Historically, underground infiltration beds have been laid out in either square or rectangular shapes, sometimes far away from where the actual rain drops fall.

These large systems are typically fed by a series of upstream catch basins and conveyance pipes. Several factors contribute to site layout, but mostly it simplifies the hydrologic and hydraulic modeling process, and keeps infiltration beds away from more sensitive underground infrastructure.

The emergence of low impact development (LID) principles, however, has encouraged designers to focus on managing stormwater onsite and close to the source using uniformly distributed, decentralized, micro-scale controls.

A site that had one or two large infiltration systems a couple of years ago might be designed with numerous smaller infiltration systems spread throughout the site today. Additionally, rectangular or square systems will not always fit the requirements of an LID site design, so designers may be forced to think “outside the box” in respect to the shapes of their systems.

Underground infiltration systems can be implemented on a site in just about any shape or configuration to allow designers to develop decentralized systems and provide infiltration on portions of the property where other LID practices may not be applicable.

In the past, many designers incorporated flow-control and flow-splitting structures into subsurface infiltration systems using a separate structure to perform each function. With advances in precast concrete manufacturing capabilities, increased plastic customization capabilities, and custom welding of metal systems, many flow-control and flow-splitting structures can be placed integrally inside the main chambers or pipe to reduce cost and the overall impact to a site’s footprint.