■ At what point is a decision made in the method using mud water? In the method of excavating the ground using water, the excavation work is considered to include the process of separating the excavated material into original soil and water. A decision is made at the point when it comes out of that integrated system, so the sand separated by the classifier is treated as soil, while the remaining excess mud water is treated as sludge. ■ Is "mud" considered construction sludge? According to the standards for the utilization of generated soil, generated soil is classified into construction-generated soil types 1 to 4 and mud based on the cone index, with mud defined as having a cone index of less than 200 kN/m². However, this classification is based on engineering judgment and does not determine whether it is classified as industrial waste. Additionally, sediment resulting from dredging in ports and rivers, as well as excavated material from ground excavation, are excluded from the Waste Management Law. ■ Is 94.6% all reused? In the fiscal year 2018, the recycling and reduction rate of construction sludge was 94.6%, an increase from 85.1% in fiscal year 2008, achieving the target of over 90%. This rate is calculated by adding the amount of reuse and recycling to the reduction amount due to dewatering and other processes. It does not mean that everything was reused.

■The properties of sludge differ depending on the construction method! Construction sludge can be classified based on its properties as follows: 1. Slurry: Excess sludge water from methods such as slurry shield tunneling. It can be reduced through mechanical dewatering. 2. Mud: Excavated soil from mud pressure shield tunneling. Mechanical dewatering is difficult, but sun drying and stabilization treatment are possible. 3. Self-hardening: Sludge from soil-cement wall methods. It contains a lot of cement and hardens if left unattended. ■How to use it as treated soil? According to the construction sludge treatment soil utilization technical standards, treated construction sludge is defined as that which has been improved in properties through processes such as incineration, dewatering, drying, and stabilization with cement or lime, and its quality is generally classified by the cone index. For example, in advanced dewatering, dewatered cakes are used as fill material or backfill. ■Confirmation of harmful substances It is also necessary to confirm compliance with soil environmental standards (leaching standards) and harmful substance content standards through analysis certificates and other documentation. ■Not necessarily valuable materials Even when used as construction materials, properties alone do not immediately determine whether it is a valuable material. ■Consultation on dewatering If you are having trouble with dewatering conditions or equipment, please feel free to consult with us first.