JP2006305543A - In-situ confining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an in-situ confining method capable of avoiding diffusion of ground water in a polluted land from a confining zone by a simple means. <P>SOLUTION: Polluted soil 4 is separated from the surrounding area 5 by an impervious wall 10 and confined inside. One or a plurality of ground water outflow ports 11 each consisting of a low section recessed downward from the top end are provided on the impervious wall 10. A cleaning section 12 comprises a mixture of a permeable material such as sand and crushed stone and a processing material such as iron powder and/or activated carbon exhibiting a cleaning function of removal, decomposition or the like of a pollutant. When the level of the ground water inside the impervious wall 10 rises, the ground water corresponding to the rise of the level of the ground water is guided to the cleaning section 12 directly or through a collection channel 14, cleaned by the cleaning section 12 and discharged to the surrounding area 5 through the ground water outflow ports 11. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an in-situ containment method for containing contaminated soil separately from the surroundings, and more particularly to an in-situ containment method for providing a water shielding wall so as to surround a contaminated area. More specifically, the present invention relates to an in-situ containment method for purifying groundwater flowing out from the inside of the impermeable wall to the surroundings when the groundwater level inside the impermeable wall rises.

  An explanation of the technical method based on the Soil Contamination Countermeasures Law that prevents contaminated soil from eluting harmful substances from the contaminated soil and contaminating groundwater outside the area by containing the contaminated soil in situ (see Non-Patent Document 1 below) )It is described in. On page 111 of the commentary, “Specifically, the extent of contaminated soil and the depth of soil contamination within that range are confirmed by a boring survey, surrounding the extent of soil contamination, A water impervious wall such as steel sheet piles is driven into the impermeable layer to prevent soil contamination from spreading outside the range, and in order to prevent the rainwater from penetrating within the range and affecting the groundwater level inside the containment. In addition, the upper surface of the containment is covered with a material having a water-blocking function, and the upper surface is covered with a concrete layer having a thickness of 10 cm or more, or an asphalt layer having a thickness of 3 cm or more, as in the case of pavement measures. Measures will be taken to cover with soil accordingly. ”“ If an abnormal rise in water level is confirmed inside the containment, take appropriate measures such as lowering the water level due to pumping or reinforcing the water shielding structure. There is a necessity. Has been described as ".

As mentioned above, if the water level rises abnormally in the contaminated area surrounded by the impervious wall, it will overflow the impervious wall and diffuse the contaminated groundwater to the surrounding area. It becomes. JP-A-2003-53317 discloses an in-situ containment method for constructing a water-impervious wall that reaches an impermeable layer so as to surround a contaminated area and contain contaminated soil in the contaminated area. It is described that a drainage groove that reaches a predetermined depth is provided and pumping water from the drainage groove prevents the overflow of the contaminated groundwater level from the inside of the impermeable wall.
JP 2003-53317 A Explanation of technical methods for investigations and measures based on the Soil Contamination Countermeasures Law First edition published in September 2003 Supervision: Ministry of the Environment Edition / Issue: Soil Environment Center

  In the said Unexamined-Japanese-Patent No. 2003-53317, the water treatment equipment which purifies the sewage groundwater pumped up with the pump is needed separately. In addition, a pump is essential, which increases equipment costs and power costs.

  An object of the present invention is to provide an in-situ containment method capable of preventing the diffusion of contaminated groundwater from a containment area by simple means.

  The in-situ containment method according to claim 1 is the in-situ containment method for constructing a water-impervious wall that reaches an impermeable layer or a hardly-permeable layer so as to surround the sewage area and contain the contaminated soil in the contaminated area. In addition, a groundwater outflow portion is provided in which the groundwater inside the impermeable wall flows out of the impermeable wall when the groundwater level inside the impermeable wall rises, and the impermeable wall passes through the groundwater outflow portion. The present invention is characterized in that a purifying means for purifying the groundwater flowing out to the outside is provided.

  The in-situ containment method according to claim 2 is characterized in that, in claim 1, the purification means includes a treatment agent for removing or detoxifying contaminants in groundwater and a water-permeable material.

  The in-situ containment method according to claim 3 is the in-situ containment method according to claim 2, wherein the purification means includes a container containing the treatment agent and a water-permeable material, and an inflow portion of groundwater is provided at one end of the container. In addition, an outflow part of the treated groundwater is provided on the other end side.

  The in-situ containment method according to claim 4 is the method according to claim 2 or 3, wherein the treatment agent is iron powder, activated carbon, hydrotalcite, rare earth compound, magnesium oxide, alumina, allophane, ion exchange resin, chelate resin, and clay mineral. It is one or a mixture of two or more selected from the group consisting of:

  The in-situ containment method according to claim 5 is the method according to any one of claims 2 to 4, wherein the plurality of purification means are provided in multiple stages in a direction from the inner region to the outer region of the water shielding wall, The treatment agent for some of the purification means is different from the treatment agent for other purification means.

  The in-situ containment method according to claim 6 is characterized in that, in any one of claims 1 to 5, the purification means is provided inside the impermeable wall from the groundwater outflow portion. It is.

  The in-situ containment method according to claim 7 is characterized in that, in claim 6, a water collecting channel is provided in the inner region of the impermeable wall to guide the groundwater inside the impermeable wall to the groundwater outflow portion. It is what.

  The in-situ containment method according to claim 8 is characterized in that, in claim 7, the water collecting channel is made of a water-permeable material.

  The in-situ containment method according to claim 9 is characterized in that, in claim 7, the water collecting channel is composed of a perforated pipe provided with a plurality of through holes in the pipe wall.

  The in-situ containment method according to claim 10 is the method according to any one of claims 7 to 9, wherein the outflow portion is provided at the same level as or lower than the water collecting channel of the water shielding wall. It is a feature.

  The in-situ containment method according to claim 11 is the method according to any one of claims 1 to 9, wherein the outflow portion communicates the inner region surrounded by the water shielding wall and the outer region of the water shielding wall. In addition, the inflow port is a drain pipe disposed in the inner region.

  The in-situ containment method according to claim 12 is characterized in that, in claim 11, the outer region is a sewer.

  In the in-situ containment method of the present invention, when the groundwater level inside the impermeable wall rises above a predetermined level, the groundwater inside the impermeable wall flows from the groundwater outflow part provided on the impermeable wall to the outside of the impermeable wall. However, since this effluent is purified by the purification means, contamination of the outside of the impermeable wall is prevented.

  As the purification means of the present invention, those containing a treating agent for removing or decomposing contaminants of groundwater and water-permeable materials such as sand and crushed stone are suitable.

  In the present invention, the purifying means includes a container that contains the treatment agent and the water-permeable material, an inflow portion of groundwater is provided at one end of the container, and treated groundwater is provided at the other end. It is preferable that the outflow part is provided. In this case, the flow of groundwater passing through the container is an extruded flow.

  Examples of the treating agent include iron powder, activated carbon, hydrotalcite, rare earth compound, magnesium oxide, alumina, allophane, ion exchange resin, chelate resin, clay mineral and the like. These treatment agents may be used alone or in combination of two or more depending on the type of pollutants in the groundwater.

  In the present invention, a plurality of purification means are provided in multiple stages in the direction from the inner region to the outer region of the water shielding wall, and the treatment agent of at least some of the purification means is different from the treatment agent of other purification means. It is good also as composition which has. By comprising in this way, the multiple types of contaminant in groundwater can be removed or detoxified efficiently, respectively.

  This purification means is preferably provided inside the impermeable wall rather than the groundwater outflow part.

  If a water collecting channel is provided in the inner region of the impermeable wall to guide the groundwater inside the impermeable wall to the groundwater outflow portion, the groundwater in the contaminated area can be collected smoothly.

  This water collecting pipe may be made of a water-permeable material, or may be made of a perforated pipe provided with a plurality of through holes in the pipe wall.

  In the present invention, the groundwater outflow portion may be provided at the same level as or lower than the water collecting channel of the impermeable wall.

  In addition, the groundwater outflow portion may be a drain pipe that communicates the inner region and the outer region of the impermeable wall and has an inflow port disposed in the inner region. In this case, the outlet of the drain pipe is preferably connected to the sewer.

  The in-situ containment method of the present invention can also be applied to an artificially constructed one corresponding to an impermeable layer or a hardly water-permeable layer.

  Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 is a cross-sectional perspective view showing an area to which the in-situ containment method according to the embodiment is applied, FIG. 2 is a plan view showing the underground structure in this area seen through the soil, and FIG. Fig. 3 (b) is a sectional view taken along the line IIIb-IIIb in Fig. 4, and Fig. 4 is a perspective view in the soil showing the water shielding wall, the purification means and the water collecting channel provided in the soil. FIG.

  As shown in FIG. 3A, the impermeable layer 3 or the hardly permeable layer is present at a predetermined depth from the ground surface 1, and the aquifer 2 is present on the upper side thereof.

  Since the contaminated soil 4 exists in all or a part of this area, the contaminated soil 4 is isolated from the surroundings 5 by the impermeable wall 10 and contained.

  The impermeable wall 10 has a lower end reaching the impermeable layer or the hardly permeable layer 3 and an upper end located near the ground surface 1 higher than the groundwater level 6. The upper end of the impermeable wall 10 may reach the ground surface 1.

  The impermeable wall 10 surrounds the entire circumference of the contaminated soil 4. In this embodiment, the planar view shape is a rectangular frame shape, but is not limited thereto.

  The water-impervious wall 10 can be constructed by applying a number of boreholes in the ground in a continuous row and pouring concrete into it, but may also be formed by driving a water-impervious steel sheet pile.

  As clearly shown in FIG. 4, this impermeable wall 10 is provided with one or a plurality of (three in this embodiment) rectangular groundwater outflow portions 11 each having a low portion recessed downward from the upper end. Yes. The lower edge of the groundwater outflow portion 11 is higher than the groundwater level 6 by a predetermined height (for example, about 0 to 100 cm).

  A purification unit 12 is provided on the inner side (contaminated soil 4 side) than the groundwater outflow unit 11. The purification unit 12 is made of a mixture of a water-permeable material such as sand and crushed stone and a treatment agent that exhibits a purification action by removing or decomposing contaminants such as iron powder and / or activated carbon. In addition, as the treating agent, hydrotalcite, magnesium oxide, alumina, allophane, ion exchange resin, clay mineral, or the like may be used.

  Plate members 13 made of steel sheet piles or the like are disposed on both sides and the lower portion of the purification unit 12. A waterproof concrete wall may be provided instead of the plate material 13.

  The upper surface of the purification unit 12 is preferably positioned higher than the lower edge of the groundwater outflow unit 11 by about 0 to 200 cm. Further, the lower surface of the purification unit 12 is preferably located 50 to 500 cm lower than the lower edge of the groundwater outflow unit 11. Although both side surfaces of the purification unit 12 are flush with the side edge of the groundwater outflow unit 11, the purification unit 12 may be provided wider than that.

  The purification unit 12 is provided so as to contact the inner surface of the water-impervious wall 10. Further, in this embodiment, a part of the purification unit 12 enters the groundwater outflow unit 11.

  The plate 13 preferably extends from 0 to 500 cm above the upper surface of the purification unit 12, and preferably extends from 0 to 500 cm below the lower surface of the purification unit 12. The plate material 13 is in contact with the inner surface of the water shielding wall 10. This abutting portion may be sealed if necessary.

  The plate material 13 covers the entire side surfaces and the lower part of the purification unit 12, and water is prevented from flowing into the purification unit 12 from the side surface and outflowing into the groundwater outflow unit 11 in a short circuit.

  A water collecting channel 14 is provided at a level parallel to the inner surface of the water shielding wall 10 and including the groundwater level 6. The water collecting channel 14 is made of a water permeable material such as sand or crushed stone. The water collecting channel 14 may be a perforated pipe.

  The water collecting channel 14 is disposed so as to be in contact with the end surface of the purification unit 12 opposite to the groundwater outflow unit 11. The water collecting channel 14 is provided so as to continuously circulate along the inner side surface of the impermeable wall 10, but the middle may be partially interrupted. Further, the water collecting channel 14 may be provided in a comb tooth shape over the entire contaminated area.

  Although not shown, the ground surface 1 may be covered with asphalt, concrete, a water shielding sheet, or the like to prevent underground penetration of rainwater.

  In the containment structure configured in this way, the groundwater level inside the impermeable wall 10 is usually the same as or lower than the lower edge of the groundwater outflow portion 11, so that groundwater flows from the contaminated area to the surrounding area 5. Will not leak.

  When the groundwater level inside the impermeable wall 10 rises for some reason such as rainfall, the groundwater flows into the purification unit 12 via the water collecting channel 14 or directly, and after being purified by the purification unit 12, the groundwater outflow unit 11 Out to the surroundings 5. This effluent water has been subjected to removal of heavy metals or decomposition or adsorption removal processing of contaminants such as halogenated organic substances in the purification section 12 and does not contaminate the surroundings 5.

  When the pollutant is a volatile organic chlorine compound, covering the ground surface 1 with asphalt or the like prevents (oxygen) from diffusing into the ground and improves the purification efficiency of the compound.

  When the pollutant is a heavy metal, the contaminated soil 4 or the water in the contaminated soil 4 may be brought into contact with air, thereby improving the heavy metal purification treatment efficiency.

  FIG. 5 is a plan view of an area where an in-situ containment method according to another embodiment is applied, FIG. 6 is an enlarged plan view of the vicinity of the groundwater outflow area in this area, and FIG. 7 is along the line VII-VII in FIG. It is sectional drawing.

  In this embodiment, a drain pipe 20 having a groundwater inflow port disposed in the inner region is provided so as to communicate the inner region surrounded by the impermeable wall 10 and the outer region.

  As shown in FIG. 5, also in this embodiment, a rectangular frame-shaped impermeable wall 10 is constructed so as to surround four sides of the contaminated soil (contaminated area) 4. As described above, the impermeable wall 10 has a lower end that reaches the impermeable layer or the hardly permeable layer 3 and an upper end that is located near the ground surface 1 higher than the groundwater level 6. The upper end may reach the ground surface 1. In this embodiment, the outflow portion 11 composed of a low portion recessed downward from the upper end of the impermeable wall 10 is not provided.

  In this embodiment, a water collection container 21 is installed in the vicinity of one corner of the inner area of the water shielding wall 10. This water collection container 21 is a bottomed cylindrical container in this embodiment, the bottom part is located lower than the groundwater level 6, and the upper part is exposed to the ground surface 1. A lid 21 a is attached to the upper end of the water collection container 21. However, the upper portion of the water collecting container 21 may not be exposed on the ground surface 1.

  One end (groundwater inlet) of the drain pipe 20 is connected to the vicinity of the bottom of the water collection container 21 which is lower than the groundwater level 6. The drain pipe 20 extends from the inner area of the impermeable wall 10 to the outer area of the impermeable wall 10 through the impermeable wall 10. The drain pipe 20 is disposed so as to have a downward slope from the inner region to the outer region of the impermeable wall 10.

  In this embodiment, the other end side (outflow port) of the drain pipe 20 is connected to a sewer (not shown) that flows in the outer region of the impermeable wall 10. In addition, when the sewer is arrange | positioned in the height which becomes higher than this drain pipe 20, you may connect the drain pipe 20 and a sewer via a pumping equipment (not shown).

  In the inner region of the impermeable wall 10, a water purification unit 12 </ b> A is installed adjacent to the water collection container 21. As shown in FIG. 6, the water purification unit 12 </ b> A accommodates water-permeable materials such as sand and crushed stone, treatment agents that perform purification action by removing or decomposing contaminants, and these water-permeable materials and treatment agents. And a container 24.

  As shown in the figure, in this embodiment, the container 24 is constituted by three plate members 24a, 24b, and 24c made of steel sheet piles and the like that are disposed in a substantially U shape so as to surround three sides of the water purification unit 12A. Has been built. Seals are applied to the joints between the plate members 24a to 24c as necessary. Of the container 24, the side that is not blocked by the plate members 24 a to 24 c is an inflow portion 24 d of groundwater into the container 24. The outflow port 24e of the treated groundwater is provided in the plate member 24b that closes the inflow portion 24d and the opposite side. The outflow port 24 e communicates with the inside of the water collection container 21 through the pipe 25. In addition, you may construct the container 24 with a concrete wall instead of the said board | plate materials 24a-24c.

  Each of the plate members 24a to 24c of the container 24 extends from 0 to 500 cm above the groundwater level 6 and preferably extends from 0 to 500 cm below the groundwater level 6. The outlet 24e and the pipe 25 are disposed substantially horizontally at a level including the groundwater level 6.

  In this embodiment, the first water-permeable material layer 22a, the first treatment agent layer 23a, and the second water-permeable material are disposed in the container 24 in the direction from the inflow portion 24d toward the outlet 24e. The layer 22b, the second treatment agent layer 23b, and the third water-permeable material layer 22c are formed in this order in multiple layers.

  Each of the layers 22a to 22c, 23a, and 23b is fully extended from one inner surface to the other inner surface of the plate members 24a and 24c facing each other, and from the inflow portion 24d to the inner surface of the opposite plate member 24b. Filled. Each of the layers 22a to 22c, 23a, and 23b has a lower surface that reaches 50 to 500 cm below the groundwater level 6 and an upper surface that preferably reaches 0 to 200 cm above the groundwater level 6.

  In this embodiment, the upper and lower surfaces of the layers 22a to 22c, 23a and 23b and the upper and lower sides of the plate members 24a to 24c are positioned at substantially the same level, but the plate members 24a to 24c are The layers 22a to 22c, 23a and 23b may extend below the lower surface of the layers 22a to 22c, 23a and 23b, or may extend to the upper side of the upper surfaces of the layers 22a to 22c, 23a and 23b.

  In this embodiment, the first treatment agent layer 23a and the second treatment agent layer 23b are composed of different types (or blends) of treatment agents. As described above, examples of the treating agent include iron powder, activated carbon, hydrotalcite, rare earth compound, magnesium oxide, alumina, allophane, ion exchange resin, chelate resin, and clay mineral. The treatment agent is appropriately selected according to the contaminant contained in the groundwater. At this time, as the first and second treatment agent layers 23a and 23b, different kinds of treatment agents may be used alone (without mixing), or two or more kinds of treatment agents may be mixed. May be used.

  The first to third water-permeable material layers 22a to 22c may be made of the same type of water-permeable material, or may be made of different types of water-permeable materials.

  In this embodiment, by surrounding three sides of the purification unit 12A with the plate members 24a to 24c, it is possible to prevent water from flowing into the purification unit 12A and outflowing into the water collecting container 21 in a short circuit. If necessary, a plate material may also be provided on the bottom surface and top surface of the purification unit 12A to prevent water from flowing into the purification unit 12A from the bottom surface and top surface of the purification unit 12A.

  In this embodiment, the water collecting channel 14 </ b> A is provided in a comb-like shape over the entire contaminated area inside the impermeable wall 10 at a level including the groundwater level 6. In this embodiment as well, the water collecting channel 14A is made of a water-permeable material such as sand or crushed stone, but may be constituted by a perforated pipe or the like.

  Specifically, in this embodiment, as shown in FIG. 5, as shown in FIG. 5, the stem collection is performed so that the rectangular contaminated area 4 surrounded by the water shielding wall 10 crosses diagonally from the corner near the water collection container 21. A water channel 14a is extended. The proximal end side of the main water collecting channel 14a is disposed so as to be in contact with the end surface of the first water-permeable material layer 22a facing the inflow portion 24d of the water purification unit 12A.

  Branch water collecting channels 14b extend from a plurality of locations along the extending direction of the main water collecting channel 14a in parallel with each side in two orthogonal directions of the water shielding wall 10 (vertical direction and horizontal direction in FIG. 5). Yes. (In this embodiment, six branch water collecting channels 14b extend from the main water collecting channel 14a at intervals in the horizontal and vertical directions in FIG. 5).

  Although not shown, in this embodiment as well, the ground surface 1 may be covered with asphalt, concrete, water shielding sheets or the like to prevent rainwater from penetrating underground.

  Even in the confinement structure configured as described above, when the groundwater level 6 inside the impermeable wall 10 rises for some reason such as rain, the groundwater flows into the purification unit 12A via the water collecting channel 14A or directly. At this time, groundwater flows into the container 24 from the water collecting channel 14A through the inflow portion 24d, and the first water-permeable material layer 22a, the first treatment agent layer 23a, and the second water-permeable material By sequentially passing through the layer 22b, the second treatment agent layer 23b, and the third water-permeable material layer 22c, contaminants in the groundwater are removed or detoxified.

  This groundwater is purified by the purification section 12A, and then flows out from the outlet 24e to the sewer flowing through the outer region of the impermeable wall 10 through the pipe 25, the water collection container 21 and the drain pipe 20. This effluent has been subjected to the decomposition or adsorption removal processing of the pollutant in the purification unit 12A, and does not contaminate the sewer.

  In this embodiment, since the water collecting channel 14 </ b> A is disposed over substantially the entire contaminated area 4, groundwater can be collected evenly over substantially the entire contaminated area 4.

  In the above embodiment, the water collection container 21 (the inlet of the drain pipe 20) is arranged near the corner of the inner area of the water shielding wall 10, but the water collection container 21 (the inlet of the drain pipe 20). The arrangement of is not limited to this. Further, the arrangement of the water collecting channel in the inner region of the water shielding wall 10 is not limited to the above embodiments.

  For example, as shown in FIG. 8, the water collection container 21 (the inlet of the drain pipe 20) may be disposed near the center of the contaminated area 4.

  In the embodiment shown in FIG. 8 as well, the water collecting channel 14B is disposed over substantially the entire contaminated area 4.

  In this embodiment, a substantially U-shaped water collecting channel 14 c is extended along the inner surface of the water shielding wall 10 surrounding three sides of the contaminated area 4, and a slightly smaller U-shaped water collecting channel 14 d is extended inside. An approximately U-shaped water collecting channel 14e that is a little smaller on the inside extends, and an approximately U-shaped water collecting channel 14f that is a little smaller on the inside extends. In addition, a water collecting channel 14g is extended along the inner side surface of the remaining one water-impervious wall 10 so as to short-circuit the vicinity of both ends of the substantially U-shaped water collecting channels 14c to 14f, and the substantially U-shaped water collecting channel 14c to 14f. A water collecting channel 14h is extended toward the center of the contaminated area 4 so as to cross the vicinity of the intermediate portion in the extending direction of the water collecting channels 14c to 14f.

  A water collection container 21 and a purification unit 12A are arranged inside the innermost substantially U-shaped water collection channel 14f. The end of the water collecting channel 14h is connected to the purification unit 12A.

  Even in this embodiment, since the water collecting channel 14B is disposed over substantially the entire contaminated area 4, groundwater can be collected evenly over substantially the entire contaminated area 4.

  Each of the above embodiments shows an example of the present invention, and the present invention is not limited to the above embodiment.

It is a perspective view which shows the area where the in-situ containment construction method which concerns on embodiment was applied. It is a top view which shows the underground structure of this area. 3A is a cross-sectional view taken along line IIIa-IIIa in FIG. 1, and FIG. 3B is a cross-sectional view taken along line IIIb-IIIb in FIG. It is a perspective view which shows a water-impervious wall, a purification means, and a water collection channel. It is a top view of the area where the in-situ containment construction method concerning another embodiment was applied. FIG. 6 is an enlarged plan view in the vicinity of a groundwater outflow portion in the area of FIG. 5. It is sectional drawing which follows the VII-VII line of FIG. It is a perspective view which shows the area where the in-situ containment construction method which concerns on another embodiment was applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Impermeable wall 11 Groundwater outflow part 12,12A Purification | purification part 13 Board | plate material 14,14A, 14B Catchment path 20 Drain pipe 21 Catchment container 22a-22c Permeable material layer 23a-23b Treatment agent layer 24 Container 24d Inflow part 24e outlet

Claims (12)

In the in-situ containment method of building a water-blocking wall that reaches the impermeable layer or the hardly permeable layer so as to surround the sewage area and contain the contaminated soil in the contaminated area,
Provided in the impermeable wall is a groundwater outflow portion through which groundwater inside the impermeable wall flows out of the impermeable wall when the groundwater level inside the impermeable wall rises. An in-situ containment method characterized by providing purification means for purifying groundwater flowing out of the impermeable wall.   2. The in-situ containment method according to claim 1, wherein the purification means includes a treatment agent that removes or renders the contaminants in the groundwater and a water-permeable material.   3. The purifying means according to claim 2, comprising a container that contains the treatment agent and the water-permeable material, wherein an inflow portion of groundwater is provided on one end side of the container, and the other end side is treated. An in-situ containment method characterized by a groundwater outflow.   4. The treatment agent according to claim 2, wherein the treatment agent is selected from the group consisting of iron powder, activated carbon, hydrotalcite, rare earth compound, magnesium oxide, alumina, allophane, ion exchange resin, chelate resin, and clay mineral. An in-situ containment method characterized by being a mixture of more than seeds. In any one of Claims 2 thru | or 4, the said some purification | cleaning means is provided in multiple stages in the direction which goes to an outer side area | region from the inner area | region of the said water-impervious wall,
An in-situ containment method characterized in that the treatment agent of at least some of the purification means is different from the treatment agent of other purification means.   6. The in-situ containment method according to any one of claims 1 to 5, wherein the purification means is provided inside the impermeable wall with respect to the groundwater outflow portion.   7. The in-situ containment method according to claim 6, wherein a water collecting channel is provided in the inner region of the impermeable wall to guide groundwater inside the impermeable wall to the groundwater outflow portion.   8. The in-situ containment method according to claim 7, wherein the water collecting channel is made of a water-permeable material.   8. The in-situ containment method according to claim 7, wherein the water collecting channel is formed of a perforated pipe having a plurality of through holes provided on a pipe wall.   10. The in-situ containment method according to any one of claims 7 to 9, wherein the outflow portion is provided at the same level as or lower than the water collecting channel of the water shielding wall.   10. The inflow port according to claim 1, wherein the outflow portion has an inflow port in the inner region so that the inner region surrounded by the impermeable wall communicates with the outer region of the impermeable wall. In-situ containment method characterized by being a drainage pipe arranged.   The in-situ containment method according to claim 11, wherein the outer region is a sewer.

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