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Specification No. : RGS0024-87 <br /> Part II - SPECIFIC CONDITIONS <br /> Section 9 - Specific Conditions <br /> for Tank Installation <br /> possibility of large boulders or sharp objects damaging <br /> exterior surface of the tank. <br /> 9 . 8. 5 Excavation for Pipe Trenches : Trenches shall be excavated <br /> to the alignment , depth and grade , to suit required pipe <br /> line slope from pump to storage tank . The trench width <br /> for pipes shall be sufficiently large to permit proper <br /> backfilling and compacting . Fuel pipes shall be minimum <br /> 18 inches below the finished grade at the pump island , <br /> vent and vapor pipes shall be minimum 12 inches below the <br /> finished grade at the pump island . <br /> 9 . 8 . 6 Pipe and Bed Backfill : Before underground pipes are laid , <br /> place and compact clean sand in the trench to a minimum <br /> depth of 4 inches . After laying the pipes , place and <br /> compact clean , air-dry sand around and over the pipes to a <br /> minimum cover of 4 inches . Fill the remainder of the <br /> trench with either sand or backfill in 6 inch maximum <br /> layers and compacted to 95 percent of the maximum density <br /> of ASTM 1557-78 , or to the density specified for the <br /> surrounding fill , whichever is higher . Backfill may be <br /> excavated material , provided it does not contain organic <br /> matter and should be placed at close to optimum moisture <br /> content . <br /> 9 . 8. 7 Tank cover shall be 4 feet including the depth of the <br /> concrete slab . <br /> 9 . 9 Testing : <br /> 9 . 9 . 1 Test all piping and calibrate with equipment . Notify <br /> inspection authorities prior to the tests so that they may <br /> be witnessed . Protect all personnel and equipment during <br /> testing . <br /> 9 . 9 . 2 Storage Tanks : Storage tanks shall be tested with an air <br /> pressure minimum 3 PSIG and maximum 5 PSIG before storage <br /> tank is lowered and installed in the excavation in <br /> addition to any tests which may be recommended by the tank <br /> manufacturer . The initial test pressure shall be <br /> maintained without pressure drop for 10 minutes before <br /> inspecting tank seams and pipe opening connections . A11 <br /> seams and connections shall be leak tested at full test <br /> pressure with a soap and water solution . If tanks are <br /> dropped or impacted after initial pressure test , remove <br /> IX-6 <br />