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A6. Burial Depth and Cover A7. Anchoring The tank hole must be deep enough to allow a minimum of l2"and a It is the responsibility of the tank owner or his technical representative to maximum of 24"required backfill bed over the hole bottom or concrete determine if mechanical anchoring is required for aspecific job site.All •slab. potential sources of water(underground water table,rain water run-off, If the total burial depth from tank top is greater than 60%of the tank etc.)should be considered. diameter,anchoring the tank is not required.(See Section A7 for details.) If water could enter the tank hole,O/C TANKS recommends the tanks be , mechanically anchored unless the minimum burial depth from tank top is �—.{—12"minimum PAD DIMENSIONS as follows: Paving must extend at least 12" 1 beyond tank outline in all Concrete Traffic r 7 mazJ directions. 1 (single Slab Thickness 0" 6" I wall) MAXIMUM BURIAL DEPTH(ALL Tank Minimum buried depth when 1;,: SIZE TANKS) p To comply with UL requirements, Diameter Mechanical Anchoring is Not Required depth of cover for tanks in both 4' 30" 27" n� traffic and no traffic conditions 6' 45" 42" j ' must not exceed 7'overtanktop. 8' 54" 51" x. For double-wall tanks,ifacon- 12' 81" 78" tinuous vacuum monitor is used, the maximum burial depth is 3 feet At the above burial depths,the overburden above the tank weighs more from the tank top to grade. than the buoyancy of the empty tank with water to grade(safety factor For deeper burial depths,contact the Fiberglas Tank Installation equals 1.2). Manager. Although tank flotations are rare,they usually occur when the tank is empty and/or has inadequate backfill over the tank.CAUTION:TO MINIMUM BURIAL DEPTH MINIMIZE THE CHANCE OF TANK BUOYANCY,BACKFILL THE TANK slope determined by No Traffic Loads AS SOON AS POSSIBLE TO TANK TOP AND THEN BALLASTWITH soil stability (4'thru 10'diameter tanks) WATER OR PRODUCT.DO NOT PLACE WATER OR PRODUCT IN TANK UNTIL BACKFILL IS EVEN WITH TANK TOP. Tanks not subjected to traffic loads X44 need a minimum cover of 24" For burial depths where mechanical anchoring is recommeded,either of backfill backfill;or 12"plus 4"reinforced two common methods can be used:a concrete anchor pad or deadman concrete.Consult local codes for anchors.Both methods include the use of Fiberglas anchor straps. 12" backful minimum allowable burial depth. pP Stra m 3 + g Me _. concrete Use Fiberglas anchor straps t2 " between the arrows(►-4)on the rere turnbuckletank sides. rj optional Anchor straps are labelled by tank triple diameter.Use only anchor straps ®� MINIMUM BURIAL DEPTH clamped designated for the same diameter tank. Traffic Loads -- (4'thru l0'diametertanks) - For double-wall tanks.without external ribs,the anchor straps - Tanks subjected to traffic loadsha; ri� must also be placed in the strap g �d:v„ must have acover depth of 36" _ guides at the tank top. 36"bk backfill or l8"minimum backfill _:;,i»^.j w�atri For any tanks 2,000 gallon capacity plus 6"of reinforced concrete. and larger,with external ribs, 1s^bkf. The reinforcements in the concrete anchor straps must be placed on top of all designated external ribs(►�). +s^reint. pad must be properly sized for the Anchor p q p concrete job conditions to assure concrete points should bes spaced equal to tank diameter plus l'on each surface sideoftank,regardless of tank diameter.Anchor points atbottom of hole pad integrity. must be aligned with designated(1--0)ribs t 1". All anchor straps must be uniformly tightened with turnbuckles or come- - a-longs.Slrapsshould besnug butcause no tank deflection.Deflection can be detected by checking tank diameter with a gauge stick before and MINIMUM BURIAL DEPTH after snugging straps.See the Installation Checklist. No Traffic Loads Triple clampthe wire rope. (12'diameter tanks) 42• Tanks not subject to traffic loads Note:Do Not Use Straps or Cables Between Ribs. need a minimum cover of 42" backfill;or380backfill plus 4"rein- 12' Concrete Anchor Pad forced concrete, The weight of overburden on top of 3e^ +4 8"min. the concrete slab provides the a6 re-bares thickness anchoring force. 12"too. ^`t eachway This pad design is strictly for buoyancy.Poor soil conditions triple may require increased reinforce- cable ment and slab size. 1 MINIMUM BURIAL DEPTH clamps Traffic Loads Imbed anchor points in concrete (12'diameter tanks) 1z}minimum and attach them to ends of straps bedwith wire rope(see table at end of 24 maximum Tanks subjected to traffic loads this section)and clamp with at must have cover depth of38" -a4 concrete Qadp ;,�s . moi least three clamps.(Sesurethere 3e bkf backfill,plush"of asphalt,orb"c is a 12"bed between concrete • `; +6 („ re-bar reinforced concrete. pad and tanks.) ( asphalt or The concrete pad m ust extend a minimum of 18 0 beyo nd sides of tank -`b - con ete and be at least equal in length to the tank.It is best to extend the slab to - 'r 1� the undisturbed native soil.