Abstract:
A portable groundwater sampling system utilizing an air pump in combination with a sampling tank, valves, and a pressure gauge to sample a liquid from a below ground surface monitoring well. The system includes a portable power supply for energizing the air pump and is mounted on wheels for mobility. The system also may include a flat work surface and a storage container.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates to groundwater sampling systems, and more particularly, to a vacuum driven ground water sampling system for collecting groundwater samples from shallow wells.  
           [0002]    Submersible pumps have been used where the depth to the water is more than 25 feet below ground surface (ft bgs). Most environmental monitoring wells are completed in the uppermost water bearing formation. In most of the United States the depth to water is less than 25 ft bgs. There are several problems with using existing submersible pumps.  
           [0003]    When using a submersible pump, the pump, electrical line, and tubing must be decontaminated prior to sampling each well. Decontamination prevents cross-contamination between wells, assuring quality control of the sampling activities. Proper decontamination is a time consuming process. In addition, in anomalous sample results are obtained, additional time and expense are required to address the anomalous results in a sampling report and the possible incurring of the expense of resampling.  
           [0004]    When using a submersible pump, it is difficult for one person to handle the pump, electric line and tubing keeping all components off of the ground as required by standard sampling protocol to prevent possible cross-contamination. Sampling is much easier for two people, however, labor is a significant portion of the expense of groundwater sampling and while the second person makes sampling easier, they have little effect on sampling times.  
           [0005]    In many cases, the groundwater removed from monitoring wells contains significant concentrations of compounds that are considered by the United States Environmental Protection Agency to be hazardous to human health. A health and safety plan is required to be prepared for all sites so that exposure of sampling personnel to these compounds is identified and minimized. When using submersible pumps, the water in the discharge lines should not be allowed to drain back into the well, to prevent cross-contamination and to minimize the effect the pumping has on water chemistry. Often, the water in the discharge lines ends up being drained on the ground and presents an exposure to sampling personnel.  
           [0006]    Small submersible pumps designed to work in 2-inch diameter wells are sensitive to handling any abrasive material which is a frequent occurrence in groundwater sampling. In addition to damage to the impeller of any centrifugal type pump, the small submersibles have Teflon wear surfaces rather than bearings. These wear surfaces are very sensitive to abrasion and frequent maintenance is required.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention provides a portable sampling system for collecting groundwater samples from shallow wells. The sampling system includes an air pump to apply a vacuum to a steel tank to draw water from a well, tubing, valves and a power supply such as a battery or a portable gasoline-power electric generator. The sampling system is mounted on a portable platform. When the tank is full of sampled water, the air flow from the air pump can be reversed to pressurize the tank and force the water from the tank through a discharge line. As many as three groundwater monitoring wells can be sampled before emptying the tank. In addition to serving as a pump, the system will also contain fluid produced while sampling, act as a sampling platform, and can be used for sample storage. Use of an air pump in combination with a tank eliminates the possibility of a change in the contaminated water chemistry due to pump interaction. Additionally, sediment and debris do not contact the air pump and thus does not affect maintenance and performance of the air pump. Furthermore, contaminated wafer from a well remaining in a sampling line may be allowed to drain back into the well without cross-contamination or changing the chemistry of the contaminated water. The vacuum may also pull all of the contaminated water into the tank thereby preventing the contaminated water from spilling on the ground and exposing personnel to hazardous materials. Disposable lines may be used to eliminate the need to decontaminate sampling lines.  
           [0008]    Other advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, a preferred embodiment of the present invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is an electrical/pneumatic/hydraulic schematic illustration of the sampling system of the present invention.  
         [0010]    [0010]FIG. 2 is a side elevation view of the sampling system of the present invention.  
         [0011]    [0011]FIG. 3 is a front elevation view of the sampling system of FIG. 2.  
     
    
     DETAILED DESCRIPTION  
       [0012]    Referring to FIG. 1, the portable groundwater sampling system of the present invention is generally indicated by reference numeral  10 . The groundwater sampling system  10  includes a DC powered air pump  12  which supplies a vacuum to steel tank  14  to draw water through sample line  16 , ball valve  18  and check valve  20  into the tank  14 . When the tank  14  is full, the flow of air from air pump  12  may be reversed to pressurize tank  14  and force the water from the tank  14  through check valve  22 , ball valve  24  and out discharge line  26  or drain valve  27 .  
         [0013]    The air pump  12  may be powered by a 12-volt DC battery  28  carried on the sampling system  10  or can be operated from a vehicle battery (not shown). Power to air pump  12  is controlled by an ON/OFF switch  30 . Although shown as one air pump in the figures, two or more smaller air pumps connected in parallel may be used. A normally-closed high-level float switch  32  in tank  14  powers an indicator light  34  to indicate when the tank  14  is full.  
         [0014]    A 4-way valve  36  switches connection of the pump inlet line  38  or pump exhaust line  40  to tank vacuum/pressure line  42 . When inlet line  38  is switched to vacuum/pressure line  42 , air pump  12  evacuates tank  14  and pump exhaust line  40  is connected to exhaust/inlet line  44 . When exhaust line  40  is switched to vacuum/pressure line  42 , air pump  12  pressurizes tank  12  and pump inlet line  38  is connected to exhaust/inlet line  44 . A filter and moisture separator  46  filters the incoming to air pump  12  through inlet line  38 . A pressure gauge  48  is provided to monitor the pressure or vacuum in tank  14 .  
         [0015]    A calibrated site gauge  50  is provided on tank  14  with a calibrated scale to indicate the amount of water in tank  14 . This allows accurate measurement of the volume of water removed from a well.  
         [0016]    During groundwater sampling, a typical protocol is followed in which three well volumes are removed prior to collecting a sample. A well volume is the amount of water standing in the casing. Typically, monitoring wells are constructed of 2-inch PVC screen and casing. A typical monitoring well may have 5 to 7 feet of water in the casing. Thus a 2-inch casing will contain approximately 0.16 gallons per linear foot of casing. This means that a typical well, assuming seven feet of water in the casing, will contain approximately 1.12 gallons of water. Accordingly, 3.36 gallons must be removed prior to sampling. In the preferred embodiment, tank  14  has a 13-gallon capacity which allows for sampling of three typical wells before emptying the tank. However, other sized tanks may be used. For example, a three to four gallon tank may be used to allow the sampling system to easily fit in the trunk of a car.  
         [0017]    Referring to FIGS. 2 and 3, groundwater sampling system  10  is shown mounted to a 2-wheel cart  52 . Cart  52  includes a handle  54  and pneumatic tires  56 . Air pump  12  along with valve  36 , filter/moisture separator  46  and pressure gauge  48 , including the connecting lines and wiring, are contained in housing  58  which is mounted to cart  52  above tank  14 .  
         [0018]    Housing  58  includes a flat work surface, generally indicated by reference numeral  60 , to serve as a writing/work surface. A small cooler and storage container  62  may be attached to cart  52  to hold samples and supplies. Most groundwater samples must be placed on ice immediately after collection to prevent volatile compounds or solvents from evaporating.  
         [0019]    Groundwater sampling system  10  is sized to fit easily through doors and gates and of a weight of approximately 70 pounds so that it may be easily loaded, unloaded and used by one person. Additional attachments may be used including flow meters for micropurging, for example. At some sampling sites micropurging is conducted where monitoring wells are evacuated at very low rates until some measurement parameter such as pH, specific conductance, or temperature has stabilized. A flow meter and necessary sensors may be attached to the sampling system  10  to measure the flow and other parameters.  
         [0020]    It is to be understood that while certain now preferred forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims.