Tackling Stormwater With Expanded Shale, Clay, And Slate

By Debbie Stringer
From the December 2023 Issue

For building owners and managers, stormwater can pose a larger problem than meets the eye. On the surface, excessive stormwater runoff can sweep debris and organic matter into large and difficult-to-access heaps, negatively impacting the visual aesthetics of a building’s exterior. But deeper than that, if a property has insufficient drainage, stormwater could collect around foundations, potentially damaging buildings.

Sometimes stormwater saturates the soil and causes it to expand, exerting pressure against the foundation wall, which can lead to structural damage due to cracking or bowing. Likewise, it can also impact the beautiful landscape around buildings by drowning flora and eroding pathways and pavements. All this damage can increase maintenance costs or shorten the life of a property entirely.

Many stormwater management solutions can be equally investment- and maintenance-intensive.

In turn, they may not be viable for commercial, institutional, and industrial facilities. When a property needs sustainable solutions that are easy to maintain and actually enhance the beauty of the surrounding area, facility managers have historically turned to expanded shale, clay, or slate (ESCS) for a cost-effective and readily available option.

Retaining Structural Strength With ESCS

Engineering soil to filter and store stormwater can help safeguard foundation stability and strength. ESCS helps facilitate this with its ability to drain water freely through an evenly distributed network of unconnected pores. Because this network is a result of vitrifying the raw materials in a rotary kiln at about 2000 degrees Fahrenheit, ESCS remains a structurally strong, environmentally inert, and non-toxic material that stands the test of time despite being porous in nature.

Decision-makers for commercial, institutional, and industrial buildings can use ESCS-engineered soil as an underground filter fill to bolster stormwater management. A layer of aggregate fill below permeable pavers absorbs excess water, which percolates into the groundwater table. Traditional aggregates increase a soil’s drainage capacity to some extent. But because ESCS’ pores increase the particles’ surface area, this aggregate can provide even more storage and free-drainage potential—further alleviating pressure exerted on foundations by soil expansion.

For example, the University of Texas at Austin employed ESCS in the structural soil below the permeable brick paving on campus. The media was compacted to support the paving system and could be installed all the way to the base of the existing landscape, which was lined with tall trees. Its non-toxic and porous properties balance appropriate oxygen and water requirement in the root zones, removing the need to disturb existing plant life. In fact, the aggregate contributed to improving clay soil conditions, which led to a landscape design that could accommodate more plants and trees.

ESCS Facilitates Plant Growth And Stormwater Management

Building owners and decision-makers often invest significant resources in landscaping to beautify a property and support public image. But stormwater can undo all that hard work. Not only does stormwater remove the top layer of the soil and wash away nutrients, plants, and seeds, but it can also wash out the fertile soil and suffocate plant roots, promoting diseases that can lead to their death.

ESCS can mitigate damage to landscaping by promoting deeper water and oxygen storage for healthier plant roots and therefore better soil stability. The aggregate, when mixed with organic matter, creates an excellent growing media that can ensure the long-term viability of turf, shrubs, trees, and other plants even during periods of intense rainfall. Additionally, the mixture results in a self-managing storm filtration and cleansing system that encourages the timely release of water and nutrients back into the plant roots as soon as the surrounding soil begins to dry.

Because ESCS can promote plant growth, it is an effective solution for beautifying properties, especially in locations that are prone to poor drainage and flooding. The material has been popularly employed in rain gardens, filter strips, and green roofs where it can drain rainwater within minutes. For instance, the Dallas Fort-Worth area often sees intense seasonal rainfall, which has led to flash floods in urban areas. However, planners for Klyde Warren Park in downtown Dallas and the Kimbell Art Museum mitigated this danger by using ESCS as a lightweight engineered fill and drainage medium.

Klyde Warren Park uses ESCS in multiple ways: to create gentle mounds for children to play in; to serve as a base beneath pathways and in plant zones due to the material’s ability to stabilize soil; and to drain water and retain nutrients that support existing vegetation. In addition, because this soil is porous and lightweight, it makes for easy digging during the renovation and installation of new plant material, irrigation, and even laying the concrete footing.

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An underrated feature of ESCS is how little it weighs—a key consideration for the expansion of the Kimble Art Museum. Spread over the four-acre outdoor “turf roof” created over the parking grounds, the material reduces the weight on the structural system and promotes vegetation growth that can capture and hold the first inch of rainfall during a storm event. This makes it an ideal choice for green roofs.

Safeguarding The Structural Integrity And Beauty Of A Facility

An impressive building often mixes a well-designed space and a well-maintained structure. Excessive stormwater can be a hazard to both. ESCS is a multifunctional material that stabilizes soil and provides a load-bearing, free-draining and air-entrained growing medium. It also contributes to maintaining the structural integrity of a building in an efficient and cost-effective way. With ESCS in their arsenal, executives at commercial, institutional and industrial facilities can mitigate stormwater damage while also reducing their operation costs.

Stringer received her horticulture degree at SCC in Pinehurst, NC. As a horticulturist and stormwater professional who has worked in the green industry for 35 years, of which 24 have been with Carolina Stalite Company in Salisbury North Carolina, Debbie represents ESCSI primarily for the landscape, stormwater, and filtration industry.

Do you have a comment? Share your thoughts in the Comments section below, or send an e-mail to the Editor at jen@groupc.com.

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