Corrugated Metal Pipe Sand Filter

Lane’s Corrugated Metal Pipe Sand Filter (CMPSF) provides a mechanism to intercept storm water flow, remove pollutants, and discharge treated flow in a manner suitable for today’s storm water regulators. Ever-changing storm water regulations continue to emphasize the importance of Best Management Practices to address water quality issues and associated mandates set forth by the EPA. Simply put, the Corrugated Metal Pipe Sand Filter is a tried-and-true means of providing treatment that not only meets the EPA’s standard for treating the “first flush,” but serves as the performance benchmark for other types of water quality devices.

The underground sand filter is a design variation of the surface sand filter, where the sand filter chambers and media are located in an underground vault. Initially, underground sand filters were typically reinforced concrete rectangular structures. However, since the 1980s, CMP alternates have demonstrated a market preference for the concrete vault due to less costly and obtrusive shipping, handling, and installation issues. Depending on any grade limitations, a circular or arched-pipe shape may be used. With the benefit of today’s premium coatings (e.g. Aluminized T2), Corrugated Metal Pipe Sand Filter has the added value of meeting the most stringent durability requirements. Lane’s CMCorrugated Metal Pipe Sand Filter PSF is a three-chamber system consisting of a sediment chamber, a sand bed filter, and a clear well. Although multiple configurations are possible, the figure below shows a typical 8' diameter model with an internal bypass.

The sedimentation (pretreatment) chamber temporarily stores runoff and captures sediment. The sedimentation chamber is connected to the sand bed filter by a submerged wall that protects the filter bed from oil and trash. The filter bed is 12" to 24" deep and may have a protective screen of gravel or permeable geotextile to limit clogging. The filter bed includes an underdrain that discharges filtered runoff into a third chamber. An in-line configuration must be able to bypass flows that exceed the filter bed capacity. Some design standards may allow an internal bypass (as above); however, regulations vary and may require an external bypass to prevent commingling with the “first flush” (i.e. water quality volume). Sand filters may also be constructed parallel to a storm drain in an off-line configuration, thereby utilizing the storm drain as a bypass provision.