Method and device for a flexible liner for a cementitious vault wall

The present invention is method and resulting assembly for applying a flexible liner to a cementitious vault wall, wherein several forms are described for attachment of the liner to flowable and fully cured cementitious vault walls.

BACKGROUND OF THE INVENTION
 The present invention relates to flexible liners for septic tanks,
 especially in a retrofit application. It is an object of the present
 invention to provide apparatus designed to facilitate the production of
 hollow cast articles such as septic tanks and concrete vaults, to
 facilitate separation between a carting and the forms used in making the
 casting, and to expedite the entire casting operation.
 The prior art is filled with references to flexible tank liners and
 adaptations to fill and drain conduits, as well as upper and side support
 devices for the sidewalls. One example of a drain tank liner is shown in
 U.S. Pat. No. 5,656,766. A flexible liner forms a gas tight seal about the
 walls of an underground concrete vault. A concrete lid pressing on a
 circumferential flap at the top rectangular edge of the flexible liner
 provides support for the liner, such that the liner does not "slump" into
 the concrete vault and allow liquid to fill a space between the inner
 concrete wall and to outer surface of the flexible liner. It is especially
 important to note that the art in this patent recognizes that some
 adaptation is important for existing inlet pipes entering the concrete
 vault at a sidewall. A gasketed set of bolted plates seals the transition
 of a pipe entering the concrete vessel and passing into the flexible
 liner. The relatively heavy construction is the result of the
 impermissibility of leakage from the inside of the liner into the space
 between the liner and the concrete wall. U.S. Pat. No.5,656,766 thus
 illustrates several advantages and problems of flexible tank liners.
 Support and sidewall inlet pipe transitions are shown adapted to the
 special application of that patent, i.e., drainage pits primarily for the
 petroleum industry. An adaptation combining support and pipe/liner
 transition is seen in U.S. Pat. No. 4,653,663, wherein a rigid plate
 supporting the outside surface of the flexible is combined in opposition
 with an elastomeric plate on the inside surface of that liner.
 Although not used to line storage tanks, the flexible liner of U.S. Pat.
 No. 4,388,357 shows that strips of liner stock can be fabricated on site
 to form a protective barrier against soil Regular Patent Application
 contamination by spilled oil, such as occurs at railroad tank car
 accidents in remote areas. The bottom of the fabricated flexible liner
 comprises a fabric screened drain so that the oil can be recovered for
 commercial use when the oil is withdrawn from the flexible liner. It would
 be especially useful to adapt flexible tank liner devices so that they
 could be used in situ, whereby none or relatively little of liquid in an
 existing storage tank would need to be removed. This is generally not
 practical in the art of lining tanks with flexible liners, i.e., the
 liquid is usually leaking into the environment outside of the tank or is
 further corroding the tank and destroying the support provided by the
 rigid tank walls.
 U.S. Pat. No. 2,807,071 describes, and such description is incorporated
 herein, a casting apparatus comprising an inner form, a cover plate
 resting upon the inner form with respect to which file upper edges of the
 inner form are slidable, and means secured to the cover plate providing
 for limited upward movement thereof to facilitate separation between the
 cover plate and a completed-casting, with special application to casket
 vaults and extendible vaults, such extension being provided by stacking of
 a second or higher section above the base device described in that patent.
 The stacked piece is adapted to securingly mate with the piece beneath it,
 i.e., the cast article of U.S. Pat. No. 2,807,071 when formed comprises an
 upper inset rim which will accommodate a stacked section above it.
 U.S. Pat. No. 3,990,673 describes the apparatus and method for casting
 concrete septic tanks, burial vaults and the like including an inner form
 and an outer form. The formation of concrete septic tanks burial vaults
 and other such structures generally contemplates the casting thereof in a
 "form". The form usually comprises an inner form and an outer form spaced
 apart from the inner form and into which the casting material, e.g.
 concrete, is poured. The outer form is usually a disassembleable rigid
 structure. The inner form comprises a rigid or expandable and collapsible
 side walls and end walls. The inner form also includes a top wall or cover
 plate which mates with the edges of the walls. The method of forming the
 cast article is basically providing a hollow inner form over which to pour
 concrete while also providing an outer form to force the concrete to be
 maintained against the inner form until the concrete hardens and the forms
 can be removed. The construction of concrete burial vaults is a very time
 consuming and labor intensive operation. The operation generally
 consisting of first constructing an inner form having a side wall and
 bottom wall configuration identical to the interior surfaces of the side
 wall and bottom wall of the vault to be formed. The inner form is then
 mounted a pallet or other flat base surface with the bottom wall of the
 inner form positioned for upwardly. An outer form consisting of four side
 walls having a configuration identical to the outer side wall
 configuration of a vault to be formed was assembled, i.e., typically
 pivotally hinged at a lower edge of the outer form, around the inner form.
 The form surfaces in contact with the concrete are next oiled. It is next
 conventional to suspend a wire mesh, "rebar" (reinforcing steel rods) or
 the like into the cavity formed by the inner form and the outer form to
 provide additional strength to concrete poured into the cavity. The form
 cavity is next filled with concrete and vibrated to remove voids and to
 fill the lower sections of the form cavity.
 SUMMARY OF THE INVENTION
 The present invention comprises devices and methods for supplying a
 flexible liner for septic tanks and for retrofitting existing, leaking
 septic tanks with such flexible liners.
 Metal septic tanks are usually welded along an seam formed from the
 intersection of an axially symmetrical plane with the cylindrical or
 rectangular shell. Thus, the weld runs down the side of the septic tank,
 along the bottom of the tank and up its opposite side. It is an almost
 universal fault the septic tanks leak along this seam within their
 "useful" lives, that is, useful in terms of support, not containment.
 Although in the past such leakage was generally permissible, current
 regulation, especially among the rural districts of the eastern states of
 the United States, undigested sewage leaking into the ground immediately
 next to the septic tank accelerates the rate of corrosion of the tank and
 unacceptably contaminates the ground water with material having biological
 oxygen demand that facilities bacterial blooms. The design of septic tanks
 requires that the sewage remain in the tank for a treatment period so that
 the BOD and COD is reduced to an acceptable level. Metal septic tank
 replacement is wasteful since much of the support function of the septic
 tank is still available, although unacceptable leakage may have occurred.
 Some septic tanks have concrete side walls and floors. Liquid sewage
 containment with concrete makes it certain that crack and fissure
 propagation via earth shifting and chemical attack will eventually result
 in unacceptable leakage as for the metal septic tanks. Repair is typically
 the only reasonable solution, although repair materials are sometimes as
 hazardous as the leaking sewage. Various patching materials are identified
 under federal regulations as hazardous if released into the groundwater.
 The eventual further cracking of the concrete septic tanks mean that both
 untreated sewage and the patching material may escape later on into the
 ground water.
 One embodiment of the present invention comprises a flexible polymer liner
 of relatively heavy gauge polyurethane, vinyl, fiber-reinforced
 polyethylene, ultrahigh molecular weight polyethylene, or the like or
 layered composites thereof with relatively few rf-welded seams.
 Preferably, a single, uninterrupted sheet of flexible lining material
 forms a floor cover, being then sealingly connected to one or more
 sidewall sheets. The sidewall sheets preferably extend in a single sheet
 from the top of the septic tank to the floor sheet, thereby having
 vertical seams. Vertical seams are less subject to separation from the
 downward pull of gravity than similar horizontal seams. The lining body of
 the flexible liner thus "effectively" seals a polygonal or round vertical
 in-ground septic tank against leakage. It will be appreciated that
 absolute prevention of leakage of untreated is preferred but not
 completely unacceptable. In other tank lining applications with flexible
 liners, the object of the device is complete sealing of the liquid within
 the vessel. For septic tanks, some small amount of leakage could be
 acceptable. Thus, crack propagation in concrete or metal septic tanks
 means that every leak must be repaired or it will get worse. With the
 flexible liner of the present invention, a seam leak is unlikely to become
 larger due to corrosion. A seam leak will likely remain small since little
 liquid motion is experienced by the flexible liner. Thus, the requirements
 for fabrication of the lining body and inlet and outlet pipe/liner
 connections are surprisingly less stringent than those of prior art
 flexible liners.
 Most septic tanks are concrete, although some are currently made with at
 least fiberglass floors and sidewalls. Patching a leak in a fiberglass
 septic tank can be challenging. The location of the crack and/or fracture
 or fiber separation area may be difficult to make sufficiently clean or
 dry to patch with commonly available materials.
 It is heretofore unknown that a retrofit of an existing septic tank could
 be accomplished for such low cost with a flexible liner. It has been
 unappreciated that, for design purposes, the septic tank remains full all
 the time with almost unmeasurable liquid flow movement against the
 sidewalls or floor. The design requirements are thus dramatically reduced
 with consideration of that freedom from absolute sealing, turbulence or
 liquid level changes.
 A lining body may be used for sidewall sealing with a relatively rigid or
 reinforced flexible material and still comprise low cost polymer material.
 Such support is an alternate embodiment to enhance the ease of initial
 installation and later drainage.
 Another embodiment of the present invention comprises a collar at the top
 edge of the lining body with flotation means circumferentially and
 sealingly attached to that top edge. In one form, the lining body flexible
 material is extended upward, over and around inexpensive flotation
 material such as styrofoam, thereafter sealing the top edge of the
 flexible material to an inner or outer surface of the lining body to form
 a collar pocket. This collar pocket contains sufficient flotation material
 to keep the upper most surface of the lining body above the liquid (and
 preferably foam) level in the septic tank. The problem of support of the
 lining body is thus solved without attachment to the septic tank support
 (i.e., the concrete or metal shell). With little or no variation in liquid
 level and little liquid turbulence, the flotation collar pocket material
 is not subject to abrasion against the inside walls of the septic tank
 support, thus maintaining an effective air pocket which may alone act as
 flotation means for the lining body.
 It is another embodiment of the present invention to provide inlet and
 outlet pipe/liner transition taking advantage again of the small change in
 liquid level and low liquid turbulence. In its simplest form, the lining
 body may have cut into it an "X" or "Y" opening, whereby the inlet and
 outlet "T" pipes may pass through and be "effectively" sealed against
 unacceptable levels of leakage with a simple metal or plastic band or
 collar. It is anticipated that this seal would have to withstand no more
 than about 1-2 psig of pressure with little liquid level change or liquid
 turbulence. Although the prior art teaches relatively heavy duty devices
 to accomplish this inlet and outlet pipe/liner transition, those prior art
 devices are directed to non-quiescent tanks. It is an inventive step to
 have realized that a much less expensive flexible liner could be made and
 installed than those of the prior art.
 With enabling reference to U.S. Pat. No. 4,388,357, it will be seen that
 perfect sealing against the environment may not be necessary or economic.
 Similarly, the present invention also comprises installing a retrofit of
 one of the embodiments of the flexible liner above into an existing septic
 tank. Typically, septic tank repair requires complete evacuation and
 cleaning of the septic tank support structure, i.e., with compressed water
 spraying and additional evacuation. Cleaning of the septic tank will not
 be absolutely necessary with installation of the present flexible liner.
 The corrosion that caused leakage in the original concrete or metal shell
 rarely affects the structural support of the shell against the earth
 surrounding it. In fact, sometimes removing the corrosion products from
 that shell by water spraying may weaken the compressed earth/shell
 structure so that the shell must be replaced.
 In yet another retrofit application, it will be possible to effectively
 tightly fold and compress the lining body of the flexible liner into a
 small package which can be submerged into a filled or partially evacuated
 septic tank. The lining body may be equipped in inflation cuffs, tubes or
 pockets that, upon inflation by an air pump above ground, will flow the
 appropriate portions of the lining body into relatively close association
 with the floor and sidewalls, thereafter moving to the liquid surface the
 upper edge of the lining body for securing at the top edge of the septic
 tank shell and adaptation for insertion of the inlet and outlet pipes. The
 sewage remaining between the flexible liner and the septic tank shell
 comprises a measurable but acceptable corrosion risk against the
 structural support shell supporting the flexible liner. Other means of
 drawing a folded lining body against the appropriate sections of the
 septic tank shell include using rigid manipulation poles or the like to
 grasp and position the lining body next to the sidewalls of a full or
 partially filled septic tank.
 In yet another installation method, the flexible liner may be placed on the
 floor of an evacuated septic tank, the main portion of the flexible liner
 arranged so that it is loosely arranged about a deflated inflatable and
 flexible balloon enclosure. This balloon enclosure will have an inflated
 volume and shape of about the same as or slightly larger than that of the
 evacuated septic tank. When the balloon enclosure is inflated, the
 flexible liner is also expanded across the floor and toward the sidewalls
 of the septic tank. The flexible liner is loosely secured around the
 balloon enclosure so that the top edge of the flexible liner is forced
 slowly upward to the top edge of the septic tank sidewall, eliminating
 manual spreading and lifting in installation of the flexible liner. Loose
 temporary securing means for the flexible liner about the balloon
 enclosure comprise elastic straps or ties that can be easily removed as
 installation aids.
 The present invention is applicable to the septic tank type known as
 "tight" tanks, which are not permitted any leaching emission, but must be
 evacuated periodically to remove accumulated sewage. The sort of
 evacuation means available in the above cited prior art may be applied to
 as evacuation means for the present invention.
 The lining body of the flexible liner may be enclosed by forming a sealing
 seam between a top closure piece and the top edge of the lining body. The
 top closure piece is preferably not gas tight to the environment, since
 some gas generation is typical of sewage digestion. However, a continuous
 "zip-loc" or other similar closure for the top closure piece may be used
 to achieve gas tight closure if such gaseous emissions are a nuisance. A
 discharge pipe is preferably sealingly attached to the gas-tight top
 closure piece to conduct away nuisance or hazardous gases for passage
 through effective cleaning means such as an activated carbon bed or
 regenerable zeolite bed.
 It is a further embodiment of the present invention to provide apparatus
 and a method for applying a flexible and inexpensive liner to the inside
 surface of a concrete vault in the concrete casting operation of such a
 septic tank, casket vault, electrical component containment vault or other
 concrete vault whereby sufficient liner adhesion and/or attachment to the
 inside walls of the concrete vault is achieved such that a liquid
 impermeable seal is provided and the flexible liner will remain
 effectively attached to the inside wall of the concrete vault during
 normal usage of the concrete vault. Clearly, the several uses of concrete
 vaults will instruct the skilled person to choose among the several
 methods of securing adhesion and/or attachment of the liner described
 herein. Some of the apparatus and methods described below comprise mainly
 adhesion of the drying concrete to the smooth or preferably embossed
 flexible liner while a non-removable liner is obtained with extension of
 the liner by seam extension or extension attachment into the wet concrete
 and permitting the concrete to dry about the extension. It is well known
 that very stiff plastic lugs secured to a stiff plastic base plate will be
 effectively projected into wet concrete for drying securement therein if
 sufficient force is maintained to keep the lugs in the wet concrete. It is
 novel that flexible liner material attached to a flexible base material
 will be effectively projected into wet concrete for drying securement
 therein.

DETAILED DESCRIPTION OF THE INVENTION
 The invention is now discussed with reference to the Diagrams. It is seen
 in Diagram 1 that an existing concrete tank 1400 is enclosed on its inner
 surface with a rigid liner 1401, as described above. In the detail
 drawing, it will be seen that a series of plastic clips 1400' along the
 upper edge of the rigid liner 1400 holds it in place. The plastic clips
 1400' are exemplary of a class of securing devices such as bolting plates,
 and the like, although the buoyant effect of the relatively constant
 liquid fill of a septic tank reduces the ultimate design requirements of
 that securing means. Also in the detail drawing of Diagram 1, it will be
 seen that an "X" incision 1402 has been made in the liner 1401 to permit
 passage of the inlet or outlet "T" pipe 1404, 1407 or 1408 through it. A
 simple and inexpensive plastic or metal adjustable band 1403 is preferred
 to seal the liner 1401 to the pipe circumference.
 "With reference to Diagram 2, it will be seen that the liquid fill of the
 septic tank 1400 compresses the liner 1401 against the floor and sidewalls
 1406 of the existing concrete structure. It is apparent from common design
 of septic tank depth that the highest pressure against the liner is at the
 bottom of the septic tank, i.e., about 9 psig. With a quiescent tank of
 liquid the design and fabrication of the flexible liner 1401 is greatly
 reduced in price. "Also in Diagram 2, the flotation collar 1405 comprises
 a simple overlap of flexible material from the lining body, such that the
 gas-tight enclosure may be inflatable or comprise additional flotation
 material such as inexpensive styrofoam. The use of styrofoam may eliminate
 the need for a gas-tight enclosure, such that only broad loops or separate
 pockets flotation material are needed at short intervals all along the
 upper edge. It will be clear from this disclosure that the flotation
 collar 1405 may be combined with the top edge securing means of Diagram 1
 to obtain an advantage in installation or cost."
 The above design disclosures present the skilled person with considerable
 and wide ranges from which to choose appropriate obvious modifications for
 the above examples.
 However, the objects of the present invention will still be obtained by the
 skilled person applying such design disclosures in an appropriate manner.
 The invention is now discussed with reference to FIGS. 3-12 and the
 application of a flexible liner at the casting operation of a concrete
 vault. A typical casting operation is now described for reference for
 application thereto of the flexible liner of the present invention. The
 apparatus illustrated in FIG. 3 shows a suspended flowable concrete volume
 in container 71 with releaseable walls 74, which flowable concrete is to
 be released in direction 300 to flow over inner form top outer surface 308
 in directions 301 to fill the form cavity, i.e., only after side walls 72
 are brought into a secured upright position to contain the flowing
 concrete. The inner and outer forms are described for reference for later
 location of the flexible liner of the present invention relative to them
 during a casting operation.
 Top corner 302 is formed by the meeting of top edges 303 and side edge 304.
 Side walls 72 have a height 305 and width 306 and an outer surface 310 and
 inner surface 309, the mating of edges 311 in the upright position causing
 the formation of an outer side edge of the concrete vault. FIG. 4 shows
 the result of forming a concrete vault on the inner form and pivotally
 opening the side walls 72 for removal of the vault after the concrete is
 sufficiently set to remove it. Vault top outer surface 308" forms what
 will be the bottom of the vault when the vault is inverted for use. Top
 vault corner 302" generally corresponds to the meeting of top outer vault
 edges 303' and side outer edges 304".
 FIG. 5 generally shows a cross section of the assembly of FIG. 4 with some
 adaptations to form a stackable vault base, i.e., the molded multi-level
 rim 317 as shown in
 FIG. 7A and the rectangular form more generally associated with burial
 vaults. Form edge 303 mates with inner vault edge 303', whereby the
 concrete vault extends to outer vault edge 303". Inner form side 307 is
 adjacent to inner vault side 307', whereby the concrete vault extends to
 outer vault side 307', which is adjacent to the inner side of the outer
 form side wall 309. Inner form top 308 is adjacent to inner vault top
 308', whereby the concrete vault extends to outer vault top 308". Side
 wall concrete 311 is continuous with top section concrete 312. Pivot 20
 provides hinging to support 18 so that the side walls may be opened
 outwardly for removal of the vault, as shown in FIG. 6. Support 22 is
 generally an angle iron reinforcement for the side walls.
 It is intended that a flexible liner be applied to the inner form before
 pouring of the concrete into the form cavity such that the liner sealingly
 covers at least all of top 308'and is continuous downward (with reference
 to FIG. 5) from edge 303' to a desired effective distance all about the
 circumference of side 307' to form a liquid tight seal between the bottom
 section of a concrete vault and the liquid to be held within in it or to
 be restricted from entering it. Liner materials comprise those typically
 used in waterbed construction, for pool or pond liners and the like, but
 especially favored are the non-reinforced vinyls with acid and chloride
 resistance with about 30 mil thickness. It is a critical requirement that
 liner material be flexible and foldable under conditions of application to
 the inner form of the concrete vault mold. The prior art has failed to
 appreciate that application of a flexible liner may be made to an inner
 form of the devices shown in FIGS. 3-7 causing effective securement to the
 inner side thereof. It is well known that an essential step in casting of
 vaults is the substantial vibrating of the inner and outer forms to remove
 voids and trapped air. It appears that the skilled person has been led
 away from using a flexible liner on the inner form during the casting
 operation for fear of tears and insufficient adhesion or attachment.
 The present invention describes actual examples wherein the liner has been
 successfully installed on relatively large septic tank molds, obtaining
 thereby adhesion and attachment by the construction and method of
 application. The invention is now described in more specific detail with
 reference to FIG. 7. Liner 400 extends from an edge 401 to rim sections
 402 and 403, and therefrom to sidewall section 404, edge 405, top section
 406, edge 407 and downward along the side of the inner form duplicating
 the other edge 401 to rim sections 401 and 402, and therefrom to sidewall
 section 404. It should be understood from this FIG. 7 that this embodiment
 of the liner is sealingly continuous from one edge to another, forming a
 liquid tight barrier between the inner form and the concrete to be poured
 into the form cavity. In the form cavity are seen radial cross sections of
 rebar 409, which are suspended within the form cavity to provide
 reinforcement to the concrete vault after the concrete has hardened. In
 one optional embodiment of the present invention, rebar loop securements
 408 are RF welded, heat sealed or otherwise adhered to the surface of
 liner 400 in appropriate locations such that when the rebar is inserted in
 the form cavity, the rebar is also passed through the securements 408.
 In another embodiment of the present invention, threaded hose connections
 410 are provided in surface 406 and adapted such that a vacuum adapted
 hoses or pipes 411 are connected to the connections 410 to remove air
 trapped between liner 400 and the inner form. Such threaded hose
 connections are well known in the waterbed industry.
 The method of forming a concrete vault with the embodiment of FIG. 7 is now
 discussed. Reference is made to the three concrete fill levels 313-315 in
 FIG. 5 and directions 301 in FIG. 1, which are important to the just
 mentioned method. When concrete is flowed over the surface of the liner
 covering top 308 in FIG. 7, the concrete flows in directions 301 to the
 side form cavities and begins to fill the side form cavities to level 313.
 At that point, an effective air tight seal is made around the bottom
 periphery of the side form cavities. Thus, as concrete fills from level
 313 to 314, substantial air typically accumulates between top 308 and the
 inside surface of the liner 400, causing the surface 406 to take on the
 cross section appearance shown in lifted surface 406'. The means for
 removal of the trapped air are usually needed even if concrete is filled
 to level 315, as the weight of the concrete on the flexible surface is
 insufficient to push the trapped air out. Connections 410 and pipes 411
 permit removal of the trapped air, whereby thereafter the connections 410
 are disconnected from pipes 411 and capped in a conventional liquid
 sealing manner. Alternatively, the surface 308 may be simple provided with
 holes therethrough to allow escape of the trapped air or vacuum-assisted
 draw conduits may be established to more forcibly remove trapped air from
 underneath the flowed concrete instead of from above, as shown in FIG. 7.
 During the concrete filling operation, concrete easily fills the
 securements 408 an irremovably secures the liner to the side and bottom
 walls of the vault upon hardening of the concrete. Such filling later
 described in more detail with reference to the Figures.
 Upon sufficient curing of the filled concrete, the side walls are opened
 and the vault removed, which removal is now more easily achieved since the
 liner surface slips smoothly from the oiled metal surface more easily than
 the dried concrete as in the prior art.
 With reference to FIG. 7A, other embodiments of the present invention are
 described. As described above, concrete vaults may be increased in height
 with application of stacked sections. The embodiment of FIG. 7A provides a
 means and method for applying the liner 400' to the full height of the
 stackable concrete vaults. The surface 404' FA[CE] extends from an edge
 405 to a lowest edge 404' FO[LD], at which point the liner continues
 sealingly to another section 404' EX[TENSION] to the edge 404' ED[GE]. The
 cross section shown in FIG. 7A is indicative of rest of the liner
 periphery about the inner form. Upon removal of the vault from the inner
 form and subsequent stacking of the next vault section upon rim 317, the
 section 404' EX[TENSION] is unfolded upwardly and secured as described
 above for retrofit application to provide a liquid tight seal for the
 entire inner surface of the stacked vault. "Additionally, in FIG. 7A are
 shown a seam extension 405 BO[TTOM] with separate material section
 extensions 405E, extending upward from the sealing seam 405D, which
 sealing may be preferably achieved with RF welding, but may also be
 produced with heat or adhesive sealing in some applications. The following
 description of the Figures further develops the concept and application of
 extensions to the outer surface of liner 400 to extend into the flowed
 concrete during the casting operation to achieve effective securement of
 the liner to the inner side and bottom walls of the vault."
 FIG. 8 shows rebar loop securement 408 with a section of rebar 409, loop
 408A and base piece 408B, which is preferably RF welded or otherwise
 adhered to the outer surface of liner 400 in a location which, when the
 liner is applied to the inner form, will accommodate passage of the rebar
 through it in the normal course of setting the rebar in place for the
 casting operation. During the casting operation, concrete flows into the
 loop 408A in directions 408C, the concrete remaining therein during
 hardening and providing a non-removable attachment of the liner 400 to the
 inner surface of the vault.
 FIG. 8A shows a preferable but optional support piece 316 for rebar 409.
 Piece 316 in a specific example was adapted to hold the rebar about 1.5
 inches from top 308, providing a rounded surface 316A to contact liner
 400. Piece 316 comprised a low cost rigid plastic piece about 3 inches in
 height with a snap-in top section for rebar, the thickness of piece 316
 being about 0.5 inches. Piece 316 applied near or between securements 408
 force the rebar away from the inner form, drawing the securements 408 into
 the flowing concrete in the casting operation, whereby piece 316 becomes
 part of the cast vault, although its rounded contact with liner 400
 provides only limited opportunity for later leaking through the cast
 passage if liner 400 fails.
 FIG. 9 presents an edge seam, such as for application to the top or side
 edges described above for the inner form. Providing extensions from the
 liner at these junctures provides an opportunity to use to stretching
 effect of the adjacent pieces of material to cause an extending
 presentation of excess material used in a seam wherein the inner faces of
 the adjacent pieces of material are joined, preferably by RF welding. In a
 specific example, adjacent materials 405A and 405B, about 30 mil vinyl
 sheets, have their inner surfaces (such as 405C) joined by RF welding at
 seam 405D, intentionally designing the fabrication process such that
 excess material extensions 405E and 405F, along with seam 405D material,
 results in a extension height 405H of the assembly. This extension height
 405H will be effectively projected into the flowing concrete 405G, forming
 an irremovable attachment of the liner with the inner edge of the vault.
 Extension height 405H has been found to be effective for the objects of
 the present invention at over 2 inches with 30 mil vinyl sheeting which
 has been RF welded to form a liquid tight seal. FIGS. 10 and 11, liner
 extensions adapted to apply to the flat surfaces of the inner form instead
 of at the edges, show a similar embodiment of seam extension as that of
 FIG. 9 although the similarly named aspects are different in the following
 manner. Adjacent pieces 405A' and 405B' of FIG. 10 and adjacent pieces
 405A" and 405B" of FIG. 11 extend generally in the same plane above an
 outer surface of the inner form. The effective extension height 405H is
 generally about the same as that of the assembly of FIG. 9. FIG. 11 is
 intended not to be a liner seam, but instead an effectively adherable
 strip which is independently applied at any outer surface of the liner,
 thereby providing freedom to form concrete-intrusible extensions at any
 point at which the flowably concrete contacts the liner applied to the
 inner form
 The assembly of FIG. 11 comprises a further adaptation applicable to the
 seam extensions of FIGS. 9 and 10. Holes 405H" and 405J" are made in
 extensions 405E" and 405F" respectively, thereby permitting concrete flows
 405G" therethrough. It has been found that this provision of offset or
 corresponding orientation holes in the material extensions produces an
 attachment with surprisingly superior strength over the same type of
 extensions without such holes. In another embodiment of the present
 invention as shown in FIG. 12, a reinforcing strip 405K' may be sealingly
 welded or bonded into seam 405D', thereby improving the attachment of the
 liner to the cast vault inner surface.
 It has been found that a liner 400 without securements or extensions as
 described above may effectively attach to the inner surface of a cast
 vault in the method described above upon providing sufficient excess
 material such that the width and/or length of the liner is about over 0.5
 inches greater than the respective width and/or length of the outer
 surface of the inner form to which the liner is applied. The excess width
 and/or length has surprisingly been compressed by the filling concrete and
 found to be drawn into a creased intrusion into the hardened concrete,
 forming an effective attachment of the liner to the inner vault surface.
 As little as 1/8th of an inch intrusion provides liner detachment
 resistance of about 10-15 pounds of force. Intrusions of over 0.25 inches
 occur that are very difficult to detach or are irremovable without tearing
 the liner. Embossment of the outer surface of the liner with some
 irregularities over a smooth surface will provide adhesion enhancement
 without other attachment means.
 FIG. 7B shows a generalized liner 400 with seam and strip extensions
 applied to provide reference for advantageous placement therefor. Liner
 400 of FIG. 7B appears as it would in place covering an inner form of a
 casting assembly. The flexible nature of the materials of construction are
 critical to ease of manufacture, transportation and application of the
 liner to the inner form. A rigid liner material loses all the above
 advantages. Extensions 405 SI[DE] form welded extensions that will extend
 into the inner side edges of the vault. Extension 405 BO[TTOM] forms
 welded extensions that will extend into the inner bottom edges of the
 vault. Extension 405' BO[TTOM] forms welded extensions that will extend
 into the inner flat bottom surface of the vault. Extension 405' SI[DE]
 forms welded extensions that will extend into the inner flat side surface
 of the vault. Extensions 405" HO[RIZONTAL] and 405" VE[RTICAL] form welded
 extensions that will extend into the inner flat side surface of the vault,
 although, as described above, such strips may be applied at any point on
 the outer surface of the liner.
 As clearly shown in FIG. 7B, some or all the liner edges corresponding to
 the inner form edges may be formed with no extensions by appropriate
 piecing and manufacturing practice. In addition, septic tank inlet and
 outlet pipe insets typically molded into the vault are accommodated with
 reinforced cylindrical extensions for attachment to the inlet and outlet
 pipes.
 In another important embodiment of the present invention, it is well known
 that it is difficult to obtain an inexpensive, liquid tight and long
 lasting seal between the inner, liquid holding cavity of a concrete vault
 and an inlet or outlet pipe. This difficulty is the natural result of
 attempting to form a liquid tight seal between the outside of an inlet or
 outlet pipe and the relatively smooth sides of a formed or drilled hole
 passing through the concrete wall. An attempt has been made with the
 frustro-conical piece 1306 of FIG. 13 (which are known to have dimensions
 of frustrum top of about 4 inches and bottom of about 7 inches diameter),
 as is well known in the art, to place such a piece in the casting mold of
 a concrete vault so as to provide a hole through one of the low liquid
 pressure containing walls of the concrete vault for the inlet or outlet
 pipes and thereby form a concrete-to-frustro-conical piece bond with the
 hope that such a bond will remain liquid tight upon forming a liquid tight
 seal between the outside of the pipe and the inner surface of the
 frustro-conical piece. The embodiment of the present invention shown in
 FIGS. 13 and 14 avoids the difficulty altogether. The liquid tight liner
 1305 of the present invention for concrete vaults and septic tanks is
 provided with a hole, around which is sealed by rf-welding or adhesives a
 base section 1304 which extends to a frustroconical section 1302 and then
 to a cylindrical section 1301, the continuous assembly of which forms pipe
 sealing adaptation 1300. Adaptation 1300 is shown in FIG. 13 with the
 section 130115 pointed in a direction such that frustro-conical piece 1306
 will easily slide over section 1301 and match its inside surface with the
 outside surface of section 1302, as in FIG. 14. Pipe 1308 is moved into a
 position within the section 1301 such that a common banding or strapping
 piece about the outside of section 1301 will provide a fully effective
 liquid seal between the inlet or outlet pipe and the liquid tight liner
 1305 of the present invention. As such, it is clear that no
 concrete-to-pipe exterior seal is needed to retain liquid within the
 concrete vault or septic tank. It is preferable for installation, material
 cost and effectiveness that the material of adaptation 1300 be of the same
 material as that of liner 1305. The adaptation 1300, being of flexible
 material, can be inverted, so as to permit installation of the liner
 material-to-pipe seal on either, with respect to the liquid containing
 cavity of the concrete vault, an inner or outer position, whereby in the
 inner position the adaptation 1300 is inverted and the outer surface of
 section 1301 in FIGS. 13 and 14 becomes the inner surface which is brought
 into relationship with the outer pipe surface for strapping sealment.
 An alternative method of forming a pipe to liner seal is shown in FIGS. 15
 and 16. In FIG. 15, a concrete side 1307 of an invention liner is shown
 with a reinforcing piece 1304 optionally overlaying that concrete side
 1307, both layers having formed in them hole 1310 with a diameter
 effectively smaller than the diameter 1309 of pipe 1308. The method of
 forming the liner to pipe seal requires insertion of a leading end of pipe
 1308 into hole 1310 along path 1311. As shown in FIG. 16, the invention
 liner is shown after securing attachment to the concrete wall, shown in
 cross section at the hole formed therein for inlet or outlet pipe 1308. An
 interior side 1312 of the invention liner is compressed with ring 1313
 which is shown in cross section and is understood to be a ring support
 device capable of holding the liner to the wall of the concrete tank
 during the seal forming process. As pipe 1308 is inserted into hole 1310,
 the flexible liner material forms a seal section 1314 about the outer
 circumference of pipe 1308 in the direction of the insertion of the pipe
 1308. The seal section 1314 may be sufficient alone for sealing purposes
 or may be supplemented with an optional pipe clamp or equivalent device
 1315 shown in broken lines. Device 1313 is removed after pipe 1308 has
 about it formed seal section 1314.
 It can now be appreciated that, in contrast to the prior art, the flexible
 liner of the present invention as applied to concrete vaults eliminates
 the need for liquid containment by the concrete structure, at least
 initially. This advance solves an especially difficult problem with
 respect to septic tank testing which requires that the sealed septic tank
 maintain a vacuum for a specified length of time. While the prior art
 concrete vault, when carefully made, could barely pass such tests due to
 the tendency of concrete to form micro-cracks that permit air to leak into
 the vault, the liner of the present invention as applied to such a
 pre-cast or cast in place septic tank easily passes such a test. The
 effectiveness of the present liner in retrofit, pre-cast or cast in place
 concrete vaults improves with the anchoring means described above. The
 flexible extensions of the liner described above may also be used in a
 retrofit if scoring of the concrete surface is made along the path desired
 for securement of the liner to the concrete wall, whereby concrete grout
 is applied and the flexible extensions are pressed therein while the grout
 is still wet and uncured.
 In yet another embodiment of the present invention, the liner to be applied
 to a mold in a pre-cast concrete vault may be fabricated such that its
 length and width are equal to or smaller than the inside mold piece,
 whereby moderate heating or physical stretching of the flexible material
 permits easy installation on the mold as described above. Once the
 "memory" of the flexible materials causes the liner to tend to its
 original size before heating or stretching, the liner forms a tightly
 stretched cover over the mold. The resulting product is visually
 impressive and desirable for the buyer, giving the impression not of a
 concrete vault, but rather of a glossy liquid container. The tension of
 the stretched liner also improves the tendency of the flexible extensions
 to self-insert into the concrete poured into the mold as described above.
 It is known to use concrete vaults for casket containment in below ground
 internment. The liner of the present invention as applied to these
 pre-cast vaults may be made with a variety of designs, colors, pictures or
 the like to accommodate the preference of the bereaved when viewing the
 lowering of the casket into the burial vault. The use of flexible vinyls
 with this embodiment makes application of such visual effects within the
 skill of the art of such flexible materials.
 In addition, a liner as described above may be effectively provided for the
 outer surface of the foundation of a structure to prevent soil attack on
 the concrete. It is taught herein that the flexible extensions of the
 present invention as applied to a flexible liner have not been heretofor
 used or proposed for application for attachment to concrete flowed about
 them. It is known in the art to use adhesives on flexible materials so
 that they bond to wet concrete flowed onto such a surface when the
 concrete dries. The present invention eliminates the need for such
 application of adhesives, which effectiveness is clearly time-limited
 under the circumstances of the chemical and temperature conditions of the
 surroundings. The present invention, on the other hand, is substantially
 independent of time, heat or chemical conditions with respect to the
 mechanical impression securement of the flexible extension of the liner
 into its adjacent concrete. As such, the location of the liner may be
 effectively made on the exterior or interior, irregardless of frame of
 orientation of such inside or outside surfaces, of any flowed concrete
 structure so long as the flexible extensions may be held within the
 concrete until it cures at the surface portion surrounding the flexible
 extensions.
 The embodiment of FIG. 7A describes a method known in the art of forming
 two precast concrete vaults with adaptation to fit them together at
 multi-level rims and so to form a "stacked" set of vaults with a vertical
 height equal to the stacked height. The top vault, for a description of
 this embodiment, is continuously molded similar to a bottom vault,
 although the top vault is inverted so that no lid is needed, i.e., the
 "bottom" of the vault forms a ceiling for the stacked vaults and extends
 continuously to the vertically descending walls. Another embodiment of the
 present invention relates to the molding and use of the top vault for
 securement of the liner of the present invention with relationship to
 stacked vaults. Before the molding of the top vault, a "collar" or
 continuous rounded or rectangular cross-section inset piece is secured to
 the concrete containing wall of the inner mold so that it runs about that
 inner mold wall in a substantially horizontal plane about at the level of
 the highest side reinforcing rebar cross-section 409 shown in FIG. 7. The
 material of the inset piece is preferably inexpensive although with
 sufficient strength to permit attachment and support therefrom the 404'
 EDGE of the liner of FIG. 7A when drawn upward into the stacked structure.
 Such inset piece material includes rigid polyurethane foam, foamed
 rubbers, rubber or elastomeric or rigid polymeric material. When the top
 vault is removed from the mold, an inner surface of the inset piece will
 be exposed on the inner surface of the side wall of the upper vault, while
 the inset piece itself will be secured into the cured sidewall of the top
 vault. Thus, an inexpensive and effective means are formed for quick
 installation of 404' EDGE to the inside of the top vault by either having
 in the inner surface of the inset piece a race or other slot for insertion
 and securement of the flexible material of the liner or having sufficient
 thickness in the inset piece to accommodate piercing the liner material
 for installation with screws or other such standard securing means.
 A composition for a liner for a concrete septic tank lined according to the
 present invention is known as a material EUO000T030D016 of Achilles USA,
 Inc. A preferable embodiment of this material comprises a gauge of 30 mil,
 a hand of 5S, and the following physical properties:

Tensile Strength: M 1840
 ASTM D-882 (PSI) T 1620
 ELONGATION: M 276
 ASTM D-882 (%) T 274
 100% MODULUS: M 1110
 ASTM D-882 (PSI) T 1040
 GRAVES TEAR: M 283
 ASTM D-1004 (LB/IN) T 235
 VOLATILITY: 72 HRS 92
 ASTM D-1203 (%) T 1620
 DIMENSIONAL STABILITY 50.degree. C. 100.degree. C.
 ASTM D-1204 (%): T -.8 -2.8
 10 MIN. M 4 1.2
 COLD IMT:
 ASTM D-1790 -20.degree. F. FAIL
 It is a further embodiment of the present invention to thermally embed or
 adhesively attach to a concrete-side of the liner material a flat and
 flexible fibrous material, such as natural burlap or equivalent synthetic
 materials, prior to embedment and/or drying and/or adhesive attachment of
 the liner material to wet, uncured concrete or cement. The effective
 adhesion of this fibrous material improves the securement of the flexible
 liner to the drying concrete or cement. It is known in the art that
 certain adhesives will effect an adhesive secure connection between a
 flexible polymer sheet material and uncured, flowable cementitious
 material. It is a further embodiment of the present invention to have
 previously applied such adhesives to the concrete-side of the liner of the
 present invention. It is also known in the art that other adhesives bond a
 flexible sheet of polymer material to another such sheet. It is another
 embodiment of the present invention to provide for sealing liner
 connection between stacked concrete sections of septic tank or concrete
 tanks via other adhesive sealing of the liner of one section to an
 overlapping section of another. As a further example of this method, a
 septic tank has a "lid" piece which acts a sealing roof for the septic
 tank, whereby for this invention an invention liner is attached to the
 interior (as to the septic tank) portion of the lid with sufficient
 overlap to be chemically adhered to an invention liner of the next lowest
 section of the septic tank, thereby forming an entire seal against the
 concrete of the tank protecting it from the liquids and gases of the
 interior of the tank which may attack the concrete of the tank.
 As to the present invention in its several embodiments, it is disclosed
 herein that the presence of a flowable cementitious material, either with
 or without conglomerate forming concrete, is a critical step in the
 process of forming a secure attachment of the invention liner to the
 surface of the later cured cementitious material. The methods and
 assemblies disclosed herein for accomplishing that sealing attachment of a
 flexible liner have not heretofor been disclosed in the art. Septic tank
 liners may have a liner thickness of about 30 mil, whereas larger catch
 basins may have a liner thickness of about 50-60 mil.
 Concrete walls are used in many enclosures. Catch basins, manhole surface
 to pipe transition pieces, clarifiers (as in oil/water separators or other
 such process separators), holding stations, grease traps, burial vaults
 and lift stations are all well known to have been widely comprised of
 pre-formed concrete structures which are appropriate for adaptation in the
 casting processes for application of the invention liner on the inside or
 outside surfaces for protection of the concrete from the interior liquids
 and gases as well as the external ground water, bacteria and gases.
 Although the present description describes the use of molds for
 cementitious vault sections to form septic tanks and similar ground
 vaults, the definition of such molds extends to the use of enclosures such
 as building foundation forms (with a floor on of the ground), tilt-up
 pre-cast wall forms and their molds, frustro-conical molds for manhole to
 pipe transition pieces, and the many other assemblies and methods for
 enclosing the flowable mass of cementitious material which is intended to
 form a vault section. A vault section is more specifically at least a wall
 which continuously encircles a central space, the central space having (1)
 no floor or ceiling as in a large diameter pipe with a vertical axis, (2)
 having a floor but no ceiling as in a septic tank base piece, or (3)
 having a floor and a ceiling with sufficient opening at some wall portion
 to introduce flowable cementitious material.
 The above design disclosures present the skilled person with considerable
 and wide ranges from which to choose appropriate obvious modifications for
 the above examples. However, the objects of the present invention will
 still be obtained by the skilled person applying such design disclosures
 in an appropriate manner.