by Chrissie Dawson
Project Manager

Join EI as we discuss STI AST SP001 External Tank Inspections in a three-part blog series. Topics will include what an STI AST SP001 External Tank Inspection is, why you may need one, some potential risks of not having one, and how often the inspections are needed.

The series will be rolled-out as follows:

Week 1 – What Exactly is an STI AST SP001 External Tank Inspection and Do I Need One?

Week 2  What Industries Typically Use ASTs?

Week 3 – How Do I Determine How Often I Need an STI AST SP001 External Tank Inspection and Find a Certified Inspector?

According to the STI AST SP001 External Tank Inspection standard, the frequency of inspections for ASTs can vary depending on several factors, including the tank’s age, the material stored and local regulations. The standard provides general guidelines for inspection intervals, but the specific schedule should be determined based on a risk assessment and the conditions of the tank and its surroundings.  It is critical to determine the AST category, which aids in establishing the appropriate inspection schedule and maintenance plan. 

The STI SP001 standard designates three categories, which are dependent upon spill control and the presence or absence of a Continuous Release Detection Method (CRDM).  CRDMs are a means of detecting a tank release though inherent design.  CRDM does not require sensors or power to operate, and any releases are visually detected by facility operators. 

Some of the commonly used CRDM systems include the following:

  1. Release Prevention Barrier (RPB) – An RPB is a physical or engineered structure, system, or control measure designed to prevent the unintentional release or spillage of hazardous materials, contaminants, or pollutants into the environment. Examples include secondary containment such as berms, dikes, or lined containment areas;
  2. Double-Walled AST or Double-Bottom AST;
  3. Elevated AST, without an RPB;
  4. Steel Diked AST, open or closed top; and
  5. Concrete Exterior AST with an integral secondary containment and interstitial monitoring opening

The STI SP001 categories are designated as follows:

  1. Category 1 – ASTs with spill control and a CRDM. 
  2. Category 2 – ASTs with spill control and without a CRDM
  3. Category 3 – ASTs without spill control

Upon determining the tank category, the STI AST SP001 External Tank Inspection schedule can be determined using the table below:

Capacity in US GallonsCategory 1Category 1Category 1
0-1,100PPP, E&L(10)
1,101-5,000PP, E&L(10)[P, E&L(5), I(10)]
[P, L(2), E(5)
5,001-30,000P, E(20)[P, E(10), I(20)]
[P, E(5), L(10)]
[P, E&L(5), I(10)
[P, L(1), E(5)]
30,001-75,000P, E(20)P, E&L(5), I(15)P, E&L(5), I(10)

Please note that only shop-fabricated tanks are included in the table. Portable containers are not included.

P – Periodic tank inspections to be conducted by owner’s inspector
E – Formal External Inspection by a Certified Inspector
I – Formal Internal Inspection by a Certified Inspector
L – Leak test by owner or owner’s designee
(#) – Maximum inspection interval in years

Now That You Have Determined What Category Your Tank Belongs to, What’s Next?
A Certified SP001 AST Inspector and other applicable parties should be contracted to provide the appropriate inspection(s).  A list of Certified SP001 AST Inspectors can be found online here.

How We Can Help
The EI Group, Inc. has Certified SP001 AST Inspectors on staff who can assist with any questions or needs regarding tank inspections and other environmental concerns. For more information, contact Chrissie Dawson at (502) 443-2455 or [email protected].