About the Surface Sand Filter
General Information Performance Data Water Quality Treatment Process Design


The surface sand filter demonstrated a moderate capacity to reduce peak flow and treat water quality. Routinely used with great success for drinking water treatment, surface sand filters have not been as widely applied for stormwater management. Local acceptance may be hindered by lack of data.


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About the Surface Sand Filter

Surface sand filters are a Low Impact Development (LID) stormwater approach in use since the early 1980s. These relatively affordable systems generally consist of two serial components. The first provides pretreatment and/or sedimentation, and the second offers water quality treatment and runoff reduction through infiltration and filtration. In the right soils, they provide infiltration similar to undeveloped areas. At UNHSC, the surface sand filter demonstrated a moderate capacity to reduce peak flow and treat water quality.

Where to Use It

As with most LID stormwater practices, surface sand filters are suitable for many situations. To achieve maximum reduction of peak flow and stormwater runoff, it is important to locate them in soils that accommodate infiltration and to minimize ponding depth. Careful site analysis is required to design an effective, integrated network of these systems throughout a landscape.

Design depends largely on the drainage area’s characteristics. Underground sand filters are suited to urban areas with limited open space and a high percentage of impervious surface. Above-ground systems are suited to large drainage areas with adequate open space—such as highway interchanges—that have soils suitable for infiltration. As with any infiltration/filtration system, when sand filters are used in pollution hotspots or in poorly draining soils, they should be lined and outfitted with subdrains that discharge to the surface.

Implementation

Acceptance of sand filters varies regionally. Routinely used with great success for drinking water treatment, surface sand filters have not been as widely applied for stormwater management. Local acceptance may be hindered by lack of data and unfamiliarity with the design.

The cost to install a surface sand filtration system to treat the runoff from one acre of impervious surface was $12,500. This does not include maintenance, which may involve routine inspection, mowing of side slopes, and periodic scraping and replacement of the top inch of sand, as needed.

For more information on the design of sand filters like the one evaluated at the UNHSC field site, see the New York State Stormwater Management Design Manual.