From Party Jokes to Precast Ponds - The Power of Precast Concrete in Stormwater Management

On the rare occasion I get invited to a party, I like preparing topical jokes, funny anecdotes, and ways of explaining my job as a stormwater engineer that won’t instantly put the other guests to sleep. So when someone asks what I do, I usually pique their curiosity by answering, “I make the world a cleaner place, one storm at a time.” This usually gets a follow-up question about what that means or a confused look and a request to tell another joke about pineapples. Sadly, I only know one good pineapple joke, so I tell them that I create stormwater storage and treatment systems that capture pollution from storm events before they flow into our lakes, rivers, and oceans. It’s my way of creating a cleaner environment for everyone to enjoy, one storm at a time.

Stormwater storage is often overlooked, but it is every bit as important as stormwater treatment. I like explaining it by placing a napkin on a table and gently sprinkling drops of water over it. I repeat this a few times as I explain that the napkin easily absorbs the water in the same way our natural environment soaks up rain. Then I set an overturned snack bowl on the napkin and perform the same sprinkling of water, this time pointing out how the water droplets roll off the bowl and saturate the napkin with each repeated storm. The plate is like our built environment of impervious surfaces like streets, sidewalks, houses, and buildings. As we cover the land, the water has less and less space to go, so it eventually flows onto an adjacent property or floods the current one. 

So what is the solution? Detention ponds, of course. By designating low-lying areas specifically for capturing stormwater runoff, we can eliminate the risk of flooding. But what about urban centers where land is expensive, and the cost of land for a pond is unrealistic? This is when I flip the napkin over the open bowl and explain that we can store water underground in a precast concrete detention system. 
Precast concrete is a lot like really big Lego bricks. They can be produced quickly at a plant and delivered to a site for easy assembly. They’re modular and can be arranged into nearly any shape and stacked on top of each other to create taller systems that are incredibly efficient. The concrete is highly durable and will last decades with proper maintenance. It’s strong enough to support pavement and vehicular traffic above, so they disappear into our built environment while providing tremendous benefits. 

With some simple tape around the joints, the system becomes soil-tight. With a membrane liner wrapped around the system, we can ensure that stormwater stays in and everything else, like corrosive soils and groundwater, stays out. 

And it’s not very expensive. The precast concrete system requires much less land than a traditional pond. The underground system is also multi-functional because the contractor can use the land on top of it for parking, roadways, or even green space. It’s precast and modular, saving the contractor a lot of time making the concrete and waiting for it to cure. The joint tape and optional membrane liner materials are widely available and can be installed without special equipment. They can even be combined with stormwater treatment devices upstream and downstream to create treatment trains for maximum stormwater treatment and pollutant removal. It’s an incredibly efficient win-win solution.