surfacing.

A layer of drainage rock used throughout the play area can interfere with the structural integrity of the playground equipment footing (see Fig. 3). For example, a playground contractor can be put in a situation where the playground equipment manufacturer has designed an 18-inch footing, and the six inches of drainage rock leave only a 12-inch footing. Use of a French drain or trench systems is recommended instead of a layer of drainage rock, which is now virtually obsolete.

In summary, for your drainage system to perform properly, consider the local climate and the playground equipment manufacturer's installation specs. Remember, don't use the play area as a discharge system for the surrounding water runoff. The goal is to discharge water away from the playground area without compromising the stability of the footings and manufacturer equipment height requirements.

About the author: Curtis Stoddard has over 25 years' experience as a playground contractor. He co-founded the International Playground Contractors Association and serves on the Consumer Products ASTM International Committee. Mr. Stoddard manages Playground Professionals LLC, home of The Play & Playground Encyclopedia and the Playground Professionals Directory.

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October 13, 2019, 6:51 pm PDT

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