Any fixed or floating roof storage tank, or change of service in any
tank, used to store chemicals or mixtures of chemicals shown in Table 478
in paragraph (8) of this section is permitted by rule, provided that all of
the following conditions of this section are met:
(1) The tank shall be located at least 500 feet away from any
recreational area or residence or other structure not occupied or used solely
by the owner of the facility or the owner of the property upon which the facility
(2) The true vapor pressure of the compound to be stored
shall be less than 11.0 psia at the maximum storage temperature.
(3) For those compounds that have a true vapor pressure
greater than 0.5 psia and less than 11.0 psia at the maximum storage temperature,
any storage vessel larger than 40,000 gallons capacity shall be equipped with
an internal floating cover or equivalent control.
(A) An open top tank containing an external floating roof using
double seal technology shall be an approved control alternative equivalent
to an internal floating cover tank, provided the primary seal consists of
either a mechanical shoe seal or a liquid-mounted seal. Double seals having
a vapor- mounted primary seal are an approved alternative for existing open
top floating roof tanks undergoing a change of service.
(B) The floating cover or floating roof design shall incorporate
sufficient flotation to conform to the requirements of American Petroleum
Institute Code 650, Appendix C or an equivalent degree of flotation.
(4) Compounds with a true vapor pressure of 0.5 psia
or less at the maximum storage temperature may be stored in a fixed roof or
cone roof tank which includes a submerged fill pipe or utilizes bottom loading.
(5) For fixed or cone roof tanks having no internal floating
cover, all uninsulated tank exterior surfaces exposed to the sun shall be
painted chalk white except where a dark color is necessary to help the tank
absorb or retain heat in order to maintain the material in the tank in a liquid
(6) Emissions shall be calculated by methods specified
in Section 4.3 of the current edition of the United States Environmental Protection
Agency Publication AP-42. This document may be obtained from the Superintendent
of Documents, Washington D.C. 20402. It is Stock Number 0550000251-7, Volume
(7) Before construction begins, storage tanks of 25,000
gallons or greater capacity and located in a designated nonattainment area
for ozone shall be registered with the commission's Office of Permitting,
Remediation, and Registration in Austin using Form PI-7. The registration
shall include a list of all tanks, calculated emissions for each carbon compound
in tons per year for each tank, and a Table 7 of Form PI-2 for each different
(8) Mixtures of the chemicals listed in Table 478 which
contain more than a total of 1.0% by volume of all other chemicals not listed
in Table 478 are not covered by this section.