Storm drain collection box filtration system

A filtration system for storm drain collection boxes includes a helical coil frame, open at both ends, which coil frame is attached at an exit end to a vertical exit side wall of the collection box with the exit end aligned with a collection box outlet opening. The opposite, inlet end of the coil frame is suspended from a ceiling of the collection box, and a filter fabric "sock", which is also open at both ends, is positioned surrounding the coil frame. The inlet end of the coil frame is positioned at a level below the ceiling of the collection box. The filter sock normally filters out silt, sediment and solid materials from storm water run-off before the water enters the storm drainage system but the open inlet end of the coil frame and sock acts as an overflow during flooding conditions to permit storm water to bypass the filtration provided by the filter sock while still filtering out solid materials via a wide mesh screen.

BACKGROUND OF THE INVENTION 
I. Field of the Invention 
The present invention relates to a filtration system for use in storm drain 
collection boxes, and, more particularly, to such a system in which a sock 
or sleeve made of filtration fabric is supported by a helical frame with 
one open end of the frame being attached to and suspended from a ceiling 
of the collection box and an opposite open end of the frame being attached 
to an exit sidewall of the collection box in alignment with an outlet 
opening in the box. 
II. Description of the Related Art 
The handling of storm water run-off is an ongoing problem in many 
communities. Residential and commercial development results in streets, 
roadways and parking lots, houses and other buildings replacing soil, tree 
and plant life. This means that the natural moisture absorbing properties 
of the soil and plants are taken away and replaced by these moisture 
impervious structures. Thus, when rain and snowfall do occur, the run-off 
of water from these developed areas is much faster and occurs with greater 
volume and erosive tendencies than previously. 
This increased run-off in developed areas is typically handled by the 
installation of below ground storm water drainage pipe systems which 
collect the water via a series of storm drain collection boxes. The 
collection boxes are typically concrete receptacles with curb drainage 
inlets positioned at collection points where water is funneled via 
roadways, parking lots and curbs. Typically these storm water drainage 
systems output collected water directly into downstream waterways and 
lakes with no water treatment or filtration. 
Ever increasing concern for the environment and more stringent government 
requirements on the passing of silt, sediment and solid materials into 
waterways have created problems in the handling of storm water. In many 
cities and states new environmental regulations require developers to 
utilize "Best Management Practices" to decrease or eliminate the 
introduction of silt, sediments, solid materials and other pollutants into 
the waterways. This presents a major problem for developers who must use 
existing techniques for handling storm water run-off. As a final 
collection point prior to release from a development site, storm drain 
collection boxes offer an opportunity to process and improve storm water 
quality before it is discharged into the waterways. The pursuit of Best 
Management Practices requires that new filtration systems must be 
developed to adapt existing storm water collection boxes to the new 
regulations. 
A common method of attempting to deal with filtration in collection boxes 
are a class of filters that are commonly referred to as "throat filters". 
These are positioned at street level at the inlet mouth of the collection 
boxes. These throat filters can be simple and economical, e.g. sand bags, 
but present a number of problems. Throat filters are typically placed over 
or around the collection box opening and function primarily as a sediment 
and solid materials barrier. They are in clear view i.e. on the pavement 
surface and are thus often removed by property owners for aesthetic 
reasons. When functioning properly, throat filters offer poor filtration 
properties and, by design, block the entrance of storm water into the 
collection box. Thus storm water either bypasses the collection box or 
begins to pool on the adjacent pavement resulting in localized flooding. 
This causes pedestrian and vehicle hazards during a heavy rain. The hazard 
continues after the storm water drains or evaporates away when it leaves 
behind a layer of deposited sediment and solid materials (cups, cans, 
papers, etc.) around the throat filters, i.e. on the pavement. Finally, 
throat filters require considerable maintenance, particularly immediately 
after a storm and are typically not anchored, which means that they can be 
lifted by hydraulic pressure during heavy rains, thus allowing unfiltered 
water to enter the collection box under the lifted filter. 
One attempt to fit existing collection boxes with an internal filtration 
system is found in U.S. Pat. No. 5,405,539 to Thomas Schneider. In the 
Schneider system, a filter frame is inserted into the collection box in 
pieces and assembled therein. The frame includes a telescoping bed portion 
which is positioned adjacent to the front of the collection box with a 
frame back portion abutting the bed portion such that, when assembled, the 
bed and back portions resemble "a bench-type seat". A sheet of filter 
material is then laid over the bed and back portions. The bed portion is 
supported off of the floor of the collection box by a series of legs and 
is urged in position against the front of the box by pneumatic cylinders. 
Water entering the collection box, as modified by the Schneider filter 
system, flows onto the bed portion and through the sheet of filter 
material, which filters out dirt, sediment and solid materials with the 
filtered water then flowing out of the collection box outlet. Should the 
filter become clogged or when water inflow exceeds the capacity of the 
filter, unfiltered water flows over the back portion and out of the 
collection box outlet. 
A number of problems are also presented by the Schneider system. The 
capacity of the Schneider system is very limited since only the bed 
portion, and the back portion in heavy rains, is available for filtration 
area and, thus, the total square footage of filtration area is relatively 
small. This means that overflow of non-filtered water may occur in fairly 
low intensity rains. The elevation of the bed portion off of the floor of 
the collection box by the legs and the positioning of the bed portion in 
front of the box makes it visible and accessible from the box inlet mouth. 
This position and the horizontal orientation of the bed portion mean that 
the capacity of the Schneider filter system for holding trash and debris 
is fairly limited and also makes collected sediment and debris visible 
from the box mouth, presenting an unsightly condition, and, when the 
filter is clogged, can result in pooling of stagnant water on the clogged 
horizontal bed surface. Finally, the Schneider filter requires frequent 
maintenance as well, preferably after each storm event, and the occupation 
of the majority of the collection box by the Schneider filter frame means 
that it is difficult to get a person inside the box to change the filter 
material and remove solid materials. 
It is clear then, that a need exists for an effective storm water 
collection box filtration system which is usable with existing collection 
box designs. Such a filtration system should preferably be economical, 
easily and quickly installed, and should occupy a minimal volume of the 
collection box, thus making the bulk of the collection box itself 
available as a solid materials collector. The filtration system should 
preferably maintain the integrity of the engineered storm water system 
design and capacity as closely as possible and should require less 
maintenance than prior art systems but yet be simpler and easier to clean 
and maintain. Finally, the filtration system should be adaptable to 
virtually any size of collection box and storm water pipe outlet, which 
sizes vary considerably by locale and local design considerations. 
SUMMARY OF THE INVENTION 
The present invention is a filtration system for storm drain collection 
boxes and includes a helical coil frame, open at both ends, which frame is 
preferably sized with an internal diameter somewhat larger than an inner 
diameter of an outlet opening in the collection box. One end of the frame 
is attached to a vertical exit side wall of the collection box with the 
coil open outlet end positioned adjacent to and in alignment with the 
collection box outlet opening. The coil end can be attached directly to 
the wall of the collection box via concrete anchors and brackets. 
Alternatively, in the case of an irregularly shaped opening or irregular 
grouting at the outlet opening, a buffer or bridge such as a sheet of 
plywood or metal collar with a regularly shaped round opening therein 
aligned with the box outlet opening, can be attached to the box wall and 
the coil end attached to the buffer surrounding the buffer opening. 
The opposite, open end of the coil frame is attached to a first end of a 
plurality of chains or cables spaced around the periphery of the coil open 
inlet end. An opposite end of each chain is equipped with a hook or other 
suspension device which is, in turn, attached to one or more brackets 
installed directly in the ceiling of the collection box, again via 
concrete anchors or the like. The chains are of a length such that the 
upper, open inlet end of the coil frame is suspended below the collection 
box ceiling, preferably just below pavement level. A filter fabric "sock" 
or sleeve which is also open at both ends, is positioned surrounding the 
coil frame with each end of the sock being anchored to a respective end of 
the coil frame. A layer of wide mesh screen can be installed around the 
chains and above the sock inlet opening to prevent larger sized solid 
materials from entering the filter sock and coil frame. 
PRINCI OBJECTS AND ADVANTAGES OF THE INVENTION 
The principal objects and advantages of the present invention include: 
providing an improved filtration system for storm drain collection boxes; 
providing such a filtration system which occupies a relatively small 
volume of the collection box; providing such a filtration system which 
allows the collection box itself to function as a solid materials 
collector; providing such a filtration system which is relatively easy to 
install; providing such a filtration system which allows unfiltered water 
to bypass the filter during severe storm or flooding conditions; providing 
such a filtration system which preserves, to the extent possible, the 
engineered design and capacity of the storm water collection system in 
which it is installed; providing such a filtration system in which the 
entire system can be easily inserted through the manhole in the collection 
box; providing such a filtration system which can be readily adapted for 
differing sizes of collection boxes and collection box outlet pipes; 
providing such a collection system which can be easily and economically 
maintained and cleaned; and providing such a filtration system which is 
efficient and reliable, economical to manufacture and which is 
particularly well suited to its intended purpose. 
Other principal objects and advantages of this invention will become 
apparent from the following description taken in conjunction with the 
accompanying drawings wherein are set forth, by way of illustration and 
example, certain embodiments of this invention. 
The drawings constitute a part of this specification and include exemplary 
embodiments of the present invention and illustrate various objects and 
features thereof.

DETAILED DESCRIPTION OF THE INVENTION 
As required, detailed embodiments of the present invention are disclosed 
herein; however, it is to be understood that the disclosed embodiments are 
merely exemplary of the invention, which may be embodied in various forms. 
Therefore, specific structural and functional details disclosed herein are 
not to be interpreted as limiting, but merely as a basis for the claims 
and as a representative basis for teaching one skilled in the art to 
variously employ the present invention in virtually any appropriately 
detailed structure. 
Certain terminology will be used in the following description for 
convenience in reference only and will not be limiting. For example, the 
words "front", "rear", "right" and "left" will refer to directions in the 
drawings to which reference is made. 
Referring to the drawings in more detail the reference numeral 1 in FIG. 1 
generally indicates a conventional concrete storm drain collection box 
with a floor 2, a manhole 3, a front wall 4, a rear wall 5, a left side 
wall 11, a right or exit side wall 12, and a top wall 13. The manhole 3 
extends through the top wall 13 and connects with an interior collection 
space 15. The front wall 4 extends upward to within a few inches of the 
top wall 13, leaving a gap which serves as an inlet mouth 21 into the 
collection box 1. An outlet pipe 22 (FIG. 3) is attached to a circular 
outlet opening 23 in the right or exit side wall 12 of the collection box 
1 which outlet pipe 22 connects to a typical below ground storm drainage 
system (not shown). 
The collection box 1 is shown installed in an excavation immediately 
adjacent a typical pavement 25, and, preferably, at a gravity fed 
collection point. Storm water is funneled into the inlet mouth 21 via 
curbs 31 which are cut to allow water to flow off of the pavement surface 
and into the collection box 1. With conventional, i.e. nonfiltered, 
installations, water, along with sediment and solid materials would simply 
flow into the collection box 1 via the inlet mouth 21 and then flow out of 
the outlet pipe 22 and into downstream waterways and lakes via the storm 
water drainage system (not shown). 
The inventive filtration system is shown in each of FIGS. 1-7, and is 
generally indicated at 32. The system 32 includes a helical coil frame 33 
which is preferably constructed from coiled steel strap(s) and is open at 
both ends. The coil frame 33 terminates at one end in a circular exit loop 
34 and at the other end in an inlet loop 35. The coil frame 33 is both 
expandable and flexible, yet can be entirely inserted into the collection 
box 1 via the manhole 3. A plurality of L shaped brackets 41 each has one 
leg attached to the exterior of the exit loop 34. The brackets 41 are 
spaced about the periphery of the loop 34 and each bracket 41 has a second 
leg which is attachable to the exit side wall 12 of the collection box 1 
via concrete anchors 44. When properly positioned, the exit loop 34 
completely surrounds the collection box outlet opening 23 which connects 
to the inlet of the outlet pipe 22 with the exit loop 34 being positioned 
immediately adjacent to the exit wall 12. 
FIG. 5 illustrates an alternative method for attaching the exit loop 34 to 
the exit side wall 12 when the entrance to the exit opening is irregular 
or discontinuous, such as where a gap 45 is formed in the grout 
surrounding the outlet pipe. A ring 46 of plywood or other suitable 
material with an opening sized to match the outlet opening 23 is first 
attached to the exit wall 12 via concrete anchors 44 or the like. The exit 
loop 34 of the frame 33 is then attached to the regular, smooth inside 
surface of the ring 46 via the spaced brackets 41a and wood screws 47 to 
form a relatively tight seal. The buffer attachment of FIG. 5 can also be 
used to adapt the filter system 32 when the exit ring 34 is smaller in 
diameter than the collection box outlet opening 23. 
A filter sock 51 is positioned surrounding the entire length of the coil 
frame 33. The filter sock 51 has an open exit end 52 which is tightly 
secured about the exit loop 34 of the coil frame 33 via an adjustable 
encircling member such as, for example, by a cord of stranded steel fibers 
53 linked by a series of linked turn buckles 53a, as shown in FIG. 1. 
The filter sock 51 also has an open inlet end 54 which, in the preferred 
embodiment, is folded over and sewn to yield an encircling pocket 55 
within which is positioned a cord 61 which can be made of stranded steel 
fibers, for example. The entrance end 54 of the filter sock 51 is attached 
to the inlet loop 35 of the coil frame 33 via a plurality of separable 
chain links 62, each of which extend through a respective cut-out 63 in 
the filter sock encircling pocket 55, around the cord 61 and through a 
respective through bore (not shown) in the coil frame inlet loop 35. Each 
separable chain link 62 is then attached to one end of a respective chain 
64. The chains 64 are then used to suspend the coil frame 33 and attached 
filter sock 51 from a ceiling surface 65 (the bottom side of the top wall 
13) of the collection box 1. 
FIGS. 2 and 4 illustrate two of a number of possible arrangements for 
attaching the chains 64 to the collection box ceiling 65. Referring to 
FIG. 2, a single L shaped bracket 71 is attached to the ceiling 65 via a 
concrete anchor bolt 72. All four of the chains 64 are then attached to a 
common spring clip 73, which spring clip 73 is then placed in an opening 
in the L bracket 71. 
In FIG. 4, a plurality of separate L shaped brackets 74 are anchored into 
the ceiling 65 via a respective anchor bolt 72, with the brackets 74 being 
arrayed in a circumference of an approximate circle on ceiling 65. Each 
chain 64 is then attached to a respective bracket 74 via an additional 
separable chain link 62. In FIG. 4, an optional additional filter 
comprising a coarse mesh screen 75 is positioned surrounding the upper 
portion of the filter sock 51 and coil frame 33 and the chains 64 to 
occupy the space between the top of the filter sock 51 and the ceiling 65. 
The screen 75, which can be attached to the chains 64 via clips, wires, 
etc. (not shown) serves to filter out large debris such as cans, bottles, 
papers, etc. so that they are retained in the collection box 1 even during 
times of flooding. 
FIGS. 6 and 7 are partially schematic drawings illustrating the inventive 
filter system 32 in operation. Referring to FIG. 6, during typical 
precipitation events, water enters the collection box 1 via the inlet 
mouth 21 and drops to the bottom of the collection box 1. The water then 
flows through the sides of the filter sock 51 and the coil frame 33 with 
the filter sock 51 filtering out silt, sediment and solid materials. Once 
the water enters the frame 33 via the filter sock 51, the combination of 
the filter sock 51 and the coil frame 33 serve as a conduit to route most 
of the water to the collection box outlet opening 23. 
FIG. 7, by contrast, represents a situation of substantial flooding, such 
as a sustained downpour of rain or a sudden melting of accumulated snow. 
In these conditions, water may enter the collection box 1 via the inlet 
mouth 21 faster than it can filter through the sides of the filter sock 
51. The collection box 1 will thus fill with water and assorted solid 
materials. When the level of accumulated water rises above the level of 
the coil frame inlet loop 35, water will pour over the top of the frame 
inlet loop 35 and enter the interior of the coil frame 33. Again, the 
combination of the filter sock 51 and the coil frame 33 serve as a conduit 
to route most of the water to the collection box outlet opening 23. Even 
under flooding conditions, the optional coarse mesh screen 75 still 
prevents larger solid materials, such as a cup 81, stick 82, can 83, etc., 
from entering the storm drainage system. 
In a preferred embodiment of the invention, the filter sock 51 was 
constructed from a length of filtration fabric such as a geotextile 
material similar to those manufactured by several manufacturers including 
LINQ Industrial Fabrics, Inc. and Amoco Fabrics and Fibers Company. 
Variations on the invention will occur to those of skill in the art. For 
example, the coil frame 33 can be modified to incorporate integral 
brackets which can be attached directly to the collection box ceiling 65. 
The filter sock 51 has been illustrated as having a tubular construction 
but it could be implemented by using a flat sheet of filter fabric which 
is wrapped around the filter frame 33, overlapped and secured to itself. 
The filter frame 33 has been illustrated as a helical coil, but other 
shapes could be used as well, including linked square frames arranged to 
form an elongate square open frame or any other suitable shape which is 
open at or near both ends and which includes a number of other openings 
along its length which allow for the ingress of water through the covering 
filter sock 51. The filter sock 51, of course, if sized correctly, will 
assume virtually any shape of the underlying frame. Instead of the 
separable chain links 62, a myriad of other connection devices could be 
used, including, without limitation, spring clips, S hooks, etc. In order 
to seal the exit loop 34 of the coil frame 33 to an irregular wall of the 
collection box 1, instead of a plywood ring, any other suitable sealing or 
buffer material can be used, including grout, butyl rubber, etc. 
It is thus to be understood that while certain forms of the present 
invention have been illustrated and described herein, it is not to be 
limited to the specific forms or arrangement of parts described and shown.