Adoption of Regulation to Define "Interstitial Liquid Level Measurement"

Adoption of Regulation to Define "Interstitial Liquid Level Measurement"

On May 19, 2005, the State Water Resources Control Board adopted a proposed regulation to define "interstitial liquid level measurement" (ILLM) methods, as the erm is used in section 25290.1(e) of the Health and Safety Code. Health and Safety Code section 25290.1(e) provides that "The interstitial space of underground storage tanks installed on or after July 1, 2004 shall be maintained under constant vacuum or pressure such that a breach in the primary or secondary containment is detected before the liquid or vapor phase of the hazardous substance stored in the underground storage tank is released into the environment." Subdivision (e) continues by stating that, "The use of interstitial liquid level measurement methods satisfies the requirements of this subdivision." The purpose of the proposed regulation is to clarify that the two sentences in subdivision (e) must be read in context with one another, given the ILLM technology existing at the time the statute was adopted, in order to effectuate the statutory performance standard of detecting breaches before there can be a release to the environment. At the time section 25290.1 was adopted, existing ILLM technology was in use for tanks only and was an "over-pressure" technology which met the statutory performance standard of detecting breaches before the substance stored could reach the environment. It was this "over-pressure" ILLM technology that the statute was intending to allow. After the statute was adopted, manufacturers developed a "non-over-pressured" ILLM technology for pressurized piping that does not meet the required performance standard. The proposed regulation clarifies that this technology was not envisioned by the statute and is not allowable.