1. (1) You must support tanks on noncombustible foundations designed for the type of tank.
2. (2) You must provide protection against flotation or other water damage, where high floodwater might occur.
3. (3) You must prevent the effects of freezing and consequent frost heaving, in tanks used for product storage at less than 32°F, by providing either support or heat supply.

4. (4) You must prevent accidental discharge of liquids from spreading into uncontrolled areas by providing, to the area surrounding a refrigerated tank or group of tanks, one of the following:

   1. (a) A drainage system provided with at least a one percent slope that terminates in an impounding basin with a capacity as large as the largest tank served; or
   2. (b) A diked enclosure with a capacity as large as the largest tank served.

5. (5) You must meet, when using a diked enclosure or an impounding basin in a drainage system, the following requirements:

   1. (a) Make the wall of earth, steel, or concrete. If made of earth, meet both of the following:

      1. (i) The top is flat and at least two feet wide; and
      2. (ii) There is a stable slope consistent with the angle of the earth used.

   2. (b) Design the wall to be both:

      1. (i) Liquid tight; and
      2. (ii) Able to withstand the hydrostatic pressure and the temperature.

6. (6) You must provide for drainage of rain water, that does not permit the release of ammonia, from diked or impounding areas.

   Note:	1. It is recommended that the ground in an impounding basin or within a diked enclosure be graded so that small spills or the early part of a large spill will accumulate at one side or corner contacting both:
   	a. A relatively small area of ground; and
   	b. Exposing a relatively small surface area for heat gain.
   	2. Shallow channels in the ground surface or low curbs of earth can help guide the liquid to these low areas without contacting a large ground area.

[Statutory Authority: RCW 49.17.010, 49.17.040, 49.17.050. WSR 15-23-086, § 296-826-30055, filed 11/17/15, effective 12/18/15. Statutory Authority: RCW 49.17.010, 49.17.040, 49.17.050, 49.17.060. WSR 06-10-067, § 296-826-30055, filed 5/2/06, effective 9/1/06.]