New neighborhoods have pond systems that are designed to provide water quantity (flood relief) and water quality benefits. The ability of the ponds to function in this capacity depends upon their condition and maintenance, or lack thereof. These ponds are designed to collect and hold stormwater for a period of time during and after a rain event to prevent flooding of the development and downstream properties. They also function to collect pollutants and sediment (dirt buildup). This collection system helps to keep the marshes and creeks cleaner than if we directly discharged out stormwater.
All ponds, lakes, lagoons and underground water quality structures are privately owned and maintained. Dorchester County does not perform maintenance, except in an emergency situation. Concerns such as algae control, mosquitoes, fish kills, dredging and trash removal must be addressed by the property owner or homeowner's association. Information on pond management can be obtained through Clemson Extension Service or the South Carolina Department of Natural Resources.
Drainage pipes should never be blocked with wood or other materials to keep the water levels in the ponds high. The ponds are designed to be at a specific level, although they may drop below this level during times of drought. The area between the top of the water and the top of the pond is called the “storage area”. This is where the system stores the storm water so that it does not flow downstream too fast and cause flooding. If pond outflow pipes are blocked to keep water levels high, the pond cannot store as much water which may cause flooding in area streets, yards and homes. In addition, the water cannot leave the pond as quickly as designed, which can lead to more flooding problems.
New storm water ponds are also designed to trap sediment (dirt) and other pollutants such as nitrogen and phosphorus from fertilizers, heavy metals from roads and vehicles, and fecal coliform from pet waste. By channeling this waste through a pond system, a portion of the waste is taken out of the flow stream and is not sent out to the creeks and marshes where it can cause damage to aquatic life and the environment. By reducing the amount of fertilizers we apply to our yards we can reduce the algae and weed growth in our ponds. By collecting pet waste and disposing of it in a garbage container, we can reduce the amounts of harmful fecal coliform bacteria.
As the pond fills up with collected material, it may become shallow. This lack of pond depth promotes vegetative growth, diminishes the pond’s ability to filter out additional pollutants before the water is released downstream, and reduces the ponds ability to retain stormwater runoff from flooding the drainage system and downstream properties. There may be a time in the future when the pond will need to be dug out or dredged.
Ponds and Water Quality Systems installed after September 2009 are required to be inspected. Inspections shall be performed at least twice a year and more regularly as listed below or as specified by a manufacturer. Inspection reports shall be generated and kept on file for two (2) years. Reports are to be made available to Dorchester County upon request. If generated by a third party, it shall remain the owner’s (or owners’) responsibility to maintain the reports.