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Hazardous Materials Program Guidance Document HMPG-025 — Underground Storage Tank Overfill Prevention A. Scope This document addresses issues associated with underground storage tank (UST) overfill prevention systems. For enforcement purposes, refer to the actual text of the regulations since the wording in this document summarizes the requirements. References to Title 23 California Code of Regulations (23 CCR) use citations in the updated regulations that are effective October 1, 2018. B. General The local agency may waive the requirement for overfill prevention equipment where the tank inlet exists in an observable area, the spill container is adequate to collect any overfill, and the tank system is filled by transfers of no more than 25 gallons at one time. [23 CCR §2635(c)(2)] [Note: This provision allows, but does not require, the UPA to waive the requirement. In cases where the UST operator allows overfilling to occur, HMCD may withdraw such a waiver and require the UST owner/operator to retrofit the UST with approved overfill prevention equipment.] All USTs that are not exempted pursuant to 23 CCR §2635(c)(2) must be equipped with an overfill prevention system which does not allow for manual override and meets one of the following options: [23 CCR §2635(c)(1)] Al Alert the transfer operator Flow restrictor (ball float) when the tank is 907o full by installed below vent riser @ restricting the flow into the tank 90% [23 CCR §2635(c)(1)(A)] A2 Or Alert the transfer operator External audible &visual VY hen the tank is 90% full by alarm unit @ 90°° triggering an audible and visual alarm. [23 CCR §2635(c)(1)(A)] g Restrict delivery of flow to the Flow restrictor (ball float) tank at least 30 minutes before installed below vent riser @ the tank overfills, provided the <_95% and external audible restriction occurs when the alarm unit tank is filled to no more than 95% of capacity; and activate an audible alarm at least 5 minutes before the tank overfills. [23 CCR §2635(c)(1)(B)] C Provide positive shut-off of flow Mechanical overfill prevention to the tank when the tank is (flapper) valve @ 95% filled to no more than 95% of capacity. [23 CCR §2635(c)(1)(C)] p Provide positive shut-off of flow to the tank so that none of the Mechanical overfill prevention fittings located on the top of the tank are exposed to product due to overfilling. [23 CCR §2635(c)(1)(D)] AND � la er valve @ >95% '� (f PP ) I i HMPG-025 Page 1 of 7 1/7 —Rev. 09/20/18