If construction work is likely to affect groundwater, thorough investigations must be carried out and appropriate measures must be taken as necessary.
When using methods such as groundwater level lowering, compressed air, and chemical grouting in combination, or when muddy water shields are used near wells or when backfilling is used, impacts on groundwater may occur. Therefore, before construction begins, it is necessary to investigate the groundwater usage situation in the surrounding area and take appropriate measures to address any potential impacts.
1) Investigate the surrounding ground and groundwater levels, water quality, flow direction, etc. to understand the overall trends (see Article 8 of the same Act).
② Investigate the existence of wells, ponds, and reservoirs in the vicinity and their usage status. In particular, thoroughly investigate wells used for domestic and commercial water.
③ If chemical grouting is used, an investigation will be conducted based on the investigation items in the former Ministry of Construction's "Provisional Guidelines for Construction Work Using Chemical Grouting Methods" (1974).
1) Adoption of auxiliary construction methods:
Water is cut off using appropriate auxiliary construction methods such as compressed air, chemical injection, freezing, and water barriers to prevent a drop in the surrounding groundwater level. In this case, the appropriate auxiliary construction method is selected taking into consideration not only the soil conditions, but also environmental conditions such as the soil cover, the overall structure of the ground, and nearby wells.
② Preventing groundwater contamination by chemical grouting
Chemical grouting must be carried out while monitoring the water contamination status by setting up side points in the surrounding area. For details, see the former Ministry of Construction's "Provisional Guidelines for Construction Work Using Chemical Grouting Methods" (1974).
When work is carried out using compressed air construction methods, investigations must be carried out in advance and appropriate measures must be taken to prevent the impact on the surrounding area due to leakage of oxygen-deficient air, etc.
When work is carried out using compressed air methods, there is a risk that oxygen-deficient air or harmful gases may leak into nearby wells, basements, or other underground construction sites depending on the ground conditions, so appropriate investigations and measures must be taken in accordance with relevant laws and regulations. Also, if the ground contains harmful gases such as methane or hydrogen sulfide, the risk factors increase and additional measures must be taken.
① Article 24 of the "Regulations for the Prevention of Oxygen Deficiency, etc. (Measures Related to Compressed Air Construction Methods)" stipulates the investigation, measurement, and prevention measures to be taken when working using compressed air construction methods in areas where there is a risk of oxygen deficiency.
② Article 6, paragraph 21 of the Enforcement Order of the Industrial Safety and Health Act stipulates the appointment of an operations chief and requires work environment measurements for work in oxygen-deficient hazardous locations. Attached Table 6 of the Enforcement Order also clearly lists oxygen-deficient hazardous locations.
① Preliminary investigation and review:
If the results of soil and groundwater investigations (see Article 8) indicate a risk of leakage of oxygen-deficient air, etc., investigations and reviews must be carried out to prevent accidents, such as an investigation of obstructing properties within the affected area (see Article 7).
②Preventive measures:
Measure the oxygen concentration in the air at wells, basements, and other locations within a 1km radius where there is a risk of leakage, and ensure monitoring. Also, if it is necessary to avoid the effects of exposure, take appropriate preventive and safety measures.
(Reference: "Tunnel Standard Specifications - Shield Construction Method, Established in 2006," Japan Society of Civil Engineers)
Environmental assessment
(environmental impact assessment)
Overview of the Japan-Korea Tunnel
