Special Topics in Environmental Management

5 Tips for Categorizing Shop Built Aboveground Storage Tanks per STI SP001

By Dylan Brown, Project Coordinator at Tank Consultants, Inc. (TCI)

To develop a quality tank inspection program, it’s important to generate a detailed breakdown of all aboveground storage tanks (ASTs) on site. This can be done by creating a simple spreadsheet or table with some basic information on each tank.

Here are 5 tips for categorizing shop built ASTs with a capacity of less than 50,000 U.S. gallons that are less than 30 feet in diameter, and less than 50 feet in height as detailed within the industry standard known as STI SP001.

1. Develop a spreadsheet or table with basic info for each AST onsite. Be sure to include:

  • Tank number
  • Diameter/height
  • Construction material
  • The construction standard the tank was built to
  • The initial service date.

The first place to look for much of information is on the tank nameplate. If the nameplate is difficult to read or is not present try to locate alternative documentation – construction drawings, previous inspection reports, or even purchase orders. Collecting basic tank data is an important step, allowing facility personnel to understand the type of inspection(s) required and determine how often these inspections are required.

2. Inspect each tank for spill control. Spill control is defined as “a means of preventing a release of liquid to the environment, including adjoining property and waterways”.  The spill control method must be able to hold the entire capacity of the tank and includes secondary containment dike/berms, remote impounding, a secondary containment AST, or a secondary containment system.  Take note of each tank and answer the question – does this tank have spill control?  The answer will be a “yes” or “no” response.

3. Next inspect the tank for a Continuous Release Detection Method (CRDM), defined as a means of detecting a release of liquid through inherent design. CRDM is passive because it does not require sensors or power to operate.  Liquid releases are visually detected by facility operators. The system shall be designed in accordance with good engineering practice. A few acceptable and commonly used systems include a release prevention barrier (RPB), secondary containment ASTs including double wall ASTs or double bottom ASTs, and elevated ASTs.  Again take note of each tank and answer the following question: Does this tank have a CRDM?  Yes or no?  Go ahead and do this for every shop built AST on site, add the data to the spreadsheet and get ready for the next step – determining the tank category and subsequently, the inspection scope and interval.

4. Once a document has been generated to organize the different ASTs onsite, the facility can begin to determine how and when to inspect a large portion of these tanks – specifically through categorizing all of the shop built or fabricated tanks as detailed in STI SP001.  Tanks fall under three categories.

Determining the category for each tank is outlined in STI SP001Section 5.4 as follows:

  • Category 1: ASTs with spill control and with CRDM
  • Category 2: ASTs with spill control and without CRDM
  • Category 3: ASTs without spill control and without CRDM

Category 1 shop built tanks with a capacity of 5,000 gallons or less, only periodic inspections are required.  Larger shop built category 1 tanks, with a capacity ranging between 5,000 and 50,000 gallons will require a STI SP001 formal external inspection once every 20 years.  Remember – All tanks within the STI standard will require periodic inspection in addition to any formal inspections.

Category 2 tanks are those that have spill control, but do not have any type of CRDM.  For Category 2 tanks with a capacity of 1,100 gallons or less, only periodic inspections are required.  Tanks with a capacity ranging from 1,101-5,000 gallons require formal external inspections and leak testing every 10 years.  Category 2 tanks with a capacity greater than 5,000 gallons will require a combination of leak testing, formal external, and formal internal inspections at various intervals depending on the tank capacity.  Specific details can be found in the STI SP001 standard within Table 5.5.

Category 3 tanks have no spill control and no CRDM in place, and should be given priority especially when no inspection history is available.  All category 3 tanks 1,100 gallons or less must have formal inspections and leak testing done every 10 years.  Again for category 3 tanks larger than 1,100 gallons there are a number of different options, but all will require some combination of formal external/internal inspections and leak testing.

The two most important factors that determine the category of each tank are spill control and continuous release detection methods (CRDM).  In other words, if there is a product leak or tank failure, where will the product end up and how will a site know if the tank is leaking?

5. Take a moment to add a new column to the tank list indicating the category of each tank.  The frequency and type of inspection required will be based on the both the category and capacity of each tank. In addition to formal inspections (if required), every AST monitored and inspected per STI SP001 must be “periodically” inspected as detailed within the STI standard.  Periodic inspections are typically completed on a monthly basis by site personnel familiar with the equipment and facility.  For some tanks this will be the only type of inspection required.

Although a fine tuned tank integrity program will require more than a spreadsheet and basic tank info, it is absolutely a step in the right direction. Identifying and categorizing the ASTs on site will start the process forward.  Determining what type of inspections are required and how often should be initiated through categorizing all tanks per STI SP001.  Maintaining a quality tank inspection program just makes sense.  It is much more than trying to meet the bare minimum, a quality tank program is an investment in your facility’s future through managing risk, predicting costs, protecting the environment, and producing the best product possible.

Dylan Brown

Dylan Brown, Project Coordinator at TCI, has been inspecting above ground storage tanks and helping customers ensure environmental compliance for over 25 years. TCI provides expertise and innovation with the highest level of credibility to the above ground storage tank industry. The core employees of TCI are engineers and inspectors who have extensive experience in the industry. TCI takes pride in being known as “the storage tank experts” with a full tank-specific service line and employees that demonstrate extensive experience and knowledge.

For additional information on how TCI can help with environmental compliance and storage tank inspection in your area, please contact Dylan Brown at dbrown@tank-consultants.com Office: 281-842-1126 Cell: 815-861-1240