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The small community of Mt. Rainier, Maryland is taking action to help protect the Chesapeake Bay. About five percent of the Bay has been classified as a dead zone because of excessive nutrients from sewage discharges, urban stormwater and fertilizer runoff, and other pollution sources. (1) Gutter filters and bioinlets installed along Route 1 as part of Mt. Rainier's pilot program are making real improvements in preventing polluted stormwater runoff that contributes to poor water quality of the Bay. What are Bioinlets and Gutter Filters? "Gutter filters are similar to sand filters which work on the principle of sedimentation and filtration," says Ameya Ulhas Pradhan, who studied these stormwater management methods in a Master's Thesis at the University of Maryland. "They are constructed below grade... [and] the filtered runoff is discharged to a storm drain or natural channel." (2) In other words, the stormwater runoff flows into the gutter filter where the water is filtered through sand, which catches many of the chemicals, metals and other pollutants before the water flows into the Bay. In Mt. Rainier, these are constructed along the roadside in the place of a traditional storm drain. Bioinlets include vegetation to help break down pollutants and provide sedimentation, filtration, soil absorption, microbial decay processes and uptake of pollutants by plants. (3) These act like bio-retention areas, which collect and hold water while it is filtered through soil and into plants. Like the gutter filter, bioinlets fit into the small area of a traditional storm drain. Results for a Cleaner Watershed With the installation of both the bioinlets and gutter filters, there was generally an even greater reduction in these pollutants. Total Suspended Solids were reduced by 83 percent, cadmium by 86-89 percent, lead by 84 percent, and zinc by 58 percent. Nitrate was reduced by 42 percent, Total Kjeldahl Nitrogen by 12 percent, and copper by 29 percent. Nitrogen and phosphorus contribute to the growth of algae, which can deplete water of life-sustaining oxygen when it decomposes, and metals can be harmful or toxic to human health and aquatic life. An Effective Stormwater Management PracticeThese small steps have an effect, and they can make a big difference in water quality if done on a large scale. They can be replicated across the region efficiently, without a lot of retrofitting, and without a huge price tag. Footnotes:
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These methods of addressing stormwater runoff are uniquely suited to urban areas where there is little land available for other methods of filtering runoff. 
A variety of tests and studies conducted confirm the effectiveness of bioinlets and gutter filters. Gutter filters were found to eliminate Total Suspended Solids by 75 percent, Total Kjeldahl Nitrogen by 50 percent, zinc by 71 percent, copper by 40 percent, lead by 69 percent, and cadmium by 43 percent. However, there was no effect on nitrate or total phosphorus. (4)