referring to fig1 the present invention employs two separate types of wells to remediate soil which is contaminated with hazardous volatile hydrocarbons . the structures will be first described for identification before a description of the operation . beginning at the left side of the figure , the above ground level is demarcated by a grade 11 line . above grade 11 , a propane gas storage tank 13 is supported . tank 13 , as well as other vessels and equipment of fig1 may be truck mounted or skid mounted and may therefore have a common means of support to provide greater ease of operation an mobility . the tank 13 is shown with grade 11 level mounting legs 15 . extending from the tank 13 is a propane gas supply line 17 connected to a valve 19 . valve 17 has a pressure tap leading to a pressure indicator 21 . as is shown , pressure indicator 21 can be used to regulate valve 17 . valve 19 is connected to a valve 25 . valve 25 is connected to a valve 29 . valve 25 has a pressure tap leading to a pressure indicator 27 . as is shown , pressure indicator 27 can be used to regulate valve 25 . valve 25 is connected to a motorized valve 29 . motorized valve 29 is controllably connected to pressure limit switch actuators 31 and 33 . pressure limit switch actuators 31 and 33 have a pressure tap connection to the other side of valve 29 . a valve 35 is also connected to valve 29 . valve 35 is connected to a flow indicator 37 , which may be a visual flow indicator , either analog or digital . valve 35 and flow indicator 37 are connected to a flow control valve 39 . flow control valve 39 is connected to a shutoff valve 41 . the other side of shutoff valve 41 is in communication with the internal portion of a fire well 45 . fire well 45 extends both above and below grade 11 . looking below the grade 11 , and along the extent of fire well 45 , it can be seen that fire well 45 is shown extending through a first sandy soil layer 47 , a clay bearing soil layer 49 and into a second sandy soil layer 51 . fire well 45 is a continuous casing and may be made of metal in direct contact with the soil layers 47 , 49 , and 51 . it is understood that multiple layers may be present , and that the fire well may extend through several layers of differing depth and several alternating layers of different types of material . at the lower extent of fire well 45 , as it extends into layer 51 , the fire well is fitted with a series of exit perforations 53 . in the figure , the exit perforations occur at the layer 51 , and beneath the clay bearing layer 49 . referring to the right side of the figure , an air filter 55 is connected to the suction side of an air blower 57 . the outlet of the blower is connected to a pressure indicator 59 , flow control valve 61 , check valve 63 and flow indicator 65 . the check valve 63 is also connected to a flow control valve 67 . the actuator of flow control valve 67 may be linked to the actuator of flow control valve 39 such that flow control valves 67 and 39 may be actuated in concert with each other . flow control valve 67 is connected to one end of another flow control valve 69 . the other end of flow control valve 69 is connected to the end of the fire well 45 . fire well 45 also has a tap 71 leading to a flame ( burner ) sensing switch 73 which is used to control valve 29 , along with inputs from pressure limit switch actuators 31 and 33 . fire well 45 also has a recirculation inlet 75 , shown slightly above grade 11 . fire well 45 is also shown with a broken line along its length to illustrate the fact that it may be of any length . a series of arrows are shown at the lowermost portion of fire well 45 , and adjacent the exit perforations 53 , to indicate the flow of hot combustion products from the fire well 45 . to the right of the fire well 45 is a vapor - extraction well 77 . vapor - extraction well 77 similarly has a series of perforations , however these are inlet perforations 81 . typically , but not always , vapor - extraction well 77 may be shorter than fire well 45 . the inlet perforations 81 are shown as being in a sandy soil layer 47 , which is above the clay bearing layer 49 . the vapor - extraction well 77 extends above grade 11 and communicates through a withdrawal port , shown in the figure as being its upper end , with a pressure indicator 83 , a temperature indicator 85 , and a knockout pot 87 . knockout pot 87 has a level gauge 89 and a drainage valve 91 . an overhead line 93 connects the knockout pot 87 with the suction side of a vacuum pump 95 . the outlet of vacuum pump 95 communicates with the recirculation inlet 75 of the fire well 45 through a series combination of a flow control valve 97 , a check valve 99 , and a flow indicator 101 . along this line of fluid communication there is a pressure indicator 103 located nearer the outlet of the vacuum pump 95 and a sample port 105 located nearer the recirculation inlet 75 of the fire well 45 . also extending below grade 11 is one or more conducting rods 111 . conducting rod 111 may have any portion of their length exposed or insulated . for example , conducting rod 111 may have its lower length exposed and its upper length insulated . conducting rod 111 is powered by either a direct - current or alternating - current power supply 113 . the power supply 113 may also be connected , as is shown in the figure , to the fire well 45 . alternatively , the power supply 113 may be connected to another conducting rod 111 , to produce a voltage difference between several conducting rods 111 and the fire well 45 , or to produce a voltage difference between one or more conducting rods 111 and another set of one or more conducting rods 111 . in the configuration of the figure , the conducting rod 111 is installed to pass current through the clay bearing soil layer 49 , between the conducting rod 111 and the fire well 45 . the temperatures at various points in the configuration of the figure may be measured to monitor the progress of the remediation activity . a first temperature probe rod 121 is inserted below grade and shown to the left of the conducting rod 111 . the temperature probe rod 121 can have a temperature indicating device , such as a thermocouple or multiple thermocouples at any point or points along its length . for example , the temperature indicating elements could be arranged to allow measurements to be taken at each of the first sandy soil layer 47 , clay bearing soil layer 49 and second sandy soil layer 51 . the temperature probe rod 121 is configured to measure the temperature surrounding the fire well 45 . another temperature probe rod 123 is configured to measure the temperature in the first sandy soil layer 47 , between the fire well 45 and the vapor - extraction well 77 . other temperature probe rods similar to the temperature probe rods 121 and 123 may be employed . temperature probe rod 121 is connected to temperature - sensing element 125 while temperature probe rod 123 is connected to temperature - sensing element 127 . another temperature - sensing element 129 is connected , as shown partially in dashed line format , to a temperature element ( not shown ) at some length within the fire well 45 . the temperature - sensing elements 127 , 125 and 129 are connected to temperature recorder 131 , so that the process operating temperatures of the remediation process may be measured . in addition , a pressure indicator 135 is also attached to the upper end of fire well 45 to indicate the back pressure within the fire well 45 . the operation of the remediation device and process of the present invention is as follows . the process removes hydrocarbons from contaminated soil by injecting hot combustion gases directly from a gas burner ( the details of which are not shown , but which will be referred to as burner 137 ), forming the upper section of the fire well 45 , into soil located below grade 11 . the burner 137 forms the upper section of the fire well 45 , and the combustion gases exit at the base of the well through the exit perforations slots provided for this purpose . as the soil adjacent to the well , and particularly the second sandy soil layer 51 is heated , hydrocarbons , eventually within all of the first sandy soil layer 47 , clay bearing soil layer 49 , and second sandy soil layer 51 are volatilized and withdrawn from the soil through the vapor - extraction well 77 . from the vapor - extraction well 77 , the vapors pass through the knock out pot 87 where entrained water in these vapors is removed , and which may be periodically drained through drainage valve 91 . the vacuum pump 95 , which may be a blower similar to air blower 57 , feeds these hydrocarbons into the recirculation inlet 75 where they are ignited , producing additional heat . the heat produced by burning these hydrocarbons accelerates the removal of more hydrocarbons from the soil , which in turn produces even more heat . the flow of hydrocarbon - bearing vapors directed into the fire well are measured with a flow indicator 101 . the area adjacent the recirculation inlet 75 is kept hot enough to combust these hydrocarbons as they enter the fire well 45 . the air blower 57 is in communication with the air - inlet port of the burner 137 , and the flow of air is measured with a flow indicator 65 . the flow of propane and air is controlled with standard flow control valves 39 and 67 designed for this purpose . the propane and air are mixed inside the burner 137 and ignited to produce a flame ; the flame projects downward from the burner 137 into the fire well 45 . the ignited gases continue downward and exit at the bottom of the fire well 45 through exit perforations 53 provided for this purpose . the hot combustion gases urged into the first sandy soil layer 51 spread out beneath the contaminated clay bearing soil layer 49 , raising the temperature of the contaminated clay bearing soil layer 49 . as the temperature of the contaminated clay bearing soil layer 49 is raised , hydrocarbons contained within this soil are volatilized and drawn toward the inlet perforations 81 of the vapor - extraction well 77 . in addition to using a hot gas to apply heat to the soil , the soil may be heated dielectrically . this is accomplished by passing a current through the soil from conducting rod 111 placed in the soil , below grade 11 , and downwardly through the clay bearing soil layer 49 , and to the casing of the metallic fire well . the amount of heat applied to the soil is proportional to the amount of current flowing through the soil . the power supply 113 is shown connected to both the fire well 45 and conducting rod 111 such that the a weak electrical current is established between the conducting rod 111 and the fire well 45 . when a direct - current ( dc ) power supply is used , the conducting rod 111 functions as the negative pole ( cathode ) of a dc circuit , and the fire well 45 functions as the positive pole ( anode ) of the circuit . heating the soil , including the first sandy soil layer 47 , clay bearing soil layer 49 , and second sandy soil layer 51 , accomplishes at least two goals . first , relatively non - volatile hydrocarbons such as those found in diesel fuel are vaporized and removed from the soil . conventional , non - thermal vapor extraction is generally limited to relatively volatile hydrocarbons such as those found in gasoline . secondly , as the soil is heated , and the vapor pressure of the volatile hydrocarbons in the soil is increased , the time required to remediate the soil is reduced . temperatures are monitored using temperature - sensing elements : temperature element 125 is used to monitor the temperature of the first sandy soil layer 51 in proximity to the discharge of the fire well 45 ; temperature element 127 is used to monitor the temperature of the second sandy soil layer 57 in proximity to the inlet of the vapor - extraction well 77 ; and temperature element 129 is used to monitor the temperature in a flame section 141 of the fire well 45 which is generally shown as extending between recirculation inlet 75 and tap 71 . these temperatures may be recorded continuously on the temperature recorder 131 . pressures are monitored using pressure - sensing elements : pressure indicator 135 is used to measure the pressure at the top of the fire well 45 ; pressure indicator 83 is used to measure the vacuum at the top of the vapor - extraction well 77 ; pressure indicator 21 is used to measure the pressure in the propane storage tank 13 ; and pressure indicator 27 is used to measure the pressure of the propane supplied to the burner . progress in remediating the soil , including first sandy soil layer 47 , clay bearing soil layer 49 and second sandy soil layer 51 may be monitored by periodically analyzing samples of the vapors drawn from below grade 11 through vapor - extraction well 77 . sample port 105 is used to collect these vapor samples . when the hydrocarbon concentration in these vapors has fallen below a critical level , the soil has been remediated . because the volatile hydrocarbons removed from the soil are generally hazardous , state and federal laws often prohibit their release into the atmosphere without treatment . treating the hydrocarbon vapors drawn from the soil , however , raises the cost of vapor extraction . in addition , heating the soil also raises the cost of vapor extraction . the instant art accomplishes both treatment of the vapors withdrawn from the soil and heating of the soil in a very simple and cost - effective manner . further , because there are no emissions to the atmosphere , an operating permit from an agency regulating atmospheric emissions is not even required . all of this is accomplished by using the vapors drawn from the soil as fuel for the fire well . donnelly , in the previously mentioned u . s . pat . no . 4 , 982 , 788 attempts to employ the advantages of the present invention , yet falls short in several aspects . although there are no emissions to the atmosphere , the heat recovered from the emission - control device , which is a simple refrigerated coil driven by a heat pump , is minimal . a secondary heat source , such as an electric heater , is needed to significantly raise the temperature of the soil . the cost of operating the electric heater is a drawback . additionally , although a portion of the hydrocarbons extracted from the ground are recovered , the condensed liquid has little , if any value . the water vapor naturally present in the soil condenses with the hydrocarbons , forming a mixture of water and hydrocarbons . such a mixture must often be discarded as a hazardous waste , further adding to the cost of the process . finally , the concentration of hydrocarbons in the vapors extracted from the contaminated soil is typically less than 1 , 000 parts per million . consequently , unless it is operated in the cryogenic range , the condensing coil used to remove hydrocarbons from the extracted vapor will operate inefficiently , and hydrocarbon vapors will be reinjected into the contaminated soil . in summary , at best , the donnelly process does little to offset the cost of non - thermal vapor extraction , and at worst may be both ineffective and more expensive . by comparison , the present invention has no waste products to dispose of , and the fuel value of the extracted hydrocarbons is utilized to help to power the process . it represents a clear advance over both the current art in conventional , non - thermal vapor extraction practiced by payne , bernhardt et al ., koerner et al ., and visser et al ., and the current art in thermal vapor extraction , practiced by donnelly . in comparison to the shu process , virtually all of the vapors drawn from the extraction well employed by the present invention are reinjected back into the soil through an injection well containing a burner . essentially all of the energy in the vapors drawn from the extraction well is used as fuel to operate the burner , unlike the shu process which uses formation ignition surrounding the well sustained only by injecting an appropriate amount of oxygen into the formation . while the present invention has been described in terms of a vapor extraction system for removing hydrocarbons from soil , one skilled in the art will realize that the structure and techniques of the present invention can be applied to many situations . the present invention may be applied in any situation where vaporous species need removal . although the invention has been derived with reference to particular illustrative embodiments thereof , many changes and modifications of the invention may become apparent to those skilled in the art without departing from the spirit and scope of the invention . therefore , included within the patent warranted hereon are all such changes and modifications as may reasonably and properly be included within the scope of this contribution to the art .