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UNDERGROUND STORAGE TAN <br />Section 13215 - Page 8 V 0 <br />E. Excavating and Backfilling Storage Tank: <br />1. Hole Size: The hole must be large enough to allow a minimum of 12" from <br />ends of tank to hole walls and wide enough to accommodate anchor slab <br />(minimum 12' x tank length x 1.0' reinforced concrete). <br />2. Bed and Backfill Material: A naturally rounded aggregate, clean and <br />free flowing with particle size not less than 1/2" in diameter should be <br />used. This is commonly called pea gravel. <br />3. All excavations shall be shored or sloped as per Title 8, Division of <br />Industrial Safety Codes and Regulations. <br />F. Burial Depth and Cover: The tank hole must be deep enough to allow a <br />minimum of 12" pea gravel or gravel crushings bed over the concrete anchor <br />slab. Tanks shall have a minimum cover depth of 3' including 6" reinforced <br />concrete. <br />Reinforced concrete paving must extend at least P beyond minimum limits of <br />excavation in all directions. Depth of cover not to exceed 7' over tank <br />top. <br />G. Installation Procedure - Dry Hole: <br />1. Bed: <br />a. Provide a minimum 12" level backfill bed over concrete anchor slab. <br />b. Bed must be smooth and slope down 0.1' per 10' toward fill end of <br />tank. Place tanks in hole on backfill bed. <br />c. Caution: Do not place glass fiber tanks directly on concrete slab or <br />grout tanks in wet concrete. Do not place tanks on timbers, beams or <br />cradles. <br />2. Backfilling: Pour backfill, using the same material as bed, to top of <br />tank in 12" layers. Insure material flows under tank and end caps. Do <br />not add water or product in tank before backfill material is to top of <br />tank. (Exception see Installation Procedure - Wet Hole). <br />3. Leveling to Grade: Excavation is to be brought to grade with the same <br />backfill material. Caution: Bricks or blocks used to support piping <br />must be removed prior to filling to grade. Do not use rock, shale or <br />debris for fill. <br />4. Barricade: Tank area must be barricaded to prevent any vehicle travel <br />over the tank until the minimum cover depth exists. <br />H. Installation Procedure - Wet Hole: <br />I. Water level shall be maintained at lowest practical level during install- <br />ation. A system of wellpoints will be used to minimize the water level <br />in the hole. The number of wellpoints required will depend on the water <br />flow rate into the hole. The anchor slab must be level, free of rock <br />and debris and covered with at least 12" of backfill material, sloped <br />.01' per 10' toward pump end of tank. <br />R060889:ds:fw MAR 702 <br />