Ground water sampling device

A groundwater sampler is disclosed which is adapted for reuse at multiple depths during a single boring, which is simple in design, which may be built with but a small number of parts, which is easy to used which is easy to decontaminate, and which is resistant to clogging from silts and fine sands.

This invention pertains to groundwater sampling devices. 
Concern about the environment continues to increase. There is a need for 
convenient techniques and apparatus to take groundwater samples accurately 
and easily, to identify locations of pollution, to monitor groundwater 
quality, and to measure the effects of remediation measures. Groundwater 
pollution investigations typically require the collection of groundwater 
samples from several different locations, at various depths. Thus it would 
be desirable to provide a sampling device which can easily be reused at 
different locations, particularly one which could be used at multiple 
depths during a single boring. 
One prior method of groundwater sampling is to install a monitor well, and 
to pump or bail water to the surface for analysis. This method will in 
many cases be too expensive and inefficient, because a separate well must 
be constructed at each sample point. 
Another general method is to take a sample with a device that is driven 
into the ground and is designed to be removed from the ground and later 
reused at other locations. There are several different types of reusable 
groundwater samplers available on the market today. Reusable groundwater 
samplers are typically designed to penetrate the earth by being driven to 
the desired depth by a hydraulic ram or impact hammer, generally in 
association with a drill rig. 
Cordry, U.S. Pat. No. 5,046,568 discloses a groundwater sampler having a 
drive cone whose diameter is apparently smaller than the diameter of the 
sampler casing, and in Which the drive cone is designed to remain in the 
bore hole following the sampling. This patent also discusses other 
samplers in which the sampler and drive cone are removed after sampling. 
See col. 1, is line 28 through col. 2, line 7. Bailing is disclosed in 
col. 8, lines 49-51 and col. 9, lines 31-35. 
Other prior patents in the general field of endeavor include U.S. Pat. Nos. 
64,192; 767,209; 1,211,415; 1,983,428; 4,176,716; and 4,807,707. 
No prior groundwater sampler allows for convenient sampling at multiple 
depths during a single boring. It would be desirable to have a sampler 
which is able to do so, because it is often not known in advance at what 
depth water will be found. Considerable time could be saved if it were 
possible to take samples at several depths during a single boring, without 
the necessity of withdrawing the sampler between samples. 
There remains a need for a groundwater sampler which is adapted for reuse 
at multiple depths during a single boring, which is simple in design, 
which may be built with but a small number of parts, which is easy to use, 
which is easy to clean, and which is resistant to clogging from silts and 
fine sands. 
These and other objects have been achieved with the novel groundwater 
sampler of the present invention. The novel sampler may be attached to a 
drill stem through conventional means, and pushed or driven to the desired 
depth with an impact device or hydraulic ram. Alternatively a portion of 
the bore hole may be "pre-drilled" through conventional means to within a 
short distance of the desired sampling depths and the sampler may then be 
pushed or driven the remaining distance to the desired depth. 
A drive cone is removably attached to the bottom of the sampler, for 
example through the frictional contact of an O-ring. The drive cone is 
fixedly attached to a screen, preferably a cylindrical screens contained 
in the interior of the sampler. The diameter of the drive cone is 
substantially the same as the diameter of the sampler casing. Once the 
sampler is at the desired depths a drill stem connected to the top end of 
the sampler is withdrawn a short distance (e.g., 19 inches or 48 cm) 
toward the surface. Frictional forces between the drive cone and the soil 
overcome the force connecting the drive cone to the sampler casing (e.g., 
the frictional forces from an 0-ring) s causing the drive cone and the 
screen to stay in place as the sampler casing is retracted. Natural 
hydrostatic pressure then fills the screen with groundwater from the 
stratum to which the screen is then exposed. This flow from the formation 
occurs with little agitation, and therefore with little loss of any 
volatile compounds that may be present. 
Water entering the screen may then be removed for analysis through means 
known in the art. For example, a bailer of sufficiently small outer 
diameter (e.g., one inch or 2.5 cm) may be lowered through the drill stem 
and casing into the interior of the screen. The sample volume is not 
fixed. If silts or fine sands clog the screens the bailer may be moved up 
and down within the screen to create agitation to dislodge the unwanted 
sediment. 
It is preferred that the sampler be configured so that the bailer may be 
lowered to the bottom of the screen. This configuration not only 
facilitates unclogging the screen as just described, but in conjunction 
with a small bailer also permits sampling both "sinkers" and "floaters" at 
the same general depth, i.e., sampling materials which are heavier or 
lighter than the water which is prevalent in the stratum. 
After the groundwater sample has been collected, the entire sampler may be 
retrieved for cleaning and reuse. The screen is fitted with a shoulder on 
the top end, which catches a lip within the casing as the casing is 
further withdrawn toward the surface. As the lip catches the shoulders the 
screen and drive cone are retrieved from the bore hole along with the 
casing. 
Alternatively this configuration allows the sampler, if desired, to be 
pushed instead into deeper strata, or to be retracted to shallower strata 
to obtain additional groundwater samples from the same bore hole during a 
single boring. When pushed deeper the screen is pushed back into the 
casing, and the entire sampler may be pushed deeper, and then reopened as 
before. Alternatively, the sampler (in the open position) may be pulled 
back to a higher stratum, and a new sample taken as before. For these 
operations to work properly, it is important that the diameter of the 
drive cone (i.e., the outer diameter of the drive cone at its widest 
point) be substantially the same as the outer diameter of the sampler 
casing. Otherwise contamination of the screen, and thus of the sample, 
from the mud or other solid particles in the bore hole is likely. 
Furthermore, having equal diameters seals the portion of the stratum 
adjacent to the screen, reducing contamination from liquids flowing in a 
vertical direction. 
It is preferred that the upper portion of the drive cone be beveled to 
facilitate raising the sampler in the bore hole after the sampler has been 
opened, with minimal contamination resulting from friction between the 
drive cone and the stratum. Similarly, it is preferred that the lower 
portion of the sampler casing be beveled to facilitate lowering the 
sampler in the bore hole after it has been opened. 
A sampler in accordance with the present invention can be made of simple 
construction, making it easy to disassemble and clean. An embodiment of 
the present invention has been constructed of stainless steel, having a 
weight of only 22 pounds (10 kg), an outside diameter of 3 inches (7.6 
cm), a length of only 29 inches (73.7 cm) in the closed position (about 
half the length of most groundwater samplers currently on the market), and 
a length of 47.5 inches (120.7 cm) with the screen exposed in the open 
position.

The Figures illustrate one embodiment of a device in accordance with the 
present invention. This embodiment may be built from only four parts, as 
illustrated in FIGS. 1A-1E and FIG. 2. 
Referring now to FIGS. 1A-1E and FIG. 2, the sampler comprises casing 2, 
drive cone 4, cylindrical screen 6, and casing head 8. 
Casing 2 is attached to casing head 8 by screw threads 10 and 12. Drive 
cone 4 is attached to screen 6 by screw threads 14 and 16. When the 
sampler is closed, drive cone 4 and screen 6 are secured adjacent casing 
2, and inside casing 2, respectively, by the friction of O-ring 18 on 
inner wall 20 of casing 2. Casing head 8 may be attached to a conventional 
drill stem 22 by means of threads 24. 
Referring now to FIGS. 3A-3C, FIG. 3A illustrates the sampler in closed 
configuration after being driven into a bore hole. 
In FIG. 3B, drill stem 22 has been retracted towards the surface slightly 
(e.g., by about eighteen inches, 46 cm) from its position in FIG. 3A. As 
drill stem 22 is retracted, it pulls casing head 8 and casing 2 with it. 
However, frictional forces from the surrounding stratum hold drive cone 4 
and screen 6 in place. These frictional forces (particularly, but not 
limited to, frictional forces on the top, bevelled end of drive cone 4) 
overcome the frictional forces between 0-ring 18 and inner wall 20 of 
casing 2, causing 0-ring 18 to become unseated, thereby allowing drive 
cone 4 and screen 6 to remain in place. 
Once the sampler has thus opened, groundwater from the adjacent stratum may 
flow into screen 6, from which it may be retrieved through means known in 
the art. For example, as illustrated in FIG. 3C, a bailer 30 may be 
lowered by stainless steel cable 32 into screen 6 to retrieve a sample. 
Bailer 30 opens on the bottom, permitting the sampling of either "sinkers" 
or "floaters" as previously discussed. If silts or fine sand have clogged 
the openings in screen 6, bailer 30 may be moved up and down to agitate 
the liquid and dislodge the clogging sediment. As illustrated, this 
sampler design permits bailer 30 to be lowered substantially to the bottom 
of screen 6, facilitating any necessary dislodging of such sediment. 
In a preferred embodiment, the entire sampler is constructed of stainless 
steel to minimize contamination resulting from the sampler itself. In a 
preferred embodiment, the openings in screen 6 are narrow rectangular 
slits (e.g., 0.5 inch.times.0.03125 inch, 1.3 cm.times.0.08 cm), in which 
the slit cut through the body of the screen cylinder does not end abruptly 
at the ends of the slit, but rather tapers off gradually to inhibit 
clogging. 
After a sample has been taken, the entire sampler may be raised to the 
surface by pulling on drill stem 22. As casing 2 then rises, lip 28 of 
casing 2 catches shoulder 26 of screen 6, pulling screen 6 and drive cone 
4 upward as well. Thus the entire sampler may easily be retrieved upon 
completion, with no components remaining in the bore hole. 
While this device has been described in the context of sampling 
groundwater, those in the art will readily appreciate that it may also be 
used for sampling other fluids present in a stratum.