Underground Storage Tank Removal: Process, Costs and Environmental Requirements

Underground storage tanks (USTs) are one of the most common sources of soil and groundwater contamination worldwide. The US EPA estimates there are approximately 542,000 active USTs and over 2 million closed USTs in the United States alone. In Canada, Australia, the UK and Europe, the numbers are proportionally similar. When these tanks leak - and many do - the contamination can persist for decades and cost hundreds of thousands to clean up.

Whether you are decommissioning a former gas station, removing heating oil tanks from a residential property or addressing regulatory requirements on an industrial site, understanding the UST removal process is essential.

Why Remove Underground Storage Tanks?

USTs are removed for several reasons:

• Regulatory compliance - Most jurisdictions require removal of tanks that have reached the end of their useful life (typically 25-30 years for steel tanks) or that no longer meet current technical standards.
• Property transactions - Buyers and lenders routinely require UST removal or proof of compliance before closing.
• Known or suspected leaks - Failed integrity tests, inventory discrepancies or visible contamination trigger mandatory removal and investigation.
• Site redevelopment - USTs must be removed before construction that would conflict with their location.
• Insurance requirements - Insurers may refuse to cover properties with non-compliant UST systems.

Types of Underground Storage Tanks

• Single-wall steel - The oldest and most leak-prone type. No secondary containment. Most jurisdictions require these to be removed or upgraded.
• Double-wall steel - Inner and outer steel walls with interstitial monitoring. Better leak protection but still subject to corrosion.
• Fiberglass (FRP) - Corrosion-resistant single or double-wall tanks. Standard for new installations since the 1990s.
• Steel with cathodic protection - Impressed current or sacrificial anode systems to prevent corrosion. Requires regular testing to verify the protection system is functioning.
• Heating oil tanks - Residential and commercial heating oil tanks, typically 500-5,000 liters. Often unregistered and discovered during property transactions.

The Removal Process

Step 1: Regulatory Notification

Before any work begins, notify the applicable regulatory authority. Requirements vary by jurisdiction:

• US: Notify state UST program (typically 30 days before closure). Some states require a licensed tank removal contractor.
• Canada: Provincial notification requirements (e.g., BC requires notification to the Ministry of Environment, Ontario to the TSSA).
• UK: Notify the Environment Agency. Compliance with the Groundwater Regulations.
• Australia: State EPA notification. Work must be performed by a licensed contractor.

Step 2: Tank Cleaning and Inerting

Before excavation, the tank must be emptied, cleaned and rendered safe:

• Pump out all remaining product and measure residual volume
• Remove sludge and scale from tank interior
• Clean with approved methods (steam, chemical wash)
• Inert the tank atmosphere with dry ice, nitrogen or foam to prevent explosion
• Confirm safe atmosphere with combustible gas indicator (LEL below 10%)

Tank cleaning waste (product, sludge, rinsate) must be disposed of as regulated waste with appropriate manifesting.

Step 3: Disconnection

Disconnect and cap all piping connections:

• Product supply and return lines
• Vent lines
• Leak detection equipment and wiring
• Fill pipes and dispensing connections

Piping should be removed or properly abandoned in place depending on regulatory requirements and site conditions.

Step 4: Excavation

Excavate around and under the tank using appropriate equipment (backhoe, excavator). Key considerations:

• Utility clearance - Locate and protect underground utilities before digging
• Shoring - Excavation sidewall support required for depths exceeding regulatory thresholds (typically 1.2-1.5 meters)
• Traffic management - Barricading and signage for active sites, especially former gas stations on busy roads
• Dewatering - Groundwater management if the excavation extends below the water table

Step 5: Tank Removal and Inspection

Lift the tank from the excavation using appropriate rigging. Once removed:

• Inspect the tank exterior for holes, corrosion, pitting and structural failure
• Document tank condition with photographs
• Record tank dimensions, material, manufacturer and serial number
• Note the location and condition of any holes or damage (potential leak points)

Step 6: Soil Sampling

This is the most critical environmental step. Soil samples are collected from the excavation to determine whether the tank leaked:

• Minimum samples: Typically 4 wall samples (one per side) and 2 base samples per tank. More samples if visual evidence of contamination is observed.
• Visual assessment: Look for stained, discolored or odorous soil. Screen with a PID (photoionization detector) in the field.
• Laboratory analysis: Petroleum hydrocarbons (BTEX and PHCs) at minimum. Metals and other parameters if the tank history warrants it.
• Groundwater: If groundwater is encountered in the excavation, collect a sample for analysis.

Step 7: Tank Disposal

Removed tanks must be disposed of at licensed scrap metal facilities or cutting yards. The tank must be:

• Cut open or punctured to prevent reuse as a storage vessel
• Transported by a licensed carrier
• Documented with disposal receipts

Step 8: Backfill and Restoration

If soil sampling results are clean (below applicable standards), the excavation is backfilled with imported clean fill, compacted in lifts and the surface restored. If contamination is confirmed, remediation is required before closure.

Step 9: Regulatory Closure

Submit a closure report to the regulatory authority including:

• Tank removal documentation and photographs
• Tank inspection results
• Soil and groundwater analytical results
• Site plan showing tank location, sample locations and excavation extent
• Waste disposal documentation

How Much Does UST Removal Cost?

The major cost variable is contamination. A clean tank removal at a residential property might cost $5,000. The same tank with a slow leak that contaminated soil and groundwater over 20 years can cost $200,000+ in investigation, remediation and regulatory management.

What If the Tank Leaked?

If soil or groundwater sampling confirms contamination above regulatory standards:

1. Extended excavation - Remove contaminated soil beyond the tank pit until clean soil is confirmed at the excavation boundaries
2. Groundwater investigation - Install monitoring wells to assess whether dissolved contamination has migrated in groundwater
3. Remediation - Active treatment (excavation, soil vapor extraction, bioremediation) or monitored natural attenuation depending on the extent and concentration
4. Long-term monitoring - Quarterly or semi-annual groundwater sampling until concentrations drop below cleanup standards

Many jurisdictions operate financial assistance programs for UST cleanups, particularly for small business owners and homeowners who inherited tanks from previous owners. In the US, most states have petroleum cleanup funds that reimburse eligible cleanup costs.

The Bottom Line

Underground storage tanks are a known environmental liability. The longer a non-compliant tank stays in the ground, the higher the risk and the higher the eventual cost. Proactive removal with proper environmental assessment protects property value, satisfies regulatory requirements and eliminates an ongoing contamination risk.

If you are buying, selling or developing a property with a known or suspected UST, the cost of proper removal and assessment is always less than the cost of discovering a leak after the transaction closes.