AGWST 5.00

Alternative Ground Water Sampling Techniques Guide (July 1994)

Title: Ground Water Sampling with the use of a Small Diameter Direct Push Point (SDDPP) (3/94)

Method Number: AGWST 5.00

Summary:

A small diameter direct push point (SDDPP) is a «-1 inch OD casing (slotted or blank) which can be driven or pushed through the soil into the ground water (Tracer Research, Geoprobe^®). It is used for the collection of a ground water sample or estimating piezometeric data. The casing can be constructed of stainless steel or carbon steel. No filter or gravel pack is used in the installation.

I PURPOSE AND SCOPE

This document summarizes the minimum requirements for the use of a SDDPP for the collection of ground water screening data for site investigations. Installation is for temporary use (less than 48 hours).

II METHOD OVERVIEW

1. Tools
   
   Several types of tools are available as SDDPPs; blank stainless steel with a sacrificial tip, mill slotted casing and a telescoping screened point (Figure I, Figure II and Figure III).
2. Applications
   
   
   1. Field screening tool for the collection of ground water samples for site investigations to evaluate the presence/absence and extent of ground water contamination.
   2. Field screening tool to aid in the placement of monitor wells.
   3. Temporary placement for the collection of ground water samples and estimating ground water flow direction (less than 48 hours)
3. Capabilities
   
   
   1. Obtain ground water samples from unconfined aquifers.
   2. Obtain samples across the water table to determine the presence of floating product (slotted casing).
   3. Capable of collecting samples to determine the vertical profile of contaminants in an aquifer (only tools with an O-ring seal-blank casing with a sacrificial tip and telescoping screen with sacrificial tip).
   4. Can be used to estimate ground water flow directions. Must remain in place for 24-36 hours to allow for stabilization prior to measurements.
   5. A comparison of the advantages and limitations for SDDPPs are listed in Table I.

III SAMPLING METHOD REQUIREMENTS

1. Installation of Blank Casing SDDPP
   
   
   1. SDDPPs constructed of blank stainless steel or carbon steel casing with a sacrificial tip or telescoping screen with a sacrificial tip are emplaced by driving the point to the desired depth with hydraulics or a rotary hammer. Caution must be used in using a hammering device since this may cause the rod threads to loosen and cross, damaging the rod.
   2. The probe should be placed a minimum of 2 feet below the water table. Once at depth, the casing is pulled back leaving the point in place and exposing the opening of the casing or the telescoping screen. Ground water fills the casing through the bottom of the blank casing or screen for sample acquisition. These tools are not capable of obtaining a sample across the water table
   3. If blank casing SDDPPs are used to perform vertical profiling of an unconfined aquifer, the sacrificial tip must provide a water-tight seal with the casing. This will prevent cross contamination of the casing from water outside the targeted sample zone. Also the practice of acquiring samples from different intervals as the casing is pulled to the surface must not be performed. This practice yields a sample of unknown quality and location.
   4. Prior to installation of any SDDPP, previous knowledge of the depth to water should be known by previous site data or from soil samples for proper placement of the probe. If no ground water data is available, then depth to water can be estimated with the SDDPP. If SDDPPs are employed for estimating piezometeric data, the point cannot remain in the ground longer than 48 hours from installation.
   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. Installation of Slotted Casing SDDPP
   
   
   1. SDDPPs constructed of a slotted section of stainless steel or carbon steel can be emplaced by driving the screened section of casing to the desired depth with hydraulics or a rotary hammer.
   2. Slotted SDDPPs can be placed across the unconfined water table to determine the presence of floating product. They are not recommended for vertical profiling of unconfined aquifers due to the potential cross contamination of the point, as it passes contaminated zones of an aquifer.
   3. Prior to installation of any SDDPP, previous knowledge of the depth to water should be known by previous site data or from soil samples for proper placement of the probe. If no ground water data is available, then depth to water can be estimated with the slotted SDDPP. If SDDPPs are employed for estimating piezometeric data, the point cannot remain in the ground longer than 48 hours from installation.
   4. Caution should be used when using slotted probes which are exposed to areas of contaminated soil. Possible cross contamination to the casing may be introduced as it passes through the zone of contamination.
3. Sampling Procedures
   
   
   1. Purging
      
      For slotted SDDPPs, three to five volumes of the standing water must be purged. This can be accomplished utilizing a peristaltic pump, inertial pump or a small centrifugal pump.
      
      Purging is not required for SDDPPs which are sealed until opened at the target depth for sample acquisition.
   2. Sampling
      
      Due to the small diameter of a SDDPP, the sampling tools are limited. The acquisition of samples and water level measurements must be performed by one of several recommended ground water sampling methodologies described in the May 1992 edition of NJDEPE Field Sampling Procedures Manual.
4. Quality Assurance/Quality Control
   
   
   1. Decontamination
      
      The SDDPP and associated equipment (points, casing, etc.) must be decontaminated between borings using the following procedure:
      
      
      1. Remove all adherent soil material.
      2. Wash with a laboratory grade detergent.
      3. Rinse with potable water and/or steam clean.
      4. Rinse with distilled and deionized ASTM Type II water.
      NOTE: For proper decontamination, stronger cleaning agents are recommended when tool has been exposed to heavy contamination. This should 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 the sample device and NDDPP prior to installation 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. Sampling Equipment
      
      Due to the small diameter of the points, the available sampling equipment may be limited. The NJDEPE Field Sampling Procedures Manual can be used as a reference for the selection of sampling equipment.
      
      All sampling equipment must be laboratory decontaminated in accordance with the NJDEPE Field Sampling Procedures Manual and dedicated to each sample point.
   4. Rod Sealing
      
      When using the SDDPP below the water table the drive rod/casing joints must be sealed. This will prevent fluid from entering the rods and potentially contaminating the sample. The rods should be sealed with TeflonR tape on the threads. Once put together the joints must be sealed with gas pipe tape. Another option is the use of drive rod with O-Rings at the threads for sealing.
   5. Formation Types
      
      SDDPPs can be installed in unconsolidated materials with limited amounts of pebbles, cobbles and boulders. The presence of these materials in large quantities may inhibit the penetration depth of the SDDPP. The soil texture will dictate the recharge rates of ground water to the well.

IV REFERENCES

1. Barker, J.F.; Patrick, GC; Lemon, L; Travis G.M.; Some Biases in Sampling Multilevel Piezometers for Volatile Organics. Ground Water Monitoring Review, Spring 1987, p48-54
2. Kerfort, William B; A Portable Well Point Sampler for Plume Tracking. Ground Water Monitoring Review, Fall 1984, p38-41
3. Robbins, G.A.; Hayden J.M.; Bristol, R.D.; Vertical Dispersion of Ground Water Contaminants in the Near-Field of Leaking Underground Gasoline Storage Tanks. In Procedures of the National Water Well Association Petroleum Hydrocarbons Conference, November 15-17 1989, Houston, TX
4. Stites, Will; Chambers, Luch W; A Method for Installing Miniature Multilevel Sampling Wells. Ground Water Vol. 29, No.3, 1991. p430-432

TABLE I

ADVANTAGES AND LIMITATIONS OF A
SMALL DIAMETER DIRECT PUSH POINT (NDDPP)

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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.