Note: Descriptions are shown in the official language in which they were submitted.
CA 02603563 2015-09-25
PATENT
STORMWATER TREATMENT APPARATUS AND METHOD
Background of the Invention
Field of the Invention
[0002] Apparatus for treatment of stormwater runoff through volume-
control-
based detention and minimization of pollutant remobilization.
Description of the Related Art
[0003] This invention relates generally to liquid purification and
separation and,
more specifically, to an apparatus for separation of pollutants in urban
stormwater runoff
from the runoff water. This apparatus utilizes gravitational separation and
tortuosity,
resulting from a plurality of baffles both perpendicular to and oblique to the
primary water
flow direction, to trap substances less-dense and more-dense than water. This
invention is
differentiated from prior art by improved resistance to pollutant
remobilization, resulting
from an iterative experimental hydraulic design process. In addition, this
invention provides
a degree of retention through volume-control that exceeds that provided by
existing
gravitational, sub-surface, stormwater treatment systems.
[0004] Impacts of stormwater runoff on receiving environments have
been
documented extensively in engineering and scientific literature. Section 402
of the Federal
Clean Water Act (CWA) regulates stormwater discharges through the National
Pollutant
Discharge Elimination System (NPDES). Treatment of stormwater runoff using
best
management practices (BMPs) is a typical requirement of state and local
regulations, as well.
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In the 1990s, there has been growing interest in 'ultra-urban / space limited'
BMP's, such as
sand filters, water quality inlets, and, reservoir/vault type of structures.
Space constraints,
high property values, soil conditions, and the proximity of other building
foundations often
preclude the use of conventional, space-intensive stormwater BMP's such as
detention ponds.
For in-fill construction or redevelopment in built-up urban areas, where
pollutant loads from
urban runoff are usually the greatest. unconventional stormwater treatment
technologies may
be necessary.
100051 Vault-type treatment technologies have been widely used for
stormwater
treatment in urban areas; however, the effectiveness of these devices for
removal of
suspended solids and oil and grease has been only marginal. A great weakness
of these types
of devices has been that large storm events tend to flush out the system,
thereby releasing
pollutants that were previously removed.
10006] Prior art in the field of this invention of which the applicant
is aware
includes the following:
= U.S. Pat. No. 4,127,488, Bell, J.A. et al., Nov. 1978, Method and
apparatus for
separating solids from liquids.
= U.S. Pat. No. 4,136,010, Pilie, R.J. et al., Jan. 1979, Catch basin
interceptor.
= U.S. Pat. No. 4,328,101, Broden, C.V., May 1982, Device for separating
particulate
matter from a fluid.
= U.S. Pat. No. 4,363,731, Filippi, R., Dec. 1982, Device for regulating
the flow of
waste waters.
= U.S. Pat. No. 4,383,922, Beard, H.J., May 1983, Waste water clarifier.
= U.S. Pat. No. 4,983,295, Lamb, T.J. et al., Jan. 1991, Separator.
= U.S. Pat. No. 4,985,148, Monteith, J.G., Jan. 1991, Improved separator
tank
construction.
= U.S. Pat. No. 5,004,534, Buzzelli, V., Apr. 1991, Catch basin.
= U.S. Pat. No. 5,186,821, Murphy, D.T., Feb. 1993, Wastewater treatment
process
with cooperating velocity equalization, aeration, and decanting means.
= U.S. Pat. No. 5,342,144, McCarthy, E.J., Aug. 1994, Stormwater control
system.
= U.S. Pat. No. 5,520,825, Rice, W.M., May 1996, Oil-water separator.
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= U.S. Pat. No. 5,536,409, Dunkers, K.R., July 1996, Water treatment
system.
= U.S. Pat. No. 5,637,233, Earrusso, P.J., June 1997, Method and apparatus
for
separating grease from water.
= U.S. Pat. No. 5,679,258, Petersen, R.N., Oct. 1997, Mixed immiscible
liquids
collection, separation, and disposal method and system.
= U.S. Pat. No. 5,759,415, Adams, T., June 1998, Method and apparatus for
separating
floating and non-floating particulate from rainwater drainage.
= U.S. Pat. No. 5,788,848, Blanche, P. et al., Aug. 1998, Apparatus and
methods for
separating solids from flowing liquids or gases.
= U.S. Pat. No. RE30,793, Dunkers, K.R., Nov. 1981, Apparatus for water
treatment.
[0007] In
addition to the patents listed above, a number of inventions in the
general field of stormwater treatment methods and devices were discovered
during the patent
search. The inventions listed below have an element or elements similar to the
invention
disclosed herein; however, additional elements, details of elements, and/or
applications of the
inventions differ significantly from the forms and functions of the present
invention. While
the inventions listed below are intended to provide stormwater treatment, the
principle of
operation for many of these devices is filtration rather than sedimentation.
= U.S. Pat. No. 4,298,471, Dunkers, K.R., Nov. 1981, Apparatus for
equalization of
overflow water and urban runoff in receiving bodies of water.
= U.S. Pat. No. 4,377,477, Dunkers, K.R., Mar. 1983, Apparatus for
equalization of
overflow water and urban runoff in receiving bodies of water.
= U.S. Pat. No. 4,664,795, Stegall, W.A. et al., May 1987, Two-stage waste
water
treatment system for single family residences and the like.
= U.S. Pat. No. 4,747,962, Smissom, B., May 1988, Separation of components
of a
fluid mixture.
= U.S. Pat. No. 4,865,751, Smissom, B., Sept. 1989, Separation of
components of a
fluid mixture.
= U.S. Pat. No. 5,080,137, Adams, T.R., Jan. 1992, Vortex flow regulators
for storm
sewer catch basins.
= U.S. Pat. No. 5,232,587, Hegemier, T.E. et al., Aug. 1993, Stormwater
inlet filters.
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= U.S. Pat. No. 5,322,629, Stewart, W.C., June 1994, Method and apparatus
for treating
stormwater.
= U.S. Pat. No. 5,403,474, Emery, G.R., Apr. 1995, Curb inlet gravel
sediment filter.
= U.S. Pat. No. 5,437,786, Horsley, S.W. et al., Aug. 1995, Stormwater
treatment
system/apparatus.
= U.S. Pat. No. 5,480,254, Autry, J.L. et al., Jan. 1996, Storm drain box
filter and
method of use.
= U.S. Pat. No. 5,549,817, Horsley, S.W. et al., Aug. 1996, Stormwater
treatment
system/apparatus.
= U.S. Pat. No. 5,702,593, Horsley, S.W. et al., Dec. 1997, Stormwater
treatment
system/apparatus.
= U.S. Pat. No. 5,707,527, Knutson, J.H. et al., Jan. 1998, Apparatus and
method for
treating stormwater runoff.
= U.S. Pat. No. 5,730,878, Rice, T., Mar. 1998, Contaminated waste water
treatment
method and device.
= U.S. Pat. No. 5,744,048, Stetler, C.C., Apr. 1998, Clog resistant storm
drain filter.
= U.S. Pat. No. 5,770,057, Filion, G., June 1998, Overflow water screening
apparatus.
= U.S. Pat. No. 5,779,888, Bennett, P.J., July 1998, Filtering apparatus.
= U.S. Pat. No. 5,810,510, Urriola, H., Sept. 1998, Underground drainage
system.
= U.S. Pat. No. 5,840,180, Filion, G., Nov. 1998, Water flow segregating
unit with
endless screw.
= U.S. Pat. No. 5,890,838, Moore, Jr. Et al., Apr. 1999, Stormwater
dispensing system
having multiple arches.
= U.S. Pat. No. 5,972,216, Acernese, P.L. et al., Oct. 1999, Portable multi-
functional
modular water filtration unit.
= U.S. Pat. No. 5,985,157, Leckner, J.P. et al., Nov. 1999, Filter device.
[0008]
Previous vault or box type treatment devices used in wastewater or
stormwater treatment applications acted as "flow-through" systems. In these
previous
devices, incoming flows enter the device, take a given period of time based on
baffles and
size to flow through the device, and then exit the device. If flows were
coming in
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continuously, they would enter and exit the device at the same flow rate.
Previous devices
have different systems within the vault to channel, divert, or reduce flow
rates inside the vault
in order to facilitate gravity separation. All of these devices are somewhat
effective at
settling out particles down to a certain size or specific gravity, but none of
these devices are
effective at removing the very small size range of particles that make up the
majority of toxic
pollutants in storm water runoff. These particles are typically in the 100-
micron and smaller
size range, and simply will not settle out of the water if there are
horizontal flow velocities
present.
[0009] Most currently available stormwater treatment devices are
designed to
reduce the concentrations of pollutants in stormwater by screen, filter or
enhanced
gravitational separation (i.e. swirl concentrators). However, such systems
provide little or no
detention capture volume to mitigate the runoff peaks for small or large
runoff events. In
other words, these systems function as flow-through devices, resulting in the
lack of capture
volume and overall poor treatment performance. Specifically, much of the
settleable
materials trapped or deposited during more numerous smaller runoff events are
agitated and
remobilized, and wash out of these devices when larger and more intense runoff
events occur.
[0010] Properly sized and maintained wet detention ponds (retention
ponds)
provide some of the most effective stormwater treatment available. Because of
site-specific
limitations, however many desirable features of wet detention ponds are not
utilized in real
world conditions. Available surface area, possible thermal pollution,
attractive nuisance
liabilities, mosquitoes and long-term maintenance access and disposal are some
of the
difficulties that must be addressed with a surface pond.
Summary
[0011] This stormwater mitigation system solves these problems and
more, and
includes the benefits of a properly designed retention pond.
[0012] The apparatus advantageously settles particles down to a size of
100
microns and smaller out of suspension in the stormwater by utilizing a unique
volume control
design. The vault of the present invention is designed to treat a given volume
of stormwater
runoff, as opposed to a given runoff flow rate as treated in other devices. In
so doing, the
horizontal flows for the entire volume of water to be treated can be nearly
eliminated, such
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that with a reduced flow rate very small particles may drop out of suspension
and collect on
the bottom of the vault. This is accomplished through a combination of
physical space to
capture and hold water to be treated, restriction of flow out of the apparatus
at a slower flow
rate than flow into the apparatus, and vertically stacked pools of water with
reduced or
eliminated relative flow velocity.
[0013] Features that are thought to provide such consistently high
quality
treatment advantageously include; a permanent pool (i.e., a pool essentially
continuously
present after it is first filled) to eliminate the resuspension of pollutants,
extended quiescent
settling conditions to promote retention of the Total Suspended Solids ("TSS")
and floatable
materials, subsurface conditions that curtail the resuspension of deposited
sediment,
sufficient volume to retain runoff from the majority of runoff events and
capture and treat the
"first flush" of the larger events, flow control system to attenuate the
runoff flow rates from
the majority of sto1111 events and prevent flushing of the captured
pollutants, and large surface
area that promotes oxygen transfer to reduce pollutant remobilization.
[0014] An aspect of this invention is to provide an apparatus for
removal of
pollutants with densities greater than and less than water from stormwater
runoff.
[0015] Another aspect of this invention is to provide an apparatus
that retains and
immobilizes trapped pollutants, even during periods when flows are high.
[0016] Another aspect of this invention is to accumulate pollutants
that are less
and more dense than water until a time when the apparatus is cleaned out.
[0017] Another aspect of this invention is to minimize velocity in the
vicinity of
the bottom of the apparatus to minimize resuspension of deposited sediments
and associated
pollutants. The slower the velocity of water in at least part of the device,
the more effective
will be the removal of particles.
[0018] Another aspect of this invention is to provide an apparatus
that can
provide treatment of stormwater for larger tributary drainage areas by
addition of modular
sections.
[0019] Another aspect of this invention is to collect stormwater
runoff and release
it at a controlled rate over a specified period of time via an outflow
opening.
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[0019a] In accordance with an aspect of the present invention there is
provided a
method of maintaining an effluent filter of a liquid treatment apparatus, the
method
comprising:
arriving at an above-ground surface access point of a liquid treatment
apparatus that is
substantially located underground and that comprises a receptacle, an inlet,
an outlet in fluid
communication with the inlet, and a plurality of baffles configured to treat
liquid at least in
part by interrupting flow of the liquid from the inlet to the outlet;
from the above-ground surface access point, detaching an effluent filter
located inside
the receptacle of the liquid treatment apparatus from an attachment point
located inside the
receptacle;
pulling the effluent filter out of the receptacle;
performing maintenance on the effluent filter;
from the above-ground surface access point, inserting the effluent filter into
the
receptacle; and
attaching the effluent filter to the attachment point;
wherein the effluent filter is attached so as to form a single assembly with
an outlet
standpipe, detaching the effluent filter comprises detaching the single
assembly of the
effluent filter and the outlet standpipe, and attaching the effluent filter
comprises attaching
the single assembly of the effluent filter and the outlet standpipe.
[0019b] In accordance with a further aspect of the present invention there is
provided a stormwater treatment apparatus, comprising:
a receptacle adapted to receive water flowing from a surface drainage area,
the
receptacle having at least a top and a bottom;
an inlet section, the inlet section supplying water to the receptacle;
an outlet section, the outlet section passing water out of the receptacle and
comprising
an outlet standpipe and effluent filter joined together into a single
assembly;
at least one mid section, the at least one mid section comprising a fluid
communication between the inlet section and the outlet section; and
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a permanent pool, the permanent pool defined by at least the bottom wall of
the
receptacle, and extending upward from said bottom wall to at least the height
of said outlet;
the permanent pool generally below the path of fluid communication; the
permanent pool
forming a region of reduced flow velocity to trap sediments therein;
wherein the outlet standpipe and effluent filter assembly of the outlet
section further
comprises an orifice plate that defines an orifice; and
wherein the orifice is positioned in a horizontal relative to the apparatus
such that the
outlet standpipe and effluent filter assembly can be inspected and maintained
from an access
point accessible from a surface of the apparatus.
[0020] Other aspects and advantages will become apparent hereinafter.
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[0021] In one embodiment, the apparatus includes a by-pass manhole,
apparatus
chambers including a plurality of interior baffles, and a junction box. This
apparatus, along
with properly sized and installed ancillary appurtenances, will advantageously
collect and
hold floatable debris, runoff bed load particulate material, free oil and
grease, settleable
sediments and those dissolved pollutants including metals, nitrogen and
phosphorus
nutrients, and soluble organic compounds the may adsorb or adhere to the
surface of
sediments and organic debris in stormwater. This apparatus, properly installed
and utilizing a
properly sized outflow opening aperture installed within an outlet opening,
can capture and
control the release of site runoff, significantly reducing erosion and stream
degradation due to
urbanization of the riparian habitat, and helps restore pre-development runoff
rates to
urbanized areas.
[0022] In one embodiment, the apparatus is a below grade modular
concrete
stormwater control device that is designed to manage and treat stormwater
runoff by
diverting a predetermined capture volume (or water quality capture volume)
into the
apparatus. As would be understood by one of ordinary skill in the art, the
capture volume is
typically sized, for example, between the mean and the maximized runoff event
as defined in
"Urban Runoff Quality Management," Water Environment Federation (WEF) Manual
of
Practice No. 23 and American Society of Civil Engineers" (ASCE) Manual and
Report on
Engineering Practice No. 87. The capture volume is surcharged into detention
storage (the
active pool).
[0023] This capture is brought about by a volume control diversion weir
that
directs the design capture volume runoff into the apparatus with a minimum
hydraulic loss
into the apparatus. Any subsequent flow beyond that of the design capture
volume is allowed
to bypass the apparatus via a volume control diversion weir returning to the
stormwater or
runoff collection system and/or receiving waters.
[0024] During wet weather and periods of site runoff, the detention
time of the
capture volume may be optimized to promote quiescent sedimentation within the
active pool
whereby settable solid particles less than 100 microns in size with a specific
gravity greater
than water will descend and insoluble oil droplets and marginally buoyant
debris will float to
the surface.
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[0025] One
aspect of the invention is a rectangular chamber of variable length,
width and height assembled in a modular fashion. The rectangular chamber
contains a system
of overflow and underflow baffles, both perpendicular to and oblique to the
primary direction
of flow from the inlet to the chamber to the outlet from the chamber, which
are located at
opposite ends of the rectangular chamber. The baffles in the chamber serve
several purposes
including: flow momentum and energy dissipation, creation of a tortuous flow
path, retention
and immobilization of pollutants less and more dense than water, minimization
of
resuspension of sediments, and minimization of remobilization of floatable
pollutants into the
water column. The primary process for pollutant removal is gravitational
separation, which
occurs while water is detained in the chamber.
[0026] A
baffle configuration for minimization of resuspension of trapped
sediments and associated pollutants was first conceptualized by the inventors
and then
optimized by iterative experimentation involving three dimensional velocity
measurements
and dye visualization for a plurality of baffle configurations using a
geometrically and
hydraulically scaled physical model. Baffle configurations were evaluated for
both dynamic
(chamber filling and draining) and steady-state (chamber full with inflow rate
equal to
outflow rate) conditions. This
exhaustive experimentation indicates that the baffle
configuration of the invention disclosed minimizes resuspension of fine and
coarse sediments
and associated pollutants to a degree that exceeds the capabilities of prior
art. In addition, a
trapezoidal underflow baffle, the shape of which was optimized during
hydraulic
experimentation, impedes material less dense than water from entering the
outflow section
and exiting the vault. The trapezoidal configuration has the advantage of
decreasing the
downward velocity of water approaching and then moving under the baffle and
into the outlet
section and, thereby, decreases the risk of entraining floatable pollutants
trapped behind the
trapezoidal baffle into the flow passing into the outlet section. As a result,
the plurality of
interior baffles and the weir configuration advantageously are designed to
provide minimum
re-suspension of settable solids from within the permanent pool.
[0027] In one
aspect, the apparatus has an inlet that delivers water to the chamber
from a tributary surface land area, either directly or via storm sewer system
piping. Water
entering the chamber passes through a system of underflow and overflow baffles
both
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perpendicular to and oblique to the primary direction of flow from the inlet
to the outlet,
which is located at the end of the rectangular chamber opposite the inflow. As
water enters
the chamber, the water level in the chamber rises above the permanent pool
water surface
elevation, which normally is less than or equal to the elevation of the invert
of the outflow
opening. Outflow from the chamber is controlled by an opening that is sized to
provide a
specified time for the water in the chamber to drain from the elevation at
which the chamber
is full to the elevation of the permanent pool. When the rate of inflow is
greater than the rate
of outflow, the water level in the chamber will rise to the elevation at which
the chamber is
full. Once the chamber is full, any flow in excess of the outflow rate under
full conditions
will bypass the chamber via an overflow structure 294. When the rate of
outflow is greater
than the rate of inflow, the water surface elevation in the chamber will
decrease at a rate
controlled by the size of the outflow opening, and the water surface elevation
will decrease to
the elevation of the outflow opening invert, at which time outflow will cease.
For
convenience and brevity, this chamber inflow volume, as described in previous
applications,
is herein called a capture volume.
[0028] By slowly metering out storm runoff back to the external
environment, the
apparatus is of great benefit as it not only removes pollutants but also
duplicates runoff
conditions that exist prior to urban development. This prevents erosion of
stream channels,
and also prevents a discharge of rapidly flowing runoff that would simply pick
up more
sediment after treatment.
[0029] Another aspect of the invention is a stormwater treatment
apparatus,
including a receptacle adapted to receive water flowing from a surface
drainage area, the
receptacle having a bottom and a top, the receptacle having an inlet and an
outlet, the inlet
and the outlet being in fluid communication with one another; and at least one
baffle
positioned within the receptacle between the inlet and the outlet, the baffle
extending from
the bottom of the receptacle, a first portion of the baffle and the bottom of
the receptacle
forming an angle therebetween.
[0030] A stormwater treatment apparatus varies from other types of
treatment
apparatus, such as septic tanks, in that stormwater treatment apparatus must
capture a wide
variety of particles of different sizes and compositions in a pulsed
hydraulics environment, as
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opposed to the more constant flow environment of a septic tank. A stormwater
treatment
apparatus also differs from septic tanks in that the goal is to permanently
trap sediments and
other pollutants less or more dense than water, rather than to degrade organic
matter and
other biodegradable substances and in that a stormwater treatment apparatus is
much larger
than septic tanks, desirably having a volume of at least 500 cubic feet, more
desirably at least
600 cubic feet and, preferably, at least 750 cubic feet. Generally, this
apparatus size
advantageously is sized to include an active pool volume sufficient to treat
the capture
volume of the area being treated. Additionally, one vault or more than one
vault maybe used,
depending on the topography of the area being treated, and size of the
vault(s) being used.
Factors effecting the size and number of vaults used in the apparatus, besides
capture volume,
include manufacturing capability, transportability to site, modularity of
apparatus, cost of
construction and installation, site topography, ease of installation, and
apparatus footprint.
[0031] The apparatus advantageously substantially reduces bottom
velocities,
thereby greatly reducing resuspension of sediments. In particular, the angle
formed between
the first portion of the baffle and the bottom of the receptacle is desirably
between 30 and 60
degrees, at is desirably inclined in a downstream direction. Further, the
height of the baffle is
desirably at least two feet to limit the washing out of sediment. To
facilitate manufacture and
cleaning the baffle desirably includes a second portion, the second portion of
the baffle
extending from the bottom of the receptacle and forming an angle with the
bottom of the
receptacle, the angle being roughly 90 degrees.
[0032] The apparatus desirably includes an inlet baffle positioned
between the
inlet and the outlet, the inlet baffle spaced from said bottom and extending
between generally
opposing walls and an outlet baffle positioned between the inlet and the
outlet, the outlet
baffle spaced from said bottom and extending between generally opposing walls
of the
receptacle. The lower end of the outlet baffle is desirably positioned below
said outlet. The
outlet baffle advantageously may define a horizontal cross-section between a
first baffle
extending from said bottom and said outlet baffle larger than the horizontal
cross-section
between said first baffle and a vertical plane tangent to an upstream side of
said outlet baffle.
This has the effect of reducing the velocity of fluid. In this regard, it is
desirable that outlet
baffle defines a center section and at least one outer section which extends
toward said outlet
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from said center section. Advantageously, however, the spaces between the
outlet baffle and
the opposing walls are sufficiently large to permit cleaning and to facilitate
manufacture.
[0033] Yet another aspect of the invention is an apparatus for cleaning
stormwater
run-off, the apparatus including a vault having a top, a bottom, two sides, a
front and a back,
the vault comprising a first baffle extending from the bottom of the vault; a
second baffle
extending from the bottom of the vault, an inlet section having an opening and
an outlet
section having an outlet opening.
[0034] The apparatus also advantageously includes vertically stacked
columns of
water, defined by, in one embodiment, varying horizontal flow rates and
bounded by baffles
creating regions of lower horizontal flow rate. When the vault is filling or
full, there is a
column of water, called for convenience an "active pool," that is filling via
the inlet, draining
via the outlet, or both. This pool is the water being held, treated, and
released by the
invention. As the active pool is treated, sediments settle to the floor of the
vault. As a result,
when there is water in the active pool, it has a significantly higher velocity
than the water in
the permanent pool. A typical flow velocity for the active pool is two to
three feet per
second.
[0035] In order to retain sediments and to prevent them from running
out of the
vault as it empties, and in order to prevent resuspension of the sediments as
the vault refills at
a later time, the apparatus advantageously includes a permanent pool. The
permanent pool
sits immediately below the active pool and receives most or all sediments as
they drop out of
the active pool. Due to the shape, design and spacing of the baffles
surrounding and within
the permanent pool and active pool, the permanent pool is an inactive pool (a
permanent pool
that has minimal to no flow velocity.) Based on tests, the inactive permanent
pool of the
preferred embodiment of this invention maintains flow velocities typically
below 0.15 feet
per second.
[0036] One of the failings of prior "flow-through" systems was their
inability to
settle small particles from smaller storm flows without resuspending those
particles in later
large storm flows due to turbulence and currents that reach all areas of the
prior vaults. The
present apparatus, by creating an active pool that fills, holds and drains
immediately above an
inactive permanent pool, eliminates small particle re-suspension. Even in
prior systems,
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simply applying baffles to create a physical barrier to sediments moving
horizontally through
the system, without creating a permanent pool, is only effective for larger,
heavier particles:
in prior flow-through systems, smaller and finer particles, which form the
majority of toxic
pollutants, are left without an inactive permanent pool area to reside in and
are simply
suspended (or re-suspended) in the flow as it moves from compartment to
compartment and
exits.
[0037] A further advantage of vertically stacked pools including a
permanent pool
is that of maintaining a compact footprint or plan area. By both treating the
incoming volume
of water and storing sediments in the same plan area more water volume can be
treated on a
given site.
[0038] Finally, the present invention advantageously includes an
overflow
structure, in one embodiment integral to the outlet section of the vault. When
inflow of
stormwater exceeds the volume capacity of the treatment system, the overflow
structure
diverts excess stormwater flow without substantially effecting the ability of
the system to
effectively treat the full volume of stormwater already in the vault.
Brief Description of the Drawings
[0039] One embodiment of this invention, the best mode, is illustrated
in the
attached drawings, in which like numerals indicate like components throughout
the several
views. Views include:
[0040] FIG. 1 -- a plan (from a perspective above the apparatus) view
of the
apparatus that is the subject of this invention;
[0041] FIG. 2 -- a profile (side elevation) view of the apparatus;
[0042] FIG. 3 -- a cross-sectional view of the inlet section of the
apparatus
(cross-section 1-1 shown on FIG. 1 and FIG. 2);
[0043] FIG. 4 -- a cross-sectional view of the outlet section of the
apparatus
(cross-section 2-2 shown on FIG. 1 and FIG. 2);
[0044] FIG. 5 -- a detailed (enlarged) profile view of the inlet
section baffle
configuration;
[0045] FIG. 6 -- a detailed plan view of the outlet section
[0046] FIG. 7 -- a detailed view of the outflow opening configuration;
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CA 02603563 2007-09-21
[0047] FIG. 8 -- an illustration of baffle spacing for this invention
for even and
odd numbers of chambers for a multi-chambered apparatus (the number of
midsections
depicted in this view, four for the even illustration and five for the odd
illustration, are
specific examples of the generalized odd and even baffle spacing rules and are
not intended
to be restrictive);
[0048] FIG. 9 -- an illustration of a modified embodiment of the
present
invention, including an external bypass structure;
[0049] FIG. 10 A, B and C -- illustrate the apparatus, in one
embodiment,
incorporating a gravity dynamic flow control orifice; and,
[0050] FIG 11 A and B -- illustrate the apparatus, in one embodiment,
incorporating an integral overflow bypass structure.
[0051] FIG. 12 A and B -- illustrate the apparatus, in one embodiment,
incorporating a standpipe and effluent filter assembly.
[0052] FIG. 13 A and B -- illustrate embodiments of a standpipe and
effluent
filter assembly.
[0053] FIG. 14 -- an illustration of an embodiment of a multi-size pipe
connector
for connecting to multiple sizes of outlook pipes.
[0054] FIG. 15 -- a side view of components of an embodiment of a
standpipe
and effluent filter assembly.
[0055] FIG. 16 -- a detail view of an embodiment of an effluent filter
and an
orifice plate.
[0056] FIG. 17 -- an illustration of an embodiment of a standpipe and
effluent
filter assembly constructed using PVC pipes.
[0057] FIG. 18 -- a side view of an embodiment of a standpipe and
effluent filter
assembly with horizontal orifice to allow surface access to the assembly for
maintenance and
inspection.
Detailed Description of Preferred Embodiments
[0058] The drawings illustrate one embodiment of an apparatus 100 for
separation
of pollutants that are less and more dense than water from stormwater runoff.
Referring to
FIG.. 1 and FIG. 2, the apparatus 100 consists of a top 140, a bottom 160, an
inlet end 170, an
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CA 02603563 2007-09-21
outlet end 150, a left side 300, and a right side 310 (left and right are
relative to the view
from the inlet end 170 to the outlet end 150). These sides define a
rectangular chamber with
an inlet section 110, an outlet section 120, and one or more midsections 130.
[0059] The length of the most basic configuration of the apparatus 100
is
desirably at most 20 ft, more desirably at most 18 ft 6 in, and, most
preferably, 17 ft 6 in
(inside dimension); and the width of the apparatus id desirably at most 10 ft,
more desirably
at most 8 ft 6 in, and, most preferably, 7 ft 6 in (inside dimension); the
height of the apparatus
is 6 ft or 8 ft (inside dimensions). Outside dimensions and inside dimensions
may vary due
to structural strength requirements of the apparatus 100. Desirably, the
length of the
apparatus 100 increases in 4-ft, 8-ft, or 16-ft increments as additional
midsections 130 are
employed. The top 140 and bottom 160 are desirably parallel to each other and
are separated
by a distance of 6-ft or 8-ft (inside dimensions). The left side 300 and right
side 310 are
desirably parallel to each other and are separated by a distance of at most 10-
ft, more
desirably 8-ft 6-in and, preferably, 7-ft 6-in (inside dimensions). The inlet
end 170 and the
outlet end 150 are desirably parallel to each other and, for the most basic
configuration, are
desirably separated by a distance of at most 20-ft and, more desirably, 17-ft
6-in (inner
dimension). The distance between the inlet end 170 and the outlet end 150
desirably
increases by 4-ft, 8-ft, or 16-ft increments as additional midsections 130 are
employed. The
thickness of the inlet end wall 170, the outlet end wall 150, the left side
300, the right side
310, and the bottom 160 is desirably at least 3-in and, preferably, 6-in or
more. The thickness
of these walls may increase or decrease as structural needs of an installation
dictate. The
thickness of the top 140 of the apparatus 100 is at least 3-in and, desirably,
6-in or more but
may increase or decrease as structural needs of an installation dictate.
[0060] Based on experience gained after the filing of the original
application, it is
currently believed that the preferred dimensions for the apparatus are a
length of about
eighteen feet (along the longest dimension of the apparatus), a width of about
eight feet, and a
depth of about eight feet. As the apparatus is made larger, though, it
advantageously can treat
a larger capture volume of stormwater. The preferred method of increasing the
size of the
apparatus is to add modular midsections to increase the length and treatment
capacity of the
apparatus. Desirably, the apparatus can thus range from a basic configuration
of about
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CA 02603563 2007-09-21
eighteen feet in length to compound, large configurations of approximately one
hundred feet
in length including a plurality of midsections. As topographical, footprint,
transportation,
manufacturing and capture volume requirements change, these structural
dimensions may
similarly change.
[0061] The ability to increase the size and treatment capacity of the
apparatus 100
by addition of modular midsections 130 is advantageous for manufacturing since
the
apparatus 100 can be manufactured in a wide range of incremental sizes using
the same set of
forms for precasting. In addition, the modular construction is favorable for
applications
requiring a large apparatus 100 as the modular sections 110, 120, and 130 can
be transported
on one or more trucks and then assembled on-site. The incremental sizing may
be
advantageous for performance at improving water quality as well when the
apparatus 100 is
sized according to manufacturer's recommendation. For example, if a user,
based on sizing
calculations, determines that the required capacity of the apparatus 100
necessary to achieve a
desired performance is equivalent to the capacity of a midsection with a
length of 11-ft, then
the user would specify that 2 midsections 130 are needed, one 8-ft long and
the other 4-ft
long (or two 8-ft long sections), since midsections 130 are discrete
components and 1 mid-
section 130 would not provide the required capacity. As a result of this
modular, incremental
sizing, the apparatus 100 specified by the user would always have a capacity
equal to or in
excess of that required and would, therefore, provide a minimum degree of
desired treatment.
[0062] A plurality of baffles 220 and 250 are positioned between the
inlet end 170
and the outlet end 150. The primary direction of flow is defined as the
direction from the
inlet end 170 toward the outlet end 150 in the horizontal plane. In the
disclosed embodiment,
the primary direction of flow is perpendicular to the inlet end 170 and the
outlet end 150 and
parallel to the top 140, bottom 160, left 300, and right 310 sides. There are
two types of
overflow baffles employed in this invention. These baffles are referenced as
components 220
and 250. Component 220 is a hybrid baffle, and component 250 is an angled
baffle. The
results of extensive hydraulic testing indicate that the baffle configuration
illustrated, as well
as the claimed baffle configurations using various combinations of hybrid 220,
vertical, and
angled 250 baffles, is highly effective at minimizing resuspension of trapped
sediments and
associated pollutants. Velocity measurements and dye visualization experiments
indicate that
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CA 02603563 2007-09-21
the apparatus 100 disclosed herein provides a degree of reduction of
resuspension that
significantly surpasses that of existing art.
[0063] Referring to FIG. 1, FIG. 2, and FIG. 5, the hybrid baffle 220
consists of a
vertical section 240 that is perpendicular to the primary flow direction and
an angled section
230 that is oblique to the primary direction of flow, forming an angle, a,
with the horizontal
plane (angle a is depicted in FIG. 5). Preferably, the vertical baffle section
240 has a length
of 1-ft and the angled section of the baffle 230 rises from the top of the
vertical section 240 at
a 45 angle for a distance of 1-ft in the horizontal plane and a distance of 1-
ft in the vertical
plane. Preferably, the total vertical rise for a hybrid baffle 220 is 2-ft
from the chamber
bottom 160, and the horizontal projection is 1-ft 3-in. in the downstream
direction (including
thickness of the vertical section 240). An angle other than 45 may be used
for the hybrid
baffle 220 as long as the lengths of components 230 and 240 are adjusted to
provide a total
rise of 2-ft and the downstream end of component 230 does not extend beyond
the
dimensions of the top 140, bottom 160, and walls 300, 310, and 170 of the
precast unit
containing the baffle. Desirably, the angle a is between 0 and 90 , and, more
desirably,
between 30 and 60 degrees
[0064] The angled baffle 250 rises 2-ft from the bottom of the chamber
160. An
angled baffle 250 is illustrated in FIG. 1 and FIG. 2 in plan and profile
views, respectively.
For the best mode, the baffle 250 forms an angle, a, of 45 with the chamber
bottom 160. An
angle other than 45 may be used, provided that a vertical rise of 2-ft is
maintained and that
the downstream end of the angled baffle 250 does not project beyond the end of
the
associated 8-ft midsection 130. Hybrid baffles 220 and angled baffles 250 may
be
interchanged to create numerous embodiments; however, the best mode utilizes a
single
hybrid baffle 220 in the inlet section 110 and angled baffles 250 in
midsections 130, the
spacing of which is described below. Other shapes and heights of baffles, up
to the full depth
of the permanent pool have been tested and are viable alternates to the "best
design" shown
herein and are part of the design claims of this apparatus 100.
[0065] Extensive hydraulic experimentation and testing of baffle
configurations
and types was conducted to determine baffle geometry that effectively reduced
velocities in
the lower section of the apparatus 100 where sediments accumulate after
settling out of the
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CA 02603563 2007-09-21
water. As will be appreciated by one of skill in the art, the creation of this
reduced velocity
region results in a region of little or no velocity near the gravitational
bottom of the vault.
That is, this region comprises an inactive permanent pool. Initial testing
indicated that angled
baffles 250 were more effective than vertical baffles at decreasing bottom
velocities in the
apparatus' midsections 130. The inventors initially tested angled baffles 250
for the purpose
of examining the effect of the angled baffles 250 on flow passing over the
crest of the angled
baffles 250. In the process of this experimentation, the inventors discovered
that the angled
baffles 250 had a favorable effect on bottom velocities between two angled
baffles 250
separated by a distance of 16-ft or less. A hybrid baffle 220 was developed
and tested for the
purpose of achieving a reduction in bottom velocities in the midsections 130
comparable to
that found using an angled baffle 250, while at the same time decreasing the
length in the
horizontal plane consumed by the angled baffle 250 by a distance equivalent to
the product of
the height of the vertical portion of the baffle 240 and the tangent of the
angle 90 - a. This
reduction in the horizontal distance required to accommodate the hybrid baffle
220 allows the
inlet section 110 to be shortened, resulting in a reduction in the amount of
material necessary
to fabricate the inlet section 110. In addition, the vertical portion 240 of
the hybrid baffle 220
has the advantage of improved access for a hose or vacuum to clean out the
area beneath the
baffle 220. An angled baffle 250 permits access beneath the baffle 250 for
cleaning only
where the distance between the under-surface of the baffle 250 and the bottom
of the
chamber 160 (inside dimension) is greater than the diameter or height of the
intake
component of the vacuum or pumping cleaning system. For both angled 250 and
hybrid 220
baffles, the experimentation conducted indicated that both types of baffles
250 and 220,
performed very well at evenly distributing flow across the width of the
apparatus 100.
[0066] Water
is supplied to the apparatus inlet section 110 via an inlet pipe or
other conveyance 180 carrying water from the tributary drainage area to the
inlet of the
apparatus 190. The invert of the inlet aperture 190 is desirably at least 3-ft
above the
chamber bottom 160 (inside dimension). The apparatus 100 may also receive
water from the
tributary drainage area directly rather than via an up-gradient, piped storm
sewer system. An
example of this configuration would be an apparatus 100 installed to receive
water from a
manhole chamber below a curb-side drop inlet.
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CA 02603563 2007-09-21
[0067] The inlet section 110 consists of several distinct components
that are
shown in FIG. 1, FIG. 2 in plan and profile views, respectively. FIG. 3 shows
a cross-section
(1-1) of the inlet section 110, and FIG. 5 shows details of the baffle
configuration for the inlet
section 110. The dimensions of the inlet section 110 are defined by the inlet
end wall 170;
the top 140, bottom 160, left 300, and right 310 sides; and a plane
perpendicular to the
primary direction of flow located a prescribed distance from the inside
dimension of the inlet
end wall 170 in the downstream direction. This prescribed distance is defined
by the length
dimension of the precast segment containing the energy dissipation baffle 200
and the most
upstream hybrid 220 or angled 250 baffle and, most preferably is 4-ft 9-in.
The dimensions
of the inlet section 110, exclusive of baffles, desirably are equivalent to
the dimensions of the
outlet section 120, providing the advantage of having the capability to cast
inlet 110 and
outlet 120 sections using the same form. The inlet section 110 desirably
includes a manhole
135 for access to the inlet section 110 for maintenance. The cover of the
manhole 135 is
desirably vented to allow exchange of air between the inside of the apparatus
100 and the
surface atmosphere to prevent anoxic conditions from developing in the
permanent pool. The
permanent pool is defined as the volume of water and trapped pollutants in the
apparatus 100
above the bottom of the chamber 160 and below the invert of the outflow
opening 280.
[0068] A component of the inlet section 110 is a flow energy
dissipation baffle
200 that is perpendicular to the primary direction of flow. The energy
dissipation baffle 200
is parallel to the inlet end wall 170 and is positioned so that the side of
the energy dissipation
baffle 200 facing the inlet wall 170 is desirably at most 1-ft 6-in and
preferably 1-ft from the
inner side of the inlet end wall 170 in the primary direction of flow. The
energy dissipation
baffle 200 desirably is connected to the left side 300 and right side 310 from
a distance of
desirably at most 2-ft and preferably 1-ft 6-in above the chamber bottom 160
(inside
dimension) to a distance of desirably at most 1-ft, and preferably 6-in from
the chamber top
140 (inside dimension). The energy dissipation baffle 200 desirably has a
thickness of 3-in.
The purpose of the flow energy dissipation baffle 200 is to decrease the
energy of the
incoming flow. For the apparatus 100 described herein, the decrease in flow
energy
translates to a decrease in the velocity of the incoming water. The space 210
is provided
between the top of the energy dissipation baffle 200 and the top 140 of the
apparatus 100 for
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CA 02603563 2007-09-21
the purpose of allowing overflow for high flows and for the purpose of
providing access for
maintenance. Hydraulic testing indicates that the energy dissipation baffle
200 is effective at
decreasing flow energy. The inventors examined several options for spacing
between the
inlet end wall 170 and the flow energy dissipation baffle 200 and found that
the above-
described spacing provided a good balance between the effectiveness of energy
dissipation
and the space necessary to access the area between the inlet end wall 170 and
the baffle 200
for maintenance.
100691 Another element of the inlet section is the inlet overflow
baffle 220. The
inlet overflow baffle 220 is a hybrid baffle (described above). The inlet
overflow baffle 220
desirably is connected to the chamber bottom 160 and the left 300 and right
310 sides of the
chamber so that water can only pass over the top of the baffle, defined by
component 230.
The vertical portion 240 of the inlet overflow baffle 220 desirably is located
a distance of at
least 2-ft 6-in, more desirably at least 3-ft, and preferably 3-ft 6-in from
the inlet end wall 170
(inside dimensions). The thickness of the inlet overflow baffle 220 is
desirably 3-in. The
vertical rise for the inlet overflow baffle 220 is desirably at most 3-ft,
more desirably at most
2-ft 6-in, and, preferably, 2-ft, and the horizontal distance in the direction
of flow is desirably
at most 2-ft, more desirably at most 1-ft 6-in, and, preferably, 1-ft 3-in
(including the baffle
thickness of 3-in) for the best mode.
100701 A midsection 130 of the apparatus 100 is defined by a top 140, a
bottom
160, a left 300, and a right 310 side that desirably are connected at 90
angles to form an
open-ended rectangular section. FIG. 1 and FIG. 2 depict an apparatus 100 with
two, 8-ft
midsections 130. The apparatus 100 desirably has at least one midsection 130
but may have
additional midsections 130. Desirably, the midsections 130 have a length of 16-
ft, more
desirably 4-ft, and, preferably, 8 ft. Angled baffles 250 desirably are spaced
at 4-ft
increments, more desirably at 8-ft increments, and, preferably, at 16-ft
increments in
midsections 130. For midsections 130 requiring angled baffles 250 to achieve
this spacing,
an angled baffle 250 (described above) is attached to the bottom of the
midsection 130 so that
the downstream tip of the angled baffle 250 coincides with the end of the
midsection 130.
Such an angled baffle 250 in a midsection 130 is shown in FIG. 1 and FIG. 2 in
plan and
profile views, respectively. While an angled baffle 250 desirably is used in
the midsections
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CA 02603563 2007-09-21
130, vertical, hybrid, or other baffle shapes 220 may be used. Since baffle
220 and 250
spacing is preferably 16-ft and midsections 130 are added in 4-ft, 16-ft, or 8-
ft increments,
not all midsection segments 130 will need baffles 220 and 250. FIG. 8
illustrates baffle 220
and 250 spacing. As FIG. 8 indicates, baffles 220 and 250 preferably are
spaced every 16-
feet, and a baffle 220 and 250 is desirable at the end of the most downstream
midsection 130.
Therefore, for an even number of midsections 130, desirably with a length of 8-
ft (four as an
example in FIG. 8), all overflow baffles 220 and 250 are preferably spaced 16-
feet apart. For
an odd number of midsections 130, desirably with a length of 8-ft, (five as an
example in
FIG. 8), however, spacing is preferably 16-feet between all overflow baffles
220 and 250
with the exception of the spacing between the penultimate and ultimate
downstream baffles
220 and 250 at the end of the most downstream midsection 130. The number of
midsections
130 depicted in FIG. 8 are shown as examples of even and odd numbers of
midsections 130
and should not be interpreted as restrictive specifications. Each midsection
130 desirably
will have a manhole 135, allowing access through the top of the chamber 140
for
maintenance. Desirably, all manholes 135 will be vented to prevent development
of anoxic
conditions in the permanent pool and will be of sufficient size to allow the
contents of the
apparatus 100 to be pumped out as a part of regular maintenance. Manholes 135
positioned
above midsections of the apparatus 100 desirably will have a collar 145 with
approximately
the same inner diameter as the manhole that extends into the chamber 3-in
below the top 140.
The purpose of the collar 145 is to limit the surface area of the water and
associated floatable
pollutants in the chamber that could potentially be forced out of the
apparatus 100 via vents
in manhole access areas 135 when the apparatus 100 fills completely.
100711 The
midsection 130 components of the apparatus 100 are the primary
treatment and pollutant collection chambers. During the time that water is
detained in the
apparatus 100, sedimentation occurs, resulting in deposition of sediments and
associated
pollutants with densities greater than water on the bottom 160 of the
midsections 130. The
configuration of baffling 220 and 250 is such that sediments deposited on the
bottom 160 of
the midsections 130 resist resuspension during subsequent runoff events. Once
the thickness
of the sediment layer on the bottom 160 of the midsections 130 increases to a
prescribed
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CA 02603563 2007-09-21
depth, the apparatus 100 is cleaned via a pump-out or other method to remove
the permanent
pool and trapped pollutants from the apparatus 100 for disposal.
[0072] In addition to sediment removal, the midsections 130 of the
apparatus 100
collect and retain materials less dense than water. During the time that water
is detained in
the apparatus 100, materials that are less dense than water rise toward the
water surface.
Since flow from the midsections 130 passes to the outlet section 120 by
flowing beneath the
trapezoidal baffle 260, pollutants on the water surface in the midsections 130
are retained on
the upstream side of the trapezoidal baffle 260. Due to the elevation of the
invert of the
outlet opening 280, the surface of the permanent pool in the apparatus 100
desirably remains
at least 1-ft above, and, preferably, 1-ft 5-in above the highest elevation at
which water can
pass below the trapezoidal underflow baffle 260. As described below, the
trapezoidal
geometry of the underflow baffle 260 is advantageous for prevention of
entrainment of
pollutants collected on the surface of the mid-sections 130 into the flow
beneath the
trapezoidal baffle 260 entering the outlet section 120. Desirably, a mat or
mats composed of
material capable of absorbing petroleum-based hydrocarbons with densities less
than that of
water will be placed in the midsections 130 of the apparatus 100 for the
purpose of
immobilizing these pollutants. Manholes 135 will be large enough to permit
removal of the
absorbent mats.
[0073] A detailed plan view of the outlet section 120 is shown in FIG.
6, and a
detail of the outflow opening configuration 280 is shown in FIG. 7. The
dimensions of the
outlet section 120 are defined by the outlet end wall 150; the top 140, bottom
160, left 300,
and right 310 sides; and a plane perpendicular to the primary direction of
flow located 4 ft 9in
from the inside dimension of the outlet end wall 150 in the upstream
direction. The
dimensions of the outlet section 120, exclusive of baffles, are equivalent to
the dimensions of
the inlet section 110, providing the advantage of having the capability to
cast inlet 110 and
outlet 120 sections using the same form.
[0074] One component of the outlet section 120, is a trapezoidal
underflow baffle
260. In the plan view (FIG. 1 and FIG. 6), the trapezoidal underflow baffle
260 desirably
consists of a center segment parallel to the outlet end wall 150 and a pair of
outer segments.
The center segment is located desirably at least 2-ft, more desirably 3-ft,
and, preferably 4-ft
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CA 02603563 2007-09-21
from the outlet end wall 150 (inside dimension of end wall to upstream side of
trapezoidal
baffle 260). The center segment of the baffle 260 is centered with respect to
the left 300 and
right 310 sides of the chamber. Preferably, the length of the center segment
260 is 1-ft and,
as a result, the distance between the ends of the center segment of the baffle
260 and each
wall 300 and 310 is 3-ft 3-in. In the plan view, the trapezoidal baffle
extends from the ends
of the center segment to the corners defined by the intersection of the left
side wall 300 and
the outlet end wall 150 and the right side wall 310 and the outlet end wall
150. In the profile
view (FIG. 2), the trapezoidal baffle 260 is located so that the bottom of the
baffle 260
desirably is at most 1-ft 11-in and, preferably, 1-ft 6-in above the bottom of
the chamber 160
(inside dimension). The baffle 260 extends to the top of the chamber 140 and
is joined to the
top of the chamber 140 along the trapezoidal-shaped top edge of the baffle 260
displayed in
the plan view (FIG. 1 and FIG. 6). The trapezoidal underflow baffle 260
desirably is also
attached to the sides of the apparatus 100 where the left and right sides 300
and 310,
respectively, form corners with the outlet end 150 from a distance,
preferably, 1-ft 6-in above
the bottom of the chamber 160 (inside dimension) to the top of the chamber
140.
100751
Initially, the inventors tested a simple, vertical underflow baffle with a
thickness of 3-in that was positioned in a plane entirely perpendicular to the
outlet end wall
150. This incarnation of the underflow baffle was located a distance of 4-ft
from the outlet
end wall 150 (inside dimension of end wall to upstream side of underflow
baffle) and
resulted in an area of 5.625 ft2 between the downstream end of the angled
baffle 250 and the
upstream side of the underflow baffle in the plan view (see FIG. 1). The
inventors
investigated the trapezoidal underflow baffle 260 of the present invention for
the purpose of
decreasing the velocity of the flow passing through the plane between the
downstream end of
the angled baffle 250 and the upstream side of the underflow baffle 260 in the
plan view.
The area in the plan view between the downstream end of the angled baffle 250
and the
upstream side of the underflow baffle 260 is preferably 18.625 ft2. Comparison
of the areas
between the underflow baffle and the upstream angled baffle 250 for the
vertical underflow
baffle configuration and the trapezoidal underflow baffle 260 configuration
indicates that for
equivalent rates of flow passing between the upstream angled baffle 250 and
the underflow
baffle, the velocity for the vertical baffle configuration preferably would be
3.3 times greater
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CA 02603563 2007-09-21
than the velocity for the trapezoidal baffle 260 configuration. The lower
velocity attained
using the trapezoidal baffle 260 configuration of the present invention is
advantageous for
protection from entrainment of pollutants residing on the surface layer of the
midsections 130
into the flow from the midsection 130 to the outlet section 120. Desirably,
the angle between
the center segment of the baffle and the outer segments of the baffle is
between 90 and 180,
more desirably between 120' and 160 , and, preferably 130 .
100761 Another component of the outlet section 120 is outlet screening
270 which
is designed to keep trash and/or debris from clogging the outlet opening 280.
The outlet
screening 270 consists of fine screening or a fine mesh configured as a semi-
circle, arch,
rectangle, or straight screen in front of the outflow opening 280. The
screening is attached to
the outlet end wall 150 a horizontal distance in front of the outlet opening
that is
proportionate to the outlet opening size, but no less than 2 times the
diameter of the outlet
opening and to the bottom 160 and top 140 of the chamber so that all water
passing through
the outflow opening 280 will have first passed through the screening 270. The
screening 270
will be attached in a manner that will permit removal and cleaning of the
screening via an
access manhole 135 located in the top of the outlet section 120. The cover for
the manhole
135 will be vented to allow exchange of air between the inside of the
apparatus 100 and the
surface atmosphere to abate development of anoxic conditions in the permanent
pool and to
relieve air pressure as the apparatus fills and drains with water.
100771 The outflow opening 280, shown in FIG. 1, FIG. 2, and FIG. 4 is
the
device controlling the release of water from the apparatus 100. A detail of
the outflow
opening 280 components is shown in FIG. 7. The outlet desirably consists of an
8-in
diameter pipe 290, desirably extending from 3-in upstream of the outlet end
wall 150 (inside
dimension), through the outlet end wall 150. The end of the pipe 290 that is
inside the
apparatus 100 desirably is covered with an 8-in cap 282. An opening 280 that
is sized to
provide a predetermined time for the water in the chamber to drain from the
elevation at
which the apparatus 100 is full to the elevation of the permanent pool is
machined into the 8-
in cap 282. The opening 280 is manufactured so that the lowest point of the
opening is
preferably at least 1/2-in above the lowest point of the 8-in pipe 290 at the
end where the cap
282 is attached.
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CA 02603563 2007-09-21
[0078] An advantage of creating the outflow opening aperture 280 in a
cap 282
that is placed over the end of the outflow pipe 290 that is inside the outlet
chamber is that the
opening size can be changed as desired during maintenance by replacing the cap
282 with
another cap 282 with a different sized opening 280. This flexibility in
opening 280 sizing is
advantageous for providing an apparatus 100 that can provide an array of
treatment levels.
The opening aperture size 284 dictates the time that water is detained in the
apparatus 100. A
smaller opening aperture size 284 would result in detention of water for a
longer period of
time than that afforded by a larger opening size. The treatment efficiency of
an apparatus 100
will increase as the time that water is detained increases. Therefore, the
level of treatment
can be adjusted by increasing the opening size (decreasing the level of
treatment) or
decreasing the opening size (increasing the level of treatment). Another
advantage of the
outflow opening configuration 280, is that the positioning of the opening
invert, preferably, a
distance of 2-ft 11-in above the bottom 160 and downstream of all baffling
200, 220, 250,
and 260 results in release of water with the lowest sediment concentrations
through the
opening 280. An outflow opening 280 positioned lower than that in the
illustrated
embodiment would draw more water from the lower part of the outlet section
120, which
would contain more suspended sediments. An outflow opening 280 positioned
higher than
that in the illustrated embodiment would result in a greater permanent pool
volume that
would need to be pumped out during maintenance.
[0079] The apparatus, being an off line type below grade structural
stormwater
control device, in one embodiment manages the recommended capture volume ¨
sized for a
mean runoff event following the sizing criteria as outlined in, for example,
the "Urban
Runoff Quality Management", WEF Manual of Practice No. 23, and ASCE Manual and
Report on Engineering Practice No. 87 or other source known to one of ordinary
skill in the
art.
[0080] Storm events are, in one embodiment, handled by diverting that
percentage
of stormwater events from the site storm drainage collection system. The
apparatus
advantageously provides adequate time for the capture volume within the active
pool for
pollutants with specific gravities of lesser or greater than water to be
captured within the
hydraulically designed plurality of baffling within the permanent pool (i.e.,
permanent pool),
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reducing sediment resuspension, retaining floating debris and hydrocarbons,
and trapping
neutrally buoyant trash.
[0081] As known to one of ordinary skill in the art, a mean runoff
event is
typically defined, for example, as the event resulting from the "mean storm
precipitation
depth, which is the depth of all runoff-producing storms (total precipitation
of 2.5 mm or
0.10" or more) from a long-term precipitation record for a given location,
using a six-hour
separation to define each storm event. This "mean storm event capture volume"
will
typically result in the capture of roughly 70% of all runoff-producing events
in their entirety
or approximately a "two-year storm," defined as a stormwater event that occurs
on average
once every two years, or statistically has a 50% chance on average of
occurring in a given
year. Other methods for determining the capture volume can similarly be
employed,
depending on site requirements.
[0082] FIG. 9 illustrates one embodiment of the present invention,
including an
external bypass structure. In this embodiment, the apparatus 100 inflow rate
is controlled by
a site-specific designed control weir 410 housed within a bypass manhole 400
of the type
well-known to those of ordinary skill in the art. Influent enters the system
from a drainage
system, as well known to one of skill in the art, from a sewer system main or,
for example, an
inflow pipe 184. The properly sized weir 410 diverts the site runoff into the
apparatus 100
through the apparatus influent pipe 180. Bypass pipes 430 divert excess water
volume
beyond the maximum capture volume by diverting excess water volume over the
control weir
410 and through the bypass pipes 430. The bypass manhole 400 is typically
accessed by an
access manhole 135.
[0083] The energy dissipation baffle 200 is so located to diffuse and
create a
laminar flow of the turbulent high velocity stormwater runoff on entry into
the apparatus 100.
The baffle is angled to extend toward the front of the vault as it extends
downward. The
reduced energy stormwater is diverted in less turbulent lower velocity
downward against the
bottom of the apparatus 100, and under the energy dissipation baffle 200 to be
directed
upward by the hybrid baffles 220. The capture area between the energy
dissipation baffle 200
and the inlet end wall provides an area for the capture and retention of the
larger and more
buoyant trash and debris, as known in the art, in a forebay trash compartment
440. This trash
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area is accessed via a manhole 135 for subsequent collection and removal of
sequestered
debris via vacuum suction lift or other mechanical means. Advantageously, the
forward
angled energy dissipation baffle 200 permits easy access via the manhole 135
while providing
additional energy dissipation.
[0084] The
hybrid-baffles 220 (including, for example, 230, 240 and 250) are so
located with respect to the energy dissipation baffle 200 to direct the
initial and subsequent
stormwater inflow in an upward direction thereby providing a laminar flow
pattern in the
active pool 450 reducing the turbulence in the inactive permanent pool 460 to
near zero, thus
preventing resuspension of previously settable materials. The available active
pool 450
above the permanent pool 460 provides a vertically stacked water column
desirably sized to
accommodate the design capture volume.
[0085] This
ability to exploit the vertically stacked water column configuration
provided by the preferably rectangular design of the apparatus 100 enhances
the ability to
capture stormwater runoff from a site. By simply selecting the appropriate
water volume, the
apparatus 100 can significantly reduce erosion and stream degradation from
increased flows
due to urbanization and help restore pre-development runoff rates. Due to an
effective
stacked water column volume control, the apparatus has superior pollution
removal and
retention capabilities the apparatus advantageously mitigates downstream
erosion and
riparian habitat degradation through retaining and slowly metering out the
capture volume,
through the properly sized outflow opening aperture 284 installed within
outlet opening 280,
flow from each event.
[0086]
Intermediate angled baffle(s) 220 are so arranged to provide optimum
volume and sediment control spacing by maintaining the upward directional
stability of the
stormwater inflow. These
sediment control baffles 220 advantageously provide an
uninterrupted quiescent area of capture volume to sequester settable solids
and pollutants,
reducing the probability of resuspension during the introduction of stormwater
into the
apparatus. The longitudinal spacing of the angled baffle(s) 220 is preferably
optimized to
provide a minimum of one manhole 135 access for every approximately 64 square
feet of
pollutant capture area for subsequent collection and removal of sequestered
sediment and
hydrocarbon material via vacuum suction lift or mechanical means. In one
embodiment, the
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minimum size for the bypass manhole 400 is typically around 36" by 36" square
or,
alternatively, 48" inside diameter. There typically is a 30" minimum spacing
between the
bypass manhole 400, outlet box 470 and the main tank 480 of the apparatus 100
to allow
sufficient space for the installation and sealing of influent connection pipes
180 and effluent
connection pipes.
[0087] As known to one of ordinary skill in the art, the influent
connection pipes
180, effluent connection pipes 290, and bypass pipes 430 are typically
supplied and cut to
proper length depending on the topography, flow, and specific requirements of
a particular
site. Similarly, the dimensions of the apparatus will vary based on site
requirements.
[0088] The decant period or drain down time is optimized to allow for
the gravity
separation of pollutants with either a specific gravity less than or greater
than water. The
retention time of the capture volume in the stacked water column provides a
quiescent period
for enhanced settling, and is consistent with recommendations shown in
"Removal Rate vs.
Detention Time for Stormwater Pollutants as defined in "Effectiveness of
Extended
Detention Ponds" authored by Grizzard et al., 1986 or other similar period
recommendations
as commonly known to those of skill in the art.
[0089] In one embodiment, the process capture volume stormwater flow
rate is
metered by a fixed aperture orifice 280 to insure proper retention of the
capture volume and
regulate maximum discharge flow rate. In one embodiment, a flow control
orifice may be,
for example, mounted in a sealed outlet tee fitting with a standpipe top rim
at such elevation
to prevent flow "short circuiting" at maximum water levels.
[0090] The orifice 280 is desirably protected from neutrally buoyant
material by a
removal screen 270, which desirably typically includes a minimum net opening
area of about
25 to 50 times the opening of the orifice, and preferably about 35 times the
opening of the
orifice. The orifice 280, standpipe, and screen 270 are preferably constructed
of non-metallic
non-corrosive materials.
[0091] FIG. 10 provides an illustration of the apparatus, in one
embodiment,
incorporating a dynamic flow control orifice.
[0092] Unlike previous devices, the dynamic flow control orifice
system 500 is a
moveable orifice that differs from all other previous devices, as its primary
purpose is to
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control the time for outflow of stormwater from said stormwater mitigation
system, by
maintaining a constant discharge rate throughout a majority of the discharge
volume without
utilizing any outside mechanical or electrical force or power. The dynamic
flow control
orifice system 500 does so by utilizing a properly sized and located orifice
510 within a
buoyant floatation collar 520 protected from surface contamination via a solid
shield 530 and
from neutrally buoyant materials by a screen 540. A combination of gravity and
buoyancy
thus keeps the dynamic flow control orifice system at an advantageous position
in the
apparatus without outside influence, while the height of the orifice 510 is
adjustable relative
to the water surface by adjusting the vertical distance between the orifice
510 and the
flotation collar 520. The vertical adjustment of the orifice 510
advantageously maintains the
predetermined discharge flow rate through the great majority of retained
capture volume. The
action arm 550 is typically pivoted on a non-mechanical swing joint 560 to arc
through the
entire vertical range of the retained capture volume, and permits the orifice
to move with the
water level. By comparison, a fixed outlet orifice 280 as shown in FIG. 9, for
example,
typically does not move with the vault water level.
[0093] The preferred construction material for this component is
synthetic
hydrophobic material with non-corrosive fasteners, however, any suitable
material such as
plastic, fiberglass, and the like are to be considered included within the
description and
application of this apparatus. The simplified gravity dynamic flow control
orifice described
presently herein can advantageously be applied to any water treatment system,
including the
embodiments described herein and other systems known to artisans of ordinary
skill in the
art.
[0094] FIG. 11 provides a detailed plan view of the apparatus, in one
embodiment, incorporating an integral overflow bypass structure. In one
embodiment, this
stormwater treatment apparatus is an integrated system whereby the above
mentioned bypass
manhole 400, volume control weir 410 and junction box 470 are combined and
advantageously made integral within the confines of the stormwater treatment
apparatus
itself, as a typically unitary below grade modular precast concrete stormwater
control and
treatment device that is designed to manage and treat stormwater runoff by
diverting the
design water quality capture volume into the apparatus as a surcharged
detention storage
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volume defined as the active pool and controlled release of said capture
volume, with
sediments stored in the permanent pool. The preferred construction material
for all structural
components is precast concrete however, any suitable material such as plastic,
fiberglass,
steel, cast in place concrete, and the like are applicable to this apparatus.
100951 The integral bypass structure apparatus utilizes a novel,
properly sized
integral weir appurtenance 410 to divert the predetermined design capture
volume water
volume into the modular apparatus 100 from a stormwater collection system
connected by,
for example, a collection system inflow pipe 184. This capture of the capture
volume is
brought about by a integral volume control diversion weir 410 that directs the
design runoff
into the apparatus through the apparatus inflow pipe 180, with a minimum
hydraulic loss into
the apparatus 100. Any subsequent flow beyond that of the design capture
volume is allowed
to bypass the apparatus 100 via the integral volume control diversion weir 410
returning to
the stormwater or runoff collection system or receiving waters through a
collection system
outflow pipe 292. Stormwater treated by the apparatus is returned via a
discharge pipe 280 to
the combination junction box 470 / bypass manhole 400 for return to the
stormwater or
runoff collection system or receiving waters through the collection system
outflow pipe 292.
100961 In one embodiment the integral bypass system is preferably
configured
with the apparatus 100 aligned perpendicular to the collection stormdrain that
is to be
intercepted. The bypass headworks is advantageously configured to provide a
minimum
footprint, through integration of the bypass manhole 400 and junction box 470
with the entire
apparatus, while allowing for a trash and debris collection assembly to be
incorporated into
the integrated apparatus treatment train. The size of the bypass headworks
400, junction 470
and integral weir 410 elevation relative to the apparatus is typically
established by the
maximum design flow rate in the collection stormdrain that is to be
intercepted. The
headworks size typically corresponds to the minimum required for the integral
weir 410 size,
location and materials of the stormdrain main and inflow pipes 184. Depending
on the
topography of the stormwater collection system for which the apparatus 100 is
going to be
connected, the position of the stormwater collection system inflow pipe 184
and stormwater
collection system outflow pipe 292 may be advantageously altered and placed in
different
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positions on the junction box 470 / bypass manhole 400, as apparent to one of
ordinary skill
in the art, in order to minimize the footprint of the apparatus 100.
100971 As would be apparent to one of ordinary skill in the art, the
apparatus
should typically be designed to withstand an AASHTO ("American Association of
State
Highway and Transportation Officials") or ASTM ("American Society for Testing
and
Materials") C 890 H-20 traffic loading with 1.0' - 6.0' of earth cover. The
apparatus is
flexible and can be designed to withstand other anticipated loads as
designated by the site
engineer and specific site requirements.
100981 To ensure acceptable hydraulic loading rates, promotion of
settling and
retention of pollutants, and enable proper maintenance, the minimum permanent
pool liquid
depth is typically between 1' to 3', or larger for large embodiments of the
apparatus. To
provide a minimum hydraulic loading ratio in order to promote the settling of
particles from
the stormwater flow, there is typically a minimum of approximately one square
foot of
surface area for about each about 60 gallons of total liquid capacity.
100991 The apparatus typically has a minimum of three access openings
for
maintenance, preferably at the inlet section, center section, and outlet
section, but the number
of openings is foreseen to vary based on site requirements. Openings typically
have a
minimum clear opening of about 30" in diameter, and are typically located over
each
compartment of the apparatus. There typically is an additional access opening
for every
about 8' of interception length in the center section of the apparatus. In one
embodiment,
there typically is an additional access opening on the bypass manhole and
outlet box.
101001 The disclosed apparatus offers the designer and the developer a
new
degree of freedom in solving a large number of stormwater quality problem
situations. Most
existing structural stormwater treatment systems rely on a flow through rate
calculation to
size their technologies, thereby not fully considering the hydraulic or water
quality impacts
on the receiving waters. The method, as defined in "Urban Runoff Quality
Management,"
WEF Manual of Practice No. 23, and ASCE Manual and Report on Engineering
Practice No.
87, addresses these concerns. Those concerns have previously defied reasonable
economical
solutions using previously available structural stormwater mitigation systems,
but are
advantageously resolved by the present apparatus.
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101011 This method may also be modified, as known to artisans of
ordinary skill,
for example, to allow sizing of the capture volume using the mean runoff
volume as defined,
for instance, by Discroll, et al. 1989 and to accommodate an approximate
recommended six
hour drain down time.
[0102] The capture volume stacked water column provides the most
efficient use
of available system footprint. Owing to this feature, the apparatus typically
requires a
minimum of about three feet, and preferably about five feet, of vertical
temporary water
storage capacity, as apparent to artisans of ordinary skill. This temporary
stacked water
column is accomplished in the standard apparatus arrangements by use of a
bypass weir sized
to provide a minimum of backwater while insuring the full capture volume
potential of the
selected vault. Alternate system configurations accomplish the stacked water
column
configuration by providing the necessary vertical separation within the
stormdrain piping
system itself or by using a pumped system. These systems can use, for example,
an external
bypass, an internal bypass, a surface bypass, pumped discharge, and/or a
bypass with a fall
system.
[0103] As is typically known to those of skill in the art, the external
apparatus
"bypass with weir" configuration is advantageously with the vault aligned
parallel to and
offset approximately three feet clear from the collection stormdrain that is
to be intercepted.
The bypass manhole is, in one embodiment, located approximately eight feet up
gradient
from the apparatus influent. The size of the bypass manhole and weir elevation
relative to the
apparatus is typically established by the maximum design flow rate in the
collection
stormdrain that is to be intercepted.
[0104] For example, in one embodiment, as familiar to one of skill in
the art, the
influent pipe typically has a minimum of about 1% slope to the apparatus, and
is preferably
constructed of SDR-35 PVC. The influent pipe typically exits the bypass
manhole at about
45 degrees to the stormdrain flowline with, in one embodiment, a 1/8-turn
elbow located near
the apparatus. The effluent pipe is typically about 8" SDR 35 PVC and has a
slope at about
1% from the apparatus to the junction box, sized equivalent to the bypass
manhole. The
orifice operating head is typically calculated from the vault soffit to the
springline of the
effluent pipe. Due to the fact that the apparatus operates with a surcharge
water column, all
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pipe sizes and angles are based on smooth wall SDR 35 PVC pipe in order to
advantageously
provide a flexible watertight connections a all penetrations. However, other
constructions are
also useable based on specific site conditions and requirements, as known to
artisans of
ordinary skill in the art.
[0105] A junction box is, in one embodiment and as familiar to one of
skill in the
art, approximately parallel, approximately 3 feet clear from the collection
stormdrain, and
approximately 8 feet down gradient from the apparatus effluent. The size of
the junction box
is established by the design flow rate in the collection stormdrain, maximum
pipe size
penetrations and relative piping angles, and is similar to those typically
used for the "bypass
manhole."
[0106] The "bypass with fall" arrangement is similar to the standard
configuration
with regard to the bypass manhole, junction box and influent / effluent pipe
sizes. However,
the bypass manhole does not require a weir in this arrangement. The orifice
operating head is
calculated from the vault soffit to the springline of the effluent pipe.
[0107] The "pumped discharge" arrangement is also similar to the
standard
configuration with the bypass manhole, by-pass pipe elevation and junction
box, except that
the effluent is discharged through a duplex pump system uniquely designed to
be contained
within the apparatus or junction box.
[0108] The pump positive operating head is calculated from the vault
soffit. The
pump discharge rate is calculated based on the outflow rate form the
apparatus.
[0109] The "surface by-pass" is unique in that because by definition
the flowline
of the storm drainage is on surface above the apparatus. The orifice operating
head is
calculated from the surface hydraulic grade line to the springline of the
effluent pipe. While
this arrangement does not require a dedicated bypass manhole or junction box
it does require
a drop inlet or catch basin at similar locations to the turning manholes as
shown on the
"overflow with weir" arrangement.
[0110] The preferred "standard internal bypass" configuration, as shown
in FIG
10, is with the vault aligned perpendicular to the collection stormdrain that
is to be
intercepted. The bypass headworks is so configured to provide a minimum
footprint while
allowing for a trash and debris collection assembly to be incorporated into
the apparatus
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=
treatment train. The size of the bypass headworks and weir elevation relative
to the apparatus
shall be established by the maximum design flow rate in the collection
stormdrain that is to
be intercepted. The headworks size corresponds to the minimum required for the
size,
location and materials of the stormdrain main and influent pipes. The orifice
operating head
is calculated from the vault soffit to the springline of the effluent pipe .
Standpipe and Effluent Filter Assembly
[0111] The paragraphs that follow describe standpipe and
effluent filter
components that can be used with any of the embodiments described or
illustrated herein. To
the extent that the foregoing embodiments require modifications to work with
the standpipe
and effluent filter components described hereafter, a skilled artisan will
appreciate, in light of
this disclosure, how to make such modifications.
[0112] FIG. 12 A illustrates an embodiment of a stormwater
treatment apparatus
that incorporates a standpipe and effluent filter assembly. A skilled artisan
will appreciate, in
light of the above disclosure, the general flow path of liquid through the
embodiments
depicted in FIG. 12 A through 18. For ease of understanding, such flow path is
described
generally with respect to the embodiment of FIG. 12 A. In general, liquid
enters the
apparatus at an inlet. Liquid enters a receptacle and flows towards an outlet.
The liquid's
flow is interrupted by a plurality of baffles collectively configured to
remove sediment,
debris, or other contaminants from the active flow of the liquid. The liquid
then enters an
outlet section that includes, for example, the effluent filter 1220 and the
solid standpipe
portion 1225. In the embodiment of FIGs. 12 A and 12 B, the outlet portion
includes a pipe
1240 through which liquid flows before exiting the receptacle at an outlet
1215.
[0113] In one embodiment, a standpipe and effluent filter
assembly comprises a
base 1202, an effluent filter 1220, and a solid standpipe portion 1225.
Preferably, the effluent
filter 1220 and the solid standpipe portion 1225 are joined such that they
form a single
standpipe 1230. In such an embodiment, the effluent filter 1220 preferably has
the same
general shape (e.g. cylindrical, cubic, or the like) perimeter dimensions as
the solid standpipe
portion 1225. Thus, for example, in one embodiment, if the solid standpipe
portion 1225 is a
cylinder with a radius of six inches, the effluent filter 1220 is also formed
into a cylinder with
a radius of roughly six inches. Preferably, the effluent filter 1220 is joined
to the solid
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standpipe portion 1225 with a seal that is sufficiently tight to prevent
liquid from entering the
solid standpipe portion 1225 without first passing through the effluent filter
1220. In this
way, the effluent filter 1220 advantageously prevents debris and large
particulates from
entering the solid standpipe portion 1225 and being discharged from the
apparatus. In a
preferred embodiment, the seal between the effluent filter 1220 and the solid
standpipe
portion 1225 comprises one or more 0-rings. In one embodiment, the effluent
filter 1220
may be detached from and re-attached to the solid standpipe portion 1225 such
that a person
can easily clean or otherwise maintain the effluent filter 1220. The preferred
shape of the
effluent filter 1220 and the solid standpipe portion 1225 is cylindrical, but
other shapes may
be used. Desirably, the shape allows liquid to adequately flow through the
solid standpipe
portion 1225 and a sufficiently tight seal exists between the effluent filter
1220 and the solid
standpipe portion 1225. In one embodiment, the effluent filter 1220 comprises
fine screening
or a fine mesh.
101141 In one embodiment, the solid standpipe portion 1225 is connected
to the
base 1202 by a seal sufficiently tight to prevent liquid from flowing through
the base 1202
without flowing through the solid standpipe portion 1225. In one embodiment,
the solid
standpipe portion 1225 is connected to the base 1202 at an 0-ring seal.
Preferably, the base
1202 is connected to an outlet pipe 1210. Preferably, the outlet pipe 1210 is
connected to and
conducts liquid to the outlet 1215. Accordingly, in one embodiment, liquid is
filtered of
debris and large particulates as it flows through the effluent filter 1220,
the filtered liquid
then flows through the solid standpipe portion 1225, then through the base
1202 into the
outlet pipe 1210, and then is discharged from the apparatus through the outlet
1215 (FIG.
12A).
101151 In one embodiment, the base 1202 is connected to the outlet pipe
1210
using a pipe connector 1205 that is configured to mate tightly with the outlet
pipe 1210.
Preferably, the outer radius of the pipe connector 1205 is roughly equivalent
to the inner
radius of the outlet pipe 1210 in order to achieve a tight fit and to prevent
leakage at the
seam. In a preferred embodiment, the pipe connector 1205 is a multi-size pipe
connector that
can be adapted to fit with multiple pipe sizes. For example, in one embodiment
the pipe
connector 1205 has a multi-size adapter configured to mate with any one of a 4
inch pipe, a 6
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inch pipe, an 8 inch pipe, a 10 inch pipe, or a 12 inch pipe. Alternatively,
the multi-size
adapter can be configured to mate with any specific selection of any number of
pipe sizes. In
practice, when a particular pipe diameter is chosen, the lower radius portions
of the adapter
may be cut from the adapter to allow maximum flow from the pipe connector 1205
into the
outlet pipe 1210. For example, when using the afore-mentioned 4 inch, 6 inch,
8 inch, 10
inch, and 12 inch adapter, the 4 inch and 6 inch portions may be cut from the
adapter when an
8 inch outlet pipe has been chosen.
[0116] FIG. 12 B illustrates another embodiment of a stormwater
treatment
apparatus that incorporates a standpipe and effluent filter assembly. This
embodiment is
essentially the same as the embodiment of FIG 12 A, except that the effluent
filter 1220
extends over and covers the solid standpipe portion 1225. Accordingly, the
radius of the
effluent filter 1220 is larger than the radius of the solid standpipe portion
1225. Preferably, a
spacer (not shown) is fit tightly around the perimeter of the solid standpipe
portion 1225 and
the effluent filter 1220 fits tightly around the perimeter of the spacer in
order to prevent
liquid from flowing into the solid standpipe portion 1225 without first
flowing through the
effluent filter 1220.
[0117] FIG. 13 A illustrates an embodiment of a standpipe and effluent
filter
assembly. In this embodiment, the effluent filter 1220 is joined to the solid
standpipe portion
1225 at a seam 1302. Preferably, the seam 1302 is sufficiently tight that
liquid may not flow
through the solid standpipe portion 1225 without first flowing through the
effluent filter
1220. Preferably, the effluent filter 1220 and solid standpipe portion 1225
are cylindrical and
have generally the same radius. Other shapes besides cylindrical may be used.
Desirably, the
shape allows liquid to flow through the solid standpipe portion 1225 and the
effluent filter
1220 and the seam 1302 is sufficiently tight that liquid may not flow through
the solid
standpipe portion 1225 without first flowing through the effluent filter 1220.
[0118] As set forth above with respect to FIGs. 12 A and 12 B, in one
embodiment the solid standpipe portion 1225 is joined to the base 1202. In one
embodiment,
the solid standpipe portion 1225 is joined to the base 1202 by a seat 1315
that establishes a
tight seal between the solid standpipe portion 1225 and the base 1202. The
tight seal
prevents liquid from flowing into the base 1202 without first flowing through
the solid
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standpipe portion 1225. In one embodiment, the tight seal is established using
one or more
0-rings. In one embodiment, when the solid standpipe portion 1225 is seated in
the seat
1315 of the base 1202, an orifice plate 1305 divides the opening of the solid
standpipe
portion 1225 from the opening of the base 1202. The orifice plate 1305 is
desirably toroidal
shaped, with an outside radius that desirably generally matches the inner
radius of the seat
1315 and an inner radius that defines an orifice 1310. In general, the radius
of the outlet pipe
1210 is chosen to be twice the radius of the orifice 1310, though this two to
one ratio is not
required.
[0119] Preferably, the orifice plate 1305 is attached to either the
base 1202 or the
solid standpipe portion 1225 in order to facilitate seating of the solid
standpipe portion 1225
in the seat 1315 of the base 1202. In one embodiment, the solid standpipe
portion 1225 may
be unseated from the seat 1315 by a person pulling on the upper end of the
effluent filter
1220. Preferably, the solid standpipe portion 1225 may be seated in the seat
1315 by a person
pushing the upper end of the effluent filter 1220 toward the seat 1315. In a
preferred
embodiment, the upper end of the effluent filter 1220 is surface-accessible
such that a person
may easily seat or unseat the solid standpipe portion 1225 from ground level
such as manhole
1228, which may be at the ground level of a parking lot. This surface-
accessibility is of
particular usefulness and importance because the stormwater treatment
apparatus is designed
to be buried in the ground, thus making it difficult, in ordinary use, to
access any component
that cannot be accessed from the surface.
[0120] In the embodiment of FIG. 13 A, the height of the solid
standpipe portion
1225 controls the liquid level. In this embodiment, liquid overflow may occur
if the effluent
filter 1220 becomes completely blocked. However, the embodiments set forth
herein
advantageously provide a surface access point such that a person can more
easily access and
clean the effluent filter 1220.
[0121] FIG. 13 B illustrates another embodiment of a standpipe and
effluent filter
assembly. In this embodiment, the effluent filter 1220 extends over and covers
the solid
standpipe portion 1225 rather than being joined at a seam. Beyond that change,
the
embodiment of FIG. 13 B shares the components and functions of the embodiment
of FIG. 13
A. For example, as in the standpipe and effluent filter assembly of FIG. 13 A,
the standpipe
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4
and effluent filter assembly of FIG. 13 B is surface-accessible and can easily
be joined to the
base 1202 at a seat 1315. In this embodiment, the seat 1315 has the additional
function of
serving as a seal between the solid standpipe portion 1225 and the effluent
filter 1220, thus
preventing liquid from entering the base 1202 without first flowing through
the solid
standpipe portion 1225. Alternatively or additionally, a spacer surrounding
the perimeter of
the solid standpipe portion 1225 may perform this sealing function. As in the
embodiment of
FIG. 13 A, in the embodiment of FIG. 13 B the height of the solid standpipe
portion 1225
desirably determines the liquid level.
[0122] As illustrated, the base 1302 may comprise a multi-size
pipe connector
1205, the structure and function of which has been set forth above. FIG. 13 B
illustrates that
the multi-size pipe connector 1205 of this or any other embodiment may have a
concentric
adapter, an eccentric adapter, or any other adapter known to a skilled artisan
in light of this
disclosure.
[0123] FIG. 14 is a detail view of an embodiment of a base. In
one embodiment,
the base 1202 comprises a seat 1315 and a multi-size pipe adapter 1205.
Preferably, the seat
1315 comprises one or more 0-rings for creating a tight seal between the seat
1315 and the
solid standpipe portion 1225. As illustrated, the multi-size pipe adapter 1205
may be adapted
to mate with pipes of various sizes, including, for example, a 4 inch pipe, a
6 inch pipe, an 8
inch pipe, a 10 inch pipe, and a 12 inch pipe. A skilled artisan will
appreciate, in light of this
disclosure, that the multi-size pipe adapter 1315 may alternatively or
additionally be adapted
to mate with pipes of other sizes.
[0124] FIG. 15 is an exploded view of a standpipe and effluent
filter assembly in
accordance with one embodiment. In the illustrated embodiment, the effluent
filter 1220 is
configured to extend over and cover the solid standpipe portion 1225 when in
use. The
effluent filter 1220 has a radius that is larger than the radius of the solid
standpipe portion
1225. An orifice plate 1305 is configured to define a boundary between an
opening of the
solid standpipe portion 1225 and an opening of the base 1202. The orifice
plate 1305 may be
attached to either the base 1202 or the solid standpipe portion 1225 to
facilitate easy seating
and unseating of the solid standpipe portion 1225. The seat 1315 preferably
provides a seal
that prevents liquid from entering the base 1202 without first flowing through
the solid
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standpipe portion 1225. Similarly, a seal preferably prevents liquid from
entering the solid
standpipe portion 1225 without first flowing through the effluent filter 1220.
[0125] FIG. 16 illustrates a detail view of an embodiment of the
effluent filter and
the orifice plate. Cross-section 1605 shows that the effluent filter 1220 may
be cylindrical in
one embodiment. The orifice plate 1305 is configured to have a radius that
essentially
matches the radius of the effluent filter 1220. The orifice plate is toroidal-
shaped, having an
inner radius and an outer radius, thus defining an orifice 1310.
[0126] FIG. 17 is an illustration of an embodiment of a standpipe and
effluent
filter assembly constructed using PVC pipes. In one embodiment, the solid
standpipe portion
1225 comprises a PVC pipe having a radius smaller than the radius of the
effluent filter 1220.
In this embodiment, a PVC reducer bushing 1705 and a screen mounting plate
1710
cooperate to attach the solid standpipe portion 1225 such that it is
positioned generally in the
center of the effluent filter 1220. The PVC reducer bushing 1705 also acts as
a seal that
prevents liquid from entering the solid standpipe portion 1225 without first
flowing through
the effluent filter 1220. The PVC reducer bushing 1705 and the orifice plate
1305 are
attached to the base 1202, formed in this embodiment from a PVC TEE. As will
be
appreciated by a skilled artisan in light of this disclosure, the PVC TEE may
also be attached
to a multi-size pipe connector, as illustrated in several embodiments set
forth above. The
embodiment of FIG. 17 may be implemented using a standard 90 degree PVC elbow.
[0127] As has been illustrated with respect to several embodiments, the
effluent
filter 1220 may have a radius larger than the solid standpipe portion 1225 and
may extend
over and cover such solid standpipe portion 1225. Positioning the effluent
filter 1220 to the
outside of the solid standpipe portion 1225 and giving it a larger radius, in
this fashion,
advantageously increases the ratio of effluent filter surface area to orifice
size. Increasing
this ratio reduces the incidence of the effluent filter 1220 becoming clogged
and thus
increases the time between cleanings of the effluent filter 1220.
[0128] Embodiments of the apparatus set forth herein allow the orifice
1310 to be
oriented horizontally rather than vertically. With the orifice 1310 in a
horizontal orientation,
the standpipe and effluent filter assembly 1230 can advantageously be
maintained and
inspected from a surface access point. FIG. 18 is a side view of an embodiment
of a
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stormwater treatment apparatus that illustrates this advantage. As shown, the
orifice 1310 is
oriented horizontally. The horizontal orientation is achieved, in one
embodiment, by
positioning the orifice plate 1305 within a T-shaped pipe, such as, for
example a PVC TEE.
In this configuration, the standpipe may act as an overflow pipe if the
orifice 1310 becomes
plugged. With the orifice 1310 in the horizontal position, the standpipe and
effluent filter
assembly 1230 is positioned such that its upper opening is just below a
surface access point
1810 on the stormwater treatment apparatus. Providing a surface access point
1810
advantageously facilitates inspection and maintenance of the standpipe. Absent
such a
surface access point 1810, inspection and maintenance would be difficult
because when the
stormwater treatment apparatus is in use, the side walls 1805 and bottom wall
1815 are
generally buried in the ground.
[0129] Providing a surface access point 1810 is advantageous both in
embodiments in which the standpipe and the effluent filter are separate and in
embodiments
in which the standpipe and effluent filter are a single assembly. For example,
in some
embodiments the effluent filter 1220 is located under or near a the surface
access point 1820
such that if the effluent filter 1220 must be cleaned, a person can unseat the
standpipe 1225
and effluent filter 1220 and pull them out the top of the stormwater treatment
apparatus at the
surface access point 1810. After the maintenance has been performed, the
person can insert
the standpipe 1225 and effluent filter 1220 into the stormwater treatment
apparatus at the
surface access point 1810 and can re-seat the standpipe 1225 and effluent
filter 1220.
Method of Maintaining an Effluent Filter
[0130] As will be appreciated by a skilled artisan in light of this
disclosure, the
orientation of the orifice 1310, the effluent filter 1220, and the solid
standpipe portion 1225
facilitate inspection and maintenance of these components from a surface
access point on the
surface of the stormwater treatment apparatus. For example, in one embodiment
of a method
of maintaining an effluent filter, the following steps are performed: a person
arrives at an
above-ground surface access point of the liquid treatment apparatus; from the
above-ground
surface access point, the effluent filter is detached from an attachment point
(such as, for
example, the solid standpipe portion 1225) located inside the receptacle of
the apparatus; the
effluent filter is pulled out of the receptacle; maintenance is performed on
the effluent filter;
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from the above-ground surface access point, the effluent filter is inserted
into the receptacle;
and the effluent filter is attached to the attachment point.
[0131] The foregoing method allows for the performance of maintenance
on the
effluent filter. An example of maintenance that can be performed is cleaning
the effluent
filter. In addition to maintenance, one could also inspect the effluent filter
from the above-
ground surface access point.
[0132] In one embodiment, the step of attaching the effluent filter to
the
attachment point is accomplished by joining the effluent filter to the
attachment point by a
seal comprising one or more 0-rings.
[0133] In the foregoing method, the effluent filter is detached from
and attached
to an attachment point. In one embodiment, the attachment point is a component
of the outlet
standpipe, such that the effluent filter is detached from and attached to the
outlet standpipe.
[0134] As set forth above, in some embodiments the effluent filter is
attached to
the outlet standpipe such that the outlet standpipe and the effluent filter
form a single
assembly. When practicing the above method on such embodiments, the steps of
detaching
the effluent filter and attaching the effluent filter may include detaching
and attaching the
single assembly of the effluent filter together with the outlet standpipe.
[0135] The description given herein describes particular embodiments of
the
apparatus and methods described herein, and other embodiments are foreseen and
included
herein and can be adapted by artisans of ordinary skill in the art, such that
the present
invention should be defined only by the following claims and equivalents
thereof.
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