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XIV — UNDERGROUND MOTOR FUEL STORAGE TANKS
<br />DOUBLEWALL FIBERGLASS & JACKETED STEEL
<br />INSTALLATION SPECIFICATIONS
<br />PEAGRAVEL BACKFILL
<br />(Revised March 1997)
<br />XIV -1 GENERAL
<br />The contractor accepts full responsibility for proper handling
<br />and installation of the fiberglass underground storage tanks &
<br />shall insure that good workmanship, practices and construction
<br />procedures are followed during the handling and Installation of
<br />the tanks, regardless of the inclusion or omission of any
<br />applicable suggestion in these instructions.
<br />Unknown situations or conditions not covered herein are the
<br />responsibility of the contractor. Manufacturer's specialists
<br />end the Shell engineer are both available for consultation. The
<br />presence of a manufacturer or Shell observer at on installation
<br />site does not relieve the contractor of this responsibility for
<br />proper installation on the tank.
<br />Fiberglass underground tanks must be installed according to
<br />these instructions and NFPA 30 & 30A. Local codes may apply
<br />and should be consulted. Failure to follow these installation
<br />instructions will void the warranty and may result in tank
<br />failure. Proper installation of fiberglass underground tanks
<br />helps to prevent tank damage and to Insure long term corrosion
<br />resistant service. It is imperative to read, understand and
<br />follow the instructions below.
<br />Fiberglass underground tanks require the backfill material to
<br />provide as much as 959 of the tank support under certain stress
<br />conditions. The installing contractor must be positive he has
<br />the correct bed and backfill and follows these instructions
<br />exactly.
<br />The contractor is responsible to know and comply with applicable
<br />sections of "OSHA Construction Standards", 29 CFR 1926, Subpart
<br />P — "Excavations" (with Appendices A, B, C) which cover the
<br />pertinent general and specific safety requirements.
<br />Our drawings do not and cannot depict all the various soil
<br />conditions which tend to govern the appropriate means to use to
<br />provide safe working conditions within an excavation for under
<br />ground tanks. The OSHA standards are very specific on trenching,
<br />shoring, and open excavation standards.
<br />There are several means available to Shell and the General
<br />Contractor to achieve compliance and, most importantly, to
<br />provide safe working conditions. The Shell Engineer will
<br />select the most appropriate and cost effective method to be
<br />used from one of the following approved options. The method
<br />chosen will be noted in the "Addenda" section of these
<br />specifications or checked off beside one of the following
<br />alternatives:
<br />NOTE:
<br />SHELL PERSONNEL MAY NOT DESIGN, CONSULT, OR APPROVE
<br />CONTRACTOR PLANS OR ACTIONS. HOWEVER, SHELL PERSONNEL
<br />MAY SHUT DOWN ANY PROJECT WHERE SAFETY IS QUESTIONABLE.
<br />1, Peagrovel backfill with appropriate sloping of sidewalls
<br />to the angle of repose
<br />Shell drawings depict appropriate excavation configurations
<br />for average soil conditions, so that on installation crew
<br />may enter the excavation to grade the tank bed and complete
<br />the under tank compaction work. The 1:1 slope depicted
<br />could be more or less depending on actual soil conditions.
<br />This option demands a much larger excavation at grade, even
<br />though the additional material to be excavated and replaced
<br />may be only 100-200 cubic yards.
<br />2. Sand backfill with water compaction
<br />Until further written notice from Head Office Marketing
<br />Engineering, no sand installations are to be attempted.
<br />Any exceptions must have prior Marketing Engineering
<br />approval.
<br />3, Shoring of the tank hole walls
<br />This method may be required at times in order to protect
<br />existing structures during tank removal and replacement or
<br />to limit the size of the excavation on small properties.
<br />FOR ADDITIONAL INFORMATION
<br />Questions regarding installation procedures or tank repairs
<br />should be directed to the Shell engineer.
<br />XIV -2 PRE—INSTALLATION
<br />1. CONTRACTOR ACCEPTANCE/INSPECTION OF TANKS
<br />Shell's approved standards are either a doublewall alcohol—
<br />compatible or a dielectric jacketed steel tank. The installing
<br />contractor shall meet the tank delivery on site and off—load
<br />the tanks after inspecting for possible damage. Notify the
<br />Shell engineer immediately if any is found.
<br />2. TESTING
<br />BEFORE PERFORMING ANY AIR PRESSURE TESTS ON ANY
<br />TANK, THE CONTRACTOR IS EXPECTED TO THOROUGHLY
<br />UNDERSTAND THE TANK MANUFACTURER'S INSTRUCTIONS
<br />FOR THE PROPER HANDLING AND TESTING PROCEDURES
<br />TO BE FOLLOWED.
<br />NEVER PERFORM AN AIR PRESSURE TEST ON THE TANK
<br />INTERSTICE IF THAT INTERSTICE HAS ALREADY BEEN FILLED
<br />WITH LIQUID. NEVER PERFORM ANY POSITIVE PRESSURE
<br />TEST ON THE INTERSTICE OF A JACKETED .STEEL TANK.
<br />WHETHER AT THE FACTORY OR ON THE JOBSITE, A DOUBLE
<br />WALL FIBERGLASS TANK INTERSTICE MAY BE FILLED WITH
<br />LIQUID ONLY BY A FACTORY TRAINED & EQUIPPED CREW;
<br />NEVER THE INSTALLING CONTRACTOR. THIS CREW WILL ALSO
<br />PERFORM A HYDROSTATIC PRECISION TEST ONCE BACKFILL
<br />IS AT TANK TOPS. ADDITIONAL TESTING IS STILL REQUIRED_
<br />All tanks must be vented since tanks are designed for
<br />operation at atmospheric pressure only. Plugs and drop
<br />tube fittings are not tightened at the plant to allow for
<br />temperature changes during shipment.
<br />For fiberglass tanks shipped with interstice already filled with
<br />liquid at the factory, DELETE the pre—installation air/soap
<br />test. Air pressure is additive to hydrostatic pressure and
<br />the total may damage the fiberglass tank. For fiberglass
<br />tanks shipped dry interstices, the installing contractor is
<br />responsible for making an aerostatic leakage test at a
<br />pressure not exceeding 5 psi prior to setting tank. Test
<br />to be conducted for a minimum of one hour without a
<br />measurable loss of pressure. Use a pressure gauge with
<br />full scale of not more than 15 psi. Isolate tanks from
<br />piping when pressure testing ANY piping. Do not approach
<br />ends of tanks or manways that are under test. Tanks under
<br />pressure should not be left unattended.
<br />While tank is under pressure, the entire tank, including
<br />fittings, should be wetted with a "soapy" solution to
<br />inspect for minor leaks which otherwise might not be
<br />evident. A garden tank—type sprayer with Seam Test
<br />Solution' manufactured by Winton Products, Charlotte,
<br />North Carolina, is recommended for this purpose. An
<br />alternate acceptable solution would be one (1) cup of
<br />dishwashing detergent such as Dove or Ivory Liquid in a
<br />gallon of water.
<br />If tanks are dropped or impacted after initial test,
<br />retest tanks and soap areas of impact to check for tank
<br />damage. If damage has occurred, do not attempt repairs.
<br />Contact the Shell engineer.
<br />Pressurizing the relatively small annular space (see
<br />chart below) between the two tank shells can occur very
<br />quickly. A pressure of over 5 psig may cause damage to
<br />the tank structure which may not be immediately apparent.
<br />For all such tests an air gauge with maximum 1/2 pound
<br />Increments should be used (maximum total gauge pressure
<br />15 prig). The tank manufacturer provides a valve and
<br />manifold arrangement to perform this test.
<br />Follow the steps as outlined in the tank manufacturer's
<br />installation and testing instructions that come with every
<br />tank shipment. It is mandatory that the air supply line
<br />NEVER be connected to the annular cavity access fitting.
<br />The inner main tank may be pressurized directly by an air
<br />compressor, but always use the manifold provided by the
<br />tank manufacturer to pressurize the annular cavity.
<br />Jacketed steel tanks are shipped with dry interstii under
<br />a vacuum. The primary (steel) tank will be tested with
<br />5 1 (max) later in the project, but the interstice may
<br />ONLY be tested by applying a 15"Hg (max) vacuum. A
<br />positive pressure test on any such jacket will structurally
<br />fail the jacket.
<br />All test results and selected installation data are to be
<br />recorded on Shell's "Doublewall Installation/Inspection
<br />Procedure and Checklist". A complete copy of this form
<br />must be returned to the Shell engineer with as—built
<br />drawings (or 35mm color pictures and the final invoice.
<br />FAILURE TO FURNISH AN ACCEPTABLY COMPLETED COPY OF THIS
<br />FORM WILL RESULT IN SHELL WITHHOLDING FINAL PAYMENT.
<br />3. HANDLING
<br />Approximate tank weights are shown by the chart below and
<br />such tanks CANNOT be driver unloaded. The installation
<br />contractor is required to unload the tanks at the jobslte using
<br />properly sized equipment. See also the tank lifting guidance
<br />configuration sketches below (5).
<br />TANK
<br />Jf K ED
<br />DOUBLEWALL
<br />ADD FOR
<br />CAPACITY
<br />S EL
<br />FIBERGLASS
<br />COMPARTMENT
<br />high winds are
<br />expected.
<br />Use a minimum
<br />BULKHEAD
<br />500
<br />0
<br />990
<br />-
<br />1000
<br />�47091
<br />adequate size
<br />-
<br />8000
<br />7 50
<br />5150
<br />st50
<br />400
<br />10000
<br />8 0
<br />6200
<br />400
<br />12000
<br />93
<br />7200
<br />400
<br />15000
<br />4900
<br />8500
<br />400
<br />to m
<br />15000
<br />1 200
<br />8450
<br />600
<br />4, CHOCKING
<br />Tanks should not be dropped, rolled, or
<br />impacted.
<br />Chock
<br />the tanks until
<br />ready for
<br />installation and
<br />tie them
<br />down if
<br />high winds are
<br />expected.
<br />Use a minimum
<br />1/2"
<br />diameter nylon
<br />or hemp rope
<br />over each
<br />tank and tie to
<br />wooden
<br />stakes of
<br />adequate size
<br />to prevent
<br />the tanks from
<br />being moved
<br />by high
<br />winds.
<br />5. LIFTING
<br />Always use lift lug(s) to handle tanks. Never lift tanks by
<br />putting a cable, strap, or chain around tanks. Guide tanks with
<br />minimum 1/2" taglines (ropes). If/when tanks need to be
<br />moved, NEVER roll them. Always set tanks on smooth ground
<br />free of debris, rocks, and foreign objects. Rechock tanks using
<br />old tires or similar objects that will not damage tanks. Capacity
<br />of lifting equipment must be verified before using.
<br />TANK LIFTING GUIDANCE
<br />ier
<br />VAX
<br />C:_�
<br />CONNECT TO
<br />EWER amNG
<br />500 To 1000 1000 To 6000 8000 To 12000
<br />15000 TO 20000
<br />6. TANK OPENINGS
<br />Tank openings shall remain closed, but tanks must be vented
<br />during handling and up to the time when pipe connections
<br />are made to prevent the intrusion of water and/or foreign
<br />matter. All unused openings are to be properly sealed with
<br />plugs per drawings when piping is being installed.
<br />7. CONTAINMENT MONITORING SYSTEMS
<br />For doublewall fiberglass tanks, a hydrostatic interstitial
<br />monitoring system will be furnished by Shell. For jacketed
<br />steel tanks, a non—discriminating liquid intrusion monitoring
<br />system will be furnished by Shell. See applicable installation
<br />drawings and manufacturer instructions furnished by Shell
<br />for additional details.
<br />NO DEVIATIONS FROM MONITORING STANDARDS PERMITTED
<br />WITHOUT PRIOR MARKETING ENGINEERING APPROVALS.
<br />XIV -3 BED AND BACKFILL MATERIAL
<br />1. GRAVEL
<br />Standard bed and backfill material should be a naturally
<br />rounded aggregate, clean and free—flowing, with particle
<br />sizes not less than 1/8' nor more than 3/4" in diameter
<br />and containing nor more than 59 (volume) fines passing
<br />a #8 sieve. This is commonly known as ASTM C-33
<br />peagrovel but may have other deignations depending upon
<br />local area customs.
<br />2. STONE OR GRAVEL CRUSHINGS
<br />Stone or gravel crushings with anular particle size not
<br />less than 1/8" or more than 1/2' in diameter, washed and
<br />free—flowing, is acceptable as an alternate material. This
<br />material must meet ASTM C-33 Paragraph 9.1 requirements
<br />limits on fines content and for soundness and quality.
<br />Caution: In freezing conditions, backfill must be dry and
<br />free of ice. Do not use other backfill materials. In
<br />areas where specified materials are not available, contact
<br />the Shell engineer for instructions.
<br />Do not allow backfill material to intermix with any
<br />excavated soil at the site. If this should occur,
<br />mechanical compaction of the backfill will be required.
<br />The minimum particle size of 1/8" (No. 6 sieve) is
<br />critical for "self— compacting" backfill.
<br />XIV -4 HOLE SIZE, BURIAL DEPTH AND COVER
<br />The contractor will be responsible for compliance with OSHA
<br />"Construction, Safety & Health Regulations, Subpart P —
<br />Excavations, sections 1926.650 through 1926.652.
<br />1. STABLE WALLS
<br />Stable walls are those which normally can be made vertical
<br />from bed to grade without use of shoring or sheet piling
<br />Because of natural cohesive soils with on unconfined
<br />compressive strength of 1.5 tons/square foot, or more.
<br />Hole must be large enough to allow the minimum spacing
<br />shown on Shell drawings between tanks and from ends/sides
<br />of tanks to tank hole walls.
<br />2. UNSTABLE WALLS
<br />Those with soils having less than 0.5 tons/sq ft cohesion
<br />as calculated from an unconfined compression test. Hole
<br />must be large enough to allow minimum of 1/2 the tank
<br />diameter from ends and sides of tanks to hole walls. A
<br />qualified soil testing laboratory can provide data and
<br />recommendations.
<br />3. HOLE DEPTH
<br />Burial hole must be deep enough to allow a minimum of 12"
<br />backfill bed over the hole bottom or concrete slab. Tanks
<br />should have a minimum cover depth of 4'-5", including 8" of
<br />reinforced concrete mat.
<br />4, MAXIMUM BURIAL DEPTH
<br />Depth of cover for tanks of 10' or less in diameter in
<br />both traffic and non—traffic conditions must not exceed
<br />7'-0" over tank top (including concrete slab).
<br />5. PAD DIMENSIONS
<br />Reinforced concrete slab must extend at least 24" beyond
<br />tank outline in all directions, as a single slab. Provide
<br />3/4" thick expansion joint all around slab for a 3—tank
<br />system. Slab to be 8" thick with 6" x 6", 4/4 welded wire
<br />fabric. A 3—tank slab will be cast with two longitudinal
<br />construction joints, keyed and dowelled. Dowels
<br />to be #4 deformed round steel bars 30" long and placed
<br />approximately 48" on center in the center of the slob.
<br />Place an 8 mil polyethylene barrier over completed
<br />backfill before pouring the slab.
<br />XIV -5 ROCK AND WATER
<br />Where a rock ledge or uncontrollable water condition is
<br />encountered in the course of excavation, the contractor shop
<br />advise the Shell engineer immediately and not proceed with the
<br />excavation until e determination and agreement Is made as to the
<br />handling of this work and the anchorage of tanks. Soft shale
<br />or boulders smaller than 1-1/2 cu. yds. that can be removed or
<br />handled by a power shovel shall be considered as part of the
<br />excavation contract and will not be considered as rock ledge.
<br />Contractor shall do all dewatering and pumping required to
<br />remove accumulations of surface water from excavated areas at
<br />no additional cost. Underground seepage that can be controlled
<br />with a single two inch diameter construction pump will not
<br />warrant an extra charge for pumping. If additional pumping
<br />equipment, well pointing, or sheeting becomes necessary, the
<br />contractor shall Immediately notify Shell regarding the problem,
<br />with recommendations for handling and an estimated extra cost
<br />to complete the work with appropriate unit prices for material,
<br />labor and equipment.
<br />XIV -6 INSTALLATION PROCEDURE — DRY HOLE
<br />Anchoring (see XIV -8) is highly recommended in soils conditions where
<br />natural soil percolation is inadequate or questionable. All 4' and 10'
<br />diameter tanks require MANDATORY ANCHORING........ NO EXCEPTIONS.
<br />ILII'- �i
<br />Backfill bed under tanks should be a minimum of 12" thick
<br />over the hole bottom or concrete slob, if used. Bed should
<br />be sloped between 2" and 4" toward the fill at end of tank
<br />unless a compartmented tank is used wherein the bed should
<br />be level. Setting of screeds is recommended for insuring
<br />smooth, properly pitched beds. Place tanks in hole on bed,
<br />after screeds have been removed. Do not place tanks on
<br />timbers, beams or cradles,
<br />2. HIGH WATER
<br />Tanks, whether strapped or not, must never be left on the
<br />bed without backfill to the top of tank if there is any
<br />chance of more than 12" of water in the hole. (See
<br />section XIV -12).
<br />3. BACKFILLING
<br />Use the some materials as initial bedding. At the start of
<br />backfilling care must be taken to push backfill material
<br />completely beneath tank bottom, between ribs and under end
<br />caps to provide necessary support. A long handled probe,
<br />or similar device, should be used to push backfill under
<br />the tank since pea gravel or stone crushings will not flow
<br />into this area (see D-97005 or D-97009 for details).
<br />Good compaction can also be obtained by "slicing" the
<br />gravel with a shovel around the entire tank perimeter.
<br />Install the first 18" of backfill in roughly 6" layers.
<br />Unanchored tanks installed with backfill to the top of the
<br />tank but without backfill to grade should be filled with
<br />product or water as ballast. Do not add ballast in tank
<br />before backfill material is even with top of tank.
<br />Complete backfilling to top of tank. Be sure backfill
<br />is free of large rocks, debris or foreign materials that
<br />could damage the tank. Avoid impacting tanks during
<br />bockfll!ing.
<br />Attempt to minimize time contractor employees are in the
<br />tank hole. When men are in the hole, supervisors must be
<br />present on top. Cave—ins ore a danger during installation.
<br />Use all precautions when men are in the hole, particularly
<br />the edges between tank hole wall and the tank.
<br />4. LEVELING TO GRADE
<br />Excavation should be brought to sub—grade with peogrovel or
<br />stone or gravel crushings meeting the specifications shown
<br />In Section XIV -3, as used for bedding and backfilling. Do
<br />not mix materials.
<br />Caution: Bricks or blocks used to support piping must be
<br />removed prior to filling to grade. Do not use rock, shale,
<br />debris, or any excavated material for fill.
<br />5. BARRICADES
<br />Tank area must be barricaded to prevent any vehicle travel
<br />over the tanks until a cured concrete slab exists. See
<br />Section XIV -4, burial depth and cover/traffic loads.
<br />Berms should be installed around the perimeter of the tank
<br />hole to prevent groundwater from running into hole during
<br />construction.
<br />XIV -7 INSTALLATION PROCEDURE — WET HOLE
<br />Anchoring is mandatory. See section XIV -8.
<br />1. WATER LEVEL
<br />Water level should be maintained at the lowest practical
<br />level during installation. A sump and pump or a system
<br />of well points and pumps is the recommended method to
<br />minimize water level in the hole. The type of system
<br />required will depend on water flow rate into the hole.
<br />The hole bottom should be level, free of rocks and debris
<br />and covered with at least 12" of backfill material. (See
<br />Section XIV -16, "Permanent Pipe Sumps").
<br />Shell Oil Company. All Riqhts Reserved 1997
<br />
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