Stormwater Protection

Stormwater runoff is when rain or snow falls and collects in impervious areas, which do not let it filter into the ground. Instead, the runoff accumulates debris, chemicals, sediment and other pollutants, which can pollute groundwater.
Photo Credit: PLR Photos

Controlling stormwater runoff in a heavy traffic area can be achieved by building constructed wetlands, rain gardens, bioswales and pervious paving.

LEED and Stormwater Management

LEED awards points to projects that limit the quantity of runoff and improve the quality of stormwater in Sustainable Sites (SS) Credit 6, Stormwater Management. SS Credit 6.1, Stormwater Management - Quantity Control awards points to projects that reduce the amount of runoff from precipitation. The intent of this credit is to limit disruption of natural hydrology by reducing impervious cover, increasing filtration, and eliminating pollutants and contaminants from stormwater runoff. The requirements vary by case: Case 1: Sites with Existing Imperviousness 50% or Less Option 1: Implement a stormwater management plan that prevents the post-development peak discharge rate and quantity from exceeding the pre-development peak discharge rate and quantity for the 1 and 2 year 24-hour design storms. Option 2: Implement a stormwater management plan to protect stream channels from erosion and includes strategies for quantity control and stream channel protection. Case 2: Sites with Existing Imperviousness Greater Than 50% Stormwater management plan: 25% decrease in runoff from 2-year 24-hour design storm Strategies for achieving Credit 6.2 include using green roofs, pervious paving, reduction of imperviousness, and reusing stormwater for non-potable uses (such as toilet flushing). SS Credit 6.2, Stormwater Management - Quality Control awards points to projects that improve the quality of runoff. The intent of this credit is to limit the disruption and pollution of natural water flows by managing stormwater runoff. The requirements are: Implement a stormwater management plan that treats stormwater from 90% of rainfall using best management practices (BMPs). The BMPs should remove 80% of total suspended solids (TSS) based on existing monitoring reports. The BMPs meet this criteria if: - They are designed according to a state or local program that has these performance standards OR - BMP data monitoring conforms to accepted protocol, such as the Technology Acceptance Reciprocity Partnership (TARP), Washington State Strategies for achieving Credit 6.2 include using alternative surfaces (such as green roofs), bioswales, rain gardens, constructed wetlands, natural and mechanical treatment systems, and disconnection of imperviousness.

Free LEED Exam PreperationBioswales

Swales are low lying or depressed tracts of land, usually manmade, that collect and filter runoff water. They are often wet or marshy and prevent erosion. Vegetated swales, also known as bioswales, are a type of depression that is planted with vegetation. The plants in these bioswales are best if they are native or adapted, different sizes, suitable to a range of moisture levels, and different species. These vegetated swales are a transition area from drier, higher land to lower, moister land, which makes it a rich center of biodiversity.

Permeable Pavement

Permeable paving, also known as pervious or porous paving, is the method of creating hard surfaces such that water can filter through them. This allows precipitation and water from other sources to trickle through the pavement and into the watershed, instead of becoming polluted runoff. The following are three permeable pavement solutions on the market: 1. Evolution Ultimate Pervious Paving The Oregon-based Evolution Paving Resources manufactures the Ultimate Series, a type of pervious concrete pavement that uses “zero runoff technology”. The pavement contains smaller particles, which keep out debris while filtering stormwater pollutants, but still has strength of 2000-2500 psi. It is cooler than asphalt, which prevents heat island effect. Because of its innovative technology, it was chosen as one of the Top 10 Green Building Products of 2010 by Sustainable Industries. It’s also meets the U.S. EPA’s Clean Water Act and the Clean River Rewards Program in Portland, OR. 2. VAST Composite VAST Composite Permeable Pavers are composed of 95% recycled materials, which include scrap tires and bottles. These materials make the paver lighter, at less than a third the weight of a typical pavers, which means they take less energy to transport. They are not only longer-lasting than conventional pavers but also contain recycled content, which lessens the amount of waste sent to landfills. VAST’s composite pavers are made using a quarter of the energy of conventional pavers, which further reduces their environmental impact. They also release 10% of the carbon dioxide of other concrete paving products. The pavers are less prone to color fading and do not suffer from efflorescence, which are unappealing mineral deposits that occur because of moisture in unsealed concrete products. They are also stronger because of their composite structure, which makes them less susceptible to weatherization and cracking. 3. EcoGrid EcoGrid permeable pavers, which are made with 100% recycled high density polyethylene, are suitable for roads, parking lots and farmland. They can either protect the surface from pedestrian or vehicular traffic, or to stabilize the soil and prevent erosion. The patented system can be covered with grass, which quickly grows over it, or filled with gravel. It is easy to install because of its patented fastening system, and is virtually maintenance free.

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