Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~L 8'r0RM IrAq~ER D~T-a"" 8YJ3TEM
This invention relates to illlyI ~v~ -nts in urban
3 drainage systems. In particular, it relates to; r-xvcd
~. handling of storm water runoff (in conjunction with storm
sewer systems).
6 The increasing urbanization of modern societies, and
7 the increased concern for water quality as an environmental
8 issue, have led to increasing concerns for the manner in which
g storm water runoff is controlled.
lo Historically, rain water fell on sand, gravel, or
11 soil covered with vegetation would seep into the ground or run
off in a controlled manner except in rare circumstances where
13 exposed soil or exceptionally heavy storms have caused
1~ flooding or erosion. Ilowever, in cities, the large areas
covered by b-]i l~inq~, parking lots, roadways, and other
16 barriers to natural drainage have resulted in drainage
17 problems which are exaggerated and concentrated. 'rO avoid
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exce6sive runoff or flooding, urban communities are designed
with a network of catch basins and underground sewer mains
3 designed to receive large amounts of rainfall and carry it off
. to a downstream destination.
Nevertheless, occasionally large amounts of water
C falls in a very short time during severe storms so that even
a well designed system is inadequate to handle the runoff.
8 The result is that the storm mains are f looded and the runof f
9 carries away soil and chemicals associated with urban and
industrial centres creating a surge of polluted water which
overwhelms treatment facilities and adversely affects natural
12 streams and lakes, etc.
13 For instance, a typical "two year" storm sewer main
1~ might be designed to handle the runoff from a storm with a
severity which only occurs every two years. An F-nh~n~
16 design to carry any possible storm would be unjustifiably
17 expensive and space cnncl~min~. Therefore, it has to be
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acknowledged that occasionally 5torms will occur which
Z overf low the system.
3 Various methods have been devised to deal with such
4 inrLe~u~l.L but large and damaging runoffs. One method is to
provide relatively deep channels with outwardly inclined sides
6 so that they can ~ te a very large f low of water at
7 their u~ banks. However, these create hazards and
8 barriers to street traf f ic requiring bridges, etc .
g Another method is to provide large ponds or
reservoirs capable of receiving and temporarily storing storm
1.~ water runoff until it can be handled by the sewer mains, but
these require the dedication of large areas of open space
13 which are expensive or unavailable in urban area6.
1~ Some systems, 6uch as proposed in U. S. Patent
lS 4,457,646, provide underground reservoirs covered by
16 playgrounds or fields, but these require expensive structural
17 designs.
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~, It is theref ore the purpose of this invention to
create a means to handle exce6sive storm water runoff
3 efficiently and ineYr~n~ively.
It is also the purpose of this invention to provide
a r- ' -ni~-~ for modifying and handling the rate of water flow
6 from surface runoff so that flooding and pollution are
7 minimized.
8 It is also the purpose of this invention to provide
g an ~nh~nc~.cl means for h~n~ll ing storm water runoff in
conjunction with existing storm sewer mains without requiring
~1 additional land or facilities.
~hese objects and other advantages are sought to be
~,3 achieved by means of the present invention in which a storm
lJ. water drainage system having a plurality or manholes connected
by storm sewer mains and having catch basins to conduct
16 surface water runoff to the drainage system includes the
17 i, .,v. ~ which comprises an excavation incorporating at
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lea6t a portion of the storm water drainage system and said
excavation i8 f illed at least in part by a porous material
3 forming a reservoir. The i, I.,v~ -nt also comprises
perforated pipes extending between adjacent manholes in
contact with the porous re6ervoir material so that some of the
6 water collected by the drainage system may be allowed to drain
7 into the porosity of the reservoir during peak runoff and may
8 be allowed to drain back out of the reservoir and into the
9 drainage system at other times.
The system may be made more ef f icient if the
11 perforated pipes are wrapped in filter cloth to prevent solids
12 in the storm water f rom plugging the system .
13 The system may also function more effectively if the
14 porous reservoir material in the excavation is also
surrounded, at least in part, by filter cloth to keep fine
16 soil material out of the reservoir.
17 In one ~-mho~ the perforated pipe extends
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between adjacent manholes below the level of the 5torm sewer
main, . ' ~~'~o~ in the porous reservoir material, and has a
3 plug ad~acent the downstream end thereof, preferably upstream
from at least one perforation.
In a second ^-' 'ir-~lt a first perforated pipe
6 extends between adjacent manholes in the excavation above the
7 level of the storm sewer main and has plugs adjacent the
8 upstream and downstream ends thereof while a second perforated
g pipe extends only from one manhole in an upstream direction
only part of the way to the next adjacent upstream manhole and
11 is: ' ~dod in the porous material beneath the level of the
storm sewer and has a plug adjacent the upstream end thereof.
13 In this embodiment the catch basin preferably has a first
lateral drain exiting at a lower elevation and connecting to
the first upper perforated pipe and has a second lateral drain
16 at a higher elevation connecting directly to the storm sewer
17 main.
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The invention may be better understood by a
2 description of one or two: '~~';-~nts thereof with reference
3 to the attached drawings in which:
4 Figure 1 is a pelD~e~;Live view of a storm water
drainage system in accordance with the
6 present invention;
7 Figure 2 is a longitudinal section of the system
shoWn in Figure 1;
g Figure 3 is a cross-sectional view of the system
shown in Figure 1;
l Figure 4 is a perspective view of an alternative
~ P~nho~li t of the present invention;
13 Figure 5 is a longitudinal section of the system
14 shown in Figure 4;
Figure 6 is a cross-sectional view of the system
16 shown in Figure 4.
17 Figure 1 illustrates a typical urban location in
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~, which re6idential lots border on a street 2 which has catch
basins 4 at intervals along the curb side thereof. The catch
3 basins may include devices such as a goss trap or similar
4 devices to restrict the flow of oil or other contaminants into
S the system. The catch basins 4 are connected by a lateral
6 pipe 6 to the main storm sewer 8 which has manhole
7 installations 10 at regular intervals along its length.
8 Manhole covers 12 are located at street level and permit
9 access to the system for inspection or maintenance.
lo All of the foregoing is relatively typical of
11 conventional storm sewer systems which are constructed along
with and in conjunction with streets, curbs, and sidewalks.
13 In addition, the illustrated embodiment in Figure 1
14 includes a pair of perforated pipes 20 and 22 located beneath
the main sewer line 8, both of which are also connected to the
16 manholes lo.
17 The system, including manholes, main storm sewer,
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and perforated pipes are originally constructed in a trench
z excavated beneath the eventual level of the street, and after
construction, the trench is filled to surround the main and
4 perforated pipes with porous material such as crushed stone 24
S better illustrated in Figures 2 and 3. In addition, the
6 perforated pipes 20 and 22 are wrapped with a filter cloth 26
7 to prevent fine rock or soil from entering the perforations of
8 the pipes 20 and 22.
9 Furthermore, the trench 28 as seen in Figure 3 is
lined with a filter cloth before being backfilled with the
11 crushed rock to prevent fine material in the soil 30 from
12 entering the pores of the crushed stone.
As seen in Figure 2, the perforated pipe 20 is
14 provided with a mechanical plug 32 which may be reached from
the manhole so that it can be installed, removed, or
16 repositioned.
17 When a storm of unusual severity creates a large
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runoff of surface water, much of it will collect on streets
iL where it runs into the catch basins 4 along the curb side of
3 the street. From the catch basins the water will travel along
4 the lateral pipe 6 to the main storm sewer pipe 8 and will
f low downstream as indicated by the arrow 14 to the next
6 manhole. In a conventional system the water would continue
through each successive line until it reaches the ultimate
8 treatment facility, reservoir, lake, or stream.
g In the present system, however, the water flows from
the main into the next manhole and f lows into the two
perforated pipes 20 and 22 which are plugged by a mechanical
plug 32 near their downstream ends. As a result, the water
passes through the pipe perforations and the filter cloth into
1~ the stone-f illed trench where it f ills the void spaces and
ultimately seeps into the ~UL ' ~ullding native soil.
lC When the amount of runof f exceeds the capacity of
17 the perforated pipes, the water level will backup in the
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. ~
~1
perforated pipes toward the upstraam manhole where it will
;~ overflow via the conventional storm sewer pipe 8 and will flow
3 to the next downstream manhole where the proces8 i8 repeated.
Thus, the de5ign of the present invention provides
means by which storm water runof f may be absorbed into the
6 void spaces of the crushed stone in the trench, and some of it
7 will seep into the iuLLuullding soil. As the capacity of the
8 soil and the crushed stone to absorb water i8 used up, the
9 f low is passed down to the next section of the sewer system in
1.0 repeated sequence. Therefore, instead of the system having to
handle the volume of runoff within the manholes and the sewer
~ 2 mains 8, a large volume is a_ - 'Ated within the crushed
13 stone and ~uLLuullding soil.
1~ If the ---h Ini~AAl plug 32 is positioned upstream
from one or more of the lowermost perforations in the pipe 20,
lC it will be appreciated that the water collected in the porous
17 reservoir in the trench and surrounding soil can, after the
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12
~ storm is over, be gradually drained from the trench into the
2 lower ends of the perforated pipe 20 to the manhole and
3 eventually back through the system so that the accumulated
storm water runoff is slowly dissipated leaving the stone-
filled trench reservoir ready to receive the runoff from the
C next storm.
7 Figure 4 shows an alternative ~mh~ t of the
8 invention in connection with a conventional storm sewer system
9 in which the roadway 2, the catch basins 4, the manholes 10,
the storm sewer mains 8, are all similar to those illustrated
11 in Figure 1.
~owever, the catch basins 4 are provided with a pair
13 of lateral pipes. Lateral pipe 46 exits the catch basin from
1~ a lower position and enters a perforated pipe 50 positioned
above the level of the main storm sewer 8. A second lateral
16 pipe 48 exits from a higher position in the catch basins and
17 drains directly into the main storm sewer 8. The perforated
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13
pipe 50 extends between adjacent manholes 10 and is wrapped in
a filter cloth similar to the arrangement in Figure 1. In
addition, lower perforated pipes 52 and 54 also covered with
filter cloth are positioned below the main storm 6ewer and
extend in the upstream direction from the manhole
6 approximately halfway to the next upstream manhole where they
7 are closed by a cap 56 at the upstream end. As in Figure 1
8 the system of Figure 4 is constructed in a trench which is
backfilled with crushed stone as illustrated in Figures 5 and
6.
As seen in Figure 5, the upper perforated pipe 50 is
12 provided with a mechanical plug 58 near each end.
~,3 In the embodiments illustrated in Figures 4, 5, and
14 6, storm water is collected in the catch basin 4 and the
lS earliest runoff is transported by the lateral pipe 46 to the
16 upper perforated pipe 50, which is plugged at both ends, so
17 that it passes out through the perforations and into the void
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1~
space of the crushed stone 24. It will gradually percolate
. down through the crushed stone to the lower perforated pipes
3 52 and 54 which carry the flow to the next downstream manhole.
Since the lower perforated pipes do not extend to the next
upstream manhole, the water must rise in the manhole until it
eventually overflows into the main storm sewer 8 and is
7 carried of f .
8 Thu6, by this system the runoff is delayed by the
g time it takes to percolate through the crushed stone from the
upper perforated pipe 50 to the lower perforated pipes 52 and
1~ 54 but the accumulation in the crushed stone and surrounding
lZ soil is not as great, and the delay is not as significant as
the system illustrated in Figure l.
It should be appreciated that the amount of delay
built into the system can be shortened by lengthening the
16 lower pipes 52 and 54, or the delay can be extended by
17 shortening those pipes which control the rate of f low .
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The catch basin arrangement shown in Figure 6 does
not permit the usual traps but the initial runoff will travel
3 the lateral pipe 46 to the perforated pipe 50 and se~p through
the crushed stone. As resistance to this flow builds up, the
water level will rise in the catch basin and eventually will
6 overflow into the lateral pipe 48 which leads directly to the
7 main storm sewer 8. By this arrangement the initial flow,
8 which carries the most pollutants, is diverted through the
g crushed stone.
Although the present invention is not restricted to
specific dimension or specification, it is the inventors'
experience that the ~mho~ t illustrated in Figure 1 is
13 workable for the treatment of 15 millimetre storm events at
1~ three day intervals under existing water quality guidelines if
the perforated pipes are standard 35 PVC gravity sewer pipes
16 of 200 m~llir Lr_ diameter with 12.5 millir tre diameter
17 holes, and wrapped with geotextile material with an effective
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lC
opening size in the range of SO to lSO microns. The trench
which should be in the order of 2 to 6 meters square in cross-
3 section is filled with crushed stone of a particle size from
SO to 100 microns.
Thus, by means of the present invention, a system is
6 provided underground within the space occupied by the
7 conventional storm sewer system which will provide an
immediate reservoir volume to absorb the initial runoff, will
g provide for seepage of some of the runoff into the surrounding
soil, and will effectively slow the rate of flow of surface
water f rom a severe storm .
Furthermore, the iulyL~/V- -~ts may be installed at
13 the time of initial installation without substantial
1~ additional cost, or can be installed at some future date, if
lS n~c~gg;~ry.
16 It is believed that particles in the runoff water
17 will be removed, bacteria will die off in the soil
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environment, and fertilizers and other nutrients will likely
2 be taken up by trees in the surrounding soil. Thus, ground
3 water will be recharged and stream flows ~nh~nced with cool
water at a relatively constant rate.
It will, of course, be realized that numerous
6 variations and modifications of the illustrated embodiment may
7 be employed without departing from the inventive concept
8 herein.
