Specifications include, but are not limited to: Tank Structural Investigation 1. Rafters, center columns, support clips, I-beams, and support elements must be spot surface abrasive blasted to an SSPC SP-10 “Near White” standard of cleanliness and inspected for corrosion by a certified NACE inspector. a. Surface blast clean a 4-6 ft of the center column support. b. Select 8 tank support rafters for inspection, with one rafter in each tank area quadrant. c. Surface blast clean a length of 2-3 ft from the point at which the tank support rafter attaches to the tank shell towards the dollar plate of the center column, including clips and other attachments. d. Surface blast clean the length of 2-3 ft from the point at which the tank support rafter attaches to the dollar plate of the center column towards the point where the tank support attaches to the tank shell. 2. Select an area of each ring of the tank shell at the highest risk of corrosion presence. Each location must be spot surface abrasive blasted to an SSPC SP-10 “Near White” standard of cleanliness and inspected for corrosion by a certified NACE inspector. Repeat this procedure for 3-4 locations each on the following: a. Shell exterior b. Shell interior c. Tank roof interior d. Tank roof exterior 3. Cut and remove twelve (12) sample plates (floor coupons) from the tank floor (16” square sections - random locations), sandblasted, and then examined for signs of corrosion. Install new patch plates, welded watertight, where sample plates were removed. 4. Contractor will provide photos and a report documenting the condition of the inspected elements and any recommendations for replacement or maintenance to the Engineer and Owners representative. Interior – Structural 1. Cut a door sheet opening large enough for the necessary employees and equipment to access the interior area. Upon completion of all interior work, reinstall or replace the sheeting at the access point and weld the opening watertight. 2. Seal the following with Sikaflex elastomeric caulk, or equivalent, to inhibit the occurrence of rust bleed: a. Gaps in the lapped plates on the roof, including the dollar-to-roof plate, roof-to-roof radial/torus plates (seams above the normal waterline). b. Roof openings and other roof penetrations. 3. Remove the existing interior ladder and replace it with a new interior ladder compliant with current OSHA guidelines. 4. Remove and install new level indicator. a. Location needs to be accessible from the interior ladder for maintenance and viewable from the access roadway. b. Interior float shall be 316 stainless steel. c. Float cable and guide wires shall be stainless steel. d. All brackets and anchors bar shall be steel and coated with the same system as the interior of the tank. Exterior – Structural 1. Remove the existing exterior ladder and replace with staircase. Staircase shall be equipped with a security door and roof access platform compliant with current OSHA guidelines. 2. Replace all shell man-way bolts and gaskets.
