Rapid leak detection system - Patent Review 4725551

Claims

I claim:

1. In an apparatus for detecting a leak from at least one of a plurality of subsurface fluid storage tanks containing fluids therein, having at least one of a plurality of subsurface fluid storage tanks surrounded by a backfill material, the improvement which comprises:

volatile liquid phase tracer means for providing a gas phase detectable component in a fluid leak

means for mixing a quantity of said liquid phase tracer means with the fluid in said at least one of a plurality of subsurface storage tanks;

at least one subsurface vapor pipe in the vicinity of said at least one of a plurality of subsurface storage tanks, said vapor pipe having a plurality of apertures along a length thereof positioned within said backfill material and having a first exposed surface end for drawing air into said at least one subsurface vapor pipe;

at least one subsurface sample pipe having a plurality of apertures along a length thereof positioned within said backfill material and a surface outlet, said at least one sample pipe positioned such that air passing from said at least one subsurface vapor pipe through the subsurface to said at least one subsurface sample pipe will be drawn in relatively close proximity past said at least one of a plurality of subsurface tanks;

means for drawing air into said first surface end of said at least one subsurface vapor pipe, through said at least one subsurface vapor pipe and out said apertures into the subsurface area around said at least one of a plurality of subsurface fluid storage tanks, past said at least one subsurface tank and in relatively close proximity thereto thereby volatilizing leaking volatile liquid tracer means to a gas phase tracer means, and drawing said gas phase tracer means into said apertures of said at least one subsurface sample pipe and out of said sample pipe surface outlet; and

means for analyzing said air drawn into said at least one subsurface sample pipe for the presence of said gas phase tracer means as an indication of a leak from the at least one subsurface tank.

2. The apparatus of claim 1 wherein the fluid in said at least one of a plurality of subsurface tanks is a liquid.

3. The apparatus of claim 1 wherein said means for analyzing the air drawn from said at least one sample pipe comprises a gas chromatograph and a tubular water separating means for removing water vapor from the sampled air drawn from the sample pipe prior to analysis by said gas chromatograph.

4. The apparatus of claim 3 wherein said tubular water separator means includes an elongated tube for receiving at one end thereof the air sample to be tested and for supplying at an opposite end thereof the air sample to be tested without any water vapor contained therein;

an outer cylindrical jacket operably disposed around said elongated tube for defining an annular space between said elongated tube and an inside surface of walls of the jacket;

said elongated tube being operative on an air sample containing water vapor passing therethrough for diffusing the water vapor through the walls of said elongated tube and into said annular space;

an inlet to the annular space at the opposite end of said elongated tube and an outlet from the annular space at one opposite end of said elongated tube;

means for supplying a pressurized stream of carrier gas through the inlet into the annular space for sweeping water vapor away as it diffuses through the walls of said elongated tube, said carrier stream containing removed water vapor being passed through the outlet at the at one opposite end of the jacket for removal from the system;

means for transmitting the air sample within said elongated tube, and having water vapor removed therefrom, from said tube water separator means into said gas chromatograph for analysis thereof; and

said gas chromatograph including means responsive to the analysis of the air sample, with water vapor removed, for detecting relatively small quantities of said tracer means therein for indicating a presence of a leak in said at least one of a plurality of subsurface tanks.

5. The apparatus of claim 1 wherein the fluid in said at least one of a plurality of subsurface tanks is gasoline.

6. The apparatus of claim 5 wherein said liquid phase tracer means is a fluorinated halocarbon compound having a boiling point less than that of gasoline.

7. The apparatus of claim 6 wherein said boiling point of said liquid phase tracer means is between minus fifty degrees centigrade and plus eighty degrees centigrade.

8. The apparatus of claim 1 wherein said liquid phase tracer means is a volatile organic tracer.

9. The apparatus of claim 8 wherein said air drawing means is an air pump coupled to said at least one subsurface sample pipe, at said surface outlet thereof.

10. The apparatus of claim 8 wherein said liquid phase tracer means is selected from the group consisting of fluorinated halocarbons, methanes, and ethanes.

11. The apparatus of claim 10 wherein said volatile liquid phase tracer means is selected from the group consisting of halogenated methanes, halogenated ethanes sulferhexafluoride, perfluorodecalin, and perfluoro 1,3 dimethylcyclohexane.

12. The apparatus of claim 11, wherein said tracer is a halogenated methane group liquid phase tracer means selected from the group consisting of chlorobromodifluoromethane, trifluroiodomethane, trifluorobromomethane, dibromodifluoromethane, dichlorodifluoromethane and tetrafluoromethane.

13. The apparatus of claim 11, wherein said tracer is a halogenated ethane group liquid phase tracer means selected from the group consisting of dichlorotetrafluoroethane, chloropentafluoroethane, hexafluoroethane, trichlorotrifluoroethane, bromopentafluoroethane, dibromotetrafluoroethane and tetrachlorodifluroethane.

14. A method for locating leaks from at least one of a plurality of subsurface fluid storage tanks buried in a backfill material surrounding each of the at least one of a plurality of subsurface fluid storage tanks, comprising:

placing at least one of a plurality of vapor pipes in backfill material on one side of at least one of a plurality of subsurface fluid storage tanks which tanks are buried in said backfill material;

placing at least one of a plurality of sample pipes in said backfill material on an opposite side of said at least one of a plurality of subsurface fluid storage tanks;

mixing a volatile liquid phase tracer with fluid in said at least one of a plurality of subsurface fluid storage tanks;

drawing air from said at least one of a plurality of vapor pipes past said at least one of a plurality of subsurface fluid storage tanks into said at least one of a plurality of sample pipes thereby volatilizing said liquid phase tracer which leaks from said at least one of a plurality of subsurface fluid storage tanks to a gas phase tracer and into said at least one of a plurality of sample pipes; and

analyzing the air in said at least one of a plurality of sample pipes for the presence of said gas phase tracer for determining when a leak is present in at least one of said plurality of subsurface fluid storage tanks.

15. The method of claim 14 further comprising probing a tracer plume when a leak is detected.

16. The method of claim 14 wherein said liquid in said at least one of a plurality of subsurface fluid storage tanks is gasoline.

17. The method of claim 14 wherein said volatile liquid phase tracer is a fluorinated halocarbon compound having a boiling point lower than that of gasoline.

18. The method of claim 14 wherein said volatile liquid phase tracer is selected from the group consisting of fluorinated halocarbons, methanes, and ethanes.

19. The method of claim 14 wherein said step of mixing further comprises mixing said volatile liquid phase tracer with a portion of said fluid form said at least one of a plurality of subsurface fluid storage tanks and subsequently injecting said fluid-tracer mixture into said at least one of a plurality of subsurface tanks.

20. The method of claim 14 wherein said step of drawiang air from said at least one vapor pipe includes the step of pumping air from a surface outlet of said at least one sample pipe in order to draw air from a surface inlet of said at least one vapor pipe, through apertures of said at least one vapor pipe, past said at least one of a plurality of subsurface fluid storage tanks, into apertures of said at least one sample pipe, and up said at least one sample pipe to said surface outlet thereof for analyzing the air sample.

21. The method of claim 14 wherein said volatile liquid phase tracer is selected from the group consisting of halogenated methanes, halogenated ethanes, sulferhexafluoride, perfluorodecalin, and perfluoro 1,3 dimethylcyclohexane.

22. The method of claim 21, wherein said tracer is a halogenated methane group liquid phase tracer means selected from the group consisting of chlorobromodifluoromethane, trifluroiodomethane, trifluorobromomethane, dibromodifluoromethane, dichlorodifluoromethane and tetrafluoromethane.

23. The method of claim 21, wherein said tracer is a halogenated ethane group liquid phase tracer means selected from the group consisting of dichlorotetrafluoroethane, chloropentafluoroethane, hexafluoroethane, trichlorotrifluoroethane, bromopentafluoroethane, dibromotetrafluoroethane and tetrachlorodifluoroethane.

24. The metod of claim 14 wherein said step of drawing air from said at least one vapor pipe includes disposing said at least one vapor pipe in a subsurface area in the vicinity of said at least one of a plurality of subsurface fluid storage tanks with an air inlet positioned above the surface;

drawing air from the atmosphere above the surface into said inlet of said at least one vapor pipe;

drawing air from said at least one vapor pipe through apertures therein into subsurface material surrounding said at least one of a plurality of subsurface fluid storage tanks;

said drawing further including drawing air from the apertures of said at least one vapor pipe through said subsurface material surrounding said at least one of a plurality of subsurface fluid storage tanks and in relatively close proximity thereto, to apertures of said at least one sample pipe; and

said drawing step yet further including drawing the air from the vicinity of said at least one of a plurality of subsurface fluid storage tanks into said at least one sample pipe and out a surface outlet thereof.

25. The method of claim 24 wherein said step of analyzing the air in said at least one sample pipe includes coupling an analyzing device to said outlet of said at least one sample pipe;

drawing at least one sample of air from said sample pipe and into said analyzing device;

removing water vapor from said sample of air taken from said at least one sample pipe; and

testing said at least one sample of air from said sample pipe with the water vapor removed and detecting for the presence of said volatile liquid phase tracer for determining the presence of a leak in said at least one of a plurality of subsurface fluid storage tanks.

26. The method of claim 25 wherein the step of removing water vapor from the air sample taken from said outlet of the sample pipe includes feeding the air sample into a water separator tube;

forming an annular space in an area around said water separator tube;

diffusing water vapor in an air sample supplied to said water separator tube through walls thereof into said annular space;

supplying a gas carrier to said annular space;

sweeping away diffused water vapaor using the carrier gas stream in said annular space; and

supplying an air sample with the water vapor removed therefrom from an output of said water separator tube into a gas chromatograph for analysis thereof to determine the presence of said tracer and an existence of a leak in said subsurface tank.

27. In a leak detection system for detecting an existence of a leak in at least one of a plurality of underground fluid storage tanks and for locating specific leaks so detected having at least one of a plurality of underground fluid storage tanks and a backfill material surrounding the at least one of a plurality of underground fluid storage tanks, wherein the improvement comprises:

a number of different and distinct volatile liquid phase tracer means, one for each one of said at least one of a plurality of underground fluid storage tanks;

means for mixing a quantity of a different one of said different and distinct volatile liquid phase tracer means with fluid within each one of said at least one of a plurality of underground fluid storage tanks;

at least one underground air inlet pipe means having an above-surface air inlet and a plurality of apertures in an underground portion thereof for supplying atmospheric air to said backfill means, said air inlet pipe means being disposed in said underground backfill means in close proximity to said at least one of a plurality of underground fluid storage tanks;

at least one underground soil gas sample pipe means having an above-surface outlet and a plurality of apertures in an underground portion thereof, said sample pipe means being disposed in said underground backfill means in the vicinity of said at least one of a plurality of fluid storage tanks;

means for drawing atmospheric air into said inlet of said at least one underground air inlet pipe means, through said at least one underground air inlet pipe means, and out apertures thereof into said backfill material, for drawing said air past said at least one of a plurality of underground fluid storage tanks through said backfill material and in relatively close proximity to at said least one of a plurality of underground fluid storage tanks thereby volatilizing leaking liquid phase tracer means to a gas phase tracer means into said air, for drawing an air sample from around said at least one of a plurality of underground fluid storage tanks into apertures of said at least one underground soil gas sammple pipe means and to said outlet thereof; and

testing means coupled to said output of said at least one underground soil gas sample pipe means for analyzing said air sample for each of said number of different and distinct volatile liquid phase tracer means for detecting leaks in said at least one of a plurality of underground fluid storage tanks, a particular gas phase tracer means detected identifying the at least one of a plurality of fluid storage tanks having leaks.

28. The system of claim 27 wherein said backfill material comprises gravel for preventing point pressure from large rocks and and other solid objects and for providing a relatively good air conduit therethrough.

29. The system of claim 27 wherein said backfill material comprises sand for providing a relatively good air conduit therethrough.

30. The system of claim 27 wherein the number of different and distinct volatile liquid phase tracer means is equal to the number of underground fluid storage tanks and one of each of said plurality of different and distinct volatile liquid phase tracer means are mixed with fluids in one and only one of each of said plurality of underground fluid storage tanks.

31. The system of claim 27 wherein said mixing means includes means for mixing a quantity of a different and distinct volatile liquid phase tracer means into fluids destined for each underground fluid storage tank before filling each storage tank with said fluid.

32. The system of claim 27 wherein said mixing means includes means for injecting a quantity of each different and distinct liquid phase tracer means into a correspondingly different and distinct one of each of said underground fluid storage tanks after said tanks have been filled with fluid; and

means for mixing each of said injected quantities of volatile liquid phase tracer means throughout the fluids.

33. The system of claim 27 wherein said mixing means includes means for supplying a quantity of each different and distinct volatile liquid phase tracer means into fluid within a different and distinct underground storage tank after said tanks have been filled with said fluid; and

recirculation means for mixing said volatile liquid phase tracer means into said fluids.

34. The system of claim 27 wherein said at least one underground air inlet pipe means is disposed on one side of at least a first one of said plurality of underground fluid storage tanks and wherein said at least one underground soil gas sample pipe means is disposed on an opposite side of said first one of said plurality of fluid storage tanks, whereby air drawn down said at least one underground air inlet pipe means passes through the backfill material surrounding said first one of a plurality of fluid storage tanks and said at least one inlet and said at least one underground sample pipe means, and flows through said apertures of said at least one underground sample pipe means for collecting an air sample which contains a unique, different, and distinct gas phase tracer means for identifying a particular tank in the backfill material having a leak.

35. The system of claim 27 wherein said at least one underground air inlet pipe means is disposed on one side of said at least one of a plurality of underground fluid storage tanks and in relatively close proximity thereto, said at least one underground sample pipe means disposed on an opposite side of said at least one of a plurality of underground fluid storage tanks, whereby substantially all air drawn in through said at least one underground air inlet pipe means passes through said backfill material surrounding said at least one of a plurality of underground fluid storage tanks, in close proximity thereto such that said air sample collected by said at least one underground sample pipe means contains one different and distinct gas phase tracer means for each leaking ones of said corresponding different and distinct storage tanks.

36. The system of claim 27 wherein said drawing means includes a pumping means coupled to the outlet of said at least one underground sample pipe means for sucking atmospheric air down said at least one underground air inlet pipe means, through said backfill material around said at least one of a plurality of underground fluid storage tanks, and up said at least one underground sample pipe means.

37. The system of claim 27 wherein said at least one underground air inlet pipe means includes a plurality of underground air inlet pipe means disposed within said backfill material on at least one side of said at least one of a plurality of underground fluid storage tanks, and said at least one underground sample pipe means comprises a single underground soil gas sample pipe operably disposed in said backfill material on an opposite side of said at least one of a plurality of underground fluid storage tanks for serving as a central sample collection point for gathering air samples to be tested.

38. The system of claim 27 wherein said testing means includes gas chromatograph means for vaporizing and testing an air sample and for detecting concentrations of gas phase tracer means contained therein; and

a tubular water separator means including an elongated tube connected to said gas chromatograph means, a cylindrical jacket means encasing said elongated tube defining an annular channel between an outer surface of said elongated tube and an inner surface of the jacket means, whereby a gas sample supplied to said gas chromatograph means and then to an inlet of said elongated tube for conduction thereof, passes through said elongated tube diffusing water vapor through walls thereof into the annular channel such that an air sample output from said elongated tube to said gas chromatograph means for detection and concentration measurement of tracer means is free from water vapor to insure more sensitive detection and concentration measurement, said tubular water separator means further includes an inlet means located at one end of said annular channel, a source of carrier gas means connected to said inlet means for supplying said annular channel with carrier gas for collecting water vapor diffused therein from said tube and outlet means at an opposite end of said annular channel for outputing an water vapor and carrier gas.

39. The system of claim 27 wherein said testing means for analyzing the air samples includes a gas chromatograph for detecting the presence of each of said plurality of different and distinct gas phase tracer means and for measuring relative concentration thereof; and

a tubular water separator means coupled to said gas chromatograph for receiving the air samples and removing water vapor therefrom prior to transporting the air samples to said gas chromatograph.

40. The system of claim 27 wherein the fluid in said at least one of a plurality of underground storage tanks is a liquid.

41. The system of claim 40 wherein said liquid is gasoline.

42. The system of claim 27 wherein said at least one underground air inlet pipe means includes a plurality of underground air inlet pipe means disposed within said backfill material on one side of said at least one of a plurality of underground fluid storage tanks and said at least one underground sample pipe means includes a plurality of underground sample pipe means disposed within said backfill material on an opposite side of said at least one of a plurality of underground storage tanks whereby, substantially all air drawn from the atmosphere into said plurality of underground air inlet pipe means passes through said backfill means past and in close proximity to each of said at least one of a plurality of underground fluid storage tanks, such that air samples collected by said plurality of underground sample pipe means contain measurable amounts of different and distinct gas phase tracer means from leaking ones of the at least one of a plurality of underground fluid storage tanks.

43. The system of claim 42 wherein said drawing means comprises a plurality of drawing means including at least one for each of said plurality of underground soil gas sample pipe means.

44. The system of claim 27 further including boring means for forming a plurality of test bores in said backfill material in the vicinity of each underground fluid storage tank for which a leak has been detected for tracking and locating a tracer plume in said backfill material; and

means for analyzing soil gas samples from each of said plurality of test bores for tracer concentrations is the soil gas samples whereby said tracer plume is located for establishing a source and a location of a leak in said at least one of a plurality of underground fluid storage tanks.

45. The system of claim 44 wherein said means for analyzing the air samples includes a gas chromatograph for detecting the presence of a particular one of said plurality of different and distinct gas phase tracer means and for measuring relative concentrations thereof; and

a tubular water separator means coupled to the gas chromatograph for removing water vapor from the air samples prior to analysis thereof.

46. A method of locating leaks in at least one of a plurality of underground fluid storage tanks substantially surrounded by an air-conducting backfill material comprising the steps of:

placing air inlet means into an air-conducting backfill material which surrounds a plurality of underground fluid storage tanks, said air inlet means being disposed on one side of at least one of said plurality of underground fluid storage tanks;

placing sample collection means into said air conducting backfill material on an opposite side of said at least one of a plurality of underground fluid storage tanks;

mixing fluid in said at least one of a plurality of underground fluid storage tanks with a different and distinct one of a plurality of liquid phase tracers;

drawing air into said air inlet means and subsequently into said air conducting backfill material;

volatilizing any liquid phase tracer escaping into said backfill material substantially surrounding said at least one of a plurality of underground fluid storage tanks from a leak in said at least one of a plurality of underground fluid storage tanks into said air drawn into said backfill material, thereby transforming said liquid phase tracer to a gas phase tracer and absorbing said gas phase tracer in said air drawn into and through said backfill material;

collecting at least one air sample from said sample collection means on an opposite side of said at least one of a plurality of storage tanks from the side on which air is drawn into said backfill material; and

analyzing said at least one collected air sample to determine a presence of any one of said plurality of different and distinct liquid phase tracers in the gas phase for indicating the existence of a leak in said at least one of a plurality of underground fluid storage tanks.

47. The method of claim 46 wherein the fluid in said at least one of a plurality of underground fluid storage tanks comprises a gasoline.

48. The method of claim 46 wherein said backfill material comprises gravel.

49. The method of claim 46 wherein said backfill material comprises sand.

50. The method of claim 46 wherein the step of mixing the fluid in said at least one of a plurality of underground fluid storage tanks with a different and distinct one of a plurality of liquid phase tracers includes the step of mixing a predetermined quantity of one of said plurality of liquid phase tracers with the fluid prior to transporting the fluid into said at least one of a plurality of underground fluid storage tanks.

51. The method of claim 46 wherein the step of mixing the fluid in said at least one of a plurality of underground fluid storage tanks with a corresponding different and distinct one of a plurality of liquid phase tracers includes mixing said liquid phase tracer throughout the fluid to obtain a relatively uniform fluid tracer mixer throughout said at least one of a plurality of underground fluid storage tanks.

52. The method of claim 46 wherein said liquid phase tracer comprises a fluorinated halocarbon compound.

53. The method of claim 46 further comprising the step of selecting said plurality of tracers from the group consisting of fluorinated halocarbons, methanes, and ethanes.

54. The method of claim 46 further comprising the steps of:

determining from said analysis that said liquid phase tracer is leaking from said at least one of a plurality of underground fluid storage tanks;

detecting a tracer plume at a main collection location; and

probing upgradient and measuring concentrations of said gas phase tracer in said drawn soil gas samples along said tracer plume, thereby, locating an exact point of said liquid phase tracer leaking from the at least one of a plurality of underground fluid storage tanks.

55. The method of claim 54 wherein said step of probing further comprises the steps of:

boring a plurality of small diameter holes into said backfill material;

collecting soil gas samples from each of said plurality of small diameter holes;

analyzing each of said collected soil gas samples and determining concentrations of said gas phase tracer in each of said collected soil gas samples; and

concurrently drilling and testing said collected soil gas samples upgradient and determining the location of maximum gas phase tracer concentration in said collected soil gas samples and determining the location of said liquid phase tracer leaking from said at least one of a plurality of underground fluid storage tanks.

56. The method of claim 46 wherein the step of mixing the fluid in said at least one of a plurality of underground fluid storage tanks with a different and distinct one of a plurality of volatile liquid phase tracers includes initially supplying the fluid into said at least one of a plurality of underground fluid storage tanks and subsequently adding a predetermined quantity of a given one of said plurality of different and distinct liquid phase tracers thereto.

57. The method of claim 56 wherein said step of mixing the fluid in said at least one of a plurality of underground fluid storage tank with a different and distinct one of a plurality of liquid phase tracers comprises mixing the liquid phase tracer thoroughly into the fluid within the tank in situ.

58. The method of claim 56 wherein the step of mixing further includes the step of recirculating the fluid together with said supplied liquid phase tracer for mixing the two within said at least one of a plurality of underground fluid storage tanks in situ.

59. The method of claim 46 further including the step of selecting said plurality of different and distinct tracers from the group consisting of fluorinated halocarbon; halogenated methanes, halogenated ethanes sulferhexafluoride, perfluorodecalin, and perfluoro 1,3 dimethylcyclohexane.

60. The method of claim 59, wherein said tracer is a halogenated methane group liquid phase tracer means selected from the group consisting of chlorobromodifluoromethane, trifluroiodomethane, trifluorobromomethane, dibromodifluoromehtane, dichlorodifluoromethane and tetrafluoromethane.

61. The method of claim 59, wherein said tracer is a halogenated ethane group liquid phase tracer means selected from the group consisting of dichlorotetrafluoroethane, chloropentafluoroethane, hexafluoroethane, trichlorotrifluoroethane, bromopentafluoroethane, dibromotetrafluoroethane and tetrachlorodiflurorethane.

62. The method of claim 46 wherein the step of mixing further comprises mixing said fluid in each one of said at least one of a plurality of underground fluid storage tanks with a different and distinct one of a plurality of liquid phase tracers;

and wherein said step of absorbing any gas phase tracer further comprises the steps of installing a plurality of air inlet pipes in close proximity to and on one side of said plurality of underground fluid storage tanks drawing air from the atmosphere into at least one of said plurality of air inlet pipes, into said backfill material, drawing said air in close proximity to said at least one of a plurality of underground fluid storage tanks, absorbing any gas phase tracer leaking into said backfill material, collecting said drawn air and detecting any liquid phase tracer, in the gas phase, leaking from any one of said at least one of a plurality of underground fluid storage tanks.

63. The method of claim 62 wherein said step of collecting said drawn air sample further comprises installing a collection pipe on an opposite side of said at least one of a plurality of underground fluid storage tanks from said plurality of air inlet pipes and collecting at least one drawn air sample therefrom.

64. The method of claim 62 wherein said step of absorbing any gas phase tracer further comprises the steps of providing a pump coupled to each of said plurality of collector pipes and pumping air from the atmosphere through said at least one air inlet pipe, through said backfill material surrounding said at least one of a plurality of underground fluid storage tanks, through said sample collection means and collecting drawn air for analysis.

65. The method of claim 64 further comprising the steps of:

determining that said at least one of a plurality of underground fluid storage tanks is leaking;

drilling a plurality of small diameter holes into said backfill material;

collecting soil gas samples by drawing air samples from at least one of said plurality of small diameter holes;

detecting for the presence of any gas phase tracer in said soil gas samples;

drilling additional small diameter holes, in a reverse tracking manner, collecting soil gas samples by drawing air samples from at least one of said additional small diameter holes, detecting for the presence of any gas phase tracer in said drawn soil gas samples from said additional small diameter holes;

tracking the source of liquid phase tracer leaking from at least one of said plurality of underground storage tanks by measuring increased concentrations of said gas phase tracer in said drawn soil gas samples from said at least one of said additional small diameter holes and, thereby, locating a plume of said gas phase tracer in said backfill material; and

determining the source of liquid phase tracer leaking from said at least one of the plurality of underground fluid storage tanks by locating a point where the maximum concentration of said gas phase tracer is detected in said drawn soil gas sample from said additional small diameter holes.

66. The method of claim 46 wherein the fluid in said at least one of a plurality of underground fluid storage tanks comprises a liquid.

67. The method of claim 66 wherein the step of collecting said at least one air sample further comprises the steps of sinking at least one of a plurality of vapor pipes into the backfill material on one side of and in close proximity to the at least one of a plurality of underground fluid storage tanks;

positioning at least one inlet end of said at least one of a plurality of vapor pipes above a surface of said backfill material for serving as an air inlet;

burying substantially an entire remaining portion of said at least one of a plurality of vapor pipes pipe in the backfill material in close proximity to said at least one of a plurality of underground fluid storage tanks;

drawing atmospheric air into said at least one of plurality of vapor pipes, down said at least one of a plurality of vapor pipes and into the backfill material;

distributing said drawn air out of said at least one of a plurality of vapor pipes and into the backfill material;

passing said drawn air in relatively close proximity to said at least one of a plurality of underground fluid storage tanks;

absorbing liquid phase tracer, in the gas phase, escaping from a leak in the at least one of a plurality of underground fluid storage tanks into said drawn air; and

directing said drawn air in said backfill material past the at least one of a plurality of underground fluid storage tanks and through collection location.

68. The method of claim 67 wherein said step of collecting said at least one air sample further includes the steps of:

sinking a collection pipe into said backfill material on an opposite side of and in close proximity to the at least one of a plurality of underground fluid storage tanks;

positioning one end of said sample collection pipe above the backfill material surface to serve as a sample collection output;

raising a drawn air sample collected in said sample collection pipe to said sample collection outlet; and

supplying said raised air sample to a gas chromatograph system for analyzing said raised air sample.

69. The method of claim 68 wherein said step of collecting at least one air sample at the outlet includes:

vaporizing water contained in said at least one air sample;

removing substantially all water vapor from said at least one collected air sample before analysis;

testing said at least one air sample having substantially all water vapor removed therefrom and detecting for any of said plurality of different and distinct liquid phase tracers, in the gas phase; and

determining which of said underground fluid storage tanks is leaking.

70. The method of claim 69 wherein said step of removing substantially all water vapor from said at least one collected air sample before analysis further comprises the steps of:

vaporizing water in said at least one collected air sample into water vapor;

conducting said vaporized sample through an elongated water separator tube;

diffusing said water vapor in said at least one collected air sample through said elongated water separator tube into a surrounding space whereby a remaining portion of said at least one collected air sample is free from water vapor; and

transporting said at least one collected air sample free from water vapor from an output of said elongated water separator tube to a gas chromatograph for analysis.

71. The method of claim 70 wherein said step of removing substantially all water vapor from said at least one collected air sample further comprises the steps of:

supplying a carrier gas under pressure;

directing a flow of said carrier gas along an outside surface of said elongated water separator tube;

absorbing water vapor which diffuses through said elongated water separator tube into said flow of said carrier gas; and

removing said carrier gas and said absorbed water vapor.