Monitoring well networks

Detailed sampling can include, but is not limited to, the installation of monitoring well networks. After the wells have been installed, aquifer tests are typically performed. Once the aquifer tests are performed and the aquifer characteristics are determined, time series sampling for a given contaminant, or a surrogate, is undertaken. The combined results of these efforts provide the basis for development of a treatment strategy. Modeling can be used as part of this effort to help determine the best technical and most cost-effective techniques to be used at a site. 

FIGURE 4.12 Gas chromatograph results for crude and refined LNAPL samples retrieved from a monitoring well network within a refinery tank farm. 

If properly designed, monitor-well networks can also aid in determining the effectiveness of ground-water protection measures. The ultimate effectiveness of... 

The objectives of installing a monitor-well network must be clearly defined before choosing the specific locations, numbers, and dimensions of the wells. The preferred design depends on the proposed uses of the monitor-well network, the dimensions and chemical characteristics of the contaminant plume, and the site hydrogeology. 

Often, the preliminary characterization wells can be incorporated in the permanent monitor-well network. However, in cases where the initial presumed ground-water flow direction turns out to be incorrect, due to the influences of nearby pumping wells, tidal fluctuations, ground-water mounds, or other hydraulic phenomena, additional regulatory wells may be required. 

After consideration of all the technical and economic aspects of expanding the existing system versus installing a completely new system, the Honeywell system was replaced by a TRK system of ouch greater speed and capacity (see Figure S). Also added waa a SCADA console at each GC control roam to allow the CC operators to monitor well pad operationa and if necessary to take control action. Another addition was a revised microwave communications network thet includes the well peds. The system has an inner dual redundant loop for the most critical communications path between GCs, HOC, and CPS, with redundant radial shots from each GC to its associated well pads. 

Although spectroradiometers appear to have many advantages, their use in comparison to simpler broadband detectors in dense monitoring UV networks is not necessarily the best choice. First, because in general are unable to produce continuous measurements, since even the faster instruments would need a few minutes to complete a typical UV scan, while broadband detectors can be sampled easily once every a few seconds. The second reason is their purchase and operational cost, which can be 5-10 times higher than for a typical broadband detector. Finally, due to their extreme sensitivity their operation and maintenance requires special experimental support and experienced, well-trained personnel. Despite these disadvantages, their superior quality imposes the existence of at least on spectroradiometer to support each network and provide proper absolute calibration of the broadband detectors. 

The NMED approved an operation and maintenance plan in November 1995, and DBS A started operation of the SVE system in early December 1995. On April 29, 1996, monitor well MW-9 was incorporated into the SVE network to provide further control of the groundwater plume (Fig. 6). 

Improved monitoring techniques that are cheaper and more robust with respect to the environment will allow networks of monitoring wells to be placed between sources of radionuclides such as repositories or disposal sites and potentially exposed populations. This will improve the acceptance of MNA. With improved modeling capabilities and better understanding of radionuclide interactions, public confidence in predictions of the risk associated with radioactive waste management will increase. 

In many situations, however, sufficient information for adequate network design may simply not be available initially, and periodic reinterpretation of groundwater flow and hydrogeochemical regimes will be required to guide network improvement and consolidation. Figure 5.1.7 shows some examples of commonly found situations where water quality monitoring wells do not always fulfil their role. 

Landfill design addresses the need to protect both surface and ground water. Waste is deposited in the unweathered clay and then capped with compacted elay. An extension of this cap into the unweathered clay makes eonstruction of eut-off walls (shown in Fig. 21.2) unnecessary. A network of multi-level monitoring wells makes possible the sampling of groimd waters—a check to ensure that wastes are being contained. Leachate formed by rainfall and/or snow melt is removed and treated by high-temperature ineineration. 

Activity levels for selected radionuclides In groundwater measured during 1981 (DOE-RL 1990 and DOE-RL 1991) show the contamination patterns that had developed by that time In the vicinity of the 116-N-l crib and trench (Table 5-10). The tritium data Indicate high levels of contamination In the entire area covered by the then-existing monitoring network. These data also demonstrate that the Impact of the 116-N-l crib and trench extended In all directions. The full extent of Influence of the 116-N-l facility at this time, particularly In the southern and eastern directions, cannot be determined because the network of groundwater monitoring wells Is limited. 

Assuming limited resomces, the wildlife component of a mercmy monitoring network would likely have to rely on analyses of tissue from a small subset of candidate species identified earlier in this chapter, so identification of key species that both meet the criteria as good current indicators (see Section 5.5) as well as... 

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