Methods and systems for in situ temporary containment of shallow contaminated soils

1. A method for installing an in situ, low-permeability temporary horizontal barrier at a depth for vertical containment of a soil mass, the method comprising:

installing a low permeability vertical barrier having a plurality of walls located to contain a predetermined soil volume, the vertical barrier having a horizontal surface area in a plane perpendicular to its walls;

injecting low permeability reagents capable of forming the in situ, low-permeability temporary horizontal barrier in a pattern suitable for creating a horizontal subsurface barrier joined to all of the vertical barrier walls to form the in situ low-permeability barrier; and

removing the in situ, low-permeability temporary horizontal barrier through application of a solution capable of dissolving the barrier.

2. The method of claim 1 further comprising implementing quality assurance and validation procedures after installation of the in situ, low-permeability barrier.

3. The method of claim 1 further comprising implementing remediation procedures.

4. The method of claim 1 further comprising site monitoring.

5. The method of claim 1 wherein the horizontal barrier degrades in a predefined duration due to environmental conditions.

6. The method of claim 1 wherein the low permeability reagents capable of forming the in situ, low-permeability temporary horizontal barrier are selected from the group consisting of sodium bentonite, enzyme-induced calcite precipitation, biopolymers, guar, microorganisms, vegetable oil, polysaccharide polymers, and xanthan gum.

7. The method of claim 1 wherein installing the vertical barrier comprises horizontal or direction drilling.

8. A system for installing an in situ, low-permeability temporary horizontal barrier for vertical containment of soil contaminants, the system comprising:

a low permeability vertical barrier having a plurality of walls located to contain a predetermined soil volume, the vertical barrier having a horizontal surface area in a plane perpendicular to its walls;

an injection tool including an injection channel and a plurality of distribution ports for boring into the predetermined soil volume and injecting low permeability reagents capable of forming the in situ, low-permeability temporary horizontal barrier to create a horizontal subsurface barrier joined to all of the vertical barrier walls to form an in situ barrier; and

removing the in situ, low-permeability temporary horizontal barrier through application of a solution capable of dissolving the barrier.

9. The system of claim 8 further comprising implementing quality assurance and validation procedures after installation of the in situ, low-permeability temporary horizontal barrier.

10. The system of claim 8 further comprising implementing remediation procedures including the injection and mixing of remediation agents in the treatment zone during placement and/or retrieval of the injection tool.

11. The system of claim 8 further comprising site monitoring.

12. The system of claim 8 wherein the horizontal barrier degrades due to environmental conditions.

13. The system of claim 8 wherein the low permeability reagents capable of forming the in situ, low-permeability temporary horizontal barrier are selected from the group consisting of sodium bentonite, enzyme-induced calcite precipitation, biopolymers, guar and xanthan gum.

14. The system of claim 13 wherein the reagent comprises sodium bentonite having a dosage in solution in the range of 10% w/v to 20% w/v.

15. The system of claim 13 wherein the reagent comprises xanthan gum having a dosage in solution in the range of 0.1% w/v to 1.0% w/v.

16. The system of claim 13 wherein the reagent comprises guar gum having a dosage in solution in the range of 0.5% w/v to 3.0% w/v.