California ESL Updates

By June 19, 2019 No Comments

We in the environmental consulting industry have just gotten used to the Environmental Screening Levels (ESLs) for contaminants in soil, groundwater, soil vapor, and air published by the San Francisco Region Water Quality Control Board (SFBRWQCB) in February of 20161. Which can only mean one thing: that it’s time for new ESLs.

In January of this year, the SFBRWQCB uploaded a revision to the ESLs2.  The newly promulgated ESLs are in many cases considerably lower than in the 2016 version.  For instance, here are the changes to the Tier 1 ESLs for tetrachloroethene (PCE) and trichloroethene (TCE), two of the most common contaminants found in soil, groundwater, soil vapor, and air.  These chemicals were used as industrial solvents and PCE is the most common chemical used in dry cleaning:




Soil Soil Vapor Air


Units µg/La mg/kgb µg/m3c



3.0 0.42 240 0.48


0.64 0.08 15






Soil Soil Vapor



Units µg/L mg/kg µg/m3




0.46 240




0.085 16


a micrograms per liter

b millgrams per kilogram

c micrograms per cubic meter


The 2019 ESLs for these contaminants are noticeably lower than those published in 2016.  These changes – and it’s not just PCE and TCE but numerous contaminants covered by the ESLs – will mean that

  • cost of cleaning up a site to the satisfaction of regulatory agencies, and therefore lenders, will increase; and
  • more properties will be viewed as environmental liabilities, thus decreasing the value of the property and possibly causing potential buyers to withdraw from the transaction and search for another property instead.

Changes to the ESLs have also resulted in many groundwater ESLs now being lower than the State Maximum Contaminant Level, meaning that in some cases potable water will be classified as a vapor intrusion risk.  This is a result of updated research on contaminants leaching from soil into groundwater.  This research has produced updated data on contaminant solubility and Henry’s Law Constant.  The leaching methodology has not changed.

What else is new with the 2019 ESL revision?  There is a new table, Short-Term Action Levels for TCE.  This table includes groundwater and subslab / soil vapor “trigger levels”, indoor air accelerated and urgent response levels, and appropriate response actions.   The vapor intrusion ESLs, which had previously been based on the Johnson and Ettinger model3, are now proposed to be based on the United States Environmental Protection Agency’s Attenuation Factors4.  This is expected to cause further headaches for property owners and managers, but we will discuss that in another blog post.

In addition, Total Petroleum Hydrocarbons (TPH) are now simply called “petroleum”, with “TPH” only used to refer to laboratory analysis methods.  Three new chemicals – 1,2,3-trichloropropane, Petroleum jet fuel, and Petroleum-hydrocarbon oxidation products – have been added to the tables.  The Human Health Toxicity Values have also been revised to agree with the update of CCR Title 22, that was updated this past September 14.  Finally, depth to groundwater is no longer a toggle for evaluating vapor intrusion.

It remains to be seen what the effect of these revisions will be on real estate transactions.  Real estate developers, property owners, and consultants may wish to review previous Phase II ESAs to see what properties that did not present environmental risks in the past would now be considered environmental risks given the same level of concentration of contaminants.  Property owners may consider additional Phase II ESAs and even remediation proactively.  2019 promises to be an interesting year for the real estate and environmental consulting industries in California.




3Tillman, F. and J. W. Weaver. Johnson and Ettinger (1991) Vapor Intrusion Model with Sub-slab Concentration. U.S. Environmental Protection Agency, Washington, DC, EPA/600/C-06/002, 2005.

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