AGWST 1.00

Alternative Ground Water Sampling Techniques Guide (July 1994)

Title: Ground Water Sampling with the use of a Screened Auger Tool (SAT) (3/94)

Method Number: AGWST 1.00

Summary:

The Screened Auger Tool (SAT) is a five foot length of laser-slotted hollow stem auger, available in 2 to 12« inch ID, constructed of carbon steel through which samples of ground water may be obtained.

I PURPOSE AND SCOPE

This document summarizes the minimum requirements for the use of the Screened Auger Tool for the collection of ground water screening data for site investigations.

II METHOD OVERVIEW

1. Tool Description
   
   
   1. The SAT is a length of laser slotted hollow stem auger which will allow the passing of groundwater into the auger for sampling (Figure I).
   2. The slots are bevel cut to a slot size of 0.007 inches which allows for quick cleaning and helps eliminate the passage of fine soil particles.
   3. The SAT must be equipped with a knock out plug at the cutting head to prevent the entrance of soil and eliminates the need for a center bit and rod while advancing. The knock out plug will not affect hole advancement and can be dislodged by a split spoon or well casing.
2. Applications
   
   
   1. Field screening tool for the collection of ground water samples to aid in the placement of monitor wells.
   2. Use of the SAT can provide a quick assessment of ground water conditions at a potentially contaminated site during auger advancement.
3. Capabilities
   
   
   1. Obtain samples from unconfined aquifers.
   2. Sampling from confined aquifers provided the upper aquifer is cased off and the casing is driven a minimum of two feet into the confining layer.
   3. Obtain samples across the water table to determine the presence of floating product.
   4. Capable of obtaining ground water samples and allows for continued auger advancement immediately after collection.
   5. Capable of collecting samples for obtaining a vertical profile of contamination in an aquifer.
   6. A comparison of the advantages and limitations of the SAT are listed in Table I.

III SAMPLING METHOD REQUIREMENTS

1. Installation
   
   
   1. The SAT is used in the same manner as conventional auger drilling techniques. It is designed to be used in well sorted, unconsolidated, fine to coarse sands.
   2. Augers, used in conjunction with the SAT, must be constructed in a manner which provides a water tight seal at the auger connection. This will prevent cross-contamination by water seepage at the joints from different depth intervals below the water table.
   3. Since a center bit and drill rod are not used with the SAT, a plug constructed of Teflon^® or polypropylene must be used in the bottom of the screened auger section when drilling. This plug prevents soils from entering the auger during drilling, development and sampling. When at the final target depth, the plug is knocked out and left in the ground for split spoon sampling or well installation.
   4. Always accurately measure the depth of the SAT and auger stick-up to determine depth of sample zone.
   5. Installation of the tool is required to comply with all permit, license, sealing and grouting requirements as per Appendices I and II. Any tool left in the ground longer than 48 hours is considered a monitor well and therefore must comply with the permit installation and license requirements for monitor wells.
2. Sampling Procedures
   
   
   1. Development
      
      The SAT must be developed by one of the standard methods used for well development prior to sampling. If an air lift development technique is used, the air outlet must be at a minimum of two feet above the screened auger. Operations must be continuous and not pulsed. The air lift pipe shall not be placed within the screened auger and only the double pipe method shall be used. Therefore this development technique cannot be used for sampling at water table locations.
      
      The well should be developed until the ground water is clear and sediment free. This clears the screen and removes all sediment in the auger.
   2. Purging
      
      After development, three to five volumes of the standing water must be purged from the SAT utilizing a submersible or centrifugal pump. This removes water agitated in the formation by the development process. Caution should be used during purging to avoid pumping to dryness. The NJDEPE Field Screening Procedures Manual can be used as a reference for the selection of appropriate purging equipment, construction and decontamination procedures.
   3. Sampling
      
      Groundwater samples are collected through the center of the auger. The acquisition of samples can be performed by one of several recommended ground water sampling methodologies described in the May 1992 edition of the NJDEPE Field Sampling Procedures Manual.
3. Quality Assurance/Quality Control
   
   
   1. Decontamination
      
      The SAT, associated augers and equipment used for development must be decontaminated between borings using the following procedure:
      
      
   1. Remove all adherent soil material with stiff bristle brush.
   2. Wash with a laboratory grade glassware detergent.
   3. Steam clean interior and exterior of the SAT and all associated augers.
   NOTE: For proper decontamination, stronger cleaning agents are recommended when the tool is exposed to heavy contamination. This can be performed prior to step 2.
   
   
   2. Field Blanks
   
   
   Field blanks must be obtained in the same manner as the sample. The blank water must pass through all the sampling equipment then into the sample container.
   
   The parameters and frequency for field blanks are designated in the May, 1992 edition of the NJDEPE Field Sampling Procedures Manual.
   
   
   3. Sample Equipment
      
      A variety of equipment may be used to obtain samples from the SAT. The NJDEPE Field Sampling Procedures Manual can be used as a reference for the selection of the appropriate sampling equipment.
      
      All sampling equipment must be decontaminated in accordance with the NJDEPE Field Sampling Procedures Manual and dedicated to each sample point.
   4. Auger Seals
      
      If drilling and sampling with the SAT below the water table, the augers used with the SAT MUST provide a water tight seal at the connection. This will prevent cross contamination of samples from formation water leaking through the auger connection and into the augers from different depths.
      
      The type of augers used should be equipped with an o-ring or other device which will ensure a water tight seal.
   5. Formation Type
      
      The design of the SAT gears itself towards use in highly permeable unconsolidated formations. If the formation contains silts and clays the formation will yield slow recharge rates and highly turbid samples.

IV REFERENCES

1. Taylor, T.W.; Serafini, M.S.; Screened Auger Sampling: The Technique and Two Case Studies. Ground Water Monitor Review, v.10 No.4 pp145-152, Summer 1988

TABLE I

ADVANTAGES AND LIMITATIONS OF THE SCREENED AUGER TOOL

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Disclaimer

This document was prepared by the New Jersey Department of Environmental Protection (NJDEP), Site Remediation Program (SRP) and has been subject to peer review. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.

Acknowledgements

The author would like to express his sincere appreciation for the review and comments to initial drafts of this document made by personnel within and outside the Department.