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Stormwater and Excess Nutrients 27
<br /> Why care about stormwater?
<br /> As we add more impervious surface to the landscape, such as rooftops, roads, driveways, and parking lots (including
<br /> gravel), we create more stormwater runoff. More stormwater runoff means less rain "soaks" (infiltrates) into the
<br /> ground. Less infiltration means less groundwater for our wells and streams, worsening the effects of drought.
<br /> What's worse...as stormwater flows across impervious surfaces or exposed soil, it picks up various pollutants, such as oil
<br /> &grease, excess nutrients, harmful bacteria, trash and sediment. Polluted stormwater flows down our storm drains and
<br /> through our ditches where it is discharged, untreated, into our streams, rivers, and lakes. Stormwater runoff pollution
<br /> can adversely impact aquatic ecosystems and our drinking water supplies. Ultimately this costs money, such as a new
<br /> well, higher water rates, or expensive environmental restoration required by clean water regulations.
<br /> Don't nutrients occur naturally?
<br /> Nutrients, nitrogen and phosphorus, occur naturally and are vital to plants and therefore the ecosystem. However, as
<br /> described above, when we increase impervious surface, fewer nutrients can infiltrate and therefore less are taken up by
<br /> natural systems. Like water, nitrogen has a "cycle" and when various forms of nitrogen cannot infiltrate into the ground
<br /> due to impervious surfaces, the excess ends up in waterbodies causing an imbalance. Phosphorus can actually bind to
<br /> soil particles and since increased impervious surface often leads to increased downstream erosion, excess phosphorus
<br /> also reaches our local waterways.
<br /> What impacts do excess nutrients have on our water?'
<br /> Excess nutrients, especially in lakes, reservoirs and estuaries, enhance plant growth and cause excessive algae growth.
<br /> Some plants, like hydrilla, are invasive and can become a nuisance, but what is even more serious is the change in
<br /> chemical composition of the water. As plants and algae die, they use up available oxygen in the water, causing fish kills
<br /> and other ecological impacts. This process, known as eutrophication, is a major water quality problem across the
<br /> country.
<br /> However, eutrophication has other serious impacts. Some of the algal blooms can be toxic and generate a range of
<br /> paralytic, diarrheic and neurotoxic effects which not only negatively impact animals, but can also directly affect humans.
<br /> For instance high nitrate levels in drinking water have been linked to various health problems in humans including
<br /> reduced red blood cell production. High nutrient levels require additional treatment which may cause elevated levels of
<br /> chemicals used to disinfect drinking water during treatment.
<br /> Excess nutrients can alter taste and odor in drinking water, which require increased treatment costs. Cyanobacteria,
<br /> (also known as blue-green algae) can be toxic and may pass through normal water treatment processes. According to
<br /> some research, ingesting water contaminated with chemicals produced by harmful algal blooms can cause
<br /> gastrointestinal complications, acute or chronic liver damage, neurological symptoms and even death. Additionally,
<br /> excess nutrients can alter habitat needed by fish and shellfish, or simply poison these animals. This can lead to
<br /> harvesting closures and consumption bans. The economic impact is staggering, and stormwater is just one source of
<br /> excess nutrients in our local waters. Across the nation, the cost of reducing nitrogen and phosphorus pollution is in the
<br /> billions of dollars annually.
<br /> What can be done?
<br /> Clearly excess nutrients are a problem and stormwater runoff is one known source. For new development, nutrient
<br /> loading limits can be set. To meet these limits, development can use both structural and non-structural controls. Non-
<br /> structural controls include proper site design, stream buffers, soil amendments and other means to encourage onsite
<br /> infiltration of stormwater. Structural controls include bioretention cells (i.e. "rain gardens"), stormwater wetlands,
<br /> detention ponds and other structural measures engineered to reduce stormwater runoff pollution.
<br /> 1 Please visit, littp://water.eiDa.gov/scitech/swguidance/standards/criteria/nutrients/effects.cfm for references,citations and
<br /> additional information.
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