JP2005088993A - Regeneration structure of underground steel tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a regeneration structure of tank, which allows an existing tank with one air-tight layer to be regenerated at low cost into a tank with high-safety two air-tight layers, having, furthermore, a structure that enables early discovery of leakage of a flammable liquid stored in the tank. <P>SOLUTION: A deterioration-preventive treatment of steel is provided on the inner wall surface of the existing underground steel tank A, thus providing a deterioration-preventive treatment layer 7, while a plurality of curved surface bodies 9 with a given thickness are provided in linkage across the whole of the inner circumferential surface of the deterioration-preventive treatment layer 7, and in between these whole of the curved surface bodies 9 in linkage, water-passage layers 8 are provided in succession that are capable of passing water or air, with an air-tight layer 14 being formed across the whole of the inner circumferential surface of the water-passage layers 8, by sticking regeneration material thereto. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  This invention is intended to prevent deterioration of a steel underground tank (hereinafter referred to as “tank”) that stores liquid combustibles such as gasoline and light oil installed underground, and a tank rehabilitation structure that facilitates the detection of stored material leakage. It is about.

  In addition to gas stations, trucks and bus terminals nationwide, and underground underground buildings have steel underground tanks for storing liquid combustibles such as gasoline. Such an existing steel underground tank has a thickness of 6 to 9 mm (the thickness of the steel is defined by the storage amount), and the outer periphery of the tank is covered with an anticorrosion layer. The steel airtight layer that blocks the passage of the inner liquid combustible material has a single structure. Currently, about 150,000 of these tanks that have been used for 20-30 years have been used, and these tanks have been exposed to liquid combustibles stored inside the tanks due to deterioration over time. May leak.

  If the liquid combustible material stored in these tanks leaks, it causes soil contamination and the damage to the environment becomes enormous, and its restoration cost becomes enormous and becomes a problem related to the existence of the company. Causes of such steel tank leakage accidents include damage to the anticorrosion layer due to construction mistakes during tank installation, oxidation deterioration of steel materials from the outer and inner surfaces of the tank, and electrical corrosion deterioration. It takes enormous costs to excavate and investigate the outer periphery of the steel.

  As a preventive measure for preventing such a liquid combustible material leakage accident which is stored in the tank, a measure is taken to rehabilitate the tank that has passed 20-30 years from the inside. As a method for rehabilitating this tank, there is a method in which a reinforced cloth impregnated with a resin solvent is attached to the inside of the tank and the resin solvent impregnated in the reinforced cloth is cured (Tokyo Fire Department) Dangerous Goods Section Manager Notice 14 Precise No. 177) requires that airtight tests (inspection before completion inspection) are carried out in tanks with predetermined pressure and water pressure before attaching rehabilitation materials to existing tanks. Rehabilitation is permitted only for tanks that pass Adhering rehabilitation material to ensure that airtightness is ensured even after carrying out an airtight test with the specified atmospheric pressure and water pressure in the tank after sticking the rehabilitation material in close contact with the inner wall of the tank that passed the airtightness test After that, the airtightness test of the rehabilitated material has not been confirmed.

  If the rehabilitation material has not been confirmed to be airtight, the liquid combustible material stored in the tank will permeate directly to the inner wall of the tank, and oxidation and electric corrosion of the steel material in the tank will proceed. May leak, the function as a rehabilitation material does not work, and the tank body does not have a leak detection function.

Tanks that store liquid combustibles are subject to legal restrictions for the storage of hazardous materials, depending on the amount of liquid combustibles that are stored. According to the Fire Prevention Inspection Manual (issued by the Tokyo Fire Department Prevention Department), there are the following three types. 1) Steel double shell tank (name: SS double shell tank), the structure is a double structure of steel plate. 2) Steel reinforced plastic double shell tank (named: SF double shell tank), the structure is a double structure in which the outer shell is reinforced plastic and the inner shell is steel plate. 3) Double shell tank made of reinforced plastic (name: FF double shell tank), the structure is plastic double structure. However, the specific structure of the water flow (detection) layer and the installation of the water storage tank in these tanks whose outer shell is made of steel and whose inner shell is made of reinforced plastic are described in this Fire Prevention Inspection Manual. Not implemented.
The existing steel underground tank rehabilitation method is the Tokyo Fire Department's Dangerous Goods Section Notice 14 Pre-Critical No. 177 (for dealing with internal lining construction of steel underground tanks), and other laws, standards and regulations, etc. There is no current situation.

  However, in this method, the hermetic layer of a steel tank that has deteriorated over time has a single structure, and the airtightness of newly renovated material has not been confirmed. There are many. Considering the seriousness in the event of a leakage accident as described above, a safer one is required, but if it is replaced with a new double-structured tank, approximately 1,000,000,000 yen is required. Therefore, there is a need for a low-cost tank rehabilitation method. Furthermore, tanks with a single airtight layer that are currently employed do not have a leak detection function inside the tank, and leak test tubes are installed at the four corners outside the tank. In the case of a trace amount, it is very difficult to detect in a leak test tube at an early stage, and when a leak is discovered, it has passed for a long time, and a large amount of liquid combustible material has leaked outside the tank, causing soil contamination. Is the current situation. There is a need for a tank rehabilitation structure that extends the life of existing tanks, detects leakage accidents early, and minimizes the leakage of liquid combustibles to the outside.

  Therefore, the present invention has a structure in which a tank with a single existing hermetic layer is inexpensive, a highly safe hermetic layer is renovated into a double tank, and leakage of liquid combustible material stored in the tank can be detected at an early stage. A tank rehabilitation structure having the above is provided to solve the above-mentioned problems.

  In the invention of claim 1, a deterioration prevention treatment layer is provided on the inner wall surface of an existing steel underground tank to provide a deterioration prevention treatment layer, and a curved surface having a constant thickness is provided over the entire inner peripheral surface of the deterioration prevention treatment layer. A plurality of sheet pieces are connected to each other, and a water-permeable layer that allows water flow or ventilation between all of the connected curved surface bodies or between all the sheet pieces is continuously provided, and the rehabilitation material is provided on the entire inner peripheral surface of the water-flow layer. A steel underground tank rehabilitation structure with an airtight layer formed by attaching

  The invention of claim 2 is provided with a plurality of grooves vertically and horizontally or obliquely on at least one surface of the curved body or sheet piece forming the water-permeable layer, and the water-permeable layer passes water through the grooves of the plurality of curved bodies or sheet pieces. The steel underground tank rehabilitation structure according to claim 1, wherein water can be passed through the entire layer. Further, the invention of claim 3 is provided such that one end of the first pipe is fixed in the water passage layer located in the lower part of the steel underground tank so that the water passage layer and one end of the first pipe can pass through the water. The first pipe is inserted through the inside of the water layer and the other end is provided outside the steel underground tank, and one end of the second pipe is fixed to the water passage located at the top of the steel underground tank. The water passage layer and one end of the second pipe are provided so as to allow water to pass through, the second pipe is inserted through the inside of the water layer, and the other end is provided outside the steel underground tank. The rehabilitation structure of the steel underground tank described in any one of the above was adopted.

  Invention of Claim 4 opens and fixes one end of said 1st pipe to the water storage part provided in the bottom part of the said steel underground tank, and the lowest part of a water flow layer, The said water flow layer, a water storage part, The steel underground tank rehabilitation structure according to claim 3 provided to allow water to pass through. According to a fifth aspect of the present invention, the water storage section is provided as a rectangular tubular water storage tank in the longitudinal direction of the bottom of the steel underground tank and at the lowest part of the water flow layer, and the water storage tank includes the first water storage tank. One end of the pipe is opened and fixed, and the steel underground tank rehabilitation structure according to claim 4 is provided so that the water flow layer and the water storage tank can pass through.

  According to the first to fifth aspects of the present invention, the existing tank can be renovated into a tank having a double airtight layer or the like at a low cost. Therefore, it can be used as it is in existing tanks, so it is extremely versatile and greatly answers the expectations of individuals and corporations that own tanks. In addition, since the leakage of the existing tank and the newly installed airtight layer can be detected quickly, the amount of leakage can be minimized. As a result, environmental destruction such as soil contamination can be prevented in advance or to the minimum, contributing to the creation of a clean environment.

  According to the second aspect of the present invention, a plurality of grooves are provided vertically or horizontally or obliquely on one surface of the curved body or the sheet piece, and according to the fourth aspect of the invention, water can be passed through the water-permeable layer. Since the water storage section is provided, according to the invention of claim 5, since the water storage tank that can pass water is provided, even a small amount of liquid combustible material that oozes out can be promptly stored in the water storage layer or the like. Can be found quickly. Furthermore, according to any one of claims 3 to 5, even a minute liquid sucked up from the first pipe may be immediately leaked from the existing tank or the inner liquid depending on whether it is groundwater or stored liquid combustible material. Leakage from the new airtight layer can be easily confirmed at all times, and the subsequent response can be made quickly, thus further contributing to avoiding soil contamination. In addition, since the first pipe and the second pipe are connected via the water flow layer, liquid or gas can be passed from the first pipe or the second pipe into the water flow layer, thereby preventing fine leakage. It can be easily confirmed and can be used for airtightness tests of existing tanks and new airtight layers.

  On the inner wall surface of an existing tank, a deterioration prevention treatment layer is provided by performing steel deterioration prevention treatment, and a plurality of constant thickness curved surfaces or sheet pieces are provided on the entire inner peripheral surface of the deterioration prevention treatment layer. A plurality of grooves are provided on one surface of the curved body or sheet piece on the deterioration prevention treatment layer side, and the other surface is provided on a flat surface, and water can be passed or vented between all the curved surfaces connected or between all the sheet pieces. A water-permeable layer was continuously provided, and an airtight layer was formed on the entire inner peripheral surface of the water-permeable layer by attaching a regenerated material. Here, the provision of the other surface on a plane means a plain surface with no irregularities even if it is a curved surface.

  Further, one end of the first pipe is fixed in the water passage layer located at the lower part of the tank so that water can pass through the water passage layer and one end of the first pipe. The other end is provided outside the tank, and one end of the second pipe is fixed to the water passage located at the top of the tank so that the water passage and the second pipe can pass through the water. The inside of the water-permeable layer was inserted and the other end was provided outside the tank. Furthermore, in the longitudinal direction of the bottom part of the tank, a rectangular tubular water storage tank is provided at the lowest part of the water storage layer, and one end of the first pipe is opened and fixed to the water storage tank. It was provided so that water could pass through the tank.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 2 shows an existing steel tank A to be rehabilitated here. The inner diameter (D) of the cylindrical portion (D) is 1,500 mm, the length (L2) is 5,234 mm, and the curved surface portions 2 of the mirror portions at both ends are shown. The removed length (L1) is 4,600 mm, and the thickness (T) of the steel plate of tank A is 6 mm. An inspection hole 1 is provided at one location on the upper side of the tank A, and an inlet 3 for a combustible material such as gasoline stored therein, a vent tube 4, a metering tube 5 and an oil feeding tube 6 are provided at the other location. ing.

  And all the liquid combustibles in the tank A are extracted, and the safety in the tank A is confirmed, such as measurement of combustible gas. Thereafter, an air tightness test in the tank A is performed, and after passing the test, an opening operation of the tank A for an operator to enter the tank A is performed, and a necessary work before entering the rehabilitation work is performed.

Steel deterioration prevention treatment is performed on the entire inner wall of the existing tank. The term “deterioration prevention treatment” as used herein refers to coating with a rust preventive material for preventing oxidative corrosion or electric corrosion of steel and attaching or applying a fiber reinforced plastic in close contact with each other. Specific examples using fiber reinforced plastic will be described below.
A rehabilitation material of a certain size made of a fiber reinforced plastic sheet impregnated with a resin solution is adhered and pasted over the entire inner wall surface of such a tank A. As the resin solution used here, a room-temperature curable thermosetting resin solution, specifically, an epoxy resin solution is used. Moreover, as a fiber contained in a fiber reinforced plastic sheet, a vinyl fiber and a glass fiber are used.

  The lid of the inspection hole 1 of the tank A is opened, and an operator enters the tank A, and a rehabilitation material made of a fiber reinforced plastic sheet impregnated with an epoxy resin solution is applied to the entire inner wall surface of the tank A. wear. The size of the rehabilitated material is determined based on the size and shape of the tank to be rehabilitated. In addition, if the curved surface portion 2 of the tank A is used with a narrow width, wrinkles generated in the regenerated material can be eliminated.

  As a specific method of attaching to the inner wall surface of the tank A, the surface of the attached rehabilitation material is pressed by a roller tool (not shown). Thereafter, the impregnated epoxy resin solution is cured to form the deterioration preventing treatment layer 7 on the entire inner surface of the tank A. At this time, even if depressions are formed on the inner wall surface of the tank A due to rust before rehabilitation, the epoxy resin solution enters and cures in these depressions, increasing the airtightness of the tank A.

  A water-permeable layer 8 is formed on the entire inner peripheral surface of the deterioration preventing treatment layer 7 provided in this way. As shown in FIG. 3 and FIG. 4, the water-permeable layer 8 is provided with a plurality of water passage grooves 9 a having a thickness of 1 to 2 mm on one surface and side surfaces on the deterioration prevention treatment layer 7 sideways and obliquely. A large number of curved bodies 9 made of plastic having a length of 5 to 6 mm and matched to the curved shape of the inner wall surface of the tank A to be installed are provided side by side. Each of these curved surface bodies 9 has one end in the longitudinal direction as a convex portion 9b and the other end as a concave portion 9c, and is provided with winding springs 10 at both ends thereof, and such curved body 9 is continuously provided in the vertical direction. . Further, since the other surface of the curved body 9 is provided as a plain surface without irregularities, an airtight layer described later can be provided easily and reliably.

  When connected in this way, each curved body 9 is strongly urged by the attached springs 10 so that the butted ends of each curved body 9 are opened and opened to the inner wall surface of the tank. It does not come off from the inner wall surface of A. A plurality of such water-permeable layers 8 are continuously provided in the lateral direction, and the water-permeable layers 8 are provided on the entire inner peripheral surface of the deterioration preventing treatment layer 7.

  In the curved surface portion 2 of the tank A, if these curved surface bodies 9 are installed in such a manner that they are supported by the edges of the adjacent curved surface bodies 9, they are fixed at the installed positions by the urging forces of the mutual winding springs 10. Therefore, the airtight layer can be stably and reliably formed on the entire inner peripheral surface of the water layer 8. Thereby, the water flow layer 8 is provided on the entire inner peripheral surface of the deterioration preventing treatment layer 7, and the grooves 9a of the curved bodies 9 of the water flow layer 8 are connected vertically and horizontally to form a water flow path.

  A rectangular tubular water storage tank 11 shown in FIG. 5 is provided at the bottom of the tank A, at the lowermost part of the water flow layer 8 and in the longitudinal direction thereof, and a through hole 11 a is formed in a part of one side surface of the water storage tank 11. 6, one end opening portion of the first pipe 12 shown in FIG. 6 is fixed to the through hole 11 a, and an infinite number of water passage holes 11 b are provided at regular intervals on both side surfaces of the water storage tank 11. These water passage holes 11 b are connected to the groove 9 a of the curved body 9 adjacent to the water storage tank 11 and are in a state capable of water passage.

  Further, as shown in FIG. 1, the first pipe 12 having one end fixed to the right side of the water storage tank 11 is extended to pass through the inside of the water passage layer 8, and the other end is taken out from the vent pipe 4 provided in the tank A. Provided outside the tank A. As shown in FIGS. 2 and 7, one end of the second pipe 13 is fixed to the upper part of the water flow layer 8 located above the tank A, and the other end of the second pipe 13 is connected to the water flow layer 8. Further, the oil is fed into the oil feeding pipe 6 from one side of the oil feeding pipe 6 and is taken out of the tank A through the inside of the oil feeding pipe 6.

  Therefore, the groove 9a in the water flow layer 8 is connected by the water storage tank 11, the first pipe 12, the second pipe 13 and the like, and is provided over the entire inner periphery of the tank A so that water can pass therethrough. A path from the one end outside the tank A of the two pipes 13 to the water passage 8 and the water storage tank 11 and from the water storage tank 11 to the first pipe 12 is formed.

  An airtight layer 14 is formed by attaching a rehabilitation material to the entire inner peripheral surface of the water-permeable layer 8 provided in this manner by the same method as that for the deterioration preventing treatment layer 7. In this case, since the airtight layer 14 is formed on the curved body 9 made of a solid having a constant thickness, the water tank 8 may be crushed by the pressure of the stored material even if the stored material is put into the tank A. There is no.

  Next, a method for detecting the leakage of the stored item in the tank A according to the present invention will be described. As shown in FIG. 2, the first end of the first pipe 12 and second pipe 13 located in the tank A outside permanently installing a pressure gauge (not shown) to one in which either. A pressure equal to or higher than atmospheric pressure or a fluid pressure prescribed by the Tokyo Fire Department is applied to the water flow layer 8 through the other end of the pipe not attached with the pressure gauge, and the pipe is sealed.

  If there is no movement in the pressure gauge pointer, it can be seen that there is no leakage in the tank A and the airtight layer 14, and if there is a movement in which the pressure decreases, water can flow through the tank A and / or the airtight layer 14. It can be seen that air or liquid inside the layer is leaking. In the conventional single tank, once buried in the basement, a minute leak that does not ooze out in the airtight layer could not be easily confirmed, but in the present invention, a minute leak can be easily confirmed at all times.

  Furthermore, a vacuum pump (not shown) is connected to the other end of the first pipe 12, and the liquid accumulated in the water storage tank 11 through the groove 9 a of the water passage layer 8 is sucked up by the first pipe 12. Even when a vacuum pump is used in this way, the second pipe 13 is provided so that suction can be easily performed. When the sucked liquid is stored, it is found that the airtight layer 14 has cracks and leaks there from, and when it is groundwater, the tank A has cracks and leaks from there. Can be determined.

  Further, after the liquid accumulated in the water tank 11 of the tank A is discharged, the liquid is discharged again after a predetermined time, and the discharge amount per unit time is obtained from the discharge amount, and the leakage amount from the tank A and the airtight layer 14 is calculated. It can be measured accurately. In addition, if a liquid sensor or the like that can be inserted into the first pipe 12 is developed, it will lead to early detection of storage leakage.

  In addition, the method of discovering the leakage of the stored matter in the tank A in the rehabilitation structure of the present invention is that the groundwater level in the place where the tank A is buried is lower than the place where the tank A is buried, and the storage inside the tank A The discovery method of the present invention cannot be used for leakage of the hermetic layer 14 above the liquid fuel level.

  Further, as another embodiment of the water-permeable layer 8 provided on the entire inner periphery of the deterioration preventing treatment layer 7 in the tank A, the water-permeable layer 8 is a sheet piece having a constant thickness, and the sheet piece is vertically or horizontally or obliquely disposed on one surface. You may use what provided the some groove | channel (illustration omitted). This is because the curved body 9 of the water-permeable layer 8 receives an impression as a solid material, but this water-permeable layer is not limited to a solid material, and may be a sheet-like flexible material. It may be provided by adhering to the entire inner surface of the layer 7. In this case, the sheet piece has a thickness of 1 to 1.5 mm, a groove depth of 0.5 to 1 mm, a groove width of 1 mm, and an interval between adjacent grooves of 30 to 50 mm.

  In the case of a sheet-like water-permeable layer provided in this way, the damage of the air-tight layer of tank A can be dealt with by a minute groove in the water-permeable layer because it is considered that the breakage of the liquid combustible material occurs. The same effect as the water-permeable layer 8 is achieved. In order not to reduce the storage amount in the tank A after the rehabilitation, it is extremely effective when it is desired to make the finished thickness of the rehabilitation material in the tank A as thin as possible.

  When there is a shake due to an earthquake or the like, in the tank A buried underground, the pipe extended from the tank A, that is, the inlet 3, the vent pipe 4, the measuring pipe 5, the oil feeding pipe 6 and the like and the tank There is a possibility that a crack or the like may occur in the connection part with A, but as a countermeasure against such a vibration, the connection part of the pipe extended from the tank A is made of a flexible member, and a vibration such as an earthquake occurs. Even if there is, the flexible member absorbs the shaking, the portion is not damaged, and the liquid combustible material does not flow out of the tank A.

  In the above embodiment, the deterioration preventing treatment layer 7 is an airtight layer, but is not limited to an airtight layer, and may be a fiber reinforced plastic sheet or simply a rust preventive material. Moreover, it describes concretely as a method of formation of the deterioration prevention process layer 7 and the airtight layer 14, and although the fiber reinforced plastic sheet is used especially as a rehabilitation material, the formation method and rehabilitation material of an airtight layer are limited to these. It is not a thing. Further, the other ends of the first pipe 12 and the second pipe 13 are taken out from the vent pipe 4 and the oil feeding pipe 6 in order to take them out of the tank A. However, the route going out of the tank A is not limited to these. . Furthermore, in the said Example, although the water storage tank 11 is provided, it is good also as not a water storage tank 11 but a water storage part widely.

  Although the curved body 9 is made of plastic, the material for forming the curved body 9 is not limited to plastic, and the groove 9a of the curved body 9 is formed on one surface of the curved body 9 on the deterioration preventing treatment layer 7 side. The groove 9a is not limited to one surface and the side surface, and may be provided on the other surface or the inside of the airtight layer 14 side. The present invention is not limited to these, and only the vertical and horizontal directions or only the oblique directions may be used. Further, although the wound spring 10 is used to connect the curved body 9, the leaf spring is not limited to the wound spring 10, and the curved body 9 connected by these wound springs 10 strongly biases the inner wall surface of the tank. However, this is not an essential requirement of the present invention. Further, a curved body 9 or a sheet piece is described as the water-permeable layer 8 provided on the entire inner periphery of the deterioration preventing treatment layer 7 in the tank A, and the specific size, type, and the like of these curved body 9 or the sheet piece, etc. However, the curved surface 9 or the sheet piece, and the size and type of the groove provided in these, if the method aims at the passage of gas and liquid, It is not limited to these. Further, the groove provided on the curved body 9 and the sheet piece may be on either the deterioration preventing treatment layer 7 side or the airtight layer 14 side. When the groove is provided on the deterioration preventing treatment layer 7 side and the airtight layer 14 side is flat, The layer 14 becomes easy to stick.

It is sectional explanatory drawing of the side surface of the tank of the Example of this invention. It is a section explanatory view of the front of the tank of the example of this invention. It is explanatory drawing of the curved surface body of the Example of this invention. It is sectional explanatory drawing of the state which provided in order the deterioration prevention process layer, the curved body, and the airtight layer in the inner wall surface of the tank of the Example of this invention. It is explanatory drawing of the square cylinder shaped water storage part of the Example of this invention. It is explanatory drawing which shows the state which fixed the end of the 1st pipe to the right side surface of the square cylindrical water storage part provided in the lowest part of the water flow layer of the bottom part of the tank of the Example of this invention. It is plane explanatory drawing of the tank of the Example of this invention.

Explanation of symbols

A tank 1 inspection hole 2 curved surface part 3 injection hole 4 vent pipe 5 metering pipe 6 oil feeding pipe 7 deterioration prevention treatment layer 8 water flow layer 9 curved surface body 9a curved surface groove 10 winding spring 11 water storage tank 12 first pipe 13 second Pipe 14 airtight layer

Claims (5)

The inner wall surface of an existing steel underground tank is subjected to a steel deterioration prevention treatment to provide a deterioration prevention treatment layer, and a plurality of curved bodies or sheet pieces having a predetermined thickness are connected to the entire inner peripheral surface of the deterioration prevention treatment layer. A continuous water permeable layer is provided between all the curved surfaces connected or between all the sheet pieces, and an airtight layer is formed by attaching a rehabilitation material to the entire inner peripheral surface of the water permeable layer. Rehabilitation structure of steel underground tank, characterized by the formation. A plurality of grooves are provided on at least one surface of the curved body or sheet piece forming the water-permeable layer vertically and horizontally or obliquely, and in the water-permeable layer, water can be passed through the entire water-permeable layer through the grooves of the plurality of curved bodies or sheet pieces. The rehabilitation structure for a steel underground tank according to claim 1, wherein the steel underground tank is rehabilitated. One end of the first pipe is fixed in the water passage layer located in the lower part of the steel underground tank so that the water passage layer and one end of the first pipe can pass through the water passage. The other end is provided outside the steel underground tank, and one end of the second pipe is fixed to the water passage located at the upper part of the steel underground tank to connect the water passage layer and the second pipe. Either of the above-mentioned 1 or 2 provided so that water could pass with one end, the inside of the water layer was inserted through the second pipe, and the other end was provided outside the steel underground tank. Rehabilitation structure of steel underground tank described in 1. Opening and fixing one end of the first pipe to the water storage section provided at the bottom of the water underground layer at the bottom of the steel underground tank, provided to allow water to flow between the water storage layer and the water storage section. The rehabilitation structure for a steel underground tank according to claim 3, characterized in that: The water storage section is provided as a rectangular tubular water storage tank in the longitudinal direction of the bottom of the steel underground tank and at the bottom of the water flow layer, and one end of the first pipe is opened and fixed to the water storage tank. And the rehabilitation structure of the steel underground tank of the said Claim 4 provided so that the said water flow layer and water storage tank could be passed.

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