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Dart Container Corporation In-Service AST Inspection Report Formal External Inspection of AST-1 Page 6 0.191 inches of remaining steel. Measured steel thickness was not less than 95 percent of the presumed original thickness for any given measurement. Data collected during the inspection will serve as a baseline when determining corrosion rates for future inspections. To obtain the residual metal thickness readings, an NDT Systems TG110 – DL ultrasonic digital thickness meter equipped with a TG-560P transducer was used. The meter has a resolution of ±0.001 in (±0.025 mm) intended for use on steel plate and piping materials used in storage tank applications. The meter is capable of collecting readings using a scan mode or single point mode. The meter was used in single point mode to collect readings. Proper operation confirmed prior to and during testing using a steel calibration block adhered to the side of the meter and a machined mild steel step block. The transducer couplant used was NDT Systems UTG1102 Ultragel II. 3. Horizontal ASTs Shell plates, welds and ancillary equipment were inspected for indications of exterior corrosion, buckling, distortion due to stress, cracking, pinholes and mechanical damage. There were no significant signs of corrosion and damage on the exterior tank surface. UT measurements and visual inspection of the tank shell revealed no significant internal or exterior corrosion. Refer to the thickness measurements and photographs attached to this report. The Tank shell was inspected for indications of modifications that may have been made after its fabrication. Refer to Section 1.9 and 1.11 for information about Tank modifications. 3.2 INSPECTION SUMMARY Leak Testing The formal external inspection of the Tank indicated that supplemental leak testing was not necessary. Requirements for Continued Tank Service The STI SP001 Standard requires the owner or operator of an aboveground tank to perform and document monthly and annual inspections. Refer to the checklists in the Facility SPCC Plan or those contained in Attachment B. These documents should be completed by the owner or operator on a monthly and annual basis as part of the Facility’s SPCC Plan. The following requirements are based on the industry standards SP001, UL142, and good engineering practices. These requirements limit potential for catastrophic discharges during operation of the Tank: 1. The operational vent must be installed on the Tank’s primary compartment. The inspector observed an undersized operational vent installed on the Tank. Adequate operational venting is required for continued service of the Tank. Install at minimum, a single 3-inch diameter operational vent, with no reduction in pipe diameter, on a minimum 3-inch diameter Tank port. Alternatively, use of the current operational vent requires the diameter of the fill pipe to be reduced to 2 inches. Reroute dispenser tubing to an available Tank port instead of the operational vent. Routine inspection and cleaning of the operational vent and ERV is required to maintain proper Tank venting.