Number Changes

Sometimes another sample number replaces the number given in the field when the sample is processed for storage, shipping, or almost always, in the commercial laboratory. Renumbering opens up the whole process to error and is not recommended. If, however, it cannot be avoided it is strongly recommended that the original sample number be kept on or with the sample even after a new number is given. In all these cases a cross-reference list relating the two different numbers must be readily available and a copy must be kept with the samples at all times.

Sample numbering and recording process mistakes will be made during the sampling.

Numbers will not be written legibly, or they will get erased or smeared and become unreadable. To the extent possible every effort should be made to eliminate or limit these types of errors. Using nonsmearing pens, using paper that can be written on when wet, and putting the sample numbers on the sample containers in several places are all good approaches to limiting these problems. It is far less expensive and less time consuming to spend extra time on sample labeling than on taking another sample or assuming a sample’s identity [1].

One way to help minimize sample labeling errors is bar coding. There are software programs, computers, and printers that can print bar codes on various media, including labels of different sizes. Not only will bar codes help prevent mistakes in labeling, they will also speed up sample handling, especially in maintaining the chain of custody. If bar codes are used, a bar code for the sample needs to be in the project notebook in which the sample is described (see Chapter 8 for more information on bar coding) [2].

A GPS unit will often be used in sampling a field. This will give the location of a sample site and may even record a sample number to be associated with that site. Even in this case it is important to have a project notebook to record these and other data about the sample when the sample is taken. At the time of sampling this will seem to be unnecessary repetition, while a week later it will be found to be an essential, time-saving step.

3.4. MAPS

Maps are the heart of the sampling process and are essential for any successful sampling program. There are many types of maps available; for example, surface, topographic, and three-dimensional. Especially valuable are aerial photographs of the specific area to be sampled. If they are not available there are both firms and computer programs that can be called upon to produce the needed maps, aerial photographs, or both. Before doing anything at a contaminated field it is essential to have several maps of different scales of the area. One map should show the contaminated field and the surrounding areas. Several maps showing details of the field itself will also be needed.

I would not, however, recommend producing a large number of very detailed and expensive maps. What is needed are many simple maps of the area suitable for recording data on. Each time some activity takes place on the field it needs to be recorded not only in the project notebook but also on a field map, so that the location is precisely known.

The place in which the activity takes place must be on the map, along with date and time and the name of the person leading the activity. It can be separate from the project notebook during the activity, but either the original or a copy must be permanently attached to the project notebook in the appropriate location when the activity is completed. Each map should have its own entry in the table of contents. Alternately, a separate page listing just the location of maps can be in the table of contents. Data recorded on a map can subsequently be entered into a computer either manually or by scanning the information. Once in a digital form GIS can be used to display and follow sampling and other field activity.

An example of a simple map of a field to be sampled is shown in Figure 3.2, and includes a symbol showing which direction is north (which must always be present). The map must also show some distinct characteristic that allows the reader to specifically locate it. In Figure 3.2 the roads specifically locate the position of the fields of interest, provided, of course, that we know the state in which these roads are located. Additional locators such as longitude and latitude can be included on the map and are recommended.

These are useful especially when using GPS for locating the

FIGURE 3.2 Simple map of three fields (12a, 12b, and 12c) to be sampled.

fields and sample sites and can be entered from the GPS unit during sampling.

A cross-sectional map of soil depths and the depths of various layers (see Figure 3.3) is also valuable to have. Such a map is helpful in developing

FIGURE 3.3 Cross-sectional map of the profile of regolith in field 12a. Units at the bottom of the map are meters.

both the transect and detailed sampling plan. It can help in determining where a contaminant may have moved and thus where more samples need to be taken. Such a map may be developed from data in the soil survey of the field, which is discussed below.

Another useful type of map is the topographical or topo map of the area. An example of a topo map is given in Figure 3.4. The topo map has lines of equal altitude drawn on it.

They thus show slopes, escarpments, and other important features of a landscape. They also show which direction water will flow in and where erosion is most likely. In many cases topological characteristics will need to be taken into consideration when sampling.

For many areas the United States Geological Survey and other government entities have digital orthophoto quarter quadrangles (DOQQ) photographs or maps of areas of interest. These are digital photographs that are placed on the Universal Transverse Mercator Projection (UTM) on the North American Datum (NAD-27). There is also a NAD-83, and others, that can be used. Digital orthophoto quarter quadrangles have a ground resolution of 1 meter and cover an area of 3.75 minutes latitude by 3.75 minutes longitude. It is useful to note that both UTM and NAD-27 are used by GPS units, and since they are digital, they are compatible with

FIGURE 3.4 A contour map of fields 12a, 12b, and 12c showing contour lines which give the elevation of different parts of the field.

FIGURE 3.5 An example of a portion of a DOQQ map from Clinton County, Ohio, showing roads, buildings, and fields.

GIS systems An example of a portion of a DOQQ map is shown in Figure 3.5 [3, 4].

The DOQQ images produced have both the look of a photograph and the geometric qualities of a map. They are a true representation of the Earth’s surface. Because of this

both distances and areas can be determined directly from the DOQQ. Software for manipulating these maps (e.g., MrSID GeoViewer) is available—some of it free—on the Internet [5].

Digital orthophoto quarter quadrangles are very useful in sampling, and are available at a minimal cost. Unfortunately they are often hard to find, even on the Internet. One relatively easy place to find information about DOQQs is the local GIS office. Many county courthouses will have a GIS office, and personnel doing GIS for the county will be very helpful in obtaining needed DOQQs. If no county GIS office is available, try the state GIS office or officer.

When sampling, site positions can be determined using a GPS unit. These site positions are saved and later loaded into a GIS system. A DOQQ is then also loaded into the GIS system. The system is then used to generate a map that shows the true location of sample sites in the field. This map and a GPS unit can be used to locate the sampling sites at any time in the future. It is also possible to enter other sampling data, such as sample depth, altitude, vegetation cover, and other information deemed necessary into the GIS system. These data can also be displayed on the thematic map, and all the data can be interrelated as needed or desired.