Maintenance & inspection of underground stormwater detention systems
It is important to note that failure to control and remove sediment build-up in stormwater tanks is the largest cause of system failure. A pretreament totally suspended solid seperator can be used and on occasion incorporating of a sediment forebay trap in a StormBrixx® infiltration system, or a silt trap in a StormBrixx® detention/retention system, can ensure effective management of silt. For details of ACO pretreatment devices, please visit acoenvironment.us.
The open design of ACO StormBrixx® allows the system to be inspected by remote CCTV either through the inlet connection, access chambers, inspection points or pipes at the sides of the ACO StormBrixx® system. This allows the system to be inspected for sediment build-up and enables collected sediment to be removed from the infiltration system or flushed through a detention/retention system.
As sediment has the potential to carry high levels of pollutant, it is important that any sediment removed from the system is disposed of by an authorized contractor and in accordance with local regulations and codes.
In order to periodically check the effectiveness of the StormBrixx® infiltration system, a percolation test can be carried out on the tank and compared with the original data.If there is a significant decrease in the infiltration rates, the infiltration tank should be filled via the inspection chamber to the invert level of the inlet pipe.
It should then be flushed through with water in order to remove sediment and unblock the geotextile.
In order to clean the ACO StormBrixx® system, if a silt trap has not been incorporated, it will be necessary to block the outflow control device, not the overflow pipe, before filling the tank to the invert of the vent pipe. The tank should be filled and flushed as above and the water effluent removed and disposed of by a suction truck with vacuum pump.
The frequency of a maintenance procedure for the tank will be determined by the inspection regime. A recommendation is not less than twice-yearly inspections, and during the first year after every significant storm event.
In order to minimise silt build-up, ACO recommends the use of pretreatment systems upstream of the detention/retention/infiltration system.