Detain H2O—detention pond retrofit device

Abstract

Aspects of a detention pond retrofit device for detention basin outlet control provide structures designed to throttle stormwater flow and maintain the rate at which water is discharged from the system below Qcritical, the flow rate at which erosion and down cutting of the receiving stream would begin, based on channel morphology and bed material resistance. The primary goal of the device is to induce increased flow detention during low to moderate rain events, while providing similar hydraulic performance during large events to that of the detention basin performance prior to the installation of the retrofit unit. This is achieved through a T or Y design with split flow paths, in which the lower path is hydraulically restricted through the installation of structures while the upper path is unrestricted.

Claims

1. A stormwater detention basin containing an existing outlet control structure, wherein a retrofit unit is mounted to said existing outlet control structure inside of the basin, said retrofit unit comprising: an unrestricted upper flow path containing a bypass; and a lower flow path containing a retrofit restriction device, wherein the retrofit unit is mounted to the existing outlet control structure at the lowest volume water flow path of the existing outlet control structure, the retrofit restriction device is configured to increase water detention in the basin in response to low to moderate rain events and reduce the rate at which water is discharged from the stormwater detention basin below Qcritical; the unrestricted upper flow path and the lower flow path of the retrofit unit are connected to form two parallel flow paths for water flow out of the stormwater detention basin, and the bypass allows a portion of the water to bypass the lower flow path in response to an extreme rain event.

2. The detention basin of claim 1, wherein the retrofit restriction device is hydraulically restricted.

3. The detention basin of claim 2, wherein the hydraulically restricted lower flow path of the retrofit unit includes at least one of a restrictor plate, filter media, filter fabric, wire mesh, debris gates, and a structural support.

4. The detention basin of claim 1, wherein the retrofit restriction device is prefabricated with adjustable components.

5. The detention basin of claim 1, wherein the retrofit restriction device is fitted with remote sensing capacity and valves with real-time control.

6. The detention basin of claim 5, wherein the remote sensing capacity and valves with real-time control are applied to regional basins and control a watershed.

7. The detention basin of claim 3, wherein the filter media are interchangeable.

8. The detention basin of claim 3, wherein the filter media are designed for hydraulic restriction and water quality filtration.

9. The detention basin of claim 2 having a design angle between the unrestricted upper flow path and the lower flow path containing the retrofit restriction device, wherein the design angle between the unrestricted upper flow path and the lower flow path containing the retrofit restriction device is a T design or a Y design.

10. The detention basin of claim 9, wherein: the design angle between the unrestricted upper flow path and the lower flow path containing the retrofit restriction device is 45, the diameter of an outlet from the detention basin, unrestricted upper flow path, and hydraulically restricted lower path are the same, and the hydraulic restriction is filter media.

11. A method of regulating stormwater flow from a stormwater detention basin containing an outlet control structure, said method comprising: splitting water flow entering the lowest volume water flow path of the existing outlet control structure into an unrestricted upper flow path containing a bypass and a restricted lower flow path containing a retrofit restriction device, wherein the retrofit restriction device is configured to increase water detention in the basin in response to low to moderate rain events and reduce the rate at which water is discharged from the stormwater detention basin below Qcritical, the unrestricted upper flow path and the lower flow path of the retrofit unit are connected to form two parallel flow paths for water flow out of the stormwater detention basin, and the bypass allows a portion of the water to bypass the lower flow path in response to an extreme rain event.

12. The method of claim 11, wherein the retrofit restriction device is hydraulically restricted.

13. The method of claim 12, wherein the hydraulically restricted lower flow path includes one or more of a restrictor plate, filter media, filter fabric, wire mesh, debris gates, or a structural support.

14. The method of claim 11, wherein design parameters of the restricted and unrestricted flow paths are optimized through hydraulic or water quality modeling of the detention basin.

15. The method of claim 14, wherein the design parameters of the restricted and unrestricted flow paths include at least one of angles between the hydraulically restricted and unrestricted flow paths, dimensions of a restrictor plate, diameter of the retrofit restriction device, the height of the retrofit restriction device to the unrestricted upper flow path, the presence or absence of wire mesh/debris gates, the presence or absence of filter media, and hydraulic restriction and filtration properties of the retrofit restriction device.

16. The method of claim 12, wherein: the restricted lower flow path and unrestricted upper flow path form a Y shape, the diameter of an outlet from the detention basin, the restricted flow path, and the unrestricted flow path are the same, and the restriction is filter media.

17. A retrofit unit mounted to an existing outlet control structure located in a stormwater detention basin, said retrofit unit comprising: an unrestricted upper flow path containing a bypass; and a lower flow path containing a retrofit restriction device, wherein the retrofit unit is mounted to the existing outlet control structure inside the basin at the lowest volume water flow path of the existing outlet control structure, the retrofit restriction device is configured to increase water detention in the basin during low to moderate rain events and reduce the rate at which water is discharged from the stormwater detention basin below Qcritical, the bypass allows a portion of the water to bypass the lower flow path in response to an extreme rain event, and the unrestricted upper flow path and the lower flow path of the retrofit unit are connected to form two parallel flow paths for water flow out of the stormwater detention basin.

18. The method of claim 11, comprising adjusting design parameters to induce increased water detention through the hydraulically restricted path during low to moderate rain events and providing similar hydraulic performance through the hydraulically restricted path to that of the detention basin prior to the installation of the retrofit restriction device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:

(2) FIG. 1 is an illustration of a profile view of a detention basin with an unrestricted flow path and with a retrofit restriction device according to an aspect of the present invention;

(3) FIG. 2 is cross-section view and a plan view of the detention basin and the retrofit restriction device according to an aspect of the present invention; and

(4) FIG. 3 is an engineering drawing of an embodiment of the retrofit restriction device according to another aspect of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures.

(6) FIG. 1 is an illustration of a profile view of a detention basin 1 with an unrestricted flow path 10 prior to installation of the retrofit restriction device 22 according to an aspect of the present invention and a detention basin 1 with the retrofit restriction device 22. FIG. 2 is a cross section view and plan view of the retrofit restriction device 22 according to an aspect of the present invention. The primary goal of the retrofit restriction device 22 is to induce increased flow detention during low to moderate rain events (e.g. up to the 2-year event), while providing similar hydraulic performance during large events (e.g. 100-year event) to that of the detention basin 1 performance prior to the installation of the retrofit restriction device 22. This is achieved through a T design (FIGS. 1 and 2) or Y design (FIG. 3) with split flow paths, comprising a staged retrofit restriction device 22 in which the lower path 30 is hydraulically restricted (through the installation of a restrictor plate 25, wire or mesh plate 31 or media 32, or combination thereof), while flow is unrestricted through the unrestricted upper flow path 20. The dimensions of the retrofit restriction device 22, including the restrictor plate 25 length (e), the diameter of the staged outlet structure (c, also referred to as the bypass), the height of the bypass 2022 relative to the existing outlet elevation, (a), the angle between the unrestricted upper flow path 20 and the retrofit restriction device 22, (), presence or absence of wire mesh or debris gates (31), presence or absence of filter media (32) and length (b), hydraulic restriction properties (x) and filtration properties (y) of the retrofit restriction device 22 can be optimized through hydraulic and/or water quality modeling of the individual detention basin 1 being retrofit.

(7) The physical mounting of the retrofit restriction device 22 and diameter of the unit (d) can be determined by the configuration of the unrestricted flow path 10. Mounting may require stabilizing bars, bolts, or straps (not shown). Custom interfaces may be needed for mounting to outlet structures of the unrestricted flow path 10 such as cylindrical surfaces and/or those structures with slot outfalls as opposed to round pipe outfalls.

(8) FIG. 3 is an engineering drawing of an embodiment of the detention basin 1 and retrofit restriction device 22 according to another aspect of the present invention. As an example of the present invention, it is a specific embodiment of the retrofit unit for a pilot installation that exhibits an angle () of 45, height of bypass (a) of 2.09 feet, bypass diameter (c) of 24 inches, and hydraulic restriction properties (x) of the media 32 and/or restrictor plate 25 of 75%.

(9) The specific combinations of design parameters are somewhat infinite, and will depend on the specific hydraulic performance needs of the detention basin 1 being retrofit. However, one embodiment could be a product line to include prefabricated retrofit restriction devices 22 of the more commonly needed size ranges to make such a product easier to market. Instruction manuals could also be developed related to optimization and sizing procedures and modeling steps. Prefabricated units with adjustable components (e.g., restrictor plate 25 height) could be field adjusted by installing a gate valve design as opposed to a fixed plate. Retrofit restriction devices 22 with remote sensing capacity and valves with real-time control could also be developed. Interchangeable media filters and specifically designed media for both hydraulic restriction and water quality filtration are also likely extensions of this technology. This real-time monitoring and control could be applied to larger regional basins and operate a watershed much like a system or treatment train in order to optimize flood control and water quality on a network scale.

(10) The hydraulic optimization procedure will resemble the conventional design procedure in which engineers optimize the outlet control structure to achieve various flow targets; but will be expanded to include the goal of releasing as many storms as possible below the flow rate that is deemed appropriate for the erosive resistance of the receiving channel. In some jurisdictions, such as New York State, guidance may suggest or require a fluvial geomorphic assessment of the receiving channel in order to estimate that critical flow. In other jurisdictions, such as Sanitation District No. 1 of Northern Kentucky, a regional target may be established such as 40% of the pre-developed 2-year peak flow. In still other jurisdictions, professional expertise may be required to estimate the critical flow of the receiving stream in the absence of other guidance.

(11) Other optimization criteria may include desired detention times of specific storms, for example, for water quality treatment. In all cases, the optimization procedure can include relevant local design criteria, including but not limited to 1) draw down requirements for mosquito control, 2) meeting the peak flow control performance of the standard design events (e.g. 2-, 5-, 10-, 25-, 50-, and 100-year). Even in the absence of local design criteria, installations should be optimized to maintain similar hydraulic performance for the 100-year event to that of the detention basin performance prior to retrofit installation.

(12) The physical mounting of the retrofit unit and diameter of the unit (d) will be determined by the configuration of the existing outlet control structure. Mounting may require stabilizing bars, bolts, or straps. Custom interfaces may be needed for mounting to outlet structures composed of cylindrical surfaces and/or those structures with slot outfalls as opposed to round pipe outfalls.

(13) Aspects of the present invention are therefore novel because they address channel protection without impacting the flood control performance of the outlet structure, as well as water quality implications. Optimizing detention facilities to economically release runoff below a critical point, Qcritical, for small and intermediate storm events should enable stormwater managers nationwide to cost-effectively achieve multiple objectives including hydromodification, water quality, and flooding issues throughout the watershed. Additionally, the above mentioned detention pond retrofit device should improve in-stream habitat and ecosystem functionality. Each retrofit restriction device will ideally be sized and properly designed with channel protection, water quality, and flood control in mind.

(14) Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.