Stockpile sampling

The theoiy enables a reasonable estimate of sample quantity needed to attain specified accuracy of a composition variable. The result is an ideal quantity—not realized in practice. Actual quantities for practical estimation are larger by an appropriate multiple to account for the reality that material is incompletely mixed when stored in stockpiles or carried on conveyors. Sample quantity to accommodate incompletely mixed sohds can be specified through evaluating variance by autocorrelation of data derived with a series of stockpile samples, or from multiple sample extractions taken from a moving stream (Gy, Pitard). 

Sampling of stockpiled soil is frequently conducted at remediation projects. The accessibility of soil for sampling usually depends on the size of the stockpile the larger the stockpile, the more difficult the sampling. That is why the stockpile size is a key factor in the design of a stockpile sampling strategy. 

A Reports by the Committee on Review and Evalnation of the Army Chemical Stockpile Disposal Program (Stockpile Committee), 45 B Biographical Sketches of Committee Members, 47 C Closnre Planning and Implementation, 51 D J AC ADS Sampling and Analysis Plan Maps and Photographs, 53 E Examples of Information Reqnired for Two Types of Einal Closnre Snrvey Reports, 61... 

ASTM D-6610. Standard Practice for Manual Sampling Coal from Surfaces of a Stockpile. 

Samples of South Blackwater and Ensham coal of +16.0 mm size were collected separately, from the stockpiles of the Gladstone Port. Before testing, both types of coals were sieved to obtain a —76.2 + 50.8 mm sized samples for the drop tests. The sample was placed inside the released hopper, which was raised by overhead crane. A sample of 10 kg was dropped each time onto an enclosed horizontal steel plate, conveyor belt and coal stockpile. The dropped coal was sieved to remove the fines (-16.0 mm size). In this way the percentage of fines produced at each drop were determined. The calculation methodology for fines percentage was given in Sahoo et al. [2],... 

The comparison of three different impact surfaces tested with cushioned coal sample, initial 10% fines coal sample and a sample of initial 30% fines of South Blackwater and Ensham coal were shown in Figs. 8-13. The cushioned coal sample of South Blackwater coal dropped on steel surface produced 8.5% more fines than the drops onto a conveyor surface and 13.4% more fines than a coal surface (coal stockpile) at 30 m total drops shown in Fig. 8. Similarly, Ensham coal produced 4.6% more fines on steel surface than... 

The degradation model of three samples (cushioned coal, initial 10% fines and initial 30% fines) of South Blackwater coal is determined on three impact surfaces (steel plate, conveyor belt and coal stockpile). Degradation model equation can be written as follows ... 

We need to make a decision related to the disposition of soil that has been excavated from the subsurface at a site with lead contamination history. Excavated soil suspected of containing lead has been stockpiled. We may use this soil as backfill (i.e. place it back into the ground), if the mean lead concentration in it is below the action level of 100 milligram per kilogram (mg/kg). To decide whether the soil is acceptable as backfill, we will sample the soil and analyze it for lead. The mean concentration of lead in soil will represent the statistical population parameter. 

Because historical data for the soil is not available, to estimate the number of samples for the stockpile characterization, we collect four preliminary samples and analyze them for lead. The concentrations are 120, 60, 200, and 180 mg/kg, with the average concentration of 140 mg/kg and the standard deviation of 63 mg/kg. We use Equation 11, Appendix 1, for the calculation of the estimated number of samples. Using a one-tailed confidence interval and a probability of 0.05, we determine the Student s t value of 2.353 for 3 degrees of freedom (the number of collected samples less one) from Table 1, Appendix 1. 

Composite samples are typically collected for soil stockpile or surface area characterization. Twenty-four-hour composite samples of water may be collected with automated composite samplers from streams or process piping composite samples may be made of several grab samples collected from different depths in a soil boring. 

Whether the intended use of soil data is the determination of its suitability as backfill or the disposal characterization, we should always determine how many samples are required to characterize a stockpile with a certain level of confidence. The minimum number of samples will depend on the size of the stockpile and the applicable action level. If soil is to be used as clean backfill, a statistical evaluation of... 

The Stockpile Statistics Worksheet, shown in Appendix 14, is a useful supplement for determining a minimum number of samples for proper stockpile characterization, if financial restrictions are not an issue. 

To use the worksheet, we must first collect a number of stockpile characterization samples based either on regulatory guidance or on a specific sampling scheme with a certain budget in mind. Analytical results for these samples are entered into the worksheet as the mean concentration the 95 percent upper confidence interval is calculated. A minimum number of samples is calculated in Worksheet Step 11 Step 12 allows determining if a sufficient number of samples have been collected. If not, additional sampling may be necessary. Examples 2.3 and 5.13 illustrate these calculations. 

Calculate the dimensions of each segment to be sampled and mark the segments along the stockpile base with stakes or flags. 

Determine the sampling point locations within each segment with a random number generator. Sample each segment either manually or with an excavator or backhoe bucket. If the stockpile is stable and safe to climb on, use a hand auger or a hand trowel to obtain samples from below the surface at the top and sides of the stockpile. 

To sample with airtight coring devices, we must have access to exposed soil, which may be the ground surface, the bottom and sidewalls of an excavation, the stockpile face or side, or soil in the excavator bucket. We may also apply this technique for sampling of subsurface soil brought to the ground level in a split spoon sampler. 

Four soil samples from a contaminated soil stockpile... 

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