Post-construction
Storm Water Management Best Management Practice SummariesBest Management Practices: - New practices will be added as they are completed.
Post-construction
Storm Water Management Best Management Practice Summaries
The following is from the University of Minnesota Standards & Procedures for Construction and current as of November 2002. Please check Sustainable Design Requirements - Page 8 #7.3.2 at http://www.facm.umn.edu/cons/2002/Prog02.pdf for updated requirements.
7.3.2. Sustainable Sites: This includes development in environmentally appropriate areas, reduced site disturbance, proper storm water management and sustainable landscape design.
Storm water drainage wells (usually considered a class V injection well) are typically shallow disposal wells designed to place storm water below the land surface. By EPA definition, a Class V injection well is any hole that is deeper than its widest surface dimension or any subsurface fluid distribution system that releases fluids underground. Storm water management BMP's that include subsurface infiltration must comply with the EPA Underground Injection Control program. For more information see http://www.epa.gov/safewater/uic/pdfs/fact_class5_stormwater.pdf
Post-construction controls can be particularly difficult in cold weather climates due to frozen soils and ponds, and sand and salt use. The Center for Watershed Protection has a Stormwater Practices for Cold Climates manual available on line at http://www.cwp.org/cold-climates.htm. Several Minnesota organizations have also put out manuals that have BMP's for post-construction storm water management. Metropolitan Council Environmental Services (MCES) offers guidance on post construction storm water controls in their Urban Small Sites Best Management Practice manual (http://www.metrocouncil.org/environment/Watershed/bmp/manual.htm), and the MPCA put out the Protecting Water Quality in Urban Areas manual (http://www.pca.state.mn.us/water/pubs/sw-bmpmanual.html).
The EPA has a National Menu of Best Management Practices for Storm Water Phase
II for Post-Construction Storm Water Management in New Development & Redevelopment
which can be found at:
(http://cfpub.epa.gov/npdes/stormwater/menuofbmps/post.cfm)
Some
examples of post-construction storm water controls:
Infiltration Basins are open earthen impoundments designed to retain storm water and to infiltrate it into the soil. The design should include an inlet-settling basin to remove coarse materials prior to flowing into the infiltration basin. The surface may be vegetated.
Infiltration Trenches are trenches that are 1 to 2 feet wide, and 2 to 10 feet deep. They are typically lined on the sides and bottom with permeable filter fabric and backfilled with coarse aggregate. Trenches may be surface or subsurface levels, and design may include a vegetative filter strip. Trenches are effective in removing suspended sediments, floating debris, and bacteria. In most cases, trenches will have some overflow connection to storm sewer pipe.
Pervious Paving Blocks are manufactured or plastic blocks that allow water to flow through the porous material into a subsurface of gravel and filter fabric, and ultimately into the soil. Excess flow will run off the paving block area and can be channeled into a swale or other infiltration structure.
Swales are vegetated, shallow channels with gentle side-slopes. Treatment occurs as storm water flows through the dense vegetation. Removal mechanisms for pollutants include filtration, sedimentation, adsorption, and infiltration into the soil profile. Swales are used to remove sediment and pollutants that adhere to the sediment.
Filter Strips are vegetated, gently sloped strip, 10 feet or more in down-slope length 950 to 75 feet is recommended for good performance). Vegetation may be turf, or forested with trees and shrubs. Filter strips must be designed to accept sheet flow, and are typically used in conjunction with other treatment control measures, such as grassy swales or infiltration trenches.
Glensheen has received two grants from the Southern St. Louis County Soil and Water Conservation District (SWCD) and the Great Lakes Commission. The first is a "Low Impact Development Storm Water Demonstration Project". Its goal is to design, construct and test innovative storm control methods near Lake Superior. The project is looking at treating runoff from Glensheen's parking lot. This will be accomplished in the form of a small pond / garden area between the parking lot and Lake Superior. The second is for a "Low-cost Lake Superior Shoreline Erosion Control Demonstration Project". The project is looking stabilizing the discharge areas from the Low Impact Development Storm Water Demonstration Project area. These projects are being design by the SWCD and are to be completed by June 2004.