Storm water flow monitoring

Apparatus and a method for monitoring the rate of flow of storm water in an individual sewer. The apparatus comprises a collector bowl mountable beneath the storm sewer manhole cover and positioned to collect all water entering through the manhole cover. A flow pipe is mounted in the bowl and projects upwardly from the bottom thereof. Water collected in the bowl must rise to a level above the flow pipe before it will flow through the pipe and into the sewer. A flow meter sensitive to the water height above the flow pipe is positioned in the bowl and measures and records the rate of flow.

BACKGROUND OF THE INVENTION 
This invention relates generally to pollution control and the measurement 
and sampling of water effluent discharge and, more particularly, to a 
monitoring method and apparatus for measuring and sampling storm water 
run-off. 
Growing concern over further pollution of rivers, streams, lakes and other 
bodies of water has given rise to more and stricter regulations governing 
the discharge and treatment of wastewater effluent. As a general rule, 
industrial run-off and municipal run-off are channeled through a sewer 
system for discharge into a large or flowing body of water. Depending on 
the flow rate and toxic material content of the run-offs, the effluent may 
require flow restraint and/or treatment before discharge. Continuous and 
relatively accurate monitoring and sampling of effluent run-off has 
thereby become essential. 
In a typical sewer system, there is a substantially continuous stream of 
water flowing through an aqueduct, pipe or channel that is substantially 
horizontal. Streams of that type, known as open channel streams or flows, 
have long been monitored by a variety of methods and devices developed for 
that purpose. Examples of such known methods and devices may be found in 
U.S. Pat. Nos. 3,719,081, showing a flume arrangement and a pressure probe 
generating an electronic signal translatable into a flow rate; 3,929,017, 
showing a weir arrangement and a bubbler device responsive to the pressure 
required for gas bubbles to rise through a head of water; and 3,954,009 
showing a float device associated with a weir arrangement. Weirs, flumes, 
and the like, are known as primary measuring devices and, as indicated in 
the said '017 patent, formulas have been developed for converting the 
height of liquid rise caused by the device into a flow rate based on the 
characteristics of the particular device. 
Another primary measuring device is a plain cylindrical tube or pipe 
through which water flows in an open channel by gravity. That type of open 
channel flow is traditionally measured by the well known Manning formula 
wherein the slope of the hydraulic gradient is a factor so that the 
measured rate of flow is proportional to the slope of the pipe which 
normally will be some variance from the horizontal. 
The various sensing devices and flow meters are known as secondary 
measuring devices which are adapted to automatically convert a sensed 
signal into a flow rate and also record the flow rate. The flow meters 
typically are programmable to the different types of primary measuring 
devices so that the proper conversion and flow rate is obtainable under 
varying flow conditions. 
More recently, another source of potential water pollution has come under 
scrutiny, namely, storm water run-off. Storm sewers can be found in 
virtually all industrial facilities as well as commercial areas such as 
shopping malls and the like. The storm sewers are positioned and designed 
to be the collection point for storm water from building downspouts and 
paved or unpaved areas that require draining. Environmental Protection 
Agency (EPA) studies recently conducted have indicated that storm water 
run-off from urban and industrial sites carries a considerable amount of 
pollutants. As a result, the EPA has in late 1990 issued extensive 
regulations which apply to industrial and municipal storm water 
discharges. 
As a general rule, storm sewers are remote from a main wastewater sewer 
system or wastewater treatment plant. Water flowing into a particular 
storm sewer thus must flow independently through its own drainage channel 
before it can be merged with and flow into the main sewer system. 
Understandably, the storm water run-off of a given individual location is 
intermittent, depending on weather conditions, and of greatly reduced 
volume compared to the wastewater discharge flowing in a main municipal 
storm sewer system. Since monitoring of individual storm sewers is often 
required by the EPA regulations, use of the described primary measuring 
devices like flumes and weirs for monitoring under such conditions is no 
longer practical or effective. 
There thus exists a need for a flow rate measurement and sampling means for 
monitoring the run-off in an individual storm sewer. A device for 
achieving such monitoring should be simple to install in a storm sewer and 
yet provide sufficiently accurate results as required by regulations. 
SUMMARY OF THE INVENTION 
The present invention provides a method and apparatus for monitoring storm 
water run-off in individual storm sewers. The apparatus may be readily and 
conveniently installed in a conventional storm sewer having an apertured 
manhole cover where it is effective for monitoring storm water entering 
that sewer. 
Briefly, the invention comprises a liquid-impermeable bowl or dish-like 
collector provided with a peripheral flange. The collector is supportable 
on the rim of a conventional storm sewer manhole and also beneath the 
apertured manhole cover which serves to hold the operationally mounted 
collector in place. Any storm water entering the sewer through the manhole 
cover necessarily accumulates in the collector. 
A drain or flow pipe is mounted in a central opening of the collector and 
projects upwardly therefrom. In one embodiment of the invention the flow 
pipe comprises an upright leg and an elbow with a substantially horizontal 
arm. Water accumulating in the collector must rise above the lower edge of 
the mouth of the flow pipe arm before it can begin to flow through the 
flow pipe and into the sewer. Rate flow sensing means, such as 
commercially available bubbler devices and flow meters, is associated with 
the collector and flow pipe. The bubbler device is positionable at the 
bottom of the collector and generates a signal, proportional to the depth 
of discharge in the horizontal arm, which signal is converted by the 
programmable flow meter into a rate of flow. In most situations, the rim 
of the sewer manhole is not absolutely horizontal so that the leg of the 
flow pipe will not be perfectly vertical nor the upper arm perfectly 
horizontal. Under those conditions, the conversion formula utilized in the 
programmed meter will be the Manning formula previously described to 
account for the slope of the arm. 
In another embodiment of the invention, the flow pipe comprises a plain 
upright pipe without the horizontal arm. Flow meters of the type described 
may be programmed to measure and record the rate of the flow through a 
vertical pipe with even greater accuracy than is obtainable with the 
Manning formula. Such measurement requires that the flow pipe be virtually 
perfectly perpendicular, which condition will obtain when the manhole rim 
is virtually perfectly level or horizontal. Alternatively, the collector 
flange may be provided with simple leveling means for achieving the 
desired level mounting. 
Means is provide for making the flow pipe easily removable from its 
mounting in the collector. As a result, pipes of varying diameters may be 
readily substituted and positioned depending on the severity of the 
impending storm or the empirically determined approximate volume of storm 
water flow at a particular site. By matching the flow pipe diameter with 
the estimated water flow rate, efficient flow rate readings can be 
consistently obtained. 
A sampling device of commercially available type is also associated with 
the collector for periodically and automatically collecting samples for 
analysis as required.

DETAILED DESCRIPTION OF THE INVENTION 
Referring with greater particularity to FIG. 1 of the drawings, there is 
illustrated a representative industrial site comprising a factory building 
10 having a downspout 12 which is a source of storm water run-off down an 
inclined drainage surface 14. Supplies or waste materials 16 are placed 
outdoors on an inclined drainage surface 18 and storm waters will contact 
or pass through the materials 16 before running down the surface 18. The 
drainage surfaces 16 and 18, as well as any additional similar surfaces, 
converge to a common storm water sewer 20. The sewer 20 comprises a 
manhole 22 having a top rim 24 on which is removably supported a 
conventional apertured manhole cover 26. Storm water entering the sewer 20 
flows independently before it merges with a regulated waterway or main 
storm sewer 28. 
A primary measuring device or monitoring apparatus 30 embodying the 
principles of the invention is operationally mounted beneath the manhole 
cover 26 and positioned so that it receives or intercepts any water 
entering through said cover. Monitoring apparatus 30 comprises a 
liquid-impermeable collector bowl 32 which is generally circular in 
configuration and has an annular sidewall 34 and a concave bottom wall 36. 
An annular flange 38 is integrally formed with the sidewall 34 and, as 
illustrated in FIG. 1, said flange is dimensioned to support the bowl 32 
on the rim 24 of the manhole 22 where it is further operationally retained 
by the manhole cover 26. The flange carries gasket means 39 for insuring a 
liquid-tight fit between the manhole rim and cover. The collector bowl 32 
may be integrally molded of suitable sturdy plastics capable of supporting 
the weight of water collected therein and said bowl is, in this respect, 
similar to bowls that have heretofore been commonly employed to block off 
a sewer where it is desired to prevent flow into that sewer. 
A central mounting hole 40 is formed in the bottom wall 36 of the collector 
bowl 32. A flow pipe 45 is operationally mounted in the hole 40 by 
removable means such as a threaded collar 42 providing a liquid-tight 
connection with the bowl 32. Accordingly, water can flow out of the bowl 
32 only through the flow pipe 45. 
Flow pipe 45 is open at both ends and comprises an upright leg 46, an elbow 
48 and an arm 50 extending from the leg at a substantially right angle 
thereto. The arm 50 thus comprises an annular mouth 52 having a fixed 
diameter D. As is apparent from FIG. 3, water cannot enter the arm 50 to 
flow through the flow pipe 45 until the level of water in the bowl is 
above the bottom 54 of the arm 50, a level sometimes referred to as the 
zero flow point. When the level in the bowl exceeds the zero flow point, 
water flows through the arm 50 and pipe 45 at a measurable depth of flow, 
such as "d". The ratio of d/D is significant in rate flow measurement by 
the Manning formula as will be understood by those skilled in this art. 
A secondary measuring device is operationally associated with the apparatus 
30 for measuring and recording the storm water flow rate. In the 
embodiment illustrated, the sensing means comprises a bubbler tube 56 
fixedly positioned on the bottom wall 36 of the collector bowl. The 
bubbler tube 56 may comprise a part of any of a number of commercially 
available flow meters. An example of such a flow meter is the Model 3230 
of ISCO, Inc. which provides a number of programmable options for 
automatically recording flow rate based on primary measuring device 
characteristics, such as, flumes, weirs, vertical columns or the Manning 
formula. 
Means 58 is provided for automatically and periodically collecting water 
samples from the storm water run-off for chemical analysis. The sample 
collector means can comprise any of the commercially available devices, an 
example of such devices being the Model 2900 Sampler of ISCO, Inc. In 
general, that type of sampling device includes a take-up line connected to 
a pump and a carousel or the like with a plurality of sample containers 
such as test tubes or the like. 
Referring to FIG. 4, there is shown another embodiment 30a of the 
monitoring apparatus. Flow pipe 45a here comprises an open-ended upright 
tube or standing pipe 60. As illustrated, the level of water accumulated 
in the collector bowl 32a must rise above the top of the pipe 60, the zero 
flow point, before water will flow down through the pipe. The sensing 
device and flow meter is responsive to the height of the water column d 
above the zero point and the meter is programmable for conversion and 
recording of the corresponding flow rate. As already indicated, this mode 
of flow rate measurement is generally the most accurate, but it is 
necessary that the pipe 60 be virtually perfectly vertical. Where 
compensation for a non-level manhole rim is necessary, the flange 38a is 
provided with a plurality of threaded leveling means such as 62 secured 
thereto. In the embodiment illustrated, the leveling means 62 comprises a 
finger-manipulatable screw projecting substantially above the flange 38a 
so that the manhole cover is removed. The leveling means could also 
comprise a regular slotted screw head requiring use of a screwdriver, but 
permitting seating of the manhole cover thereover as in FIG. 2. 
From the foregoing, it should be apparent that the invention provides a 
novel primary measuring device which may be easily operationally installed 
to monitor the storm water run-off of an individual site and individual 
storm water sewer. Two modes of flow meter measurement are possible 
depending on conditions of use, and the ready removability of the flow 
pipe permits substitution of flow pipes of varying diameters to best match 
the estimated flow rate. 
It should be appreciated that preferred embodiments of the invention have 
been described herein for illustrative purposes only and are not otherwise 
limiting of the structural and method concepts of the invention. 
Accordingly, changes and variations may be made by those skilled in the 
art without departing from the spirit and scope of the invention as 
defined in the appended claims.