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Double-Walled Tanks and SPCC/OPA90 Plan Secondary Containment

CFR received an interesting call from one of our air clients regarding a U.S. EPA SPCC inspection at one of the company’s rail car biodiesel off-loading stations. The company off-loads rail cars into two portable “frac” tanks, each with a 10,000-gallon capacity. The company had hired a local consultant to prepare a SPCC Plan for this operation. The local consultant did not believe that the double-walled frac tanks met the secondary containment requirements of 40 CFR Part 112.7 and went as far as stating in the SPCC Plan that the installation was non-compliant with these requirements.

Based upon what was written in the SPCC Plan, the EPA inspector was prepared to cite the operation for failure to comply with 40 CFR Part 112.7. The client called us in a bit of a panic as the other consultant only agreed “to work with” the company in arriving at a solution. At CFR, we researched this issue and found some interesting information that applied directly to this situation that would assist our client in complying with EPA secondary container requirements.

During out research we learned that EPA issued two memorandums to address how the secondary containment requirements of 40 CFR Part 112.7 apply to double-walled tanks. The first applicable EPA memo, issued April 29, 1992, said that shop-fabricated aboveground double-walled tanks that meet certain industry construction standards, with capacities less than 12,000 gallons, installed and operated with protective measures such as overfill alarms, flow shutoff or restrictor devices, and constant monitoring of product transfers, would generally comply with the SPPC Plan secondary containment requirements. That memo was later amended on August 9, 2002 to remove the 12,000-gallon tank capacity limitation and to discuss additional SPCC requirements that apply to double-walled tanks.

In summary, the required elements for double-walled tanks are as follows:

  1. Containers are shop fabricated;

  2. The inner tank is an Underwriter Laboratories (UL) listed steel tank;

  3. The outer tank is constructed in accordance with nationally accepted industry standards (e.g., API, STI, the American Concrete Institute);

  4. The tank is equipped with the following overfill prevention measures to contain overfills from tank vents

  5. Overfill alarm; and

  6. Automatic flow restrictor or flow shut-off; and

  7. All product transfers are constantly monitored.

As an alternative to the overfill prevention measure described in item 4, the container may be equipped with either active or passive secondary containment methods to address the typical failure mode and the most likely quantity of oil that would be discharged from the tank’s vents during transfer operations. Integrity testing is also required whenever repairs are made, and inspections are the same as for any other tank or container.

CFR has expertise in preparing SPCC and OPA 90 plans. Please consider us next time you’re revising or upgrading your plans.

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