Underground Water And Chemical Tanks

Double-Wall FRP Underground Tanks for Fuel Storage; Specification short Form

Contractor to provide a double-wall fiberglass reinforced plastic (FRP) Underwriters Laboratories-labeled underground storage tank as shown on the drawings.


The tank size, fittings and accessories shall be as shown on the drawings. The fiberglass tank shall be provided by Tanksystems.Com of Houston –

The tank shall be tested and installed according to the Installation Manual and Operating Guidelines for Single-Wall and Double-Wall Fiberglass Underground Storage Tanks in effect at time of installation.

Part I: General

1.01 Quality Assurance

  1.  Acceptable Manufacturer: Tanksystems.com
  2.  Governing Standards, as applicable:
  3. Underwriters Laboratories (UL) Standard for Safety 1316, File MH 9061 for storage of flammable liquids. A UL label shall be attached to each tank.
  4. National Fire Protection Association (NFPA) Standards:

NFPA 30: Flammable and Combustible Liquids Code

NFPA 30A: Automotive and Marine Service Station Code

NFPA 31: Installation of Oil-Burning Equipment.

  1. City of New York Department of Buildings M.E.A., Division #161-89-M.
  2. Los Angeles Fire Department.

Part II: Products

2.01 Double-Wall Fiberglass Reinforced Plastic (FRP) Underground Storage Tanks

  1.  Loading Conditions – Tank shall meet the following design criteria:
  2. Internal Load – Tank certified to pass a maximum 5-psig air-pressure test with 5:1 safety factor. Contractor shall individually test tanks for leakage prior to installation.
  3. Vacuum Test – To verify structural integrity, every standard 10′-diameter tank and smaller shall be vacuum tested by the manufacturer at the factory to 11.5″ of mercury.
  4. Surface Loads – Tank shall withstand surface H-20 axle loads when properly installed according to manufacturer’s current Installation Manual and Operating Guidelines.
  5. External Hydrostatic Pressure – Tank shall be capable of being buried in ground with 7′ of  overburden over the top of the tank, the hole fully flooded and a safety factor of 5:1 against general buckling.
  6. Tank shall support accessory equipment – such as heating coils, drop tubes, submersible pumps and ladders –when installed according to tank manufacturer’s current Installation Manual and Operating Guidelines.
  7.  Product Storage
  8. Tank shall be capable of storing petroleum products with specific gravity up to 1.1.
  9. Tank shall be vented to atmospheric pressure.
  10. Tank shall be capable of storing products identified in the manufacturer’s current standard limited warranty.
  11.  Materials
  12. Tank shall be manufactured with 100% resin and glass-fiber reinforcement. No sand fillers.
  13.  Tank Dimensions (Refer to Xerxes literature on gallonage.)
  14. Tank shall have nominal capacity of _____ gallons.
  15. Tank shall have nominal outside diameter of _____ feet.
  16.  Interstitial Space
  17. Tank shall have a space between the primary and secondary walls to allow for the free flow and containment of leaked product from the primary tank. The space also allows the insertion of a monitoring device through a monitoring fitting.

2 Accessories

  1.  Optional Anchor Straps
  2. Straps shall be FRP anchor straps as supplied by tank manufacturer.
  3. Number and location of straps shall be specified in current literature by tank manufacturer.
  4.  Manways
  5. All manways shall be flanged and 22″ I.D., complete with UL-listed gaskets, bolts and covers. (30″ and 36″ I.D. manways are also available on certain larger tanks.)
  6. Location is shown on tank drawings.
  7. Optional manway extensions shall be FRP and 24″ long.
  8.  Optional Fill Tubes
  9. Fill tubes shall be FRP, 4″-diameter, with a 6″ x 4″ double-tapped reducer bushing, and include a 6″ NPT fitting. Tubes shall terminate a minimum of 4″ from the bottom of tank (a minimum of 6″ for a 12′-diameter tank).
  10.  Gauge Plates
  11. Gauge plates shall be installed under each service fitting and manway opening.
  12.  Optional Heating Coils
  13. Optional heating coils shall be installed in a separate 22″ manway and shall be as supplied by tank manufacturer.
  14.  Optional Ladders
  15. Ladders shall be the standard ladder as supplied by tank manufacturer (aluminum, carbon steel or fiberglass).
  16.  NPT Threaded Fittings
  17. All standard threaded fittings shall be half-couplings and shall be 4″- or 6″- diameter. Reducers are to be used for smaller sizes where shown and provided by contractor.
  18. Strength – NPT fittings shall withstand a minimum of 150 foot-pounds of torque and 1,000 foot-pounds of bending, both with a 2:1 safety factor.
  19.  Monitor Fittings
  20. Each monitor fitting shall consist of a 4″ NPT fitting on the tank. Tanks with a hydrostatic monitoring system do not have a monitor fitting.

Part III: Testing and Installation

3.01 Testing

  1. Tank shall be tested according to the Xerxes Installation Manual and Operating Guidelines for Single-Wall and Double-Wall Fiberglass Underground Storage Tanks in effect at time of installation.

3.02 Installation

  1.  Tank shall be installed according to the Xerxes Installation Manual and Operating Guidelines for Single-Wall and Double-Wall Fiberglass Underground Storage Tanks in effect at time of installation.
  2.  Contractor shall be trained by the tank manufacturer, the state or other approved agency.

Part IV: Warranty

4.01 Warranty

  1.  Warranty shall be manufacturer’s limited warranty for double-wall underground petroleum tanks in effect at time of purchase.