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4.2.3 Tank Plate Thickness Plate thickness measurements were taken using ultrasonic methods (UTM). The readings were taken using a digital readout Nova D-100 Ultrasonic Thickness Gage that has a dual element probe (transducer). The probe's transmitter element sends a short ultrasonic pulse to the material. The pulse, reflected as an echo from the opposite side of the plate, returns to the probe's receiver element. The round trip time is directly related to the material's thickness. 4.2.4 Coating Thickness Interior and exterior coatings, where accessible, were tested in accordance with Steel Structures Painting Council SSPC-PA2 “Measurement of Dry Film Thickness with Magnetic Gages”, using Type 2 Magnet Flux Gages with a fixed probe. 4.2.5 Coating Adhesion Adhesion testing of the coating to the steel was performed by ASTM D3359 Shear Adhesion Test, Measuring Adhesion by Tape Test. In addition, a subjective coating adhesion evaluation was performed using a penknife. 4.2.6 Coating Serviceability The estimated remaining coating life, or serviceability, evaluation was performed using a wide variety of inspection instruments such as dry film thickness gauge, penknife, 30x microscope, and serviceability evaluation experience (minimum experience 20 years). The instrument inspection was combined with a close visual inspection of all the interior coating's accessible areas. This was done to detect any holidays (misses), skips, runs, sags, surface contaminants, overspray, dry spray, poor coating cohesion, inter-coat delamination, loss of adhesion to the substrate, adverse conditions of the steel underneath the coating, or any other defects affecting the intended service. 4.2.8 Coating Lead and Chromium Content Analysis Lead test results indicated that the show that the percent of lead in the coating was below the recoding limit set by the EPA 6010C (ICP AES Method for Determination of Metals). See test results for all eight heavy metals in Appendix E. 11