Catch Basin for Stormwater

A catch basin is an inlet to a stormwater drain system with a grate cover. The function of the catch basin is to capture sediments, debris, and associated pollutants. The purpose of the catch basin is to prevent the downstream pipes from being clogged with sediments or other pollutants and to reduce the amount of pollutants discharged to rivers and streams.

The catch basin captures the pollutants by settling or infiltration mechanisms. In the first mechanism, pollutants settle at the bottom of the catch basin sump. In the second mechanism, a leaching basin is used.

The leaching basin is similar to the standard basin. The bottom of the leaching basin is made from loose aggregates, through which stormwater flow and infiltrate into the soil below.

The leaching basin should not be used if there a possibility of ground contamination. The figure no: 1 showing standard catch basin and figure no: 2 showing leaching catch basin. Catch basins are located at low points and otherwise spaced to provide adequate drainage of surface water runoff. 

Figure 1

Figure 2

Frequent cleaning of the catch basin will maintain their ability to trap sediments and other pollutants. Studies have shown that periodically cleaned catch basin can trap up to 50% of coarse sediments (particles of 0.4in or 1mm) and lower removal for other pollutants. Periodic cleaning of the catch basin will reduce the foul odors, solids, and other pollutants.

Sewer vacuum is considered as an efficient and reliable method of cleaning catch basin. The Vactor truck will be used to suck the materials from the catch basin sump. Catch basin should be clean when the depth of sediments reach 30% to 50% of sump total depth. In-frequent cleaning of the catch basin will result in filling up the sump with sediments, at this point, the sediments and pollutants will pass through catch basin without being trapped. 

Figure 3

Catch basins cannot remove pollutants as well as other systems such as wet ponds, sand filters, or storm wetlands. In reality, a catch basin can become a source of pollutants if not maintained and cleaned periodically. Therefore it should be cleaned regularly.