Patent Application: US-40101106-A

Abstract:
a method and device for sampling pore water , including an elongated tubular outer body having a grid framework forming multiple perforations throughout the entire outer body . the grid framework surrounding the perforations has raised and beveled sides . an elongated , perforated tubular inner body is contained within the outer body . the inner body has a diameter less than a diameter of the outer body , which forms a cavity between the inner body and the outer body . the cavity is filled with an inert granular filler material . a first outer cap and a second outer cap cover respective ends of the outer body . a coupling is placed in fluid communication with the inner body and protrudes through the first outer cap . a tube is attached to the coupling protruding through the first outer cap to transfer a water sample to a sample collection site .

Description:
fig1 illustrates a pore water sampler 10 according to one embodiment of the present invention . a lengthwise , partially disassembled view of the pore water sampler 10 is shown in fig2 . an outer perforated pipe 12 , forming an outer screen , provides structural support and protection from abrasion during installation of the sampler 10 . a first mesh 14 is located on the inner surface of the outer perforated pipe 12 and a second mesh 16 is wrapped around the outer surface of an inner perforated pipe 18 , which forms an inner screen . a bulkhead union 24 ( also see fig9 ) is inserted through an opening in a first inner cap 20 . a nut 32 ( see fig3 ) is screwed onto the bulkhead union 24 to attach the bulkhead union 24 to the first inner cap 20 . referring to fig2 , the first inner cap 20 covers one end of the inner perforated pipe 18 and may be held in place by a fastener 22 , such as a zip tie . a second inner cap 31 ( see fig4 ) covers the other end of the inner perforated pipe 18 . a first outer cap 26 ( fig2 ) covers the outer perforated pipe 12 at the end adjacent to the bulkhead union 24 . a second outer cap 28 covers an end of the outer perforated pipe 12 opposite the bulkhead union 24 . the first outer cap 26 has an opening 30 through which the bulkhead union 24 extends . tubing 34 ( see fig5 ) attaches to the bulkhead union 24 by , for example , being pushed into the bulkhead union 24 . other ways of attaching the tubing 34 are possible , including using screw - type fittings . the tubing 34 extends to the shoreline . fig5 shows an end view of the pore water sampler 10 from the end containing the bulkhead union 24 , with the first outer cap 26 removed . in fig5 , the inner perforated pipe 18 wrapped in the second mesh 16 extends lengthwise behind the first inner cap 20 . an inert granular fill material 35 , such as sand , is packed between the outer perforated pipe 12 and the inner perforated pipe 18 , and is contained within the pore water sampler 10 by the first mesh 14 , the second mesh 16 , the first outer cap 26 , and the second outer cap 28 . the thickness of the sand pack 35 may be varied by changing the diameters of the outer perforated pipe 12 and the inner perforated pipe 18 . an example of a mesh sheet ( e . g ., the second mesh 16 ) is shown in fig6 . the first mesh 14 and the second mesh 16 are constructed of nylon or another inert substance , such as polypropylene , for example . the sizes of the mesh openings should not be larger than the grain size of the sand or granular fill material 35 . the mesh openings can be less than 10 microns , but are preferably greater than about 10 microns to reduce clogging potential . the sizes of the mesh openings should be slightly smaller than the diameters of the granular fill 35 , and the granular fill 35 should be sized to effectively limit transmittal of particulates in the size range of the site - specific deployment area . the first mesh 14 and the second mesh 16 can be attached to the outer perforated pipe 12 and the inner perforated pipe 18 , respectively , with fasteners , such as zip ties , or can simply be held in place by the granular fill 35 . an example of a perforated pipe ( e . g ., the inner perforated pipe 18 ) is shown in fig7 a . the diameter of the outer perforated pipe 12 ranges from about 1 . 5 inches to about 4 inches , and the length ranges from about 0 . 5 feet to about 3 feet . preferably , the outer perforated pipe 12 is approximately 2 . 5 inches in diameter and about 0 . 7 feet in length . the length of the inner perforated pipe 18 is approximately the same as the length of the outer perforated pipe 12 . the diameter of the inner perforated pipe 18 ranges from about 0 . 2 inches to about 1 . 5 inches , and preferably about 1 . 4 inches for a length of about 0 . 7 feet . a close - up view of a perforated pipe ( e . g ., the outer perforated pipe 12 ) is shown in fig7 b . both the outer perforated pipe 12 and the inner perforated pipe 18 contain perforations 36 throughout the entire structures . the perforations 36 are square - shaped , for example , and can have sides ranging from about 0 . 01 inches to about 0 . 50 inches . in the embodiment shown in fig7 b , the perforations 36 are about 0 . 015 inches by about 0 . 015 inches . the perforations 36 are surrounded by a grid framework with edges that are raised and preferably beveled . a close - up edge view of a pipe used to form either the outer perforated pipe 12 or the inner perforated pipe 18 is shown in fig8 a and 8b to illustrate the raised , beveled framework surrounding the perforations 36 . the grid framework includes elongated , parallel ridges 37 ( also see fig7 b ) that rise above the outer surface of the pipe 12 , 18 to form an irregular outer surface . the irregular outer surface allows circuitous pathways of flow into the perforations 36 to counteract the potential for leaf debris to blanket and obstruct large parts of the outer perforated pipe 12 . the height h of the ridges 37 may range from about 0 . 01 inches to about 0 . 2 inches . the sizes of the perforations 36 and the heights and shapes of the ridges 37 in the outer perforated pipe 12 and the inner perforated pipe 18 , as well as the mesh sizes of the first mesh 14 and the second mesh 16 , may vary as desired . rather than using the inner perforated pipe 18 , a perforated tube 60 surrounded by the second mesh 16 may be used as the inner screen , as shown in fig9 . the sizes of the perforations in the perforated tube 60 may vary as desired . the perforations of the perforated tube 60 can be as small as will allow effective transmission of water and as large as will maintain structural integrity of the tube . the perforations of the tube 60 shown in fig9 are approximately 0 . 1 inches in diameter . in the embodiment shown in fig9 , the perforated tube 60 attaches to one end of the bulkhead union 24 , and the bulkhead union 24 attaches to the first outer cap 26 . the diameter of the perforated tube 60 is about ¼ - inch . following deployment , a peristaltic or other type of suction pump ( not shown ) is attached to the tubing 34 onshore , and the sampler 10 is pumped slowly to develop the sand pack 35 . the suction induces water flow into the sampler 10 through the sand pack 35 . the outer perforated pipe 12 limits potential blockage by sheet debris , such as leaf matter . the sand pack 35 reduces the amount of fine - grained material pumped from the sampler 10 . after acceptably non - turbid water is observed in the pump discharge , the sampler 10 is left in place until the deployment disturbance re - equilibrates to ambient conditions . at the time the sample is collected , the peristaltic pump is attached to the tubing 34 at the shore and used to extract a sample by first purging the blank tubing 34 ( typically , about a few hundred milliliters of water are purged ) and sampling the water immediately following purging of the sampler 10 . following sample collection , the sampler 10 is left in place , where it can be used for subsequent sampling to provide long - term monitoring of the same location . the pore water sampler 10 is buried in bottom sediment below surface water . there is not a limit to the distance from shore for the installation of the sampler 10 . longer distances simply mean that more tubing 34 will be used to extend to shore and a slightly longer pre - sample purge time would be needed . because the peristaltic pump is limited to a lift of about 18 feet to about 20 feet , the discharge end of the sampler 10 on shore should be less than about 18 feet to about 20 feet above the water surface . deployment of the sampler 10 in deep water may require the use of divers or other remote installation methods . various types of plastics may be used to construct any part of the sampler 10 , such as polyethylene , polyurethane , teflon ®, as well as other non - metal materials . the nut 32 shown in fig3 , 5 , and 9 is constructed of stainless steel , but it is in a position that is distant from the flow - through areas of the sampler 10 . the nut 32 may also be constructed of plastic . according to another embodiment of the present invention , the outer surface of the sampler 10 may be covered with a mesh sleeve 70 , as shown in fig1 . this layering of mesh and pipe openings or perforations decreases the potential for clogging by large matter . the mesh sleeve 70 may be constructed of flexible plastic with raised ridges 72 , as shown in the close - up view of the mesh sleeve 70 in fig1 . the present invention has advantages over existing diffusion sampler technology . the present invention allows pore water samples to be collected from the same location indefinitely , as long as sufficient time elapses between sampling events for the ambient water to return to prepumped conditions . also , there is no need to refill the sampler 10 with any kind of water because it is self filling with ambient formation water . the present invention also has advantages over existing prepacked well screens . the present invention does not need a standpipe that extends to the surface . instead , water is extracted from the sampler 10 through the tubing 34 that runs from the sampler 10 to the shoreline , where samples can be collected using the peristaltic pump without the need for a boat . parameters of interest in pore water investigations may be adversely affected by stainless steel . in the present invention , the outer perforated pipe 12 does not need to be constructed of stainless steel to withstand deployment abrasion . the rigid outer perforated pipe 12 of the sampler 10 protects the first mesh 14 and the second mesh 16 from abrasion . this allows less expensive construction materials to be used . the nut 32 on the outside of the sampler 10 that attaches the bulkhead union 24 to the sampler 10 can be constructed of plastic . even if the nut 32 is constructed of stainless steel , the nut 32 is in a position that is distant from the flow - through areas of the sampler 10 . thus , in the present invention , stainless steel is not part of the sampler 10 that is in intimate contact with sampled water . in addition , the present invention differs from existing technology in that the outer perforated pipe 12 contains perforations 36 throughout the entire structure . the perforations 36 are large relative to existing technology . in addition , the edges of the perforations are beveled and raised . the size of the perforations 36 and the raised , beveled borders of the perforations 36 present an irregular outer surface that allows circuitous pathways of flow into the ports to counteract the potential for leaf debris to blanket and obstruct large parts of the outer perforated pipe 12 . the sand pack 35 within the outer perforated pipe 12 further excludes organic debris from the sampler 10 and allows the sampler 10 to be used effectively both in the leaf - litter environment of bottom sediment and in more sandy sediments . the present invention is a stand - alone , pre - packed pore water sampler having a small - diameter tubing that connects the sampler to the shore . the sampler is constructed almost entirely of plastic and polymers , making it substantially less expensive than prepacked screens constructed of stainless steel . the sampler also has no stainless steel in intimate contact with water movement , minimizing potential chemical effects that can be associated with stainless - steel well screens . the outer layer is a rigid plastic perforated pipe with a raised framework to counter the potential blockage effects of sheet debris , such as leaf matter . it will be appreciated by those skilled in the art that modifications and variations of the present invention are possible without departing from the principles and spirit of the invention , the scope of which is defined in the appended claims and their equivalents . 1 . church , p . e ., vroblesky , d . a ., lyford , f . p ., and willey , r . e ., 2002 , guidance on the use of passive - vapor - diffusion samplers to detect volatile organic compounds in ground - water - discharge areas , and example applications in new england : u . s . geological survey water - resources investigations report 02 - 4186 , 79 p . 2 . imbrigiotta , t . e ., ehlke , ta ., and lacombe , p . j ., 2002 , comparison of dialysis membrane diffusion samplers and two purging methods in bedrock wells : paper 1d - 02 , in : a . r . gavaskar and a . s . c . chen ( eds . ), remediation of chlorinated and recalcitrant compounds — 2002 . proceedings of the third international conference on remediation of chlorinated and recalcitrant compounds ( monterey , calif . ; may 2002 ). isbn 1 - 57477 - 132 - 9 , published by battelle press , columbus , ohio , www . battelle . org / bookstore . 3 . jacobs , p . h ., 2002 , a new rechargeable dialysis pore water sampler for monitoring sub - aqueous in - situ sediment caps : water research , v . 36 , p . 3121 - 3129 . 4 . karp , k . e ., 1993 , a diffusive sampler for passive monitoring of underground storage tanks : ground water monitoring & amp ; remediation 13 , no 1 : 101 - 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