US3485049A

US3485049A - Underground fluid storage tank

Info

Publication number: US3485049A
Application number: US736109A
Authority: US
Inventors: Karl R Rohrer
Original assignee: Individual
Current assignee: Individual
Priority date: 1968-06-11
Filing date: 1968-06-11
Publication date: 1969-12-23
Anticipated expiration: 1986-12-23

Description

Dec. 23, 1969 K. R. oHRER UNDERGROUND FLUID STORGE TANK 2 Sheets-Sheet 1 Filed June 11, 1968 INVENTOR. KARL R. ROHRER ATTORNEYS Dec. 23, 1969 K. R. llam-mm 3,485,049

UNDERGROUND FLUID STORAGE TANK Filed June 11, 1968 2 Sheets-Sheet 2 2lb 80 l/ /w l AW INVENTOR. KARL R. ROHRER ATTORNEYS United States Patent O 3,485,049 UNDERGROUND FLUID STORAGE TANK Karl R. Rohrer, 264 Kenilworth Drive, Akron, Ohio 44313 Filed June 11, 1968, Ser. No. 736,109 Int. Cl. B65g 5/00; EZlf 17/16 U.S. Cl. 61-.5 9 Claims ABSTRACT OF THE DISCLOSURE A method of storing fluids in a subterranean cavity including placing a flexible substantially fluid impermeable membrane on the bottom and sides of the cavity and substantially lling the cavity with an aggregate such as gravel or other hard filler material and covering this material with another flexible impermeable membrane. Inlet and outlet means interconnect the interior of the storage unit thus formed with a source of lluid supply and the earth is then back-filled over the top or second membrane up to the desired grade level.

BACKGROUND OF THE INVENTION This invention basically relates to the underground storage of fluids such as overflow storm water from a sewer system, for example, while permitting full utilization of the land overlying the tank. The inventive concept, which is essentially described herein in relation to the storage of liquids, can be utilized for the underground storage of any desired fluid.

DESCRIPTION OF THE PRIOR ART The following prior art is known to applicant: Hodges, U.S. Patent No. 870,433; Warren, U.S. Patent No. 3,068,- 654; Crawford et al., U.S. Patent No. 3,113,699, and Canadian Patent No. 696,484.

None of the art listed above discloses the inventive concept herein set forth. For example, Crawford discloses an underwater storage system while the Canadian patent discloses an inflatable device and Hodges shows a simple drainage pit.

SUMMARY OF THE INVENTION In conventional underground storage systems, a cavity is first excavated and then a rigid storage tank is constructed within the cavity. This is usually a concrete structure which is then covered with earth and provided with the necessary inlet and outlet means.

The disadvantages encountered in utilization of such conventional systems, in addition to the obvious expense involved in construction, are twofold.

First, there is a problem of utilization of the surface area above the tank due to the lack of sufficient support to enable this area to be utilized for conventional purposes such as buildings, parking lots, etc.

Second, and on the other hand, if the tank is strengthened to a sufficient degree to enable the overlying ground surface to be utilized for other purposes, the cost factor is considerably increased so as to make the same nearly prohibitive.

In some other conventional storage systems, open lagoons are used but problems are encountered with evaporation and also the land area cannot be used for any other purposes. Rubber tanks are also sometimes employed, but here again, the overlying surface is not capable of use for buildings, for example, due to a lack of support.

It has been discovered, therefore, that the above noted disadvantages can be overcome by providing a cavity into which a flexible impermeable membrane is laid. The cavity is then substantially filled with gravel or other ice similar aggregates and a second membrane can be placed over the filler material.

It is known that a certain ratio of void volume remains in a given volume of aggregate such as gravel so that storage volume of the tank can thus be readily calculated.

Inlet and outlet means are provided to interconnect the interior of the tank thus formed to the source of supply for the uid and -overflow and venting means can also be provided.

It has also been discovered that after the second membrane is placed into position, that. the earth can be back-filled up to the existing or any desired grade level and that due to the structure of the tank, that this surface can easily and readily be utilized for any desired purpose thereby giving a dual use to a given area of land.

Accordingly, production of an underground storage system having the abo-ve noted characteristics becomes the principal object of this invention with other objects thereof becoming more apparent upon reading the following brief specification considered and interpreted in view o-f the accompanying drawings.

In the drawings:

FIGURE 1 is a top plan view of the improved underground storage tank.

FIGURE 2 is an elevational view taken on the line 2-2 of FIGURE 1 partially broken away.

FIGURE 3 is an enlarged partial view of the point of interconnection between the top and bottom membranes.

FIGURE 4 is an elevational view, partially broken away, of a modified form of the invention.

FIGURE 5 is an enlarged perspective view of the inlet and outlet means of FIGURE 4.

FIGURE 6 is an elevational view, partially broken away, of another modified form of the invention.

Considering first then FIGURES 1 and 2, it will be noted that a cavity 10 is provided in the earth with the dimensions thereof being determined by the quantity of fluid that the system is intended to accommodate and with this quantity being calculable due to the ratio of void volume that will remain in a given amount of aggregate. It should be noted that while a particular configuration is shown with regard to the cavity that the invention is not intended to be limited to any particular size or shape.

A shallow trench or depressed area is also provided around the top surface of the cavity for reception of an overflow pipe and the edges of the membranes as will be subsequently more fully described.

Considering next then the storage tank 20 per se and referring particularly to FIGURE 2, it will be noted that the same comprises a liner or lining means which is shown as a first flexible impermeable membrane 21 which is laid into the bottom of the pit so as to cover the bottom and substantially lall of the side walls thereof. This membrane may be of any suitable material such as clay, plastic or rubber, for example.

The peripheral edge 21a of membrane 21 is then laid into the trench which has been described above and an overflow pipe 50 can be laid on edge 21a. This pipe 50 is either slotted as at 51 or perforated to communicate between the interior of the completed tank 20 and the surrounding earth and need only extend along a portion of the rim of the cavity. Actually this pipe can feed overflow to any desired point and, in the case of storm water, would probably lead to a stream, for example. l

The inner surface of the membrane 21 is next filled with a filler material or aggregate 30 which can be of any suitable hard material in particle form such as gravel or boulders, for example.

After the interior of the cavity, which is covered by the first membrane 21, has been filled with the storage media comprising the filler material 30, a second membrane 22 is laid over the gravel so as to completely cover the top surface thereof. It should be noted here that the peripheral edge 22a of membrane 22 is tucked around edge 21a of membrane 21 and 'pipe 50 in the form of the invention shown so that when the cavity is back-lled, as will be described below,a secure seal Can be obtained. It is also possible to merely lay edge 22a of membrane 22 over edge 21a of membrane 21 or the edges may be positively secured together if desired by stitching, cementing or other conventional means. Y

Inlet and outlet means, generally indicated by the numeral 40, are shown located in the bottom of the tank formed by the

membranes

21 and 22 although their location is a matter of choice. These means generally include a connecting pipe 41 and iilter means 40a adapted to filter out the larger particles. The pipe 41 of inlet and outlet means 40 is connected to a source of liquid supply such as, 'for example, a storm sewer (not shown).

It should be noted here that when the tank is used in conjunction with a sewer system that conventional means for chlorinating the water can be installed in the pipe 41 of inlet and outlet means 40.

Once the installation has been completed by positioning the second membrane 22 in place, the earth can be backiilled to the existing grade level or to any other level as clearly shown in FIGURE 2.

At this point, the tank 20 is ready for the reception of uids and the surface of the earth S is ready for utilization for any desired purpose for which such land would be normally utilized with the aggregate or filler material 30 supplying the necessary support.

In use or operation the fluid can be introduced into the tank through pipe 41 by a pump or by gravity from the source of supply. The tank can be utilized as a semipermanent storage means if desired but is mainly envisioned as a temporary storage device and removal of the liquid can also be accomplished through pipe 41 by conventional pumping means when desired.

It should be noted here that while certain materials have been suggested as suitable for the membranes 21 `and 22, that the inventive concept herein disclosed is not intended to be limited to any specific material and any material which is substantially impermeable and has some degree of exibility to enable it to conform to the contour of the pit or cavity may be utilized.

Similarly, while the iiller material has been illustrated as gravel, it is believed apparent that any material having a suitable hardness and resistance to being crushed may be utilized. Similarly, the invention is not intended to be limited to any particular size with regard to the particles which make up the ller material.

It should also be noted that overflow pipe 50 is generally necessary when liquids are being stored but may be dispensed with if the installation is designed for the storage of gases.

Turning next then to FIGURES 4 and 5 which show a modified form of the invention, it will be noted that a cavity a is provided similar to the cavity provided with` regardto the form Of the invention shown in FIGURES 1, 2 and 3. The bottom membrane 20a and top membrane 2lb are also identical in this form of the invention.

Similarly the interior of the4 cavity is filled with a filler material .30 as noted above. However in this instance, a layer of fines, such as the sand 31, is provided on the bottom membrane a before the ller material 30 is inserted. This layer of sand prevents punctures or ruptures in the membrane 20a either due to the jagged or rough surfaces of the. particles -of the filler material or due to the weight of the overlying earth pressing such particles against the membrane.

This form of the invention also discloses a specific form of inlet valve suitable for use with regard to either the tank shown in FIGURES l, 2 and 3 or that shown in FIGURES 5 and 6.

This valve is principally illustrated in FIGURES 4 and 5 and is generally indicated by the numeral 60. This valve has a series of vertical float guides 61, `61 which are held in place by a plurality of annular support rings 62, 62 which may be secured to

guides

61, 61 by Welding or other suitable means. The structure formed by the support rings and float guides is mounted on a scour plate 63 which is in turn mounted on the end of the inlet and outlet pipe 41.

A iloat is shown received within the iioat guides and is adapted to move vertically within the

guides

61, 61. It is believed apparent that upon the entry of liquids through the pipe 41 that the oat 70 will rise and similarly that as liquids are pumped out of the tank that the float 70 will return to its seated position on the scour plate 63. The action of the liquid as it is passed out of the tank will cause float 70 to have a scouring action in conjunction with plate 63 for sediment removal purposes.

An access cover is also provided for seating on the top support ring 62 and is designed so as to be readily removable so that the valve mechanism can be cleaned when necessary. It is believed apparent that this cover 80 can be mounted in flush relationship with the earths surface so as to not interfere with the secondary uses of the land. Cover 80 also can be provided with apertures S1, 81 to serve as a vent to prevent an air lock during lling of the tank. If desired, when gases are being stored, cover 80 can be imperforate in which case a conventional venting system can be run from the cover to an open ilame, for example.

Float guides 61, 61 also can be provided with a series of

perforations

61a, 61a which can be attached to suitable spray means so that the valving system can be ushed when desired.

In this regard, FIGURE 5 shows a tube or rod 90 leading away from hollow ring 62 to a suitable Source of pressurized liquid 91 which is illustrated schematically. Thus, liquid can be forced through tube or rod and thus through the

perforations

61a, 61a of

guides

61, 61 to flush the valve when desired.

In addition to the form of the invention described above, it is believed that the inventive concept herein disclosed is also applicable to existing installations. Thus, in FIGURE 6 an existing reservoir 100 is shown. In order to employ the invention in conjunction therewith, it is merely necessary to ll the existing reservoir bed or lining 101 with aggregate 130 and cover the same with membrane 122 following which the earth may be back-lled as described above.

In this way, the existing reservoir can still be utilized for storage while the land over it can be used for other purposes as well.

It should be noted here that while the inventive concept disclosed in general with regard to the tank per se can be utilized with any fluid including liquids or gases, the valving arrangement 60 is primarily designed for utilization with liquid storage.

It is believed apparent, therefore, that a new and improved underground storage tank has been disclosed which presents a considerable savings in cost over the conventional storage tanks while providing increased utilization of the land overlying the tank.

It is also believed pertinent to point out that the unique tank disclosed herein is not subject to deterioration as is the case with conventional tanks and accordingly, utilization of the overlying surface of the land is further enhanced by this feature.

It should also be noted that while a hopper shaped cavity is shown, the cavity could take any desired shape due to the -exibility of the

membranes

21 and 22 in the form of the invention shown. Furthermore, this characteristic of the membranes makes it possible to avoid the need for precise grading of the bottom and sides of the cavity since the membranes can accommodate themselves readily to minor irregularities.

What is claimed is:

1. A tank for storing uids in a subterranean cavity of the character described, comprising;

(A) bottom lining means covering the bottom and at least a portion of the sides of said cavity;

(B) a `quantity of filler material disposed on said lining means and substantially filling said cavity;

(C) a top impermeable membrane covering said filler material and overlapping the peripheral edges of Said lining means; and

(D) inlet and outlet means interconnecting the interior of said cavity with a source of fluid.

2. The device of claim 1 further characterized by the fact that said bottom lining means includes a bottom flexible, impermeable membrane.

3. The device of claim 1 further characterized by the presence of filter means connected to said inlet and outlet means between said source of fluid supply and the interior of the tank formed by said lining means and said top membrane.

4. The device of claim 3 further characterized by the presence of means for ushing said lter means.

5. A device of claim 3 wherein said filter means comprises:

(A) a body portion interconnecting said inlet and outlet means and the atmosphere;

(B) a float carried interiorly of said body and adapted to move vertically therewithin in response to the entry and withdrawal of said fluid into and out of said tank.

6. The device of claim 2 further characterized by the presence of a layer of fines on said bottom membrane beneath said liller material.

7. The device of claim 1 further characterized by the presence of overflow means communicating between the interior and exterior of said tank.

8. The device of claim 1 further characterized by the presence of venting means adapted to communicate the interior of said tank with the atmosphere.

9. A method of constructing a subterranean Storage tank for liquids including the steps of (A) excavating a cavity;

(B) lining the bottom and at least a portion of the walls of said cavity with a ilexible, impermeable membrane;

(C) placing a quanity of hard ller material on Said rst membrane;

(D) covering said filler material with a second flexible impermeable membrane;

(E) interconnecting the area between said rst and second membranes with a source of liquid supply; and

(F) covering said second membrane with earth to grade level.

References Cited UNITED STATES PATENTS 870,433 11/ 1907 Hodges. 1,051,344 1/1913 McKnight 61-10 2,755,630 7/1956 Freyssinet 6l.5 3,052,380 9/1962 Prins 61-.5 X 3,068,654 12/1962 Warren. 3,113,699 12/ 1963 `Crawford et al..

FOREIGN PATENTS 696,484 Canada.

PETER M. CAUN, Primary Examiner