Advanced Stormwater Skimmer with No Moving Parts

Sediment-laden runoff is the primary pollutant in many watersheds, so sediment basins are commonly used to remove sediment before it leaves the site. In fact, for construction sites such basins are often required by statute. Sediment basins are usually drained by perforated vertical risers and more recently by floating skimmers. Whereas a traditional riser discharges primarily from its lower orifices because of the higher heads that exist at greater depths, skimmers drain the cleaner water at the top of the water column, thereby increasing sediment retention. The authors have developed an alternative solid state skimmer (given the moniker “solid state” because it has no moving parts) that provides a similar skimming function, but also provides the additional benefits of varying flow rate with head and serving as its own principal spillway. The solid state skimmer is comprised of two concentric vertical risers. Columns of orifices cut into each riser act in series such that the flow into the outer riser is always dominated by flow through the uppermost wetted orifices, enabling skimming of water from a basin for the purpose of increasing sediment retention.