Storm drain baffle to decrease sediment washout

Some examples includes a flow-through stormwater sump having a bottom and defining an inlet opening, an outlet opening and a top access opening, an inlet conduit coupled to the flow-through stormwater sump at the inlet opening, an outlet conduit coupled to the flow-through stormwater sump at the outlet opening and a flow-path baffle disposed in the stormwater sump, the flow-path baffle being substantially planar and defining a plurality of openings, the flow-path baffle oriented such that a centerline of the inlet conduit intersects a major plane of the baffle at a point and a centerline of the outlet conduit intersects the major plane at a further point, the flow-path baffle disposed in the stormwater sump in a direct impingement inlet flow-path of the inlet conduit and a direct impingement outlet back-flow-path of the outlet conduit.

BACKGROUND

Storm drain systems often include a stormwater sump or well. Some sumps are designed to allow access to the storm sewer. Some sumps serve as a junction for multiple storm drains. In some instances, the stormwater sump collects sediment for occasional removal by a refuse hauler instead of allowing the sediment to travel through the entire storm system and ultimately into a lake or river. Existing stormwater sumps often cannot retain sediments under high flow conditions and undesirably permit sediment to travel out of a sump. Systems, apparatus and methods are needed to improve sediment retention.

SUMMARY

This document describes, in various examples, a system for baffling at least one stormwater flow-path so it does not excessively disturb sediment at the bottom of the sump. Some examples include a flow-through stormwater sump. A sump includes at least one inlet and at least one outlet, and has a top access opening, in some examples. An access opening is for workers to enter through, or for inserting a suction hose to pump out sediment, in some examples. In some instances, an access opening includes openings to allow water from the ground surface to drain into the sump. According to various examples, the sump is coupled with at least one inlet conduit and at least one outlet conduit, and a flow-path baffle is positioned in the sump such that water flowing into the sump, such as through an inlet conduit during a storm, flows into the baffle. In some instances, this baffle is flat and has at least one opening for water to flow through. In various examples, the baffle distributes the high flow velocity of at least one inlet jet across the baffle. The baffle provides head loss to reduce the concentration of flow energy in an inlet flow, in various examples. The position, size and shape of the baffle, and the size and shape of the openings, are selected to reduce or eliminate scour and washout, i.e. sediment undesirably leaving the sump, according to several examples.

DETAILED DESCRIPTION

This description includes examples of a flow-path baffle to interrupt fluid flow into a stormwater sump. Several examples describe a flow-path baffle that includes at least one opening and that is placeable or formed into a flow-through standard sump such as a manhole. The flow-path baffle examples described here improve sediment collection and reduce or eliminate sediment scour or washout.

Sediment transport into, out of or though a flow-through sump is, in part, dependent upon a fluid circulation pattern in the sump, during operation. For example, as water enters a sump during a rain event it plunges from at least one inlet of the sump into a bottom portion of the sump. The plunge is due to the deflection of fluid momentum as it impinges on the far wall, across from at least one inlet. According to several examples, plunging movement of the fluid can create an undesirable fluid circulation in the sump. The undesirable fluid circulation begins with a fluid entering the sump, for example through at least one inlet, and creating a downward fluid flow at a downstream end of the sump proximal a sump outlet. The fluid circulation additionally includes an upstream fluid flow at the bottom of the sump, i.e., in a direction from an outlet toward at least one inlet. Finally, the fluid circulation includes an upstream upward fluid flow from the bottom of the sump toward the sump inlet opening.

In several examples, if this circulation pattern is sufficiently strong, sediment at the bottom of the sump can be mobilized by the fluid flow and can then be moved upstream, lifted back into the inflow jet travelling through at least one inlet. In some examples, the sediment is removed from the sump, such as through an outlet of the sump. In various examples, sediment includes, but is not limited to, that which is disclosed in Unified Soil Classification System, ASTM D 2487, which is incorporated herein by reference in its entirety. In some examples, flow-path baffles described here provide an improvement over sumps with no baffles by collected materials that float, including, but not limited to, polymeric objects such as plastic bags.

The flow-path baffle examples described here reduce undesirable fluid circulation. Some examples spread the fluid flow from at least one inlet laterally, i.e. from a center of the sump towards exterior walls of the sump. At high discharge the inflow appears as at least one jet into the sump. An inflow jet, instead of entering the sump and plunging into water at a downstream end of the sump, flows into a flow-path baffle that disperses the flow and reduces the inertia of the jet. In some examples, the baffle disperses an inflow jet, dissipating energy and reducing or eliminating downward flow in the downstream portion of the sump. At least one jet of lower inertia reduces or eliminates downwelling that occurs at the far end of the sump, across from at least one inlet, and thus reduces or eliminates the upwelling and washout of sediment that has previously been deposited in the sump.

Placement of the flow-path baffle in the sump influences the effectiveness of the sump. Various examples position a bottom of the flow-path baffle above the sediment or in-use water level. Some examples that use a predetermined distance of less than 1 foot from the bottom of the flow-path baffle to the top of the sediment height will cause washout or scour below the flow-path baffle. In some instances, if the bottom of the flow-path baffle is closer to at least one inlet conduit invert than 1 foot, the entire jet may not be intercepted by the flow-path baffle. A parameter used in some examples to govern flow-path baffle design is the location of the bottom of the flow-path baffle and the available depth for sediment deposition. In some instances, the sump is periodically cleaned, such as when the sediment comes closer than 1 foot to the bottom of the flow-path baffle. In some examples, a deeper sump will require less maintenance than a shallow sump.

The orientation of the flow-path baffle with respect to the flow-path is also important. Some examples position the flow-path baffle perpendicular to the flow, such as being perpendicular to at least one flow-path vector. In some examples, the flow-path baffle is disposed vertically in the sump, i.e. the baffle is substantially planar and a major plane of the flow-path baffle is substantially vertical in the sump. In some examples, the flow-path baffle is centered in the sump, such as to ease entry into the sump and to ease installation of the flow-path baffle into the sump. In some examples, a centerline of the baffle intersects with a diameter of the sump. In some examples, a center line extending out of an inlet conduit intersects a center line of the flow-path baffle as well as a vertical center line of the sump. Additional examples include an inlet conduit that has a centerline that does not intersect with a vertical centerline of the sump.

In some examples, the flow-path baffle includes at least one opening. In various examples, the at least one opening is through the flow-path baffle, with each extending from one major surface of the flow-path baffle to a further major surface of the flow-path baffle opposite the major surface. The percentage of open area for the flow-path baffle is sized in association with a particular application. In some examples, if the percent open area is less than 40%, flow resistance will be too low, causing washout or scour below the flow-path baffle. In some examples, a proper percentage is determined using experimental models. In additional examples, if the percent open area is larger than 50% the resistance will not be large enough to dissipate a sufficient amount of energy to decrease downstream downward flow and to spread the flow. In various examples, the percentage of the flow-path baffle that is open is approximately 46%.

In various examples, the size of at least one opening is associated with the amount of trash that is captured. If the size of at least one opening is below 1 inch, debris will be collected, in some examples. These examples increase the flow resistance provided by the fluid flow-path baffle, which can diminish its effectiveness and requiring more frequent maintenance. A large size of at least one opening of 5 inches passes trash in several examples, and requires less frequent maintenance.

FIG. 1Ais a plan or top view of a storm drain, according to some examples.FIG. 1Bis a cross sectional side view taken along line A-A ofFIG. 1A, according to some examples.FIG. 1Cis a side view of the storm drain ofFIG. 1Ashowing a partial detail of the flow-path baffle, according to some examples.FIG. 1Dis a cross sectional side view taken along line B-B ofFIG. 1A, according to some examples.

Various examples include a system100that includes a flow-through stormwater sump112. In various examples, the flow-through stormwater sump112has a bottom114and defines an inlet opening116, an outlet opening118and a top access opening120. Although the pictured sump112is substantially cylindrical, other sump shapes are possible, include sumps having a regular orthogonal shape, some other quadrilateral-faced prismatoid or a curvilinear shape.

In some examples, at least one inlet conduit102is coupled to the flow-through stormwater sump112at an inlet opening116. In some instances, at least one outlet conduit104is coupled to the flow-through stormwater sump112at an outlet opening118. In various examples, at least one inlet conduit is substantially tubular proximal the flow-through stormwater sump. In various examples, at least one outlet conduit is substantially tubular proximal the flow-through stormwater sump. In various examples, one or both of an inlet conduit102and an outlet conduit104are substantially horizontal proximal the flow-through stormwater sump

In various examples, a flow-path baffle106is disposed in the stormwater sump112. In various examples, the flow-path baffle106is substantially planar, and in additional examples, the flow-path baffle106is nonplanar. In various examples, the flow-path baffle106defines at least one opening. In some examples, the flow-path baffle106defines a plurality of openings. The flow-path baffle106, in certain examples, is oriented such that a centerline, for example one parallel to A-A, of an inlet conduit102intersects a major plane B-B, B′-B′ of the baffle at a point122. In some examples, a centerline, for example one parallel to A-A, of an outlet conduit104, intersects the major plane B-B at a further point. In some examples, the point and the further point are along a long parallel to A-A. In various examples, the flow-path baffle is106disposed in the stormwater sump112in a direct impingement inlet flow-path124of an inlet conduit102. In various examples, the flow-path baffle is106disposed in the stormwater sump112in a direct impingement outlet back-flow-path of an outlet conduit104.

In some examples the flow-path baffle106is sized to function with a particular sump. Table 1 includes example dimensions of a flow-path baffle106.

In some examples, the vertical flow-path baffle is centered in the sump. In some examples, a major plane B-B, B′-B′ that bisects the flow-path baffle between the major face108and the further major face110intersects with a centerline of one or both of at least one inlet and an outlet. In some examples, the intersection is orthogonal. Other examples angle the baffle106with respect to the one or both the B-B and B′-B′ axis. In various examples, the flow-path baffle106is substantially vertical. In some of these examples, the flow-path baffle106is substantially perpendicular to one or both of an inlet flow-path124and an outlet flow-path126such as a back-flow-path. In some examples, the flow-path106baffle is centered along a total flow-path length, which is sump diameter A in some examples.

The flow-path baffle106defines at least one opening128in various examples. In various examples, the percent open area is between around 40% open and 50% open. In some examples, the flow-path baffle106is approximately 46% open. In various examples, at least one opening128is of a shape of shapes including, but not limited to, circular, rectangular, regular, irregular and curvilinear. In some examples, multiple openings are similarly sized. In some examples, multiple circular openings each have a diameter of from about 1 inch to about 3 inches. Certain examples determine the diameter of at least one opening by constructing a test model and then selecting an opening size that reduces washout or scour to a predetermined level.

According to some examples, the diameter of the at least one opening128is determined by multiplying an inlet diameter “C” by a scale factor. Examples include at least one opening128that is 1/18*C, ⅙*C, ⅓*C and ½*C. In some examples, an inlet diameter “C” is 18 inches, and as such, 1/18*C corresponds to 1 inch, ⅙*C corresponds to 3 inches, ⅓*C corresponds to five inches and ½*C corresponds to nine inches.

In various examples, the flow-path baffle geometry is dimension M by dimension I+C+K by dimension A. According to several examples, the dimension M is between 1.404 millimeters (0.055 inches) and 4.211 millimeters (0.166 inches). According to several examples, the dimension M is between 1 millimeter and 4 millimeters. In various examples, the flow-path baffle106is around 0.125 inches thick. In some examples, the flow-path baffle106has a width that approximately spans the sump112diameter if circular. In some examples in which the sump112is shaped otherwise, the flow-path baffle106has a width sized to span the full width of sump as measured perpendicular to flow through one or both an inlet conduit and an outlet conduit. In some examples, the flow-path baffle106is formed of stainless steel. Some examples include steel that is 0.125 inches thick. In some examples, the flow-path baffle106is formed of a plastic. In some examples, the flow-path baffle106is welded to the sump. In some examples, the flow-path baffle106is bolted to the sump.

In various examples, the top 130 of the flow-path baffle106is positioned such that a sediment height132does not exceed the top of the flow-path baffle106during a predetermined fluid flow event. In some examples, a top of the flow-path baffle106is vertically below a crown134of an inlet opening116.

In some examples, the system100results in a head loss increase of around 0.2 foot with flow-path baffle installed versus head loss of the system100without a flow-path baffle106. In various examples, such a head loss correlates with a top of the flow-path baffle that is around 0.5 foot above the crown134of an inlet conduit.

In various examples, the bottom of flow-path baffle is around 1 foot below an inlet conduit invert136. In some examples, the flow-path baffle106is less effective if a distance between the bottom of the flow-path baffle106and the top of the sediment is less than around 1 foot.

FIG. 2is a cross sectional side view of a storm drain including a stand, according to some examples. The sump212has at least one inlet202, and outlet204and a flow-path baffle206installed in the sump212. In various examples, the sump constrains the flow-path baffle106laterally. For example, if the baffle is shaped like a sheet, the edges of the sheer are constrained in the baffle such that the sheet extends along a diameter of the sump212. In various examples, a stand constrains the baffle vertically. In some examples, the stand includes a plurality of legs252. In additional examples, the stand is a single leg stand252. Optionally, the stand includes an adjustment turnbuckle.

FIG. 3is a plan view of a storm drain including arms to resist rotation of the baffle, according to some examples. The sump312has an inlet302, and outlet304and a flow-path baffle306installed in the sump312. In various examples, at least one arm350is coupled to a major face308of the flow-path baffle306, such as via hinge. In some examples, the at least one arm350is to rotate into the one of an inlet opening316and outlet opening318. Some examples include an arm350and a further arm352opposite the arm that is coupled to the flow-path baffle306and extends into one of an inlet opening and outlet opening and constrains the rotational orientation of the major plane308with respect to the opening. In various examples, the at least one arm350is coupled to the flow-path baffle206extend into one of an inlet opening and an outlet opening and constrain the rotational orientation of the major plane308with respect to the opening.

FIG. 4is a plan view of a storm drain including a deformable arm to resist rotation of the baffle, according to some examples. The sump412has an inlet402, and outlet404and a flow-path baffle406installed in the sump412. In various examples, at least one arm extends into one or both of an inlet opening416and an outlet opening418. In some examples, the arm450is a deformable spring. In various examples, a further arm452opposite the arm450is coupled to the flow-path baffle406and extends into the other of the inlet opening and outlet opening and constrains the rotational orientation of the major plane408with respect to the inlet416and outlet418openings.

FIG. 5is a plan view of a storm drain interference fit into a sump, according to some examples. The sump512has an inlet502, and outlet504and a flow-path baffle506installed in the sump512. In some examples, the flow-path baffle506is constrained to the sump512via a rod550. In some examples, the rod550is coupled to the flow-path baffle506such as by fasteners554. In some examples, the rod550is adjusted to interference fit into the sump512. In some examples, the rod550includes a turnbuckle552adjusted to the interference fit. In some examples, the flow-path baffle comprises a plurality of plates joined to one another with at least one hinge558. In various examples, the hinges allow the baffle to be folded up when inserted through a manhole, and then unfolded in use.

FIG. 6Ais a front view of a furled flow-path baffle, according to some examples. In various examples, at least one center spool664is used to for furling a baffle606. In various examples, a furled flow-path baffle606is compact and sized to fit through a sump entry such as a manhole entry.FIG. 6Bis a front view of a furled flow-path baffle, according to some examples. In some examples, a mounting leg662is positioned for fastening to a sump612. In some examples, a fastener such as a bolt670is used to fasten the mounting leg to the sump612. The present subject matter is not limited to examples in which the mounting leg662is mounted to a sump before unfurling of a flow-path baffle. The mounting leg662is an example of a mounting leg, and other devices are compatible with mounting the flow-path baffle606in a sump612. In some examples, a detent mechanism668applies a spring bias to maintain the flow-path baffle in a furled configuration. In some examples, the detent mechanism includes at least one detent to hold the flow-path baffle in an unfurled position once a spring bias of the detent mechanism668is overcome, such as by an operator during installation.

FIG. 7is a front view of an unfurled flow-path baffle spanned out to interference fit into a sump, according to some examples. The flow-path baffle706includes at least one opening. In some examples, flow-path baffle706is shown partially furled around at least one spool764. In some examples, the flow-path baffle is not furled at all in use. In various examples, at least one rod assembly750is interference fit a flow-path baffle assembly700into a sump. In some examples, at least one foot756forms part of the at least one rod assembly750. In some examples, at least one foot756is pliant. In additional examples, the feet756are not pliant. Some examples include spikes, and other foot types are possible.

Some examples include an adjuster752to adjust a width of the rod assembly750as illustrated. In examples, the rod assemblies are orthogonal to the spools764, but in additional examples, they are parallel. In some examples, the rod assembly is integrated with a spool eliminating vertical or height-wise supports for the flow-path baffle706.

FIG. 8is a plan view of a baffle angled with respect to an inlet flow-path vector, according to some examples. A sump802is shown from the top. A covering such as a manhole is omitted from the figure in order to show the internal configuration. A flow-path baffle804is positioned in the sump802. According to some examples, at least a portion of an inlet flow-path806travels along an inlet flow-path vector808. In some examples, an inlet flow-path vector808is aligned with the baffle804such that an inlet flow-path is into a planar surface810the baffle804. In some examples, an inlet flow-path vector808is other than parallel to the planar surface810of the baffle804. In various examples, a planar surface810of the baffle804is parallel to a height812of the sump802. The height812of the sump is shown as an arrow coming out of the figure, toward the viewer.

According to some examples, at least a portion of an outlet flow-path814travels along a flow-path vector816. In some examples, an outlet flow-path vector816is aligned with the baffle804such that an outlet flow-path is into a planar surface818the baffle804. In some examples, an outlet flow-path vector816is other than parallel to the planar surface818of the baffle804. In various examples, a planar surface818of the baffle804is parallel to a height812of the sump802.

FIG. 9is a side view of a baffle angled with respect to an inlet flow-path vector, according to some examples. A sump902is shown from the side. A covering such as a manhole920is shown. A flow-path baffle904is positioned in the sump902. According to some examples, at least a portion of an inlet flow-path906travels along an inlet flow-path vector908. In some examples, an inlet flow-path vector908is aligned with the baffle904such that an inlet flow-path is into a planar surface910the baffle904. In some examples, an inlet flow-path vector908is other than parallel to the planar surface910of the baffle904. In various examples, a planar surface910of the baffle904is parallel to a width912of the sump902. The width912is orthogonal to a height922of the sump902. The width912of the sump is shown as an arrow coming out of the figure, toward the viewer.

According to some examples, at least a portion of an outlet flow-path914travels along a flow-path vector916. In some examples, an outlet flow-path vector916is aligned with the baffle904such that an outlet flow-path is into a planar surface918the baffle904. In some examples, an outlet flow-path vector916is other than parallel to the planar surface918of the baffle904. In various examples, a planar surface918of the baffle904is parallel to a width912of the sump902. In some examples, an inlet flow-path vector908is parallel to an outlet flow-path vector916. In some examples, they are collinear.

FIG. 10shows a method of baffling flow, according to some examples. Various examples include a method of installing a flow-path baffle. At1002, the method includes determining an inlet flow-path from an inlet conduit of a stormwater sump and into the stormwater sump. At1004, the method includes determining a back-flow-path from an outlet conduit of a stormwater sump and into the stormwater sump. At1006, the method includes inserting a flow-path baffle, which includes at least one opening, into the sump with an inlet flow-path and the back-flow-path directly impinging on the flow-path baffle. At1008, the method includes constraining the flow-path baffle in the sump such that the baffle is above a top sediment height associated with the stormwater sump filled with stormwater and sediment.

Some examples include sizing a plurality of openings in the flow-path baffle to reduce energy from an inlet flow-path to a level associated with a predetermined decrease in upstream upwelling of the sump. Some examples include sizing a plurality of openings in the flow-path baffle to reduce energy from an inlet flow-path to a level associated with a predetermined decrease in washout or scour of the sump. Some methods include studying a sump and determining at least one of: baffle size, including height and width, baffle orientation including baffle angle with respect to one or both of flow-path vectors and vertical position of baffle in the sump, and the size of at least one opening of a baffle. Some methods include studying one or both of a flow-path of a sump and determining at least one of: baffle size, including height and width, baffle orientation including baffle angle with respect to one or both of flow-path vectors and vertical position of baffle in the sump, and the size of at least one opening of a baffle. Some examples include cleaning the sump when sediment rises above the sediment height. Some examples include bolting the flow-path baffle to the sump. Some examples include lowering the flow-path baffle into the sump and adjusting the height of a stand to elevate the flow-path baffle from a bottom of the baffle. Some examples include adjusting includes turning a turnbuckle. Some examples include locking the turnbuckle in place with at least one of a lock nut, a cotter pin and safety wire.