Abstract:
A method and apparatus for isolating a section of sewer line. In one embodiment, a chamber is provided that extends into the ground and intersects a sewer pipe. Thereafter, the fluid in the sewer pipe is exposed to an interior of the chamber and a dam is placed in the chamber to isolate an upstream portion of the chamber from a downstream portion. As fluid collects in the upstream side of the chamber, at least one pump is used to control the fluid level in the upstream portion by transferring the fluid from the chamber to a predetermined, remote location.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to subterranean fluid lines. More specifically, the invention relates sewage systems. More particularly still, the invention relates to improved methods and apparatus for isolating a section of a fluid line. 
     2. Description of the Related Art 
     Pumping stations in sewage collection systems, also called lift stations, are normally designed to handle raw sewage that is fed from underground gravity pipelines (pipes that are laid at an angle so that a liquid can flow in one direction under gravity). Sewage is fed into and stored in an underground pit, commonly known as a wet well. The well is equipped with electrical instrumentation to detect the level of sewage present. When the sewage level rises to a predetermined point, a pump or pumps will be started to lift the sewage upward through a pressurized pipe system from where the sewage is discharged into a gravity manhole. From there, the cycle starts all over again until the sewage reaches its point of destination—usually a treatment plant. By this method, pumping stations are used to move waste to higher elevations. 
     Sewage pumping stations are typically designed so that one pump or one set of pumps will handle normal peak flow conditions. Redundancy is built into the system so that in the event any one pump is out of service, the remaining pump or pumps will handle the designed flow. There are a lot of electronic controllers designed specially for this application. The storage volume of the wet well between the ‘pump on’ and ‘pump off’ settings is designed to minimize pump starts and stops, but is not so long a retention time as to allow the sewage in the wet well to overflow. In the case of high sewage flows into the well (for example during peak flow periods and in system also handling rain water), additional pumps will be used. If this is insufficient, or in the case of failure of the pumping station, a backup in the sewer system can occur leading to a sanitary sewer overflow—the discharge of raw sewage into the environment. 
     Pump stations and/or sections of sewer lines are taken off-line for a variety of reasons including equipment failure and/or maintenance. Breakdown due to corrosion is typical. Sewage infrastructure corrosion occurs when sewage gas (H 2 S) is converted to sulfuric acid (H 2 SO 4 ) by the action of bacteria. Currently, the stations are taken off-line using methods that are time-consuming, difficult and dangerous. For example, in one method an inflatable pig-like device is inserted in the sewer via a manhole at some location upstream of the trouble zone. Thereafter, the pig is inflated in order to expand and block the flow of fluid. At the same time, the fluid is re-routed at a location downstream of the pig. Isolating a section of sewer in this manner is effective, but working downstream of an inflated pig is inherently dangerous in the event of deflation or rupture of the pig, which can result in a renewed flow of fluid in the direction of workers in the sewer who may not have an avenue for safe exit. In other instances, lift stations at water treatment facilitates fail and the resulting repairs on pumps is inefficient due to the presence of temporary pumps and flow lines in and around the facility. 
     What is needed is an efficient and safe way to isolate one section of a sewer from another section or from a lift or treatment facility. 
     SUMMARY OF THE INVENTION 
     The invention includes methods and apparatus for isolating a section of fluid line. In one embodiment, a chamber is provided that extends into the ground and intersects a sewer pipe. Thereafter, the fluid in the sewer pipe is exposed to an interior of the chamber and a dam is placed in the chamber to isolate an upstream portion of the chamber from a downstream portion. As fluid collects in the upstream side of the chamber, at least one pump is used to control the fluid level in the upstream portion by transferring the fluid from the chamber to a predetermined, remote location. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is top view of a diversion chamber installed in the ground and intersecting a sewer pipe. 
         FIG. 2  is another top view of the diversion chamber showing a pump assembly at an upper edge of the chamber and a dam installed in the chamber. 
         FIG. 3  is a side view of the chamber, in section, showing the dam and its position relative to the sewer pipe. 
     
    
    
     DETAILED DESCRIPTION 
     In this specification, the term “sewage” or “sewer line” refers to any subterranean fluid path in a conductor regardless of the type of fluid. For instance, the principles of the invention are equally usable with waste sewage or storm sewage or both. 
       FIG. 1  is a top view of a diversion chamber  100  formed in the ground to access a sewer line  200 , which in the case of  FIG. 1  is a tubular member. The chamber is a relatively large diameter (typically 20 feet) and is either constructed over an existing, large diameter sewer pipe (48 inches in diameter for example) or constructed at the time the sewer is originally installed. The chamber  100  is made of reinforced structural concrete usually by driving piles in the ground and then using the inwardly facing surface of each pile to form the wall  110  of the chamber. The interior walls are lined with a non-corrosive material  120 , like PVC, to prevent corrosion. The location of the chamber is typically adjacent to and just upstream of a pump station wet well or influent junction box that might need to be taken off-line at any time. The most likely candidate for a diversion chamber is a lift station at a sewage treatment facility where current methods of diversion cause the most disruption. In another instance, a chamber might be built upstream of a problem area of sewer pipe (due to breakage or collapse) or even to bypass a section of sewer while unrelated road or other infrastructure work takes place. 
     Sewer lines can be anywhere from 20 to 100 feet or more underground, and the chamber is designed and built whereby the floor  125  of the chamber is at a depth of the centerline of the sewer pipe  200 . In this manner, the top half of the sewer pipe can be removed and the bottom half left in place to operate as a trough for fluid. For example, if the chamber is retrofit to an existing sewer line, the depth of the line is determined and the chamber is excavated to a depth equal to the centerline of the sewer pipe. If the chamber is built at the time the sewer pipe is laid, its floor is similarly positioned relative to the pipe. The chamber is typically round and includes a precast, removable top slab (not shown) that can be covered with any material including pavement to conceal the existence of the chamber. Under normal conditions, the chamber is a static access point to the sewer and includes no permanent equipment like valves, gates or pumps. The purpose of the chamber  100  is to remain protected from long-term deterioration but be functional when needed. 
       FIG. 2  is another top view of the diversion chamber  100  showing a pump assembly  300  at an upper end of the chamber and a dam  400  installed in the chamber. In  FIG. 2 , the chamber appears as it would just prior to a diversion operation. The pump assembly  300  includes a frame  310  designed to be a temporary and simple means of providing pumps  350  at the location of the chamber in the event a diversion is necessary. The frame  310  is supported by the walls  110  of the chamber and in turn supports the weight of the pumps  350  that are used to divert fluid from the chamber  100  to a remote location. In  FIG. 2 , three pumps  350  are shown but any number can be used depending on requirements of a particular diversion job. The pumps  350  are lowered into the chamber  100  with a crane (not shown). Thereafter, they are suspended from the frame  310  by steel pipes (not shown) which provide a conduit for the fluid between the pump output and the top of the chamber. High-density PVC pipe (not shown) carries the diverted fluid to another location where it is re-introduced into the permanent sewer line, or in some cases, directly into a treatment plant. Pipe used to carry diverted fluid can be of most any construction and type so long as it is sized to handle the given volume of fluid. The pumps  350  are typically submersible pumps that are powered either by a generator or a nearby power source, and temporary controls, including fluid level sensors, are installed with the assembly  300 . 
     Also visible in  FIG. 2  is dam  400 , like a coffer dam that serves as an enclosure within a water environment to allow water to be pumped out and replaced by air for the purpose of creating a dry environment. The dam is shown in other detail in  FIG. 3 . The dam  400  includes vertical sections  401 ,  402  that can be stacked to increase the overall height of the dam depending upon the level of fluid in the chamber  100  during a diversion. For example, if fluid is expected to rise to a level of 50 feet, five 10-foot sections  401 - 405  can be assembled and installed in the chamber to provide the adequate height. A tongue portion  425  formed at a lower end of the lowermost section  401  of the dam  400  is constructed and arranged to extend into and seal against a half-circle shape  205  of the sewer pipe  200  that remains after the top portion of the pipe is removed. The dam  400  is also designed to seal against the chamber wall  110  due to hydraulic pressure of fluid acting upon a convex side  430  of the dam. Corrosive resistant rubber seals (not shown) between the edges of the dam and the chamber wall ensure a watertight seal. Both the dam  400  with its multiple sections  401 ,  402  and the pump assembly  300  are intended to be easily installed in the chamber  100  when they are needed and easily removed after a diversion job is complete. Typically, each will be stored in a location where they are rapidly deployable. 
     In the event a nearby, downstream lift station needs to be taken off-line for maintenance or in the event of a failure, the chamber  100  is exposed when the top is removed, making the chamber fully accessible from above. First, the pump assembly  300  and the dam  400  are deployed to the site. Thereafter, the pumps  350  are installed and the piping plumbed to the top of the chamber  100  and onwards to a downstream point where the fluid will be re-introduced into the sewer. The dam  400  is assembled using the required number of portions to ensure its height in relation to the fluid level expected in the chamber  100  during the diversion job. Prior to installing the dam, with the flow at some reduced level through the sewer line, the top half of the sewer pipe  200  is removed, leaving the trough-shaped lower portion  205 . At this point, the floor  125  of the chamber  100  might be poured and extend over the remaining edges of the pipe  200  as shown in  FIG. 3 . The dam is then installed in the chamber, and all personnel are evacuated from the chamber. Thereafter, with fluid flow blocked in a downstream direction, the fluid level in the chamber  100  rises. At a predetermined level, one or more of the pumps  350  will begin operating to move the fluid through the diversion pipe. With the sewer section and/or station isolated, work can begin while the chamber and its equipment keep the fluid diverted. After the repairs or maintenance are complete, the dam  400  is removed along with the pump assembly  300 , and associated equipment and the top is retuned to the chamber. At any time thereafter, the chamber can be used to again isolate a section of sewer or a facility. 
     The chamber  100  and dam  400  may include a built-in safety feature to prevent fluid from overflowing out of the top of the chamber  100 . In some instances, the chamber  100  may receive an unexpected increase in fluid flow and/or the pump assembly  300  may fail, which can lead to an overflow of fluid in the chamber  100 . To prevent fluid from flowing out of the top of the chamber  100  and into the surrounding environment, the height of the dam  400  may be constructed such that the fluid will flow over the dam  400  and into the open trough portion of the pipe  200  prior to reaching the top of the chamber  100 . As illustrated in  FIG. 3 , the height of the wall of the dam  400  is less than the height of the chamber  100 , e.g. the top of the dam  400  (illustrated by reference numeral  403 ) is at an elevational height less than the top of the chamber  100  (illustrated by reference numeral  103 ). Thus, as the fluid level in the chamber  100  exceeds the height of the dam  400 , the fluid will flow into the dry side of the dam  400  and out through the pipe  200 . 
     Using the apparatus and methods described, a pump station or section of sewer line can be completely bypassed and all parts of it accessible for repairs, maintenance or modifications. When bypassing is no longer needed, the dam will be removed, the pump station restarted and the bypass pumps removed. The dam and pump support frame can be returned to storage. The same dam and pump support frame can be used at other similar facilities. This same type of chamber can be constructed as part of a new pump station to provide a way to effectively deal with emergencies in the future. The installation of the diversion chamber can be done relatively quickly and does not require a shored excavation or an extensive groundwater pumping system. 
     The invention has been described as utilizing a number of steps. While the steps have been described as occurring in a certain order it will be understood that such a particular order is not necessary. For instance, the order in which the pump(s) and dam are installed is flexible so long as an upstream side of the chamber is isolated from a downstream section prior to evacuation and transfer of fluid from the upstream side to a remote location. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.