1. Field of the Invention
This invention relates to improvements in the field of land development, particularly with water quality treatment and volume reduction of storm water runoff by retention, infiltration, evapo-transporation as is commonly required when constructing new areas or revitalizing/reconstruction of already developed areas. These water quality and volume removal features fall into a class of facilities referred to as best management practices or “BMPs”. Some common representation of BMP facilities include but are not limited to: biorention cells, infiltration trenches, constructed wetland, detention basin, retention basins, et al. BMPs are sometimes also referred to as “green infrastructure”.
The subject of water quality treatment and volume removal of storm water is of interest to those looking to attain construction permits from a county, state or federal entity such as the Environmental Protection Agency or any other organization or entity charged with the protection of environmental resources. Another reason for construction of green infrastructure would be to reduce additional storm water runoff volume from entering a combined sewer. Combined sewers is a term describing collection and conveyance systems within an urban or suburban area may collect runoff from rainfall events as well as sanitary discharges from residences or businesses into a single conveyance, which would then be directed to a waste water treatment plant (WWTP). Combined sewers are still a common practice in older urban areas. In many cases with urbanized areas, the benefit with using BMPs or “green infrastructure” would be as a means of reducing sewer operation fees, which are typically proportional to whatever volume of influent (flow in) would be to a waste water treatment plant (whether or not this influent would be sewage or rainwater). In particular, the application of the device described herein relates to the pretreatment of storm water runoff before entry into green infrastructure areas; a necessary step in order to ensure the longevity and viability of these planted zones, that also serve the function of infiltrating storm water volume in lieu of discharge into combined sewers or steams.
2. The Prior Art
Pretreatment of storm water runoff into green infrastructure or BMPs is known to be an important step in providing for the long term function and operation of urban green infrastructure is to be maintained in a cost effective way. A green infrastructure facility that is not outfitted with a means of pretreatment may undergo scouring or loss of stabilization and plant matter, its planting zone may be overwhelmed with trash and debris, its soil may become clogged with fine sediment rendering its purpose as an infiltration facility useless, excessive oil and heavy metals may kill plant growth especially in urban areas where green infrastructure would more readily encounters such pollutants.
Current practices include the use of fabric or small diameter stone to provide pretreatment by screening pollutants and trash. Some attempts at a manufactured solution have been the use of screens to filter out trash and sediment. However, due to the small cross-sectional flow area presented by these various screening methods, these types of configurations quickly clog and render not only the means of pre-treatment useless, but potentially the whole BMP facility.
prior art teaches nets be used to capture trash from the flow of water from pipes. Prior art also teaches inclined cells be used to efficiently settle sediment from the flow of water. This invention introduces the combination of both technologies in a stacked fashion. This is possible with the reversal of the traditional flow path in the settling cells. Prior art teaches the flow inside the settling cell to be substantially upward, i.e. From the bottom to an overflow weir. This invention teaches a method where the water flows from the top of the settling cells to orifices below the water surface and thus the water is substantially flowing downward. This method has shown to promise remarkable results in test models. The deterministic flow regime of flowing substantially with the direction of gravity proves to enhance the inherent settling direction of the sediment on the cell bottoms and the subtle directional change of the hydraulic flow toward an escape orifice as well as the eddy current in the settling cells all contribute to the separation of sediment from the water flow in this device. Because this device departs from traditional settling regimes claimed in U.S. Pat. Nos. 3,706,384 and 6,676,832 and substantially improves settling efficiency of the Happel et al U.S. Pat. Nos. 6,797,162; 6,428,692; 7,153,417; 724,256 where settling cells operate in series instead of in parallel and do not provide the overlapping features of the settling cells. This invention places a screening or netting surface above a cell settler and among other enhancement this device is new in its form and promises to be compact, cost effective and useful to the implementation of pretreatment of storm water run-off dedicated for evaporation and infiltration in green infrastructure designs, as well as being useful in other circumstances were treatment or cleaning of a liquid is required.