Patent Publication Number: US-7216725-B2

Title: Soil sampling system and method that allow headspace screening at spaced intervals without disturbing soil sample

Description:
RELATED APPLICATIONS 
   This application is a continuation-in-part of U.S. Utility patent application Ser. No. 10/456,800 filed on Jun. 6, 2003, which claims priority of U.S. Provisional Application No. 60/387,041 filed on Jun. 6, 2002. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to devices for obtaining soil samples from below the surface of the ground. In particular, the present invention relates to soil sampling systems that allow access to a portion of the soil core for headspace screening without violating the integrity of the remaining soil core, and soil sample containment devices used to protect soil samples after the samples are collected by the soil sampling system. 
   2. Description of the Related Art 
   Soil sampling systems are commonly used to obtain soil samples from below the surface of the ground. The collected soil samples are used to determine soil conditions prior to construction, to locate mineral deposits, to study chemical dissipation and residue, to determine the concentration of environmental contaminants, to investigate hazardous waste sites, and in other ways well known in the art. 
   Unfortunately, the equipment and methodology for collecting and preserving soil samples do not allow for consistent and accurate soil analysis. It is common practice to retrieve a soil sample from the subsurface via a soil sampler, remove the soil sample from the soil sampler, and place the sample in a separate container. During this process, the handling and exposure of the soil sample increases the loss of contaminants which may be contained within the soil sample. 
   The existing process involves a user taking a core section of soil, cutting open the tube, screening the whole length of the tube for contamination vapors, and if the contamination is not high, putting that core section aside and going on to the next one until the user finds the highest level of contamination. The user cannot be sure which one has the highest contamination until all of the cores have been screened. In the meantime, the exposed soil samples of the open cores are volatilizing and the integrity of the soil samples is deteriorating. 
   For accurate soil analysis, it is important that the sample be collected without disruption of the soil structure, that the sample not be subsampled, and that the sample is sealed in a manner to prevent leaks of contaminants around the seal. This is particularly difficult when soil is being tested for contamination by volatile organic compounds (VOC) because the VOCs tend to volatilize when exposed to air. The sample should be isolated from air to maintain substantially the same level and type of contamination as when the sample was first cored from the earth. The ideal soil sample is one that is representative of its origin in the subsurface. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an improved soil sampling system and sample containment device that overcome the problems and shortcomings of the prior art. 
   A further object of the present invention is to provide an improved soil sampling system that allows access to the soil core sample for headspace screening at spaced intervals, that minimizes the handling and exposure of soil samples in the field, and that better maintains the integrity of the soil sample. 
   A further object of the present invention is to provide an improved soil containment device that can be used effectively to preserve soil samples with minimal handling and disturbance, and that is economical to manufacture and easy to use. 
   A further object of the present invention is to provide a soil containment system that allows soil samples to be sealed and maintained within individual liner sections of a soil sampler liner without requiring subsampling. 
   A further object of the present invention is to provide an improved soil sampler liner that includes a plurality of liner sections having different lengths and/or materials corresponding to particular tests to be performed. 
   In order to accomplish these and other objects of the invention, a soil sampling system is provided that allows headspace screening of soil samples at spaced intervals along a soil sample liner without disturbing the soil samples that will be shipped to a laboratory for further testing. The soil sample liner includes a plurality of cylindrical liner sections positioned end-to-end in a linear array, with each liner section having a sidewall and open ends. A shrink-wrap material covers the liner sections and holds the liner sections together as an assembled unit. Some of the liner sections have access openings formed in a sidewall thereof for providing access to the soil samples contained therein. The liner sections having access openings are interspersed between other liner sections that do not have access openings. The liner sections without access openings can be used as part of a soil sample containment device by covering the respective ends of each liner section with first and second end caps. The access openings can be used during soil sampling operations by piercing the shrink-wrap material covering the access opening, removing some soil from within the liner section through the access opening to form a headspace, and inserting an analytical probe tip through the access opening into the headspace to measure contamination in the headspace air. 
   According to a broad aspect of the present invention, a soil sample liner is provided for use in a soil sampling system, comprising: a plurality of liner sections positioned end-to-end in a linear array, the liner sections each having a sidewall and open ends; a shrink-wrap material covering the plurality of liner sections and holding the liner sections together as an assembled unit; and at least one of the liner sections having an access opening formed in a sidewall thereof for providing access to a soil sample contained therein without disturbing a soil sample in an adjacent one of the liner sections. 
   According to another broad aspect of the present invention, a soil sample liner for use in a soil sampling system is provided in combination with a soil sample containment device. The soil sample liner comprises: first and second liner sections positioned end-to-end in a linear array, the liner sections each having a cylindrical sidewall and open ends; a shrink-wrap material covering the liner sections and holding the liner sections together as an assembled unit; and the first liner section having an access opening formed in the sidewall thereof for providing access to a soil sample contained therein without disturbing a soil sample contained in the second liner section. 
   According to another broad aspect of the present invention, a method of collecting soil samples is provided, comprising the steps of: providing a soil sample liner comprising at least first and second liner sections positioned end-to-end in a linear array, the liner sections each having a cylindrical sidewall and open ends, the first liner section having an access opening formed in the sidewall thereof for providing access to a soil sample contained therein without disturbing a soil sample contained in the second liner section, and a shrink-wrap material covering the liner sections and holding the liner sections together as an assembled unit; collecting a core soil sample within the soil sample liner; and screening the soil sample contained within the first liner section by piercing the shrink-wrap material covering the access opening, removing some soil from within the first liner section through the access opening to form a headspace, and inserting an analytical probe tip through the access opening into the headspace to measure contamination in the headspace air. 
   Numerous other objects of the present invention will be apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of the present invention, simply by way of illustration of one of the modes best suited to carry out the invention. As will be realized, the invention is capable of other different embodiments, and its several details are capable of modification in various obvious aspects without departing from the invention. Accordingly, the drawings and description should be regarded as illustrative in nature and not restrictive. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more clearly appreciated as the disclosure of the invention is made with reference to the accompanying drawings. In the drawings: 
       FIG. 1  is a side view of a complete soil sampler liner set according to the present invention with a shrink wrap covering. 
       FIG. 2  is a side view of the soil sampler liner set with an opening in a sidewall of one of the sections being used to provide access to the soil core for headspace screening. 
       FIG. 3  is a side view of the soil sampler liner shown in  FIG. 1  with the shrink wrap covering removed. 
       FIG. 4  is an exploded side view showing the individual sections of the soil sampler liner of  FIG. 3 . 
       FIG. 5  is a plan view of an end cap of the soil sample containment device of the present invention. 
       FIG. 6  is a cross section view of the end cap taken along line A—A in  FIG. 5 . 
       FIG. 7  is a side view of the end cap. 
       FIG. 8  is a perspective view of the end cap. 
       FIG. 9  is a side view of the soil sample containment device of the present invention before the end caps are assembled over the soil sampler liner section. 
       FIG. 10  is a side view of the soil sample containment device with the end caps assembled over the soil sampler liner section. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A soil sample liner  11  and soil sample containment device  10  according to a preferred embodiment of the present invention will now be described with reference to  FIGS. 1 to 10  of the accompanying drawings. 
   The soil sample liner  11  of the present invention is an improvement over the soil sample liner described in the Applicants&#39; parent application Ser. No. 10/456,800, while the containment device  10  of the present invention is the same as previously described. 
   The soil sampler liner  11  has several individual liner sections  12 ,  13  formed of cylindrical tubing, as shown in  FIGS. 1 to 4 . In the preferred embodiment, some of the liner sections  12  are plastic and some of the liner sections  13  are metal. A linear array of the liner sections  12 ,  13  are assembled end-to-end and held together as an assembled unit with a shrink-wrap material  14  covering the liner sections  12 ,  13 . The liner sections  12 ,  13  will normally be assembled together and shrink-wrapped at the place of manufacture and transported to the field site as assembled units. 
   The plastic liner sections  12  are each provided with an access opening  15  formed in a sidewall thereof for providing access to a soil sample contained within the liner section  12 . As shown in  FIG. 1 , the liner sections  12  with access openings  15  are positioned at spaced intervals along the soil sample liner  11 , and the liner sections  13  without access openings are interspersed between the liner sections  12 . The access openings  15  in the liner sections  12  are preferably circular in shape and have a diameter of about 0.25 to 0.5—inch, but a variety of other shapes and sizes can also be used. The access openings  15  are preferably formed at an approximate midpoint along a length of the liner sections  12  so that soil samples within the adjacent liner sections  13  are not disturbed by screening the soil through the access openings  15 . The exact location of the access openings  15  along the length of the liner sections  12 ,  13  is not critical, as long as the access opening  15  is spaced a sufficient distance (e.g., about one inch or more) from the adjacent sections  13  so that the integrity of the soil sample is not disturbed. 
   The liner sections  12  are made of a transparent material that allows visual inspection of the soil sample at spaced locations along the soil sampler liner  11  before the liner  11  is cut open and disassembled. A suitable material for the transparent liner sections  12  is plastic, and particularly PETG. The ability to view the soil sample allows the user to avoid areas in the soil sample that may contain voids or other unwanted media. It also allows the user to observe possible changes in soil type or strata before disassembling the soil sampler liner  11 . 
   At least some of the liner sections  13  without access openings are preferably made of metal, and particularly stainless steel. Some of the liner sections  13  can also be made of plastic or other nonmetallic materials. The use of both plastic and metal liner sections may be advantageous because it allows a wider variety of standard tests to be performed on the sampled soil, particularly when the liner sections  13  themselves are used as part of the soil sample containment device  10 , as described below. 
   The complete soil sampler liner  11  is made up of a series of long soil sampler liner sections  12  and shorter soil sampler liner sections  13 . The shorter liner sections  13 , for example, can be one inch in length to hold approximately 25 grams of soil, or 1.25 inches in length to hold approximately 30 grams of soil. These particular sizes correspond with the soil mass requirements used in most soil tests performed in the United States. The American Society for Testing and Materials (ASTM), the U.S. Environmental Protection Agency (US EPA), and other federal and state governing bodies have adopted various standard soil tests that typically require a certain mass (e.g., 25 or 30 grams) of soil to be used to conduct the tests. Other countries, such as Japan, have adopted different standards for testing that call for different masses of soil (e.g., 50 grams). With the present invention, the liner sections  13  can be sized to provide a particular volume that corresponds with the desired mass of soil called for by a particular test. 
   A combination of liner sections  12 ,  13  can be used such that, when assembled, the combined length of the liner sections  12 ,  13  corresponds with the length of the soil sampler being used (e.g., 24″, 36″, 48″, etc.). The use of both short and long liner sections  12 ,  13  allows for many soil sampler liner combinations. 
   In operation, the soil sample liner  11  of the present invention is used in conjunction with a sampling probe to collect a core soil sample within the liner  11 . The soil sample contained within the liner  11  can then be visually inspected through the transparent liner sections  12  to check for strata changes or obvious pollution staining. The collected soil sample can then be screened at multiple, spaced locations along a length of the liner  11  using the access openings  15  in the liner sections  12 . The screening process includes piercing the shrink-wrap material  14  covering the access opening  15 , removing a small amount of soil S from within the respective liner section  12  through the access opening  15  to form a headspace within the liner section  12 , and inserting a tip T of an analytical probe of a field tester (e.g., a photo ionization detector meter) through the access opening  15  into the headspace to measure contamination in the headspace air. The contamination in the headspace air, which is caused by contaminants from the soil volatilizing into the headspace air, is directly correlated with the contamination of the soil sample. 
   The core sample is thus kept intact, except for the small amount of soil S removed through the access opening  15  to create a headspace for the probe tip T. Once the screening process is completed for the soil sample liner  11 , the liner  11  can be set aside or stored on ice while other core samples are collected and screened. The user can then go back and decide which one(s) of the several liner sections  13  to collect samples from for further testing at a laboratory. The selected liner sections  13  can be removed from the soil sample liner  11  by cutting open and removing the shrink-wrap material  14  from the soil sample liner  11  and scraping both ends of the selected liner section  13  with a spatula or the like. The liner section  13  can then be assembled into a soil containment device  10 , as explained below, for transporting the soil sample to a laboratory for further testing without losing volatiles or otherwise disturbing the integrity of the soil sample. 
   The soil containment device  10  includes first and second locking end caps  16 ,  17  for covering and sealing the respective ends  18 ,  19  of a single soil sampler liner section  13 . Each end cap  16 ,  17  has a cylindrical portion  20  with a coupling structure comprising two locking arms  21 ,  22  extending from an outer circumference. The cylindrical geometry of the locking end caps  16 ,  17  accommodates the cylindrical soil sampler liner section  13 . 
   The two locking arms  21 ,  22  include a single hook arm  21  and a single eye arm  22 . The hook arm  21  of the first end cap  16  can be coupled with the eye arm  22  of the second end cap  17 , and vice versa, to secure the end caps  16 ,  17  together over the ends  18 ,  19  of the liner section  13 . The hook arm  21  of each end cap  16 ,  17  has a wedge-shaped hook  23  protruding outwardly from its outer surface. When assembled, the wedge-shaped hook  23  is held in an outward fashion by the outer surface of the soil sampler liner section  13  to prevent inadvertent removal of the locking end caps  16 ,  17  from the soil sampler liner section  13 . 
   The eye arm  22  of each end cap  16 ,  17  has one or two eyes or rectangular-shaped holes  24  that receive the wedge-shaped hook  23  of the hook arm  21  of the opposing end cap  16 ,  17 . Multiple eyes or holes  24  in the eye arm  22  can be used to accommodate soil sampler liner sections  13  having different lengths, such as one inch and 1.25 inch lengths. The ends  25 ,  26  of the eye arm  22  and the hook arm  21  are chamfered such that the arms  21 ,  22  slide past one another rather than butt up to one another during assembly. 
   A flexible sealing material  27  is positioned within each end cap  16 ,  17  for providing a compression seal over a respective end  18 ,  19  of a soil sampler liner section  13 . The flexible sealing material  27 , also referred to as a “septum,” preferably comprises a silicone substrate and a thin Teflon™ coating. The coupling structure provided by the arms  21 ,  22  of the end caps  16 ,  17  is such that a predictable spacing will exist between the end caps  16 ,  17  when they are assembled over a liner section  13  and coupled together (using a properly selected eye opening  24  if multiple openings are provided in the eye arm  22 ). As a result, the end caps  16 ,  17  can be made to properly compress the flexible sealing material  27  over the ends of the soil sampler liner section  13  with a highly predictable amount of compression. 
   The construction of the hook arms  21  and the eye arms  22  is such that the flexible sealing material  27  will not be over compressed or under compressed, thereby improving the integrity of the sample. Research by the Applicants has shown that under compression of the sealing material  27  does not create an adequate seal, while over compression can cause the sealing material  27  to be ruined and become difficult to secure. The latching mechanism provided by the hook arms  21  and the eye arms  22  has been designed to apply a designated predetermined loading to the sealing material  27 . When the user inserts the latching mechanism to its proper end point, achieving closure, the compressible sealing material  27  is placed under the correct loading against the end  18 ,  19  of the liner section  13  to achieve the desired compression seal. 
   Other flexible materials or combinations of flexible materials can also be used for the sealing material  27  as long as they create a flexible and nonpermeable compression seal with the ends  18 ,  19  of the soil sample liner section  13 . As used in this application, the phrase “compression seal” means any seal created by compressing one member against another member in a manner sufficient to prevent loss of volatiles from a soil sample. Other forms of compression seals, such as annular sealing rings, can be used instead of the septa described above. 
   Each end cap  16 ,  17  includes a relief opening  28  to allow for any small protrusions at the ends of the soil sample. The relief opening  28  allows the flexible sealing material  27  to flex outwardly and accommodate any protrusions without compromising the sealing effect of the device. 
   Each end cap  16 ,  17  also includes a plurality of centering tabs  29  to center a soil sampler liner section  13  within the cylindrical portion  20  of the end cap  16 ,  17 . The centering tabs  29  are tapered at their leading edges to guide the ends of the liner section  13  into a centered position. 
   The first and second end caps  16 ,  17  have a substantially identical structure and can be interchanged end-to-end when being assembled over a soil sampler liner section  13 . This allows a single inventory of end caps  16 ,  17  to be used and eliminates any hassle of having to find a male component to match a female component, and so forth. 
   In operation, the soil sample containment device  10  of the present invention is assembled by placing two locking end caps  16 ,  17  over the respective ends  18 ,  19  of a soil sampler liner section  13  and fastening or snapping the hook arms  21  together with the opposing eye arms  22 . This assembly seals both ends of the soil sampler liner section  13 , thereby preventing loss of the soil sample or contaminants contained within the soil sample. To disassemble the soil sample containment device  10 , both eye arms  22  on the locking caps  16 ,  17  must be physically pulled outward to uncouple from the wedge-shaped hooks  23  of the hook arms  21  and thereby release the locking coupling structure of the end caps  16 ,  17 . 
   An important advantage of the soil containment device  10  of the present invention over other related devices is the relationship between the soil sampler liner  11  and the locking end caps  16 ,  17 . Other soil sample containers require excessive exposure and handling of the soil sample before it is actually sealed within a soil sample container. The present invention eliminates a substantial amount of the exposure and handling. In addition, the locking mechanism of the locking end caps  16 ,  17  essentially guarantees that the soil sample integrity will be preserved until the soil sample containment device  10  is disassembled. 
   Another important advantage of the soil containment device  10  of the present invention is that the soil sampler liner sections can be made in appropriate lengths to provide a volume of soil that corresponds closely with the mass required for a particular soil test. As a result, the invention eliminates the time consuming and expensive step of subsampling (i.e., collecting a small soil sample from a larger soil sample) within the laboratory to obtain the desired mass of soil for a particular soil test. 
   A method of containing soil samples using the soil containment device  10  described above will now be explained. The method uses a soil sampler liner assembly having at least one liner section, and preferably uses the soil sampler liner assembly  11  having a plurality of liner sections  13 . A soil sample is collected within the liner sections  13  in a known manner using a soil sampling system, for example, that drives a soil sampler into the subsurface. The soil sampler liner assembly  11  is then removed from the soil sampling system and cut apart to separate the individual liner sections  13  from each other. The liner sections  13  (or at least one of them) are then sealed at their respective ends by end caps that form compression seals at the ends of the liner section, as described above, to prevent loss of volatiles from the soil sample. At least one of the liner sections has a predetermined volume corresponding to a mass of soil required for a standard test. As a result, substantially all of the soil sample from this liner section can be extruded in the laboratory for the test without subsampling. 
   It will be appreciated that certain features of the present invention described above can be changed without departing from the scope of the invention. For example, the soil sampler liner  11  may incorporate a core catcher or soil check valve to assist in sampling soil from the subsurface. Also, different sizes of soil sampler liner sections  12 ,  13  and locking end caps  16 ,  17  may be developed. Also, structures other than the mating hook and eye structures of the preferred embodiment can be used to couple the end caps  16 ,  17  together. For example, an external lever or screw clamp separate from the end caps themselves can be used to secure the end caps together over the ends of the liner section. 
   While the invention has been specifically described in connection with specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.