Patent Publication Number: US-4921115-A

Title: Method and system for secondary containment

Description:
This is a continuation of copending application Ser. No. 07/182,342 filed on Apr. 18, 1988 now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. FIELD OF THE INVENTION 
     The present invention relates to systems and methods for providing secondary containment for petroleum dispensing apparatus and particularly to fiberglass containers used for containment when leaks occur in such apparatus. 
     2. PRIOR ART 
     The increased awareness of potential groundwater contamination from petroleum products and the regulations to deal with the issue has resulted in a number of methods and apparatus for prevention or reduction of such contamination. 
     Presently, there are two principal methods and several products for the reduction of contamination caused by leaks used in and around petroleum storage tanks and dispensing islands and gas stations. The first method involves the use of double wall piping. This method is excellent for containing leaks associated with product pipes, but the double wall protection terminates just below the dispensing unit and does not afford protection to the ground lying directly beneath the dispensing units. 
     The second method for the reduction of contamination caused by leaks utilizes containment systems. This method involved placing large petroleum-resistant plastic liners under storage tanks and around the base of pumps and piping at dispensing islands. While this system is adequate, the methods and products involve custom manufacturing and custom installation at the site. The materials are also very costly, cumbersome and awkward to use. 
     What is most desired in secondary containment is a method and system that provides adequate containment and can be used with any type piping, whether steel or fiberglass. The apparatus should be usable with any dispensing islands and be compatible with any other secondary containment. The apparatus should also lend itself to mass production to minimize the cost. 
     The present invention utilizes a fiberglass container as a reservoir for the collection of leaked petroleum products. The container is mounted underneath a pump or other outlet to be installed on a dispensing island. A container has an outwardly extending flange integral to the perimeter of the upwardly facing open top. Four vertical sides extend downward and are integral with a horizontal bottom. 
     The container according to this invention is positioned vertically on the excavated area partially back filled after the installation of the main storage tanks used in the system. Backfill is installed to a level spacedly below the flange after the necessary field connections for the supply line and pump power are provided therethrough. The upper surface of the back fill is then covered with concrete after the installation of a temporary cover over the container to prevent concrete from flowing thereinto. The cover is removed prior to the connections being made to the specific dispensing apparatus that will be used. The particular system and method used in accord with this invention offers substantial advantages in cost and efficiencies over the prior art. This is especially true when it is necessary to retrofit existing storage and dispensing facilities. The ease of use of a single container connected with a concrete surface as compared to fabric that is custom-cut, sealed and installed is self-evident. 
     SUMMARY OF THE INVENTION 
     This invention relates to methods and systems for providing leak containment for petroleum dispensing apparatus which is mounted to a foundation slab which includes an elongated rigid container having an open top portion positioned within the foundation and beneath the dispensing apparatus. The container has at least one vertical side wall contiguous with the top portion and an oppositely disposed bottom portion integral with the side wall. The top portion has a generally horizontal outwardly extending flange for securing the container to the foundation slab. A first depth of soil is provided beneath the foundation slab which has an upper surface onto which the bottom portion of the container rests. A second depth of soil has an upper surface and is provided above the upper surface of the first depth of soil. The foundation slab is made of concrete formed on the upper surface of the second depth of soil with the container being substantially located in the second depth of soil with its side wall being laterally supported thereby and the flange being embedded permanently within the concrete slab. The concrete slab has an opening generally vertically therethrough aligned above the open top of the container for allowing petroleum that leaks from the apparatus to flow into the container and to be retained therein. The flange of the container is positioned generally in the midplane of the concrete slab and the open top portion is closed with a removable covering when the concrete slab is being poured and formed. 
     The system also has a covering means for closing the open top portion when the concrete slab is being poured and formed, the covering means having a removable center portion and peripheral portion permanently positioned on the upper surface of the flange and affixed in the concrete slab. Normally, the removable center portion is slightly larger in size to accommodate a downwardly directed sleeve portion of the dispensing apparatus. The container is adapted to receive at least one conduit through an opening in the side wall for supplying petroleum to the dispensing apparatus and includes sealing means for providing a leak-proof seal between the side wall and outwardly of the conduit. Likewise, an electrical conduit is suitably sealed through the side wall of the container. 
     In one aspect of the invention a method is provided for leak containment for the petroleum dispensing apparatus mounted on a concrete slab foundation and having a petroleum inlet supply conduit is seen to have the following steps: positioning a rigid petroleum impervious container having a flange at its upper end beneath the dispensing apparatus; sealing the inlet supply conduit to and through a side wall of the container; and embedding the flange of the container generally medially of the thickness of the concrete slab foundation. 
     The inside of the container is protected during the pouring of concrete using the following steps: positioning a cover over the top of the container during the pouring and forming of the concrete slab; and removing at least a central portion of the cover from the top of the container when the concrete slab has sufficiently set so that access to the inside of the container is obtained through the concrete slab. 
     In another aspect the method includes a foundation having a first depth of soil, a second depth of soil placed on the first depth and a concrete slab formed on the second depth wherein the following steps are employed: positioning a container with an outwardly extending flange adjacent its open top end portion with its closed bottom on the surface of the first depth of soil beneath the prospective position of the petroleum dispensing apparatus; filling the second depth with soil on the first depth of soil to a height spaced closely below the flange in a manner to surround and provide lateral support for the wall of the container; positioning a cover over the top of the container; pouring and forming the concrete slab in a manner to embed the flange generally vertically medially in the concrete slab; and removing at least a generally central part of the cover from the top of the container to provide access through the slab into the container. The method may include the steps of: placing a removable form on the top surface of the cover generally centrally thereof; and removing the removable form. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a sectional view of the containment system in accord with this invention as it appears at an intermediate point in its installation; 
     FIG. 2 is a top view of the container shown in FIG. 1; 
     FIG. 3 is a sectional view of the system after installation of the housing for the petroleum dispensing apparatus; 
     FIG. 4 is a pictorial view of the system associated with an installed dispensing island; and 
     FIG. 5 is a partial detail in cross section of the sealing technique used at the point where a supply pipe passes through the sidewall of a container in accord with this invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, the system for secondary containment is generally designated at 10 in FIG. 1. A rigid fiberglass or plastic container 11 resistant to petroleum includes an outwardly extending flange 12 around the perimeter and vertical side walls 13 which are integral to a flat bottom portion 14, as shown in FIG. 1 and 2. The container 11 rests on the surface 19 of foundation 18, which is a depth of soil covering petroleum supply tanks such as those used in gas stations and similar applications. During installation, holes 16 and 17 are cut out of the container 11 at points that will be specific to the particular tank type and arrangement being used. 
     The container 11 has an open top portion 12a sized to accommodate a wide variety of dispensing pumps and associated apparatus as will be described herein below. FIG. 2 illustrates the preferred form thereof of a substantially rectangular shape, but may be of any other appropriate shape and size, but should have a capacity of 20-40 gallons. The container 11 is positioned on surface 19 of foundation 18 and suitable piping and electrical conduits are sealed through the side walls of the container. Thereafter a second depth of soil 20 is added to surround and laterally support the container 11 to a height spacedly below the flange 12 as indicated by surface 21. A removable cover 24, typically of corrugated fiberboard or the like, is placed over the open top 12a to the edge 15 of container flange 12. A concrete slab 22 is formed on the surface 21, preferably 21/2 inches above and below the flange 12 and extending inwardly onto the cover 24 a distance based upon the particular pump that will be used. A wooden knock-out panel 25 is placed on the cover 24 to allow for dispensing station housing 26, as will be discussed hereinbelow. Field connections for petroleum supply conduit 27 with cap 28 and electrical conduit 29 with cap 30 have been done including leak proof sealing around the conduits in a conventional manner. The conduits 27 and 29 are accessible via knockout panel 25 to be connected to the dispensers to be attached to slab 22. 
     After the concrete slab 22 has been formed and set, panel 25 is removed and removable panel 24 is cut away to the edge 31 that is in vertical alignment with the formed concrete surface 32. In the preferred embodiment of the system according to the invention, the remaining material 24a of the cover 24 is left in place, as illustrated in FIG. 4, but may be partially removed if desired. 
     A pump or dispenser housing 26 is placed on the upper surface 23 of the concrete slab 22 with an integral downwardly extending annular sleeve 33 extending to at least the lower edge 31 of the removable cover material that remains in the secondary containment system. Conduits 27 and 29 are pulled upwardly and will be secured to the pump (not shown) placed within housing 26. The size of the panel 25 to be employed in making the hole 32 in the concrete slab 22 is based upon the exterior dimensions of the sleeve 33 of the particular housing 26. 
     The container 11 is thus positioned as an enclosed reservoir which acts as an extension of the pump housing 26, providing containment of liquid which may be leaked from the dispensing apparatus container therewithin. The containment system according to the invention is thus easily and quickly installed with a minimum number of parts. In addition, the use of rigid containers 11 eliminates the rips and tears commonly associated with fabric liners. 
     FIG. 4 pictorially illustrates the containment system installed at a dispensing island having two pump housings 26 and 26a, receiving supply lines 16, 16&#39; respectively, two containers 11, 11a mounted beneath the pump housing 26, 26a, and the electrical connections not being shown for ease of illustration. 
     Conventional monitoring systems for detecting the presence of liquid in container 11 and means to pump the liquid therefrom may be installed either through one of the walls 13 of the container or routed via the pump housing sleeve 33 as dictated by the circumstances. 
     FIG. 5 illustrates a preferred method of sealing around the conduits 27, 29 at the point they pass through side wall 13 of the container. A hole 16 is cut out and a conduit such as 27 is pulled through. Fiberglass patches 16a, 17a are then applied to provide a leak proof seal. 
     As known to persons skilled in the art, conduit 27 may be an approved stainless steel flexible connector or, if rigid piping is employed, a three-dimensional swing joint (not shown) may be used conforming to N.F.P.A.--30 &amp; 31. Construction and safety codes of various governmental entities must be followed, as commonly known, in initially constructing and/or retrofitting a petroleum station island with the leak containment system in accord with the disclosed invention. 
     While the invention has been described with respect to a certain specific embodiment, it will be appreciated that many modifications and changes may be made by those skilled in the art without departing from the spirit of the invention. It is intended, therefore, by the appended claims to cover all such modifications and changes as fall within the true spirit and scope of the invention.