Site reconnaissance

Selection criteria include toxicology, physical/chemical characteristics, and environmental fate information. These data are used to evaluate individual chemicals and estimate the degree of hazard associated with each site. For nonpoint source contamination from pesticide application, rating values include the amount of chemical applied. Final ranking is based on well logs, hydrogeology, and other data derived from on-site reconnaissance. 

Information that has been assembled on potential sources is analysed to identify the types and locations of possible contamination on the site. These are then mapped on to the physical description of the site and an initial identification is made of receptors that might be at risk. Consideration of the possible pathways between potential sources and receptors leads to a preliminary conceptual model for the site, in terms of candidate source-pathway-receptor linkages. The preliminary conceptual model is then tested and refined by observation, during a site reconnaissance. 

Before making a site reconnaissance, health and safety concerns need to be identified and addressed, by preparation of a plan for safe access and personal protection. Sites often present physical dangers, such as deep water and insecure banks, as well as possible exposure to hazardous chemicals. 

The objective of site reconnaissance is to explore the assumptions and conclusions of preliminary work that has been based on paper and other records. It should include land adjacent to the study site, where access is available. Firstly, the physical site description is confirmed as accurate. Then it can be extended by observations, such as the presence of unrecorded features, tanks, waste tips, surface water pounding and flow, vegetation and surface types and conditions. Secondly, the general presence and extent of sources can be confirmed. Thirdly, the presence of possible receptors can be confirmed or eliminated. Fourthly, pathways by which contamination can reach receptors, such as drains, streams or surface run-off are identified, although obviously sub-surface and airborne... 

Keen visual observation is the most important task during a site reconnaissance. Flowever, some basic in-held chemical testing equipment is useful. Commercial kits are available, mainly based on colorimetric reactions. These kits can be used to check for the presence or absence of common contaminants and to measure soil pH. However, the results obtained using these test kits should only be regarded as qualitative, not least because samples taken at the surface may not represent the bulk of materials on the site. For site reconnaissance, the use of in-held instrumental testing is not justihed. An exception is hand-held equipment to test for the presence of gaseous and volatile contamination—photo-ionisation and other detectors are useful where such contaminants are anticipated. While a Phase la study does not normally include intrusive investigation, a small number of samples may be taken for laboratory analysis. These can be important when waste and other potentially contaminated materials of unknown composition have been spread, deposited or are stored on the site. 

While potentially useful, a chronological list does not show task overlaps or interdependencies. For example, presumably Task C in Table 6.1, which calls for specification of soil borings, should be done after completion of Task A, which involves site reconnaissance and surveying. However, such interrelationships and overlaps are not shown in the simple chronological listing. Therefore, the elapsed time required to complete a project is not apparent. Nevertheless, sometimes a simple chronological list is all that is needed project scheduling. Frankly, sometimes not even this is done ... 

It is important to understand that any geophysical method which is successful at one site may or may not have the same success at another site. There are many variables associated with all geophysical techniques as presented in Table 6. Someone with the experience to know the limitations of each of the techniques should be consulted prior to developing a large geophysical reconnaissance program. 

Styker 8-Wheel Drive Armored Combat Vehicle. Defense Industries, Industry Projects. Available at http//www.army.mil/fact files site/stryker/. PM Recond, Sensor Suite for the XM1135 Nuclear Biological, Chemical Reconnaissance Vehicle (NBSRV) Stryker. Joint Program Executive Office, Chemical Biological Defense. Currently available at http //www.jpcocbd.osd.mil/ca nbcrv.htm. 

Generally, there is little data available on site conditions with the possible exceptions of seasonal average temperatures and river flow rates at USGS gaging stations (question 3). Thus, reconnaissance of study sites is often needed to assess exposure conditions and potential problems. A reconnaissance of study sites is also an important part of assessing the potential for vandalism and theft (question 6)... 

Midcontinent Herbicide Project. During 1989, a reconnaissance study of 147 streams in 10 midwestem states was conducted to determine the geographic and seasonal distribution of herbicides and their degradation products. Sites were selected to ensure geographic distribution and regional-scale interpretation of the data (Figure 30.4). The streams were sampled before application of herbicides, during the first major runoff period after application of herbicides,... 

Data from the reconnaissance survey indicated that bulk sediment concentrations of all COPCs were greater than apparent effect levels (AELs Environment Canada, 1995), indicating that contamination was widespread. A 20% reduction in toxicity test endpoint performance (relative to the negative control) was used to evaluate toxicity data. Such a reduction typically indicates real differences from the control. All samples demonstrated greater than a 20% reduction in bivalve normal development, however, similar reductions in amphipod survival were not observed, with the exception of one marginal hit for a single sample. As a result of the bivalve toxicity and elevated COPC concentrations observed in the reconnaissance survey, a full SQT was considered necessary for the site. 

Perform a reconnaissance site investigation using exploratory sampling. This may include nondestructive geophysical methods and field screening tests to refine the conceptual model... 

The term reconnaissance study relates to studies conducted for the first time, covering extended areas, to be completed fast and with minimal costs. The purpose of reconnaissance studies is to get a general picture of the water systems involved, to locate promising sites where large amounts of high-quality water can be found, to scan the area for features of special interest, to locate possible pollution processes, and to arrive at a conceptual model. The results of reconnaissance studies are the basis for the planning of... 

The affected area is surveyed by ground surveys, aerial reconnaissance, or aerial videos. Usually all three methods are combined. The team completes observations and measurements on a segment, produces a sketch map of the site, and fills in forms or checklists of observations on the site. During the field work, the SCAT team documents the distribution and character of stranded oil, the amount and location of subsurface oil, shoreline characteristics, and the character of the substrate. Ecological and human resources in the segment are documented. 

ACE forces should avoid the TIC release hazard area as long as possible. However, if the Commander determines that ACE forces are required to operate near or within the TIC hazard area, he shall direct the conduct of an NBC Survey to determine the extent of the hazard. The ground reconnaissance team shall use protective posture as above. Additionally, the commander shall direct aerial visual reconnaissance that may provide important information on the extent of a TIC release site. 

The elemental mercury vapor measurements were made in areas of Northern California known or suspected to be sites of mercury contamination. Early reports (2) cited only two small industries in California as having mercury-bearing eflfluents. Other sites were visited because of suspected emissions or were simply discovered during reconnaissance traversing. Thirteen specific sites of contamination were located (Figure 3). Of these, seven were clearly natural, and six were most likely cultural. Table I summarizes the data obtained at these sites. 

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