Beach Sand Filter - Stormwater Discovery Tours

Where is this located? It is located along the shoreline areas of the park from Electric Avenue to the boat ramp.

What’s special about this place? The sand on this beach is much more than it appears. It is an inviting beach as well as a stormwater filtering facility installed in 2015 to protect Lake Whatcom water quality. Prior to this project’s installation, this area had high phosphorus and fecal contamination. Although phosphorus and fecal bacteria were draining off this area at one time, they weren’t higher than other similar lawn areas. The City Parks and Recreation Department uses phosphorus-free fertilizer and bags lawn clippings. A bulkhead used to armor part of this shoreline and was replaced with a sandy beach that improved recreational use of the area. Check out the images and maps below to see how the media filter drain wraps around the entire shoreline of the park from Electric Avenue to the boat ramp. It is estimated that the park’s 6-acre area has reached a 90% stormwater treatment goal with a significant phosphorus reduction in large part due to this smart development strategy.

There are several types of stormwater filters, including cartridge filters, media filter drains, sand filters, and gravel filters.

Water Quality Benefit: As water soaks through filter materials, pollutants are physically trapped, chemically neutralized, or biologically recycled back into the environment. Filters prevent particles of dirt and other pollutants, including hydrocarbons, fertilizers, and metals like zinc and copper (which are toxic to fish), from being released into creeks and lakes.

Cartridge filters are cylinder-shaped containers filled with special material that traps particles and absorbs pollutants. Cartridges are used in vaults or tanks. Just like an air filter in a car, cartridge filter materials need to be replaced to remove pollutants and maintain their ability to treat runoff.

Sand and gravel filters use layers of sand, gravel, and/or rock to trap and strain particles out of the water. By slowing the water down, most of the sediment, small particles, and some of the pollution can settle out into the crevices of the sand and gravel. Sand filters are better at removing pollution than gravel filters because they have more surface area to collect pollutants. The smaller the gravel size, the smaller the particles that are removed. Pollutants stick to the sand particles where chemical and biological processes break them down.

Media filter drains (MFDs) use special materials, or media, that target tough-to-capture pollutants, such as dissolved metals and nutrients. MFD media can be used inside a trench or vault, or along a shoreline. The media is made of tiny washed rocks, slightly larger than grains of sand, with perlite, dolomite, and gypsum added to it. The perlite absorbs water and expands, physically trapping particles of pollution. Next, dolomite and gypsum chemically react with water to trap nutrients including phosphorus, nitrogen, and potassium. Then, with the help of naturally occurring microbes, nutrients are recycled back into the environment.

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