PORTABLE GROUND THAWING SYSTEM AND METHOD

Abstract

A portable ground thawing system for excavating Shovel Test Pits (STPs) includes a cylindrical heat chamber having an open bottom and a closed top. A charging inlet is disposed on one side and a flue is on the other. An adjustable baffle is stationed in the flue. A salamander style heater is positioned to emit a stream of hot gas through the charging inlet, creating a swirling internal current of hot gas that loops through an internal heat loft. The heat loft provides both radiant heat properties as well as supports convection via the gas current that sweep across the frozen ground before exiting the flue. Electricity to power the heater is supplied by a generator. The method of use includes orienting the heat chamber so that its charging inlet is leeward and its flue is windward relative to the prevailing wind direction.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Provisional Patent Application US 62/929,190 filed on Nov. 1, 2019, the entire disclosure of which is hereby incorporated by reference and relied upon.

BACKGROUND OF THE INVENTION

Field of the Invention.

The invention relates generally to a portable ground thawing system and method for placing shovel test pits (STPs) in frozen ground.

Description of Related Art.

Prior to developing a tract of land, it is sometimes required to make an archaeological survey to determine whether the planned development might negatively impact ancient cultural remains, buried artifacts or other generally hidden objects of historical value.

A shovel test pit (STP) is a standard method for performing an initial assessment phase of an archaeological survey. In many cases, shovel testing strategies are designed to identify archaeological resources and to delineate their boundaries. Within a specified project area, a series of small test holes are dug by hand using a shovel (typically) in order to determine whether the soil contains cultural remains. A hand shovel is used due to its relative gentleness and finesse compared to chipping or hacking with an axe pick, or other forms of aggressive digging. Artifacts buried in the soil are less likely to be damaged using a hand shoveling technique, through which haptic feedback can inform a trained technician of conditions as they are encountered. Soil excavated from the STP is sifted or screened through a wire mesh to determine whether any relevant artifacts are contained in the soil. The collected results of STP findings can be mapped over the project area to determine whether further archaeological investigation is necessary.

The depth of an STP depends on the depth at which either the bedrock or the sterile subsoil is found. Occasionally the excavation of shovel test pits (STPs) into frozen ground becomes necessary. Frozen ground presents at least two very serious obstacles to excavating STPs. First, digging in frozen earth can be very labor intensive and time consuming. Second, frozen earth tends to remain in large clods that are resistant to sifting and screening through wire mesh. For these reasons, it is generally disfavored to excavate STPs in frozen ground. This reluctance to perform STPs in freezing conditions can result in development delays for many months.

The project area over which STPs must be placed is often remote and/or rugged undeveloped terrain which must be traversed by foot or with the aid of off-road vehicles like four-wheelers. In Northern climates during the winter months, snowmobiles may be the only effective means of transport. As a result of these often-difficult conditions, all equipment used to perform STP survey must be easily packable and transportable by foot, four-wheeler, or snowmobile. Large and/or heavy equipment is simply impractical for performing STPs, especially during the winter months in Northern climates.

Moreover, State Historic Preservation Office standards, as well as guidelines established by other agencies, typically prohibit or discourage archaeological investigations in frozen ground, during times when the ground is snow covered, or when it is snowing or raining heavily. For this reason, the industry has avoided the development of solutions designed for winter field conditions.

There is therefore a need in the art to facilitate the placement of STPs in frozen ground using equipment that is easy to transport.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the invention, a portable ground thawing system comprises a heat chamber having an open bottom surrounded by a sidewall and a closed top. A charging inlet is disposed in the sidewall. An exhaust flue is disposed in the sidewall. A heater has a discharge nozzle configured to emit a stream of hot gas along a discharge vector. The heater is disposed proximate to the heat chamber with the discharge vector passing through the charging inlet. The flue is located generally opposite the charging inlet.

According to a second aspect of the invention, a method is provided for excavating a Shovel Test Pit (STP) in frozen ground. The method comprises the steps of: preparing a test area by clearing debris and removing snow accumulations above a threshold limit, placing the open bottom of a heat chamber on the test area, orienting the heat chamber so that its charging inlet is leeward and its exhaust flue is windward relative to the prevailing wind direction, directing a stream of hot gas from a heater along a discharge vector passing through the charging inlet, and circulating hot gases through a heat loft within the heat chamber above the charging inlet prior to exiting through the flue.

The system and method of this invention enable in-season soil conditions, i.e., not frozen ground, to be easily replicated for taking geological samples and any other expedient purposes. The invention thaws earthy sediments to the point that they could be removed from the ground by standard shovel testing operation and subsequently passed through a mesh during a typical screen operation. The system and method are effective, at least in part, by controlling heated gas so as to flow consistently across the frozen ground surface below the heat chamber. As a result, the invention enables winter-time near-surface archaeological testing to be conducted during urgent or emergency situations, such as buried utility repair, or to conduct further investigations surrounding the inadvertent find of human remains. This invention offers a solution to the prevailing local standards and guidelines that typically discourage archaeological investigations in frozen ground.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein:

FIG. 1 is a perspective view of a portable ground thawing system according to one embodiment of the invention;

FIG. 2 is a top view of the portable ground thawing system of FIG. 1;

FIG. 3 is a perspective view showing the heat chamber and heater according to an embodiment of the invention;

FIG. 4 is a simplified side elevation view, in cross-section, showing the heat chamber and heater disposed for use over frozen ground in which below the surface resides a buried artifact and a frost line;

FIG. 5 is a view as in FIG. 4 showing the section of ground below the heat chamber thawed and the baffle inverted;

FIG. 6 is a perspective view of the baffle according to one exemplary embodiment of the invention;

FIG. 7 is a fragmentary perspective view showing the lower portion of the heat exchange with baffle oriented as in FIG. 4, the baffle being moved to a fully open position in solid and a fully closed position in phantom;

FIG. 8 is a side elevation of the heat chamber with baffle oriented as in FIG. 5, the baffle being moved to a fully open position in solid and a fully closed position in phantom; and

FIG. 9 illustrates the process of placing a shovel test pit (STP) by digging a hole in the thawed ground, transferring soil excavated from the hole to a screen mesh, and sifting the excavated soil through the screen mesh to locate artifacts.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the figures, wherein like numerals indicate like or corresponding parts throughout the several views, a portable ground thawing system is generally shown in one exemplary embodiment for use in placing shovel test pits (STPs) and such other applications as may be found expedient to excavate small portions of earth during the winter months in Northern climates.

The portable ground thawing system includes a heat chamber, generally indicated at 10. The heat chamber 10 is a hollow construction having an open bottom 12 surrounded by a sidewall 14 and a closed top 16. The sidewall 14 can be made of steel or other suitable heat-compatible material. In the illustrated examples the heat chamber 10 takes the form of a generally cylindrical volume in which case the sidewall 14 is generally cylindrical and the top 16 is generally circular and the bottom 12 is also generally circular. It has been discovered that a commercial grade steel drum of 30-gallon size will suffice for construction of the heat chamber 10. However, the heat chamber 10 can take many different shapes and forms, including cube-like, dome-like, pyramid-like and cone-like to name a few. Naturally, other (non-cylindrical) forms of the heat chamber 10 will dictate corresponding adaptations to the shapes of the bottom 12, top 16 and sidewall 14 features. In all contemplated variations, the open bottom 12 end is posited to face the underlying ground surface.

At least one handle 18 is attached to the heat chamber 10 to facilitate handling. It has been found expedient to attached two such handles 18 adjacent the top 16, diametrically located opposite one another on the sidewall 14. The handles 18 can be economically fabricated from a section of metallic rod bent to form a D-shaped loop that is welded or otherwise affixed directly to the heat chamber 10. A thermal resistant metal can be used, if desired, to reduce the risk of burn injury to the operators. The loop configuration shown in the drawing is advantageous for naturally shedding heat so as to reduce the risk of burn injury when the system is in operation. Of course, handles 18 of other numbers, shapes and mounted locations can be substituted for those illustrated in the figures if desired.

A charging inlet 20 disposed in the sidewall 14. The charging inlet 20 has an upper extremity 22 and a lower extremity 24. The lower extremity 24 of the charging inlet 20 is axially spaced from bottom 12 by a lower extremity distance IL. The charging inlet 20 is shown to have a generally rectangular shape throughout the accompanying illustrations, however other shapes are certainly possible, including but not limited to circular. Regardless of shape, the charging inlet 20 will have upper 22 and lower 24 extremities. In one example, the charging inlet 20 is an opening approximately 8-inches high by 12-inches wide.

Particularly beneficial results have been achieved when the upper extremity 22 of the charging inlet 20 is axially spaced generally midway between the bottom 12 and the top 16 of the heat chamber 10. More specifically, the upper extremity 22 is preferably located within ±10% of the midline between the bottom 12 and the top 16 of the heat chamber 10. Thus, in the example of a heat chamber 10 having an overall height of 30 inches (i.e., axial distance between top 16 and bottom 12), the midline will fall at 15 inches as measured from either end 12, 16. Thus, ±10% equal 3 inches on either side of the midline. In other words, in this example the upper extremity 22 will preferably fall between about 12 inches and 18 inches as measured from the bottom 12.

In use, the heat chamber 10 is positioned so that the charging inlet 20 is located on the leeward side relative to the wind direction W. By maintaining the upper extremity 22 of the charging inlet 20 within 10% of the midline, a substantial volume of upwardly confined space can be established in a heat loft 25 inside the heat chamber 10. The trapped volume inside the heat chamber 10 above the upper extremity 22 is the heat loft 25, as indicated in FIGS. 4 and 5. In cases where the heat chamber 10 is cylindrical in shape, the heat loft 25 will, normally, be likewise cylindrical in shape as an included space. A hovering body of hot gas is loosely contained inside the heat loft 25 region. This body of hot gas performs beneficial radiant and convective functions. In terms of radiant functionality, the heat loft 25 behaves like a radiant heat body directing heat energy downwardly through the open bottom 12 toward the exposed ground surface. In terms of convective functionality, internal eddy currents circulate through the heat loft 25 and refresh their heat energy in the heat loft 25 before passing down toward the ground. These heating attributes will be discussed further below in connection with FIGS. 4 and 5. By maintaining a floating bubble of heat in this heat loft 25 region inside the heat chamber 10, rapid thawing of the ground can be achieved through a combination of radiant and convective heat transfer mechanisms.

An exhaust flue 26 is disposed in the sidewall 14 to emit excess gas from the heat chamber 10. The flue 26 is located generally opposite the charging inlet 20. Thus, in examples where the heat chamber 10 is cylindrical, the flue 26 can be seen as diametrically opposed to the charging inlet 20. In use, the heat chamber 10 is positioned so that the exhaust flue 26 is located on the windward side relative to the wind direction W.

The flue 26 has a first edge 28 adjacent the bottom 12 and a second edge 30 adjacent the top 16. The first edge 28 of the flue 26 is axially spaced from bottom 12 by a first flue distance F1, whereas the second edge 30 is axially spaced from bottom 12 by a second flue distance F2. In practice, a first flue distance F1 of approximately 4 inches has been found to provide satisfactory results. The second flue distance F2 is less than or equal to the lower extremity distance IL of the charging inlet 20 on the opposite side of the heat chamber 10. That is to say, the lower extremity 24 of the charging inlet 20 may be configured so as not to extend as low as the exhaust flue 26. As a result, cooler gas will be more effectively forced to exit the heat chamber 10 below the level of the charging inlet 20.

In the illustrated examples, the flue 26 is generally rectangular, with the first 28 and second 30 edges being parallel to one another and extending horizontally relative to the ground. In practice, a flue 26 having a size of 6-inches high by 8-inches wide has been found effective. However, the flue 26 can take many different shapes. In some contemplated embodiments, the flue is circular or oval. In some contemplated embodiments, the flue is louvered.

In the illustrated examples, a baffle 32 is moveably connected to the flue 26. The baffle 32, best seen in FIGS. 6-8, may be configured with at least one directional fin 34. The directional fin 34 is outwardly angled so as to facilitate the egress of excess gas from the heat chamber 10. Preferably, the baffle 32 is invertible in the flue 26 so as to invert the directional fin 34 to vector exiting gas upwardly (FIG. 4) or downwardly (FIG. 5). In this manner, the pattern of circulating currents within the heat chamber 10 can be manipulated by the user to maximize ground thawing performance.

Furthermore, a moveable interface 36 can be incorporated to support the baffle 32 for movement relative to the flue 26. The moveable interface 36 is shown in one exemplary form in FIG. 6 as a curved slot-like formation in a curved L-shaped flange 38 on the baffle 32. The curvature of the slot and of the L-shaped flange 38 match the curvature of the sidewall 14 so that an even fit is maintained therebetween. As perhaps best understood from FIGS. 7 and 8, the L-shaped flange 38 is adapted to hook over either the second edge 30 (FIG. 7) or the first edge 30 (FIG. 8). The slot-like moveable interface 36 is threaded onto the sidewall 14. A gentle torque is created by the outward handing directional fin 34, thus causing the edges of the slot-like moveable interface 36 to grip on the sidewall 14 holding the baffle 32 in position. In use, an operator can slide the baffle back-and forth horizontally to adjust the exit area of the flue 26, thereby controlling the build-up of heat inside the heat chamber 10. In FIGS. 6 and 7, the flue is shown slid to full-open positions in solid, and to full closed positions in phantom.

Those of skill in the art will readily appreciate alternative designs by which to achieve a moveable interface 36. In one contemplated embodiment, relative sliding movement between baffle 32 and flue 26 is achieved by seating a suitably configured baffle in external tracks affixed to the sidewall 14 above and below the flue 26. In this example, the tracks are open at each end enabling the baffle 32 to be removed, inverted, then re-installed in the tracks. In another contemplated embodiment, the baffle 32 is rotatably attached relative to the flue 26 with features enabling both redirection of exhaust (via directional fin 34) and alteration of the flue 26 exhaust area. In still other contemplated embodiments, the baffle 32 can be mechanized to effect directionality and restrictions much like the vent controls found in passenger cars and other HVAC applications. Indeed, many alternative designs are possible and within the scope of the person having ordinary skill in this art.

The ground thawing system further includes a portable heater, generally indicated at 40 in FIGS. 1-5. The heater 40 can be any suitable type, but in the illustrated examples comprises the well-known and ubiquitous variety of portable forced-air or convection space heaters, often using kerosene or propane as fuel but also requiring electricity. In practice, a heater 40 rated at approximately 155,000-BTU has been found to provide satisfactory results. Such heaters are often found at construction sites. Heaters 40 of this type are variously referred to as “torpedo” or “salamander” furnaces. The heater 40 has a discharge nozzle 42 configured to emit a stream of hot gas along a discharge vector V. The heater 40 is disposed proximate to the heat chamber 10 with the discharge vector V passing through the charging inlet 20 as shown in the several figures.

A mounting base supports the heater 40 at an incline so that the discharge vector V passes through the charging inlet 20 in a downward trajectory. The mounting base can be any of several forms, including bi-pod and tripod arrangements, as well as mechanically adjustable tilt tables. In the illustrated examples, however, the mounting base is depicted in the basic but effective form of a generally flat sub-base 44 combined with a plurality of shims 46. The shims 46 serve as easily adjustable props when disposed between the sub-base 44 and the heater 40 to achieve the desired downward trajectory of the discharge vector V. Simplicity is favored in view of the need to transport the components of the system over harsh terrain during cold weather as well as avoiding unnecessary mechanical function that would be subject to freezing and inoperability.

To supply electrical power to the heater 40, an electricity generator 48 is provided with appropriate electrical extension cord. A fuel source 50 is also provided for supplying suitable combustible fuel to the heater 40. In FIGS. 1 and 2, the fuel source 50 is depicted as a propane tank which will be suitable for heaters 40 configured to burn propane. In other contemplated embodiments, the fuel source 50 could be a kerosene or fuel oil tank which would be suitable for heaters 40 configured to burn fuel oil. Naturally, accommodations can be made for the type of fuel required by the heater 40.

The method of using the system to thaw frozen ground will now be described. In particular, a novel cold weather method is provided for replicating in-season soil conditions, i.e., not frozen ground, such that sediments are thawed to the point they can be removed from the ground by standard shovel testing operation (no chipping or hacking) and pass through mesh of specified size during typical screen operation. In one example, the mesh size is approximately 0.635-centimeter (0.25-inch).

A designated test area 52 (FIG. 1) larger than the footprint of the heat chamber 10 is first cleared of loose debris until the ground or ground cover is exposed as best possible. Uneven ground surface may prevent the heat chamber 10 from lying flush on the ground. Ground cover includes tree leaves, evergreen, moss, dune grass, lawn grass, etc. Prevailing wind direction W is determined. The heat chamber 10 is placed in the center of the prepared test area 52 with its open bottom 12 facing the ground. The heat chamber 10 is rotated, as needed, so that its flue 26 is pointing windward and its charging inlet 20 is leeward relative to the wind direction W.

In some cases, it may be desirable to leave a threshold limit of snow on the ground. In practice, a threshold limit of 4-6 inches has been found satisfactory. Leaving a thin layer of snow on the test site 52 may help reduce the risk of biomass ignition and the melt-water expedites the thawing process. Also, the heat chamber 10 will eventually sink toward the ground, helping to seal any gaps created by an uneven ground surface. In operation, additional snow can be shoveled around the bottom 12 of the heat chamber 10, if desired, to maintain a seal due to uneven ground features and produce additional melt-water.

A suitably rated heater 40 is placed on mounting base supports 44, 46 so as to direct hot gas into the charging inlet 20 along a downward discharge vector V. The nozzle of the heater 40 is preferably positioned about 2 to 3 inches from the charging inlet 20. Operative connections are made between the heater 40 and its sources 48, 50 of electricity and fuel.

To commence the thawing operation, the heater 40 is ignited so as to force a jet stream of hot gas through the charging inlet 20 at a downward angle V that is also pointing in the upwind direction. By reference to FIGS. 4 and 5, it will be understood that by locating the flue 26 close to the ground and directly opposite the charging inlet 20, hot gas is drawn across the ground surface and exits through the flue 26. Also, a swirling gas flow is generated within the heat chamber 10 that swirls into the heat loft 25 in a looping pattern that naturally escapes through the flue 26. The heat chamber 10 is thus intentionally designed to prevent the escape of gas from the heat chamber through the charging inlet 20. It would be undesirable for the hot gas to escape through the charging inlet 20 due to the likelihood of blow-back on the heater 40. Built-in safety switches are common in commercial grade heaters 40. In the event of blow-back, the heater 40 would automatically shut down thus halting the thawing operation.

Considering the desire to avoid blow-back, one might incorrectly assume that the heat chamber 10 should be rotated on the test area 52 so that its charging inlet 20 is pointing windward and its flue 26 is leeward relative to the wind direction W—i.e., opposite to that described in this present method. Logic would seem to indicate (incorrectly as it turns out) that if the charging inlet 20 is pointed windward, that wind pressure would assist in preventing blow-back and even help in evacuating exhaust gasses through the flue 26. However, the present invention defies natural logic by orienting the inlet 20 and flue 26 features as previously specified. The novel arrangement of elevated charging inlet 20 relative to flue 26 combined with a downwardly directed discharge vector V produces a powerful and effective natural swirling flow of gasses within the heat chamber 10. The induced currents are sufficiently powerful to overcome the pressure of the wind W, such that the wind pressure can be exploited to supplement the effects of the baffle 32. That is to say, the wind W provides (to the degree available) additional back-pressure against the escaping gases, thus enabling the operator more control over temperature stabilization inside the heat chamber 10. Additionally, wind W blowing into the rear of the heater 40 can produce negative operating effects.

As previously mentioned, a relatively large heat loft 25 established inside the heat chamber 10 above the charging inlet 20 performs beneficial radiant and convective functions. As a radiant heat body, the heat loft 25 continuously projects heat energy through the open bottom 12 onto the exposed ground surface. Convectively, internal currents circulating through the heat loft 25 recharge with high heat energy before circulating across the ground surface. Thus, the intentionally induced swirling gas flow as indicated in FIGS. 4 and 5 within the heat chamber 10 produces a constant sweep of hot gas across the ground before escaping through the flue 26.

By manipulating the baffle 32 via the moveable interface 36, the internal currents can be adjusted and altered in relation to ambient conditions to maintain the desired internal temperatures inside the heat chamber 10. If the wind W is blowing more or less strongly, or more or less consistently, the operator may wish to orient the baffle 32 to either of the inverted positions represented in FIGS. 4 and 5. Likewise, the temperature inside the heat chamber 10 can be regulated by adjusting the area of the flue 26. That is, by sliding the baffle 32 back-and-forth, more or less restriction to exhaust can be controlled. In mild ambient conditions it may be necessary to maximize the flue 26 opening, whereas in extreme low ambient temperatures it may be desirable to minimize the flue 26 opening. Experimentation will indicate the better baffle 32 orientation and position relative to the flue 26.

It has been found that in at least some sub-freezing climates, an STP can be completed using the method described above in approximately one hour on average replicating field-season ground conditions where ground cover was present (excluding lawn grass). In cases where lawn grass cover was present, or no ground cover was present, STPs could be completed on average in approximately three hours replicating normal field conditions. It is suspected that rather than the ground cover itself causing significant differences in time, the variance may instead be attributable to the amount of moisture present below a grassy ground surface trapped within finer, less-well-drained sediments.

Once field-season ground conditions have been replicated, the heater 40 is switched off and removed from the test area 52. The heat chamber 10 is also removed from the test area 52 with the aid of the handles 18 to avoid burn-related injury. In the thawed earth, an STP can be excavated. In some cases, a suitable STP may be hand-dug with shovel 54, as depicted in FIG. 9, to a depth of about 50 cm (20 in) and having a typical diameter of about 35-40 cm (14-16 in). The actual depth to be excavated can vary from one test area 52 to the next. In general, the objective is to stop digging upon encountering either sterile subsoil or bedrock or impermeable gravel/rock concentrations.

Soil from the STP is passed through suitably sized mesh 56 to identify artifacts 58. Information about the soils observed in each STP is typically recorded in a field logbook to assist with interpretation of how the site deposits formed over time and to help evaluate whether soil disturbances have occurred. Upon completion of the STP, the excavated soil is returned to the hole and tamped down in an effort to return the test area 52 to its initial condition.

The foregoing invention has been described in accordance with the relevant legal standards, thus the description is exemplary rather than limiting in nature. Variations and modifications to the disclosed embodiment may become apparent to those skilled in the art and fall within the scope of the invention.

Claims

1. A portable ground thawing system comprising:

a heat chamber having an open bottom surrounded by a sidewall and a closed top, a charging inlet disposed in said sidewall, an exhaust flue disposed in said sidewall,

a heater having a discharge nozzle configured to emit a stream of hot gas along a discharge vector, said heater disposed proximate to said heat chamber with said discharge vector passing through said charging inlet, and

said flue being located generally opposite said charging inlet.

2. The system of claim 1 wherein said heat chamber is a generally cylindrical volume as defined by a generally cylindrical said sidewall and a generally circular said top and a generally circular said bottom, said flue being diametrically opposed to said charging inlet.

3. The system of claim 1 wherein said charging inlet has an upper extremity and a lower extremity, said lower extremity being axially spaced from bottom by a lower extremity distance (IL), said flue having a first edge adjacent said bottom and a second edge adjacent said top, said second edge being axially spaced from bottom by a second flue distance (F2), said second flue distance (F2) being less than or equal to said lower extremity distance (IL).

4. The system of claim 1 wherein said charging inlet has an upper extremity and a lower extremity, said upper extremity being axially spaced within 10% of a midline between said bottom and said top of said heat chamber.

5. The system of claim 1 further including a baffle moveably connected to said flue.

6. The system of claim 5 further including a moveable interface supporting said baffle for sliding movement relative to said flue.

7. The system of claim 5 wherein said baffle has at least one directional fin.

8. The system of claim 7 wherein said baffle is invertible in said flue so as to turn said directional fin upside down in use.

9. The system of claim 1 further including a mounting base supporting said heater at an incline so that said discharge vector passes through said charging inlet in a downward trajectory.

10. The system of claim 1 wherein said heat chamber is a generally cylindrical volume as defined by a generally cylindrical said sidewall and a generally circular said top and a generally circular said bottom, said flue being diametrically opposed to said charging inlet, further including a pair of handle loops attached to heat chamber, said handle loops being diametrically arranged from one another on said sidewall.

11. The system of claim 1 wherein said heat chamber is a generally cylindrical volume as defined by a generally cylindrical said sidewall and a generally circular said top and a generally circular said bottom, said flue being diametrically opposed to said charging inlet, and at least one of said charging inlet and said flue being generally rectangular.

12. The system of claim 11 wherein said flue having first edge adjacent said bottom and a second edge adjacent said top, said first edge of said flue being axially spaced from bottom by a first flue distance (F1), further including a baffle moveably connected to said flue, said baffle has at least one directional fin, said baffle being invertible in said flue so as to turn said directional fin upside down in use, and a moveable interface supporting said baffle for sliding movement relative to said flue.

13. The system of claim 1 further including an electricity generator for supplying electrical power to said heater.

14. The system of claim 1 further including a fuel source for supply combustible fuel to said heater, said fuel source comprising a propane tank.

15. A portable ground thawing system comprising:

a heat chamber having an open bottom surrounded by a sidewall and a closed top, said heat chamber being a generally cylindrical volume as defined by a generally cylindrical said sidewall and a generally circular said top and a generally circular said bottom, a pair of handles attached to heat chamber, each said handle comprising a loop extending from said sidewall adjacent said top, said handles being diametrically arranged from one another on said cylindrical sidewall, a charging inlet disposed in said sidewall, said charging inlet having an upper extremity and a lower extremity, said lower extremity being axially spaced from bottom by an lower extremity distance (IL), said upper extremity being axially spaced generally midway between said bottom and said top of said heat chamber, said charging inlet being generally rectangular, an exhaust flue disposed in said sidewall, said flue being diametrically opposed to said charging inlet, said flue having first edge adjacent said bottom and a second edge adjacent said top, said first edge of said flue being axially spaced from bottom by an first flue distance (F1), said second edge of said flue being axially spaced from bottom by a second flue distance (F2), said second flue distance (F2) being less than or equal to said lower extremity distance (IL), said flue being generally rectangular, a baffle moveably connected to said flue, said baffle having at least one directional fin, said baffle being invertible in said flue, a moveable interface supporting said baffle for sliding movement relative to said flue,

a heater having a discharge nozzle configured to emit a stream of hot gas along a discharge vector, said heater disposed proximate to said heat chamber with said discharge vector passing through said charging inlet,

a mounting base supporting said heater at an incline so that said discharge vector passes through said charging inlet in a downward trajectory, said mounting base including a generally flat sub-base, said mounting base including a plurality of shims disposed between said sub-base and said heater,

a electricity generator for supplying electrical power to said heater, and

a fuel source for supply combustible fuel to said heater.

16. A method for placing a Shovel Test Pit (STP) in frozen ground comprising the steps of:

preparing a test area by clearing debris and removing snow accumulations above a threshold limit,

positioning a heat chamber having an open bottom on the test area,

orienting the heat chamber so that a charging inlet thereof is leeward and an exhaust flue thereof is windward relative to the prevailing wind direction,

directing a stream of hot gas from a heater along a discharge vector passing through the charging inlet, and

circulating hot gases through a heat loft within the heat chamber above the charging inlet prior to exiting through the flue.

17. The method of claim 16 further including the step of pointing the discharge vector in a downward trajectory as it passes through the charging inlet.

18. The method of claim 16 further including the step of inverting a baffle in the flue to manipulate the flow of exhaust gases through the flue.

19. The method of claim 16 further including the step of moving a baffle relative to flue to constrict the exit flow rate of exhaust gases through the flue.

20. The method of claim 16 further including the steps of: removing the heat chamber from the test area when the underlying ground is thawed, digging a hole in the thawed ground, transferring soil excavated from the hole to a screen mesh, sifting the excavated soil through the screen mesh, removing any artifacts captured by the screen mesh, and returning the sifted soil to the hole.