California Dewatering & Groundwater Treatment: What You Need to Know

California’s construction, infrastructure, and environmental projects face a unique and growing challenge: groundwater management. From large-scale infrastructure builds to urban developments and remediation projects, dewatering, the process of removing groundwater to enable construction or excavation, is a routine necessity. However, in California, dewatering is not just an engineering task; it is a regulatory, environmental, and public health issue.

This is where water treatment in dewatering operations becomes essential.

• What groundwater & dewatering mean in the California context

• Why dewatering is heavily regulated in the state

• The risks of untreated groundwater discharge

• How proper water treatment protects projects, ecosystems, & communities

Understanding Groundwater & Dewatering in California

What Is Groundwater?

Groundwater is water stored beneath the Earth’s surface in soil and rock formations known as aquifers. In California, groundwater supplies over 40% of the state’s water during drought years, making it a critical resource.

What Is Dewatering?

Dewatering involves pumping or draining groundwater from construction sites, tunnels, excavations, mines, or remediation zones to:

• Stabilize soil

• Prevent flooding

• Allow safe & efficient construction activities

Common dewatering applications in California include:

• Infrastructure & transportation projects

• Commercial & residential construction

• Environmental remediation sites

• Utility & pipeline installations

Why Dewatering Is Especially Challenging in California

California’s regulatory and environmental landscape makes dewatering more complex than in many other states.

1. Strict Environmental Regulations

Dewatering discharge is regulated under:

• Clean Water Act (CWA)

• National Pollutant Discharge Elimination System (NPDES)

• California State Water Resources Control Board

• Regional Water Quality Control Boards

Discharged groundwater must meet stringent water quality standards before being released into:

• Storm drains

• Surface waters

• Municipal sewer systems

• Ground infiltration systems

2. Variable Groundwater Quality

California groundwater often contains:

• Sediment & turbidity

• Heavy metals (arsenic, iron, manganese)

• Petroleum hydrocarbons

• PFAS & other emerging contaminants

• High salinity or total dissolved solids (TDS)

Without treatment, discharging this water can cause serious environmental harm and regulatory violations.

3. Drought & Water Scarcity

California’s recurring droughts have elevated groundwater from a hidden resource to a strategic asset. Treated dewatering water can sometimes be:

• Reused on-site

• Safely discharged for beneficial use

• Reintroduced into groundwater basins

Why Water Treatment Is Essential in Dewatering Operations

Protecting Waterways and Ecosystems

Untreated dewatering discharge can:

• Increase turbidity in rivers & streams

• Smother aquatic habitats

• Introduce toxic contaminants into ecosystems

Water treatment systems remove harmful constituents, ensuring compliance with discharge permits and protecting sensitive environments.

Regulatory Compliance & Risk Reduction

Failing to treat dewatering water can lead to:

• Project shutdowns

• Costly fines & penalties

• Permit violations

• Legal & reputational damage

Proper water treatment helps contractors and operators:

• Meet NPDES permit limits

• Avoid enforcement actions

• Maintain project timelines

Supporting Sustainable Construction Practices

Modern dewatering water treatment supports:

• Water reuse & recycling

• Reduced reliance on potable water

• Compliance with ESG & sustainability goals

In a state like California, sustainability is no longer optional, it’s expected.

Common Water Treatment Technologies Used in Dewatering

Depending on site conditions and contaminants, dewatering treatment may include:

Sediment & Turbidity Control

• Settling tanks

• Lamella clarifiers

• Bag & cartridge filtration

Chemical Treatment

• pH adjustment

• Coagulation & flocculation

• Oxidation or reduction

Advanced Treatment

• Activated carbon for hydrocarbons & PFAS

• Ion exchange for metals

• Membrane filtration for dissolved contaminants

Modular & Mobile Treatment Systems

Mobile treatment units are especially popular in California due to:

• Tight urban sites

• Temporary project durations

• Rapid permitting requirements

The Role of Water Treatment in Long-Term Groundwater Protection

California’s Sustainable Groundwater Management Act (SGMA) underscores the importance of protecting groundwater basins for future generations. Dewatering projects that integrate effective water treatment:

• Reduce aquifer contamination

• Support basin sustainability

• Align with state-wide water management goals

In many cases, treated dewatering water can even become a beneficial resource, rather than a waste stream.

Dewatering Is More Than Pumping Water

In California, dewatering is inseparable from water treatment. Proper treatment:

• Ensures environmental protection

• Maintains regulatory compliance

• Reduces project risk

• Supports sustainable water use

As regulations tighten and water scarcity increases, integrating effective water treatment into dewatering operations is no longer just best practice, it’s a necessity.