Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 62

3.5. PRELIMINARY FIELD SURVEY
Before any sampling an initial survey of the field should be carried out. This means
looking at the field from all directions. The first step is to walk completely around the
field looking at it from all aspects and noting all the conditions in and around it. During
this process keep asking what is seen and what is going on. Another important question to
keep in mind is whether there are additional sources of contamination that might affect
the sampling, analytical results, or the cleanup plan.
Field characteristics that should be noted during this first survey are given in Table 3.2.
The topics in this list and others, such as the clay and clay type, bulk density, roots, pH,
electrical conductivity, and organic matter content, will be given in the local soil survey.
In spite of this it is a good idea to check these data by making observations in the field,
because significant changes may have occurred between the time the soil survey was
made and the sampling undertaken.
An example of such a situation occurred at a Superfund field. This field was 1 ha in
size. On the upslope side of the area was a railroad siding consisting of three sets of
tracks that carried heavy freight train traffic. On another side was an electrical power
substation. Of concern here would be heavy metals, grease, tar, and creosote from the
railroad. This was of particular concern because the tracks were upslope from the site.
The other concern would be polychlorinated biphenyl (PCB) contamination from the
electrical substation.
Although this is a relatively simple and obvious example it is not an unusual situation.
In this case routine sampling and analysis might not show additional needed cleanup and
remediation work. On the other hand, a routine analysis might have indicated additional
contamination requiring additional sampling and analysis, which could have been
minimized by recognizing the sources of additional and continuing contamination [6].
Another similar problem is that different, unrelated contaminants may interfere with each
other in analytical procedures. This could mean that the analytical laboratory might
obtain confusing results related to the additional sources of contamination from a rail line
TABLE 3.2 Types of Field Characteristics to Be Noted During Preliminary Survey
Characteristic Types of observation
Slope Steep, gentle, flat, depressional a
Climate Arid, semihumid, humid
Wind direction Note predominant direction
Vegetation Luxurious, sparse, crops, grass, trees
Erosion Obvious evidence of erosion? Rills, gullies, etc.
Water Evidence of water movement into, over, or through area
Contamination Sources of contamination and continuing contamination
a An area or field in which water from surrounding areas collects during a rain event. Often this
area does not have an outlet.