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be done case by case. The federal government can provide only general guidelines on where <br /> to collect samples. Actual sampling locations are based on information obtained during a <br /> preliminary assessment of the property and on the professional judgment of the person <br /> collecting the samples. <br /> If sample analysis costs were trivial, then numerous soil samples could be collected at <br /> each residence to fully characterize lead levels. But analytical cost, in the range of $15 per <br /> sample, is not trivial. Therefore, to keep costs affordable, the sampling strategy must limit the <br /> number of soil samples analyzed. <br /> When collecting only a limited number of samples from a yard, the major source of <br /> uncertainty in the results is from collecting samples from very small areas relative to the total <br /> area of interest. Imagine that a single soil sample is collected from an unusually high, but <br /> small, lead-contaminated area, or from a small section of the yard that recently had lead-free <br /> potting soil spilled on it. Most of these variations are out of the control of or unIcnown to the <br /> person collecting samples. One simple approach to reduce this problem is to sample from <br /> larger areas. <br /> The easiest and most cost-effective way to sample from larger areas is to collect field <br /> composite samples. A field composite sample consists of individual sub-samples collected <br /> from two or more locations and combined into one sample for analysis (the composite sample). <br /> When only a few samples can be feasibly analyzed at a residence due to time and money <br /> constraints, composite sampling offers a more cost-effective approach and provides more <br /> accurate information than collecting a few single location samples. <br /> At least two composite samples per dwelling or building should be collected where bare <br /> soil is present. General sampling locations are as follows: <br /> ■ one from bare soil in the child's principal play area(s) and <br /> ■ one from bare soil areas in the front or back yard (if present) and/or from the <br /> foundation drip line. <br /> Vegetable gardens, pet sleeping areas, and bare pathways are also potential sampling sites, <br /> depending on the situation. <br /> Once sampling areas are identified, sub-sampling locations within these areas need to <br /> be determined. No more than ten sub-samples should be collected into one composite sample <br /> in composite samples may add extra costs to laboratory lead analysis. <br /> 2 <br />