Underground Cistern

Underground storm water chambers are manufactured to be effective long-term storm water management systems. They are primarily used for landscape irrigation with gray water or to temporarily store and release at a predictable rate storm water flow. They are viable, low cost, low tech solutions to decentralized storm water drainage capture that has been approved by the EPA since 1997. If they are planned, designed, installed and maintained properly they become a very useful method of storing storm water on site. Nyloplast, ADS, Contech, Lane, Prinsco, Invisible Structures, Cultech, Storm Tech and Storm Trap are just a few of the manufacturer’s that build underground chambers out of pvc, polyethylene, corrugated steel or concrete. In many instances, underground chambers have been installed under parking lots to detain, filter and clean sheet flow from concrete, asphalt roof lines and other impervious surfaces. They can be adapted with special storm water treatment chambers to soak up oils and other human made petrochemical pollutants that are commonly associated with automobile parking areas of horticultural maintained turf grasses. A very simple system of storing water underground is an old fashioned farm drain system that uses perforated pipe in an underground pattern to dissipate and infiltrate storm water.

Ex-filtration beds of sand and gravel are used to soak up and filter any storm flows not leached back into the ground directly under the chamber line or bed. The filter medium is typically sand, but it can consist of sand, soil, gravel, peat, compost, or a combination of these materials. The purpose of the filter bed is to remove smaller sediments and other pollutants from the storm water as it percolates through the filter medium. Finally, treated flow exits the sediment filter system via an outflow mechanism to return to a storm water conveyance system or a permanent retention pond. Surface storage with sun light systems takes precedence over underground storage where possible.