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UST Program - Statutes and Regulations

UST Program - Approved Rulemaking – Definition of the term “Interstitial Liquid Level Measurement”


The proposed regulation defining the term “interstitial liquid level measurement method” as used in section 25290.1(e) of the Health and Safety Code was approved by the Office of Administrative law and formally adopted into the California Code of Regulations on August 19, 2005.

This regulation adds the following definition has been added to Title 23, section 2611:

“Interstitial Liquid Level Measurement" Method (as used in section 25290.1 of the Health and Safety Code) or "Hydrostatic Monitoring" Method means a release detection method that continuously monitors the liquid level within a liquid-filled interstitial space of an underground storage tank. The term includes only those release detection systems that are capable of detecting a breach in the primary or secondary containment of the underground storage tank components(s) being monitored before the hazardous substance stored is released to the environment. To accomplish this, the liquid in the interstitial space shall be maintained at a pressure greater than the operating pressure found within the component(s) being monitored. This pressure may be achieved, for example, by adequately elevating the liquid reservoir or by pressurizing the liquid-filled interstice. Hydrostatic monitoring methods shall meet the requirements of section 2643, subdivision (f).

The documents listed below are excerpts from the complete rulemaking records, which is available for review upon request. Please direct questions on this regulation to Mr. Scott Bacon at sbacon@waterboards.ca.gov or (916) 341-5873.