- Drains and slow-moving streams, since contamination and dilution from other sources are minimized.
- Stagnant pools of water if the pools of water are part of chemical waste areas, such as a landfill or chemical disposal area. Chemicals may percolate into stagnant pools or sumps close to the site.
NOTE
If an oil film, globules of organic materials, or an unnatural appearing powder-like material is visible on the water's surface, collect a surface sample of the material. If not, collect the sample from near the bottom of the water source (stream, lake, pond, water container). The upper layers of water may have lesser amounts of contaminants, due to higher temperatures that promote decomposition. Since most chemicals of interest are more dense than water, contaminants usually sink to the bottom of the water source.
h. Collect the sample without the Sep-PakTM by immersing a capped or stoppered container to the desired depth, removing the cap or stopper, letting the container fill, and then capping the container. An alternate method for deeper water is to use a plastic, pump-operated siphon to pump water from a specific depth.
i. The best time to collect a sample of water from a location is when intelligence or local reports indicate that a process of possible interest is ongoing. In the absence of reliable reporting, this may be indicated by increased activity, higher than normal amounts of security, or increased flow from facility chimneys or water discharge pipes. In field areas where a toxic agent has been sprayed or disseminated over a land area, the best time to collect water samples is just after the start of a rainstorm when runoff is beginning. Natural surface drainage will concentrate any remnants of toxic compounds in depressions, streams, or ditches.
B-10. Collection of Soil Samples
Soil is a suitable medium to collect as samples for toxic organic compounds. A critical point, however, is that the precise site of the agent deposition must be sampled for best results. Contamination may be recognized by discoloration or apparent deposition of material on the soil's surface. If discoloration or deposits of material are evident, only collect the discolored soil or deposited materials, if possible. Dead, malformed, and wilted foliage is an indicator of contamination. Soil samples should be collected from open areas, along the drip line tents, stationary equipment, bottom of ditches and terrain depressions.
a. Collect the soil samples by using a knife, spoon, spatula, or similar item to scrape a square of topsoil (2×5×1 centimeters) from areas that appear to have been contaminated in to a collection container. If chunks or clods of earth are collected, select those that are no larger than 10×5×1 centimeters (see [Table B-4]). Also, collect a control sample of soil of the same type and texture from a nearby uncontaminated area.
b. Use a glass bottle, jar, or TeflonTM jar as the container when available. When these containers are not available, Mylar bags may be used. When using a glass bottle, jar, or TeflonTM jar, seal the cap with either pressure-sensitive or TeflonTM tape, and mark for identification. When using Mylar bags, place each sample in a separate bag, push excess air out, and seal by folding the open end over two to three times and wrapping the bag with tape. Insert the first bag into a second bag, seal, tape, and mark for identification. If possible, place the samples in a piglette.