Gas Station & Petroleum Hydrocarbon Cleanup

Pangea has extensive experience cleaning up sites impacted by petroleum hydrocarbons, including gas stations and industrial/other properties. 

Pangea principals have worked on over 500 sites in Northern California and numerous sites in Southern California and beyond, including managing large portfolios for Chevron, Shell Oil, BP, Arco, Texaco, and Olympian. Within the past two decades, Pangea principals transitioned to assisting smaller oil companies, independent service stations and other property owners.

Driving forces for industry hydrocarbon remediation include conversion of gas stations for mixed use buildings and the state requirement from SB 445 for removal of all single-walled USTs by December 31, 2025.  Residual or discovered petroleum releases requires assessment, remediation, and/or mitigation.       

Pangea coordinated rapid response action after an overnight catastrophic release of 14,000 gallons of gasoline from a UST in San Jose, California.


We frequently support gasoline service stations and petroleum impacted sites with: 

  • Full service UST Cleanup Fund cost reimbursement assistance 
  • UST removal compliance soil and groundwater sampling 
  • Soil disposal/import during UST removal and upgrades 
  • Site characterization, involving investigation and sampling 
  • Soil remediation, involving excavation or vapor extraction 
  • Groundwater remediation, involving injection and extraction techniques 
  • Ongoing monitoring of groundwater, soil vapor, and indoor air 
  • Vapor intrusion mitigation  
  • Determination if contamination ‘old’ or ‘new’ when multiple site operators 
  • Case closure pursuit  
  • Litigation support 

Sampling of soil, soil gas, and/or groundwater is often first used to confirm the existence and scope of contamination.  

The Membrane Interface Probe (MIP) system is used to determine the depth and extent of VOCs in groundwater. Yellow circles (above) show the estimated influence area for each remedial injection point. 

Sodium persulfate injections are used to quickly oxidize MTBE in soil and groundwater, with injections at multiple points simultaneously for cost control.


Excavation of source material at an operating retail service station. Excavation is commonly used to remove hydrocarbon impact, especially when shallow impact and clayey soil present. 

A site model of underground gasoline impact prepared using rapid assessment to select and design appropriate remediation. Most gasoline contamination found partially contained by finer grain soil at 25 ft and 60 ft depth, with little impact to groundwater.  

Soil vapor extraction (SVE) can cost effectively remediate soil impact when excavation is too costly or impractical. The system shown above was designed to match the surroundings to minimize visual impact, with thermal and catalytic modes for cost control.


Petroleum hydrocarbon contamination frequently starts with an unauthorized release (“leak”) from an underground storage tank (UST) system. In the 1980s, UST regulations and oversight ballooned in California to respond to this contamination. In 1992, the California UST Cleanup Fund (UST Cleanup Fund) was created and began providing cost reimbursements up to $1.5 million for petroleum cleanup directed by an agency. Petroleum hydrocarbon assessment and remediation expanded further until 1995, when a Lawrence Livermore National Laboratories study documented that groundwater plumes tended to reach a maximum length (e.g., 250 feet) before shrinking in size.   

In 1996, as the clean industry also shrank in size, it was discovered that a new gasoline additive MTBE (an oxidant to improve fuel combustion efficiency) was leaking into the subsurface. Once in the ground, MTBE moves rapidly into groundwater where it migrates quickly based on its different properties from petroleum hydrocarbons. In 1999, California’s governor issued an order that MTBE use in gasoline phased out in California by the end of 2002.

In 2012, the Low Threat UST Case Closure Policy (Low Threat Closure Policy) was promulgated by the State Water Resources Control. This policy established specific criteria for soil, soil gas, and groundwater to expedite case closure. As a result of this Low Threat Closure Policy, case closures accelerated and hydrocarbon cleanup costs shrank drastically over the next few years.

Today, regulatory oversight staff has transitioned to the cleanup of dry cleaners and other projects, facilitated by funding from SB 445. Currently, removal of all single-walled USTs is required by January 1, 2026. The UST Cleanup Fund is also scheduled to “sunset” by January 2026, although Pangea Principal Bob Clark-Riddell is prepared to again support legislation to extend the UST Fund. Pangea Principal Clark-Riddell supported the extension of the UST Cleanup Fund by 10 years (2016 to 2026) via SB 445 when acting as the Vice President of Legislative and Policy Affairs for industry non-profit CORE Environmental LLC.