UNDERGROUND STORAGE TANK POLICY–DESIGNATED TANKS RATING CONSIDERATIONS

(November 2022)

INTRODUCTION

The Insurance Services Office (ISO) rules that apply to underground storage tank rating are in Rule 53, Underground Storage Tank (UST) Coverage in the Commercial Lines Manual (CLM). ISO’s separate rating system groups various tanks with similar characteristics into specific classifications that reflect hazards common to each. Classifications are based on tank construction and age, the type of contents stored, and the extent of any protective devices provided. This approach results in a five-digit code for each tank or group of tanks that have the same characteristics.

CLASSIFICATIONS

Underground storage tanks are classified and coded according to their contents, construction, age, and any detection or protective devices used with them. These factors are summarized in the following chart.

CODE	CLASSIFICATION
First Digit Code	Underground Storage Tank Policy (UST) Designation
2 (always)	Underground Storage Tank
Second Digit Code	Contents
1	Gasoline. This includes all grades.
2	Oil. This includes kerosene, diesel, and waste oil.
3	Other types of petroleum products
Third Digit Code	Construction: Underground Storage Tanks
1	Fiberglass or synthetic–with a suction pumping system
2	Fiberglass or synthetic–with a pressure pumping system
3	Steel–with corrosion protection–including fiberglass coated–with a suction pumping system
4	Steel–with corrosion protection–including fiberglass coated–with a pressure pumping system
5	Steel–without corrosion protection–including tar-coated–with a suction pumping system
6	Steel–without corrosion protection–including tar-coated–with a pressure pumping system
7	Not Otherwise Classified (NOC)–with a suction pumping system
8	Not Otherwise Classified (NOC)–with a pressure pumping system
9	Above ground tanks. This classification may be used only when the policy is endorsed to change the definition of tanks to include above ground tanks.
Fourth Digit Code	Age
6	Five years or less
7	More than 5 but not more than 10 years
8	More than 10 but not more than 25 years
9	More than 25 years

CODE	CLASSIFICATION
Fifth Digit Code	Protection Devices
4	Only automatic leak detection
5	Only automatic overfill protection. This cannot be a collection well.
6	Both automatic leak detection and automatic overfill protection
7	No protection devices
9	All other types of protective devices

Example: An eight-year-old steel tank, without any corrosion protection or protective devices, with a pressure pumping system, and used to store oil has classification code 22677.

Example: A four-year-old synthetic tank, with a suction pumping system, with both automatic leak and overfill protection, that stores gas has classification code 21166.

PREMIUM BASIS

The premium basis for all classifications is each insured tank.

MINIMUM PREMIUMS, DEDUCTIBLES, ADDITIONAL INTERESTS, LIMITS OF INSURANCE, AND DEFENSE EXPENSE AMOUNT

The risk must be referred to the insurance company for the rating factors and other considerations that apply to minimum premiums, deductibles, additional interests, limits of insurance, and defense expense amount. The factors that apply are at the insurance company's sole discretion.

RATING FORMULA

ISO has not developed a specific rating formula for underground storage tanks. Each insurance company develops and applies its own rating formula. The factors usually include the classification factors of contents, construction, age, and protection devices outlined above. Additional factors apply for increased Limits of Insurance and the Defense Expense Amount.

EXPERIENCE RATING PLAN/SCHEDULE RATING PLAN

The ISO Commercial General Liability (CGL) Experience Rating Plan and Schedule Rating Plan do not apply to underground storage tank rating and there is no other equivalent plan available to use with it. Each insurance company that provides this coverage determines its own such plan or approach at its sole discretion.