The Colorado Department of Labor and Employment (CDLE) Division of Oil and Public Safety (Division) recently published updated Storage Tank Regulations that became effective January 1, 2025. While storage tank owners and operators may be familiar with the Environmental Protection Agency’s (EPA’s) Spill, Prevention, Control, and Countermeasure (SPCC) regulations, they should also be aware that their storage tank systems may be subject to the Division’s Storage Tank Regulations. These regulations govern the design, construction, installation, operation, and record-keeping for underground storage tanks (USTs) and aboveground storage tanks (ASTs) that store regulated substances. The regulations also include release identification and response requirements, tank system closure procedures, and the Division’s enforcement policy. This article provides an overview of Colorado and federal requirements for storage tanks, specifically regulated ASTs.
 

Colorado Storage Tank Regulation Overview

Regulatory Applicability

The Division regulates USTs and ASTs that meet the following requirements:

• USTs with a capacity greater than 110 gallons that contain petroleum products.
  • Exemptions include on-site heating oil tanks, farm tanks with a capacity of 1,100 gallons or less, stormwater/wastewater collection systems, and oil-water separators.
• ASTs with a capacity between 660 and 39,999 gallons that contain fuel or lubricants.
  • Exemptions include tanks associated with crude oil production, storage, and gathering, tanks on farms or residential properties, tanks at construction or earth-moving sites, and on-site heating oil tanks.

Application and Installation Process

Installing a new or used AST that will store a regulated substance involves a three-step process:

1. Application & Permit: Submit an application to be approved by the Division prior to the construction of any new or reinstalled AST. The application must include:

• A site plan with a dimensioned drawing of the facility showing existing and proposed tanks, piping locations, buildings, loading/unloading facilities, guard posts, fences, property lines, and street names.
• A written application using the form provided by the Division.

2. Installation: Obtain an installation permit, valid for up to six months after issuance.

• A notification must be made at least 72 hours prior to replacing or adding underground piping and before filling the tank system, to allow for inspection by the Division.

3. Registration: Submit a registration form within 30 days of using the AST to store a regulated substance.

• There is a $35 registration fee per tank that must be paid annually.

AST Operational Requirements

Colorado Storage Tank Regulations provide detailed requirements for operating ASTs. While facilities with SPCC plans may use SPCC compliance documentation to demonstrate compliance with overlapping Colorado storage tank requirements, there are additional state operational requirements that must be met.

• Pressurized and Suction Piping: Pressurized underground AST piping must be equipped with automatic leak detectors (unless no pump is installed between the tank and the underground piping) that either shuts off flow or triggers an alarm. The leak detection system must be tested annually. In contrast, suction piping may be exempt from release detection requirements if it meets specific piping requirements outlined in the regulation regarding pressure, slope, and valving. Additionally, for both pressurized and suction piping, operators are required to conduct periodic line release detection tests annually or monthly, depending on the test method used. Notably, these pressurized and suction piping requirements are unique to the Division’s tank regulations and are not found in federal SPCC regulation.
• Corrosion Protection: ASTs and pipelines installed after September 30, 1994, in contact with soil or an electrolyte that may cause corrosion must be protected by either a cathodic corrosion protection system or an approved corrosion-resistant material (e.g., certain alloys, reinforced plastics/coatings). For tanks without cathodic protection, additional biennial testing is required, which may include an external visible test (including the tank bottom), a leakage test, or an internal inspection. However, if a tank is elevated from the soil, an external coating provides sufficient corrosion protection.
• Spill and Overfill Prevention: For ASTs installed after September 30, 1994, overfill prevention equipment is required. The means for determining tank liquid level must be accessible to the delivery operator. Records must be maintained to demonstrate that electronic and mechanical gauges are calibrated annually.
• AST Inspections: ASTs, secondary containment tanks, and piping must be visually inspected monthly to detect leakage from seams, connections, and fittings. These monthly inspections can be satisfied by completing the monthly, annual, and periodic inspections required by the Steel Tank Institute (STI) SP001, “Standard for the Inspection of Aboveground Storage Tanks.”
• Tightness Testing: As part of the installation process, all new and used tanks and connections must undergo tightness testing after installation and before being placed into service in accordance with manufacturer instructions or National Fire Protection Association (NFPA) 30.
• Record-Keeping: Records must be maintained, including installation permits, registrations, repairs, visual inspections, underground piping precision tests, cathodic protection system tests, and gauge calibrations. The required retention period for these records varies, ranging from one year to five years or the lifetime of the tank, depending on the specific record type.
• Additional Requirements: Requirements for temporary closures, permanent closures, and service changes, including Division notifications and site assessments, can be found in the regulations.

Federal Oil Storage and Tank Regulation Overview

Spill, Prevention, Control, and Countermeasure Regulation

Many facilities with storage tanks subject to the Division’s Storage Tank Regulations are also subject to EPA’s SPCC regulations. Originally enacted under the Clean Water Act, SPCC regulations aim to prevent oil discharges from reaching navigable waters. Non-transportation related facilities with aboveground oil storage capacity exceeding 1,320 gallons or underground capacity exceeding 42,000 gallons are generally subject to SPCC regulations. Moreover, all bulk oil storage containers, oil-filled equipment, and portable containers (such as drums or totes) with a capacity of 55 gallons or more must be included in a facility’s total oil storage capacity to determine SPCC applicability.
 
Facilities exceeding these thresholds must develop an SPCC plan that includes oil storage locations and volumes, a detailed site map, secondary containment and diversionary structures, inspection procedures and forms, oil transfer procedures and equipment, and facility drainage. A critical component of the SPCC plan is the description of secondary containment measures designed to prevent oil discharges from reaching navigable waters. Specifically, bulk storage tanks and portable oil containers require sized secondary containment, such as dikes, berms, containment tanks, and spill pallets, capable of holding the contents of the largest container in the area plus adequate freeboard for precipitation. Other equipment, including oil-filled equipment, mobile refuelers, and oil piping and valves, must have general secondary containment measures (e.g., spill kits with sorbent materials or drain covers) to address potential oil discharges or spills.
 

New Source Performance Standard Regulation

In addition to SPCC regulations, certain large storage tanks may be subject to EPA’s New Source Performance Standard (NSPS) Subpart Kb or Subpart Kc. Subpart Kc, which became effective on October 15, 2024, applies to tanks that meet the following criteria:
 

1. Constructed, modified, or reconstructed on or after October 4, 2023;
2. Have a capacity of 20,000 gallons (476 barrels) or more; and
3. Have a maximum true vapor pressure (TVP) of 0.25 psia or greater.

For more information on the applicability and requirements of NSPS Subpart Kc, please refer to this article.
 
If you would like to discuss Colorado or federal oil tank regulations and how they may impact your facility, please email Matt Petrosky in Trinity’s Denver office or call 720.638.7647.