1. Soil Management Plan

The Soil Management Plan for the Ulaanbaatar Metro Project is designed to minimize soil degradation, contamination, erosion, dust generation, and risks associated with excavated material during construction. The plan covers all soil-related activities, including earthworks, station and tunnel excavation, shafts, temporary access roads, stockpiles, fuel and chemical handling, dewatering, and site reinstatement. It has been developed in line with Mongolian standards, municipal regulations, and the environmental requirements of international financing institutions.

2. Why this plan is important

The Ulaanbaatar metro corridor passes through areas with mixed soil conditions, including urban fill, potential legacy contamination, groundwater interaction, spring thaw effects, and freeze–thaw cycles. For this reason, an integrated soil management approach is essential to maintain construction stability, protect the surrounding environment, and reduce risks to workers and nearby communities.

Key risks

• The plan identifies several major soil-related risks during construction, including:
• excavation collapse and settlement
• erosion and sediment runoff during spring thaw
• dust generation and wind-blown soil
• soil contamination from fuel, oil, or chemicals
• mixing of contaminated spoil with clean excavated material
• instability caused by groundwater and dewatering activities.

3. Main soil protection measures

During construction, exposed soil areas will be kept to a minimum and protected through temporary stabilization measures. These include dust suppression by watering, geotextile protection, silt fencing, sediment retention basins, temporary seeding, stockpile covering, and windbreak barriers. In deeper or steeper excavations, the plan also provides for benching, shoring systems, shotcrete, and temporary slope protection. Additional controls and more frequent inspections are required during snowmelt periods and strong spring winds.

4. Topsoil salvage and reuse

Topsoil suitable for landscaping and restoration will be identified, stripped separately, and stored in protected stockpiles for future reuse. In general, topsoil will be stripped at a depth of 15–30 cm and will not be taken from contaminated or industrial legacy areas. Stockpiles will be limited in height, clearly labelled, protected from runoff and wind, and monitored regularly. Reused topsoil will support landscaping at the depot, station entrances, roadside greening, and slope reinstatement.

5. Excavated material management

The construction of the metro will generate large volumes of excavated spoil. The plan requires all spoil to be classified as either clean or contaminated. Clean spoil may be reused for backfilling, embankments, road sub-base, or site leveling where technically suitable. Contaminated spoil, however, must be segregated, stored in lined containment areas, and transported only to licensed disposal facilities. Transport controls such as covered trucks, designated haul routes, and spill prevention measures are also required.

6. Contaminated soil identification and handling

If unusual staining, odor, discoloration, buried waste, or other signs of contamination are encountered during excavation, work must stop immediately in the affected area. Samples must then be collected and tested by an accredited laboratory. If contamination is confirmed, the material must be isolated, labelled, stored safely, and managed as hazardous waste. Workers handling contaminated soil must follow specific safety procedures and use appropriate protective equipment.

7. Prevention of soil pollution during construction

To prevent pollution during construction, fuels, oils, and chemicals will be stored in controlled areas with secondary containment systems. Equipment maintenance zones will include drip trays, absorbent materials, and spill kits. Concrete wash water and dewatering effluent must also be managed carefully to avoid contaminating soil and groundwater. These controls are intended to reduce both accidental spills and long-term soil pollution risks.

8. Monitoring and reporting

Implementation of the plan will be monitored through daily, weekly, monthly, and quarterly inspections and reporting. Monitoring includes soil quality sampling, erosion and stockpile inspections, contaminated soil tracking, photographic and GIS documentation, spill reports, and corrective action records. The plan also establishes a clear reporting and escalation process for incidents such as spills, contamination, or unexpected soil exposure.

9. Training and awareness

All project personnel working on site will receive induction and refresher training on soil protection, spill response, erosion control, and contaminated soil handling. Staff in higher-risk roles will receive specialist training, while safety signs and awareness materials will be displayed regularly across the construction areas.

10. Restoration and final reinstatement

Once construction is complete, disturbed areas will be backfilled, graded, compacted, covered with topsoil where required, revegetated, and restored to a safe and stable condition. Temporary facilities and construction impacts will be removed, and the land will be reinstated to support long-term environmental stability and urban functionality.