Abstract:
A manhole for a storm sewage system comprising a structure having at least two outwardly extending substantially vertical flat panels projecting outwardly from the exterior surface a predetermined distance on opposite sides of the base portion of the manhole.

Description:
This appl. claims benefit of Prov. No. 60/123,368 filed Mar. 8, 1999. 
    
    
     FIELD OF INVENTION 
     This invention relates to a device which is applicable to storm water filtration and exfiltration systems wherein a storm sewer system is designed to return at least a portion of the runoff water into the soil during periods of rainfall. 
     BACKGROUND OF THE INVENTION 
     For many years, the primary object of a storm sewer system in urban and suburban developments has been to collect runoff water in catch basins, etc., duct the water from catch basins into a storm sewer pipe and provide suitable ducting to lead the captured water to a suitable dumping site such as a lake, river or ocean. Little thought has been given to returning some or all of the runoff water to the soil through which the storm sewer system passes. 
     Because of increasing public awareness of the gradual depletion of the underwater aquifer, more and more attention has been given to the conservation and replenishment of the underground aquifer. 
     To this end, extensive studies have been done to determine possible methods of restoring the aquifers in areas of urban development which are serviced by storm sewer systems which, until recently, have functioned in the classical manner of ducting all the runoff water into some type of sink. 
     Such a study was carried out in the city of Etobicoke and is reported in publication ISBN 0-7778-72854 entitled Post-Construction Evaluation of Stormwater Exfiltration and Filtration Systems by A. M. Candaras Associates Inc. (Project No. 9321) under publication PIBS 3622E (Queens Printer for Ontario 1997). 
     This study details methods of controlling runoff and the introduction of storm sewage effluent into the soil surrounding a storm sewer installation. In the system studied, a conventional storm sewer system is augmented by connecting a parallel drainage system comprising a system of perforated drainage pipes located in a sewer trench just below the standard storm sewer pipe used (previously) to carry the total runoff water. The sewer trench, in which the perforated pipes are located, is purposely filled with stone aggregate. The perforated pipes and the storm sewer pipe are connected into a conventional manhole system, so that the storm sewer pipe is located in the sewer trench a predetermined distance above the perforated drainage pipes. The perforated pipes are plugged at each connected downstream manhole to prevent the passage of the runoff water contained in the perforated pipes into the downstream manhole and to encourage the water in the perforated pipes to flow into the stone aggregate surrounding the perforated pipes. 
     At times of substantial runoff events, it will be found that the perforated pipe system may not be able to contend with the entire runoff and as the water in the manholes builds up to the storm sewer outlets, the standard storm sewer begins to conduct the excess runoff to the usual sink. 
     SUMMARY OF THE INVENTION 
     A modified manhole will be described which will prove invaluable to the success of returning the water contained in the perforated pipe-stone aggregate system into the underground aquifer. Each manhole in the runoff recovery system is provided with a pair of extension wings which will function as a dam in the storm sewer excavation trench where the stone aggregate is located. The extension wings are preferably an integral part of the manhole or they may be accessories readily attachable to the existing manhole structure. 
     PERTINENT PRIOR ART 
     U.S. Pat. No. 5,511,904 Apr. 30, 1996 Van Egmond 
     This patent describes a funnel structure for filtering and discharging storm sewage water into an underground aquifer by providing a conductive path for the escape of water through a sump provided in the bottom of the manhole. The sump is basically an open pipe which allows filtered sewage water to flow into the soil beneath the manhole. Filtration is provided by a sack filled with suitable filtering materials which is placed in the sump where the sewer water enters the sump. In this manner, water is encouraged to enter the soil beneath the manhole. 
     This patent, which requires a minimum of expense to install in new or existing installations, will function to return a portion of the runoff water to the soil surrounding the base of a manhole, requires substantial maintenance in order to periodically remove the filter sacks from the manhole sumps when they become clogged through use. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional elevation of a sewer trench of an exfiltration sewer system. 
     FIG. 2 is a sectional view of a manhole of this invention. 
     FIG. 3 is a sectional view along the section line  3 — 3  of FIG.  2 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 is an elevational sectional view of a sewer water ground recovery system with exfiltration means. FIG. 1 shows three manholes,  10 ,  12 ,  14  located in soil  16 . A roadway having surface  18  is provided with sewer manhole covers  20 ,  22  and  24  on manholes  10 ,  12  and  14  respectively and a pair of catch basins  26  and  28  are shown in surface  18 . 
     Catch basins  26  and  28  have standard sumps or they may be provided with goss traps. The catch basins  26  and  28  are provided with drainage pipes  30  and  32  which are connected into sewer pipes  34  and  36 . 
     Sewer pipes  34  and  36  are sloped and connected into manholes  10 ,  12  and  14  in a standard manner at locations  38 ,  40 ,  42  and  44 . In addition to the storm sewer pipes, each manhole is provided with connections to a plurality of perforated pipes such as  46  and  48  which are connected into manholes  10 ,  12  and  14  at locations  50 ,  52  and  54 , and  56  respectively. The perforated pipes are carefully sealed into manholes  12  and  14  at locations  52  and  56  and each of the perforated pipes  46  and  48  are provided with plugs  58  and  60  at these locations. 
     The sewer pipes  34  and  36  and the perforated pipes  46  and  48  are laid in a bed of stone aggregate  62  which is laid to a predetermined depth in the sewer system and usually the entire width of the excavation trench in which the storm sewer is located. The trench is usually filled with soil  16  above the stone aggregate  62  and is compacted according to regulations. 
     The entire stone aggregate bed  62  may be encased in a suitable geotextile fabric (not shown) to provide the final exfiltration required by regulations established by the governing sewer authority in which the system is installed. 
     The system functions as follows: 
     Rainfall which falls on surface  18  and is collected in catch basins  26  and  28 . When the rainfall has reached a predetermined level, it exits via catch basin pipes  30  and  32  to storm sewer pipes  34  and  36 . The collected water now flows in sewer pipes  34  and  36  to manholes  12  and  14  respectively where it falls into the bottom of the manholes  12  and  14 . The runoff water then builds up in the manholes until it reaches the level of installation of the perforated pipes  46  and  48  at  50  and  54 . Water now begins to flow into perforated pipes  46  and  48  as shown by arrows  64  and  66  and into the stone aggregate  62  (water dissipation system). The runoff water which flows through the pipes  46  and  48  gradually escapes through the perforations in pipes  46 ,  48  filling the stone aggregate  62 . Water cannot flow from manhole  10  to manhole  12  or from manhole  12  to manhole  14  through the plurality of perforated pipes  46  and  48  because of plugs such as  58  and  60  installed at the downstream ends thereof. 
     Then the groundwater runoff in pipes  46  and  48  is gradually dissipated in the soil surrounding the stone aggregate  62 . 
     If the runoff event is intense, the perforated pipes  48 ,  48  may not have sufficient capacity to dissipate the entire runoff water in the stone aggregate  62  as fast as the catch basins  26 ,  28  transfer runoff water into the sewer pipes  34 ,  36 . In this event, water continues to build in manholes  10 ,  12  and  14  until it reaches the level of the outgoing sewer pipes  34  and  36  at locations  38 ,  42  whereupon water flows in a conventional manner as indicated by arrows  68  and  70  through the storm sewer pipes such as  34  and  36  into the ultimate water disposal area or sink. Of course the sewer pipes will perform this same function when the stone aggregate  62  becomes waterlogged as would occur during a long, heavy and persistent rainfall. 
     It will be seen that the system functions to produce a water head in the perforated pipes  46  and  48  between the existing manholes  10 ,  12  and  14 . The head produced causes water to be introduced into stone aggregate  62  and establish hydraulic pressure in the stone aggregate  62  as the water levels in the manholes  10  and  12  increase. The resulting pressure will assure that the runoff water in the trench (absent some damming means) will establish a flow in the stone aggregate  62  along the trench until it reaches the disposal site. 
     Because the stone aggregate  62  is the sewer trench provides an excellent conduit for the storm water delivered thereto by the perforated piping system to flow toward the ultimate sink, it has been found that a specially constructed manhole will provide an effective dam which prevents the unrestricted flow of storm water at each manhole location. Without such a restriction it will be found that a diminished amount of the runoff water will be dissipated into the soil surrounding the sewer trench, and in addition, soil surrounding the sewer trench may be carried by the unrestricted water flow in the stone aggregate, leading to erosion of soil above and around the trench and leading to the ultimate failure of the road above the trench. 
     The modified manhole shown in FIGS. 2 and 3 will prevent the unobstructed water flow in the stone aggregate  62  is the subject of this invention. 
     FIG. 2 shows a sectional elevational view of a manhole structure  200  having the structure which illustrates this invention. In this illustration, the manhole  200  comprises three components: a tapered top section  202 ; and in this instance an adapter  204  and an exfiltration base  206 . The manhole is supplied with a standard cover  208  and a ladder  210  in the interior thereof. 
     The manhole is provided with Knock out access holes  212 ,  214  and  216  for the accommodation of storm sewer pipe and perforated pipes such as  46  and  48  of FIG. 1 which will be subsequently connected into the manhole  200 . 
     The base  206  of manhole  200  is constructed to have a pair of outwardly extending wings or extensions in the form of vertically extending flat panels  218  and  220 , which in this instance, are integrally attached to the base  206  of manhole  200 . 
     FIG. 3 shows a sectional plan view of the base  206 . The panels  218  and  220 , in this instance, are integrally cast into the base  206 . The length and width of the panels  218  and  220  may be tailored to the dimensions of the sewer trench and the depth of stone aggregate in the trench. 
     It will be seen that the panels  218  and  220  are made to extend the entire width of the excavated trench for the sewer installation and, hence, the resulting structure effectively provides a dam for the bypass of water which in the absence thereof would flow around and past the manhole  200  in the stone aggregate such as  62  in FIG.  1 . 
     In this illustration, the panels are shown as being integral with the manhole  200  as will usually be the case. The most efficient construction for the “dam manhole” is of course precast construction where the complete unit may be delivered to the construction site. In some instances it may be necessary or more convenient to manufacture the panels separately and subsequently install the panels as “add on” accessories to the manhole. In new installations, it may be convenient to have a collar which surrounds the manhole into which the manhole base  206  fits and which includes the extensions as projections from the collar. In any event, the panels must seal at the manhole to prevent bypass of the water in the stone aggregate around the manhole. 
     It will be seen that the panels  218  and  220  will improve the dissipation and absorption of water in the soil surrounding the sewer trench by the increase in head pressure of the water in the stone aggregate provided by the blockage produced by manhole panels  218  and  220 . Subsidence of the fill above the stone aggregate as might occur due to the continuous unobstructed water flow in the trench of stone aggregate is largely avoided. The capacity of the entire sewage system has been increased because of the ability of the system to introduce a generous amount of water back into the soil in the immediate vicinity of the sewer trench. 
     While rectangular or square manholes have been illustrated in the disclosure herein, it will be understood that other shapes of manholes will function as a dam for the water flowing in the aggregate of the sewer trench. The manhole may be of single unit or multi unit construction. 
     While other methods of providing obstructions to the water flow in the sewer trench aggregate will appear as obvious substitutions for applicant&#39;s “dam manholes ” applicant wishes to limit the scope of protection by the following claims.