This plan defines an integrated framework for managing water abstraction, use, reuse, discharge, and protection of both surface water and groundwater during the construction and operation of the Ulaanbaatar Metro Project.

The plan aims to prevent water pollution, optimize water use, and protect the Tuul River Basin and associated aquifers.

Key Objectives

Protect water resources from pollution and depletion

Reduce water consumption and promote reuse

Ensure wastewater is treated and discharged in compliance with standards

Comply with national legislation and international standards (IFC, WB, etc.)

Baseline Conditions

Tuul River:

Average flow: 12–15 m³/s

Annual precipitation: 200–280 mm

Seasonal variability: low flow in spring, peak in summer

River water quality:

Selbe and Tolgoit Rivers – elevated COD and BOD

Tuul River – quality deteriorates downstream of WWTP

Groundwater:

Depth: 1.1–12.3 m

Supplies >90% of the city’s water

Total extraction: 145,000–155,000 m³/day

Key risks:

Over-abstraction → declining groundwater levels

Urban wastewater → surface water degradation

Key Risks

-Construction Phase

Surface water contamination (concrete washout, fuel, sediments)

Increased sediment and turbidity (TSS exceedance)

Groundwater drawdown (~1–1.5 m)

Accidental spills and chemical leakage

Wastewater from labor camps

Water demand:

30–40 m³/day per site

Operation Phase

Wastewater from stations and depots (oil, detergents)

Stormwater runoff contamination

Groundwater seepage into tunnels

Emergency/firefighting water use

Mitigation Measures

Construction Phase

-Surface Water Protection

Use closed-loop systems for concrete washout

Neutralize high pH water before reuse/discharge

Maintain buffer zones:

≥50 m from rivers

-Sediment and Turbidity Control

Install silt traps and sedimentation ponds

Ensure discharge meets:

TSS ≤ 25–30 mg/L

Restrict earthworks during heavy rainfall

-Groundwater Protection

Use cut-off walls and grouting

Control dewatering:

Drawdown ≤ 1.0 m

Use recharge wells where required

-Pollution Prevention

Fuel and chemicals:

Secondary containment (≥110%)

Maintain spill kits at all sites

Spills >20 L → report within 24 hours

-Wastewater Management

Labor camps:

~50 L/person/day

Use temporary treatment systems

Discharge only after meeting standards

-Water Use Efficiency

Reuse water:

Tunnel water

Wheel-wash water

Minimize freshwater abstraction

Operation Phase

-Wastewater Management

Install oil separators and treatment systems

Discharge standards:

SS ≤30 mg/L

Oil ≤1 mg/L

-Stormwater Management

Provide drainage systems with:

    Sediment traps

    Oil interceptors

-Groundwater Protection

Apply waterproof tunnel lining

Monitor and control leakage

Water Reuse

-Use rainwater for:

    Flushing

    Landscaping

Monitoring and Reporting

-Water quality:

pH, BOD, COD, TSS

-Groundwater:

Level and flow monitoring

-Reporting:

    Monthly

    Quarterly

KPIs / Requirements

Wastewater: 100% compliant with standards

Water reuse: increased and optimized

Groundwater: controlled (drawdown ≤1 m)

Reporting: 100% monthly compliance

Importance

Protects water resources and ecosystems

Safeguards the Tuul River Basin

Prevents additional pressure on city water supply

Ensures compliance with international environmental standards