A FIELD SAMPLE IS ONLY AS RELIABLE AS THE COLLECTION METHODS USED.
For Operators that would prefer to collect field soil samples themselves and ship to our labs, ATOKA recommends the following sample procedures:
Items you will need:
- Hand Trowel or Grub Hoe
- Black Permanent Magic Marker
- Zip-Lock Sandwich Bags (1 bag per sample)
- Global Positioning System (GPS) or Topographic Map to Record Sample Locations in the Field
DETERMINE SITE GRID SIZE AND SPACING
Atoka was the first company to push forward the use of grids. Atoka’s personnel and owner all having mining background where geochemical surveys utilizing grids has been common place for over three decades. The grid approach to sampling was developed in World War II to search for submarines. Grid spacing is based on the premise that if the grid is fine enough then statistically it will be possible to define the target or all the targets within the grid. Therefore knowing target size is critical to a successful survey.
The use of line data can be quite useful for reconnaissance work in terms of a new basin or for a land sale but for defining a target area for drilling or a seismic survey it has, at least in recent years, a low chance of success. Most companies that push this method are either desperate for business or the client probably cannot even afford to lease the land. They typically, beyond reconnaissance mode, are a waste of time.
For a gird, if the target size is known then spacing can be determined. A target that is 320 acres in size, Atoka recommends a 2/10ths of a mile spacing across a 3 mile square area. This will allow a potential 12 to 24 samples to fall on top of or adjacent to the target. The additional data provides good background coverage so statistical analysis of the data is simplified and more definitive.
Larger targets can allow a wider spaced sample grid; smaller targets require a tighter spacing. Atoka is always ready to help in laying out a grid for sampling. Please call us at your convenience.
PREPARE SAMPLE BAGS
Atoka recommends preparing sample bags before entering the field. This has proven to be the best way to avoid collection errors and mistakes in the field. The best method is labeling the bags in sequential order. Atoka recommends assigning a three letter prefix; this avoids mistakes that can occur such as getting mixed with other surveys being collected or separating from other surveys in the lab. The three letter prefix is followed by a number series starting preferably with 1. It is common in the mining industry to use the coordinates of each location as labels.
Sample bags that are pre-numbered and organized prior to collection avoid duplicate and skipped sample numbers. Marking a map ahead of time also allows the collector to recognize when he or she has misplaced or lost a sample bag. Also having the bags and map prepared ahead of time reduces time spent at each location. Therefore Atoka recommends putting them in groups of ten and taping them together.
COLLECTION PROCEDURES FOR MAGNETIC SUSCEPTIBILITY, IODINE, EH, PH, TRACE ELEMENTS AND CONNECTIVITY
Atoka recommends that at each sample point to collect six representative samples at six separate points from within five feet of each other. Clear away the vegetation at each point and scoop a 1⁄4 to a 1⁄2 a shovel full and place it in the bag. Vegetation just bulks up the sample and has to be removed anyway by sieving in the lab. In some environments, such as Northern Michigan, this may be difficult, so the sampler needs to do as best as he or she can. After all six samples have been placed in the bag, seal the bag. The bag should be 1⁄2 to 3⁄4 full. If the soil is silt or clay rich then the bag can be 1⁄2 full or less. If the soil is predominantly sand and gravel then filling the bag is recommended. The laboratory analyzes the fine fraction. Place in a cool spot inside the vehicle or backpack and out of the sun. It is believed that the sun is a possible catalyst for ioodorganic compounds being formed or broken up. By removing the samples from the sunlight, this minimizes the chance for this to occur. But also more importantly, it is less likely that the label made by the magic marker will fade.
After the sample is taken, mark each sample number clearly on the map. Many GPS systems will provide a sequential numbering “mark” function that can be used to record the bag number.
COLLECTION PROCEDURES FOR ACID EXTRACTION SOIL GAS
Augers are available for sale from a variety of forestry or engineering suppliers, therefore it is relatively easy to obtain an auger and collect your own samples for acid extraction. This method does not work with head space.
To begin collecting the sample, pick an ideal spot, preferably flat ground where soil is present and not bed rock. Clear away vegetation. Auger down three to four feet. The last soil taken is the sample to be placed in the sample bag. The bag should be 1⁄2 to 3⁄4 full. If the soil is silt or clay rich then the bag can be 1⁄2 full or less. If the soil is predominantly sand and gravel then filling the bag is recommended. The laboratory analyzes the fine fraction. Place in a cool spot inside the vehicle or backpack and out of the sun. By keeping the sample bags away from sunlight, the label made by the magic marker is likely not to fade.
After the sample is taken, mark each sample number clearly on the map. Many GPS systems will provide a sequential numbering “mark” function that can be used to record the bag number.
SHIPPING SAMPLES
The best way to ship samples is either by UPS or FedEx. The postal service, the bus, airplane or even the sampler’s vehicle can take a wrong turn. They maybe cheaper, but not if you lose samples and potentially important data.
The best way to ship the samples is in either a book carton available at a packing store or a heavy duty plastic storage container. Fifty samples per box placed in two trash can bags. Tie the bags closed. This prevents any water on the outside of the sample bags to damage the shipping container.
Before sealing the box, place inside a list of the sample number, state and county the samples came from, your address and contact information. Shipping within the U.S. for the most part does not require a special permit. International shipments require a Department of Agriculture number permit. Each permit number is specific to a laboratory and cannot be used by any other laboratory. Our number is S-47646. Many times a copy of the permit is required. Please call us to get a copy so we can schedule your samples. Results are usually delivered within 10 to 15 days.