BALLASTED STORM WATER RETENTION SYSTEM

摘要

A roof system designed to retain water during storms and release it slowly over a period of time includes a polymeric water impervious membrane covered with a drainage board in turn covered with a water retention mat. The water retention mat and drainage board are held in position by ballast, preferably gravel. The mat is designed to retain at least about 25% of a one-inch per hour rainfall and release it gradually over 2 to 3 hours, thereby reducing rain runoff during storms and reducing the load on a storm sewer system