Phase 1: Reconstruction of Drainage Channel and Bioinfiltration Basin
Water Quality Structures
Bio-filtration basins are areas of engineered landscaping and soils to aid in the reduction of runoff rates and pollutant discharge into adjacent storm water systems or receiving waters. Bio-filtration structures are recognized as a form of best management practices (BMP) for of achieving water quality standards in many municipalities as well as the United States Environmental Protection Agency (US EPA).
Bio-filtration structures are comprised of several components to lessen runoff rates, filter pollutants, or both. As the sites runoff enters the structure, rock check dams quickly dissipate the runoff. These rock check dams, constructed with large stone, act as pretreatment filters and manifolds. After the runoff fills the depression, it proceeds through a gradual sloping grass area. The grass area further reduces the runoff rate and aids in removing larger suspended solids. The vegetative retention area finally receives the storm runoff. These areas contain strategically selected plantings that thrive in moist and drought conditions. Engineered soil, surrounding the plantings, allows for a specific range of permeability as well as removal of pollutants. An underdrain and overflow system is required to remove excess water from the bio-filtration area.
In karst areas injection wells are used to move surface stormwater runoff into the porous rock formations below the soil. The injection well is a drilled shaft that quickly conveys the runoff below the surface in order to minimize the potential for flooding. A disadvantage is that the water flowing into the underground water system is unfiltered.
Bio-filtration areas are aesthetically pleasing options to meeting stormwater quantity and quality requirements. Landscaping is a requisite for many municipalities' development plans. This alternative meets landscape requirements, potentially reducing drainage conveyance and landscaping area allotments.
Below is a diagram that shows how the system is constructed.
Construction began with the drainage culvert at Glen Lily Rd, August 2012. To the left of the tree is where the water flowed through a property owner's backyard.
Twenty-four hundred tons of rock was removed from the channel and basin. The basin was refilled with a thick layer of gravel, soil and mulch to improve the drainage.
Three old injection wells were replaced with two new injection wells.