Underground Stormwater Management

By Scott Sertich, P.E.

For thousands of years, stormwater management has been an integral component of human civilization.

More than 4,000 years ago, early inhabitants of the Greek island of Crete designed storm drains and channels to collect and reroute precipitation. Many of these structures are still in place today. Ancient Egyptians diverted water annually from the Nile River to their fields so they could harvest their crops with minimal labor.

Today, we collect and reroute stormwater out of necessity because our built environment does not allow it to naturally percolate. No matter what the situation, stormwater management is crucial, and the material chosen for the job makes all the difference.

Two options

One solution for stormwater management is a man-made detention pond. However, in many areas – including urban infill and areas where land is expensive – above-ground detention ponds are not an option. An alternative solution is underground storage.

Underground storage captures stormwater runoff so it can infiltrate directly back into the water table, be detained for periodic release to stormwater infrastructure and treatment plants, or retained for beneficial reuse.

Stormwater can be contained underground in a range of sizes, shapes and materials. These solutions include circular corrugated metal pipes, plastic arches and precast concrete.

Pros and cons

With circular corrugated metal pipes, backfilling and compacting can be difficult and, if not done correctly, lead to voids and uneven pockets at the surface. Plastic arches provide greater efficiency but don’t offer the same strength and require minimum and maximum heights of cover. Plastic arches are also typically very short, making access and maintenance by personnel difficult to impossible.

Strong, reliable, versatile

Concrete has been a reliable building material since the Romans first invented it more than 2,000 years ago, and its properties provide benefits for underground stormwater solutions that other construction materials do not.

Concrete is strong, which allows for minimal cover. When it comes to precast concrete stormwater management structures, construction vehicles can drive over them immediately after installation with as little as 6 inches of cover. In heavy-loading and deep-fill applications, the concrete can be further reinforced.

Precast concrete boxes can be as short as 2 feet or as tall as 14 feet, making them extremely versatile. This also makes maintenance easy and comfortable. They are placed side-by-side, which minimizes the footprint area, reduces the amount of fill material and speeds up installation.

Precast concrete stormwater management solutions come in a variety of shapes, sizes and layouts from standard pieces to completely custom jobs. To see images of a variety of underground precast concrete systems, use our stormwater detention calculator and view technical documents and case studies, visit our stormwater management page.

A preferred solution

Although concrete is nearly as old as civilization itself, it continues to improve. Advancements in precast concrete technology allow for unlimited sizes, shapes and varieties of stormwater solutions. Performance-engineered precast with 15-to-30% voids allows rainwater to percolate through and recharge local groundwater supplies. In ancient times and modern times, concrete is the preferred engineering solution for stormwater management.