J. Pit/Perforation Treatment: Excessively pitted or perforated areas shall be either filled with weld metal and ground smooth or covered with a metal plate of the same plate thickness, as determined necessary by the Engineer. Plate shall extend three inches beyond pit or perforation with a 100% fillet weld around perimeter of plate.
K. Grinding: Excessively corroded areas that comprise of sharp edges from sandblasting shall be ground smooth and rounded, as determined necessary by the Engineer.
L. Straighten Rafters: Existing rafters shall be straightened by the following process:
1. Starting at one of the straighter rafters, weld four 5" gussets to the roof plate equally spaced along the rafter to be used with a come-along to straighten out the rafter.
2. Stabilize the newly straightened rafter with six 3" long (3 ½" x 3 ½" x ¼") keepers welded to the roof plate perpendicular to the rafter equally spaced alternating sides of the rafters.
3. Take the next adjacent rafter and jack it into position by pushing or pulling the second rafter to the first one until the second one is also straightened. The rafter may need to be loosened at the center support and the earthquake rod.
4. The second rafter would then be secured to the first rafter by welding a 3 ½" x 3 ½" x ¼" angle lateral brace in place at the midspan of the rafters. If rafter is loosened from the center column, reconnect it to the center column.
HARPER & ASSOCIATES AMADOR TANK PHASE II REHABILITATION July 2022 ENGINEERING, INC. 33 16 19 – MISCELLANEOUS STRUCTURAL MODIFICATIONS 7 of 9
5. Continue in a clockwise direction, straightening subsequent rafters as outlined above. Variations on the above noted process must be submitted by the Contractor for review by the Engineer.
M. Rafter Replacement (Full Length): Remove existing severely corroded rafters, as determined necessary by the Engineer, and replace with new rafters in like-kind. The top of the rafters shall be shop coated in accordance with Section 09 97 14 prior to installation.
The Contractor shall field verify the rafter sizes and lengths prior to fabricating. Work shall be accomplished on the basis of each. The gusset plates, nuts and bolts shall be replaced.
The Contractor may NOT cut holes in the roof to install the rafters.
1. Existing rafters are W10x17 and approximately 41 feet in length.
2. The existing rafters are welded to the center support plate and the shell connection. The Contractor will be required to furnish and install new gusset plates and nuts and bolts at the center support plate connection or at the shell connection.
N. Rafter Replacement (3-Foot Section): Remove existing severely corroded 3-foot section of each rafter at the center support plate, as determined necessary by the Engineer, and replace with new rafters in like-kind. The top of the rafters shall be shop coated in accordance with Section 09 97 14 prior to installation. The Contractor shall field verify the rafter sizes and lengths prior to fabricating. Work shall be accomplished on the basis of each.
1. Existing rafters are W10x17 and approximately 41 feet in length.
2. The existing rafters are welded to the center support plate, but the Contractor will be required to furnish and install new gusset plates and nuts and bolts for connection at the center support plate.
3. The Contractor may NOT cut holes in the roof to install the rafters.
O. Roof Patch Plates: Seal weld patch plates over holes in the exterior roof, as determined necessary by the Engineer. Furnish and install ¼" thick steel plate and seal weld with a 100% fillet around the perimeter of the plate on the exterior and interior of the tank. Plate shall extend a minimum of three inches beyond hole.
P. Overflow Pipe: Remove the existing 8" overflow piping, weir box, and supports and furnish and install new 8" overflow and supports in like-kind, as determined necessary by the Engineer. The weir box shall be removed and replaced with the new overflow pipe. Verify and mark freeboard height prior to overflow weir box removal.
3.4 FOUNDATION AND ANCHOR BOLTS
A. A new concrete ringwall foundation, 3 ft. 4 in. wide by 3 ft. deep with reinforcing and fortytwo (42) anchor bolts and chairs shall be installed under the tank perimeter, in accordance with the plans. The 1 ¼" anchor bolts shall be placed equal distance around the perimeter of the tank and set in the concrete foundation. Design shall be in accordance with the requirements of ANSI/AWWA D100-11, Section 12 and in accordance with the details noted on the plans.
HARPER & ASSOCIATES AMADOR TANK PHASE II REHABILITATION July 2022 ENGINEERING, INC. 33 16 19 – MISCELLANEOUS STRUCTURAL MODIFICATIONS 8 of 9
1. Prior to burying the foundation and anchor bolts, plastic caps shall be placed on the exposed threads of the anchor bolts.
B. Existing reinforced concrete slab under the tank shall be removed as needed for installation of new foundation. Existing concrete slab is 12 inches thick and reinforced with No. 5 bars at 7 inches on center each way on the top and bottom of the slab.
C. Prior to placing the concrete foundation, a permanent benchmark shall be established and the existing grade elevation at the perimeter of the bottom plate extension shall be recorded. The elevations shall be established with the tank empty. The recorded checkpoints shall be located next to the new foundation. Checkpoints shall be located at 10-foot centers around the perimeter of the tank. The final elevation of the foundation shall maintain the recorded elevation of the tank shell.
D. The plan for excavation and placing the new foundation and anchor bolts shall be submitted to the Engineer for review and approval. Excavation for the foundation shall not commence prior to review and approval of the plan by the Engineer. The maximum circumferential distance the tank shell area can be undermined is approximately 35 feet, unless an approved method of supporting the tank is submitted.
E. Shoring at the booster pumps building and along the fence shall be accomplished as needed in accordance with Section 31 23 17, Sheeting, Shoring, and Bracing.
F. The bottom of the foundation excavation shall be compacted to 95% relative compaction, in accordance with the plans and Section 31 22 13, Earthwork. Contractor shall not overexcavate to install the foundation. The foundation shall be laid upon soil cut true and even, so that bottom will have a bearing for its full length. Any part of the excavation cut below the needed grade by the Contractor shall be corrected with approved material and thoroughly compacted.
G. The Contractor shall legally dispose of the spoils from the foundation excavation in an offsite area approved the Owner.
H. The foundation shall be installed under the tank perimeter in accordance with the plans and shall be continuously poured, unless other method is approved by Engineer.
Foundation shall be poured in accordance with Sections 03 10 00, Concrete Formwork, 03 20 00, Concrete Reinforcement, and 03 30 00, Cast-In-Place Concrete of these comprehensive specifications.
I. The Contractor shall cut 6" diameter holes in the bottom plates on the interior of the tank 16" from the shell and at 6' on center for inspection of the pour and pumping as needed.
J. Backfill against the concrete foundation shall not be performed until the concrete has developed strength of not less than 70% of full strength.
K. The perimeter of the tank shall be sealed between the concrete foundation and the bottom by either ½-inch-thick impregnated expansion joint material conforming to the requirements of ASTM Standard D1751, a cement grout system, or other approved method. Any voids under the bottom plate extension that cannot be brought into the original shape, based on the above-noted elevations, shall be shimmed and grouted.
HARPER & ASSOCIATES AMADOR TANK PHASE II REHABILITATION July 2022 ENGINEERING, INC. 33 16 19 – MISCELLANEOUS STRUCTURAL MODIFICATIONS 9 of 9 L. All equipment, piping and surfaces of the tank shall be protected from all damage and dust or other deleterious material infiltration during the operations of the Contractor. Any items damaged by the operations of the Contractor shall be replaced in kind or acceptably repaired to the satisfaction of the Engineer by the Contractor at no cost to the Owner.
3.5 TESTING
A. The Contractor shall furnish all material, labor and equipment necessary to test the modifications as specified herein. Testing shall be completed prior to acceptance of work as complete and meeting the requirements of the specification.
B. Spot examination of the welded joints shall be made as the work progresses by magnetic particle, dye penetrant method, or by spot radiographic examination as applicable.
C. All defects uncovered by testing process shall be corrected and retested until such defects are eliminated.
D. Contractor shall provide a watertight installation. After flushing of the chlorinated water and upon filling of the tank, any leaks, which occur on the tank or appurtenant piping shall be repaired by the Contractor at his expense and to the satisfaction of the Engineer. All chlorinated water shall be de-chlorinated in accordance with the Owner’s NPDES permit prior to disposal.
3.6 CLEANUP
Upon completion of the work, all staging, erection brackets, scaffolding and debris shall be removed from the tank and site and disposed in a manner approved by the Engineer.
The entire job site shall be left in a clean condition.
END OF SECTION