Stormwater or stormwater runoff is precipitation, such as rainwater, that falls to the ground but is not absorbed into the natural landscape. When stormwater is absorbed into the soil, it is filtered and flows into local waterways. When it isn’t absorbed, it runs off surfaces including rooftops, driveways, lawns, parking lots, roads, etc. and moves through a system of stormwater pipes and ditches. In Cobb County, eventually, all stormwater ends up in Lake Allatoona and the Chattahoochee River.
In developed areas, impervious surfaces such as pavement and roofs prevent precipitation from naturally soaking into the ground. Instead, water runs rapidly into storm drains, sewer systems, and drainage ditches, which can cause:
- Downstream flooding
- Stream bank erosion
- Increased turbidity (muddiness created by stirred up sediment) from erosion
- Habitat destruction
- Infrastructure damage
- Contaminated waterways
Cobb County is approximately 22% impervious surface area. It’s critical that our stormwater is managed to reduce flood risks, protect waterways from pollutants, and help our streams, the source of our drinking water supply, remain healthy.
Cobb County Water System’s Stormwater Management Division (SWM) manages both stormwater quality and quantity to ensure the health of the community and local ecosystems are sustained. The County maintains a five year municipal separate storm sewer system (MS4) permit with United States Environmental Protection Agency (USEPA) which grants Cobb County the right to discharge stormwater from municipal stormwater management facilities into waters of the State and requires the implementation of a Storm Water Management Program (SWMP).
Basin studies conducted by Cobb Water show that regional detention facilities provide significant improvement in watershed protection as well as flood control. SWM has constructed four regional facilities to date: the Echo Mill Regional Detention Facility in the Powder Springs Creek Basin and Chestnut Hill, Chastain Meadows, and Mark Avenue Regional Facilities in the Noonday Creek Basin. SWM is currently in the process of rehabilitating the Laura Lake Dam on Noonday Creek Tributary #4 to serve as an additional regional facility.
Stormwater management in Cobb County began in the early 1970’s. Originally a part of the Public Works Department and later the Development Control/Community Develop Agency, Stormwater Management was transferred to the Cobb County Water System in 1993.
The Stormwater Management Division maintains stormwater infrastructure that has been conveyed to the County for perpetual maintenance. There are multiple types of infrastructure that are designed to manage and convey stormwater runoff.
Stormwater Management inspects County owned infrastructure to assess condition and identify impediments to function or need for repair. Additionally, Stormwater Management monitors local commercial and residential property for compliance of County ordinances as well as state and federal environmental standards.
The extent and level of service vary across utilities. CCWS provides services that other utilities do not provide, such as accepting detention ponds in new subdivisions. There are services some other utilities provide that CCWS does not provide, like maintaining open channels for a short distance from the end of a public pipe.