PHMSA field inspections of breakout tanks typically include a check for a 1 % slope away from the tank bottom in all directions for 50 feet for tanks built after October 2, 2000. This requirement is in 195.264 which incorporates by reference (IBR) NFPA standard 30 2012 edition. It was very common to find slopes that did not meet the minimum 1 % requirement. The way this is written in 195.264 it is a one-time requirement. If an operator could produce a record showing that at construction the slope was 1 %, I would not cite them. Without the record, I would submit this as a compliance issue to PHMSA management. Typically, a compliance order requiring regrading was issued.
I used a clinometer to estimate the slope within 50 feet and if not 1 % would request a survey to confirm this rough estimate before taking compliance action.
- 195.264 Impoundment, protection against entry, normal/emergency venting or pressure/vacuum relief for aboveground breakout tanks.
(a) A means must be provided for containing hazardous liquids in the event of spillage or failure of an aboveground breakout tank.
(b) After October 2, 2000, compliance with paragraph (a) of this section requires the following for the aboveground breakout tanks specified:
(1) For tanks built to API Spec 12F, API Std 620, and others (such as API Std 650 (or its predecessor Standard 12C)), the installation of impoundment must be in accordance with the following sections of NFPA-30 (incorporated by reference, see § 195.3);
(i) Impoundment around a breakout tank must be installed in accordance with section 22.11.2; and
(ii) Impoundment by drainage to a remote impounding area must be installed in accordance with section 22.11.1.
NFPA 30 2012
22.11.1.1 The drainage route shall have a slope of not less than 1 percent away from the tank for at least 50 ft (15 m) toward the impounding area.
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