Beach Sand Filter
Beach Sand Filter
Beach Sand Filter
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.
image gallery
select any photo to see a slideshow
The water at this popular swimming area is kept clean through innovative stormwater treatment.
Once a bulkhead is removed, see how beach gravel, sand, logs, vegetation are added to recreate natural conditions and processes.
Disguised as a beach, this sand contains a special media filter designed to treat stormwater runoff from the grassy areas of the park.
Without the former bulkhead, layers of sand and small pea gravel treat stormwater and make access to the beach seamless. Under the sand is the media filter.
In 2015, this bulkhead was removed to improve beach access and shoreline habitat and to soften a formerly hardened shoreline.
From the air, see shoreline improvements including a beach, sidewalks, and native plantings that perform onsite stormwater treatment.
Park maintenance crews use phosphorus-free fertilizers on the grass to limit the nutrients entering Lake Whatcom.
This small outfall has runoff from Electric Avenue which has been treated by two filter systems near the edge of the park.
The area outlined in the picture shows where stormwater treatment occurs. Water flows off various areas of the park into the sand. Then the cleaned stormwater seeps into the lake.
This is an example of a typical media filter drain showing how runoff first passes through sand, then through the media filter material, and lastly through sand and/or gravel.
Four basins or drainage areas were identified in the park. These are shown on this map. Knowing the size of these areas helps engineers design the right size of filter.
There are two primary designs for the media filter system in the park as shown here in yellow and green.
One part of the beach has the configuration shown in Section A-A' while the other is shown in Section B-B'. Note how the existing bulkheads were incorporated into the designs.
