VECTOR Systems for Site Characterization

Few tools in the expedited site characterization kit are as potentially powerful as the ability to quickly, continuously, and unambiguously track subsurface contami-nant movement over time.

The ideal expedited site characterization is built around the premise that a VECTOR system has been installed and is continuously operated in order to determine the direction and magnitude of background and induced ground water flow vectors during all phases of the remediation process at the site. The site is underlain by the ususal variety of unconsolidated, permeable sediments with a reasonably accessible ground water table.

Although the expedited process was designed to incorporate sampling flexibility and make the most of extensive low-quality chemical sampling during the characterization, remediation, and close-out processes at a site, the same principles can be applied with respect to "sampling" the ground water flow vector. VECTOR technology, however, provides a nearly infinite number of "inexpensive samples" each of which are high quality, quantitative samples not prone to the uncertainties associated with comparing flow models to drawdowns predicted by a given analytical solution.

Hydraulic Property Characterization:

Collect multiple (qualitative) chemistry samples and determine initial approximate contaminant location (i.e. push probe and organic vapor monitor) Use all known site parameters to establish optimum VECTOR placement that will maximize future sampling locations, pump test location, and treatment system evaluation and positioning: You may find, based on these VECTOR results, that you must put a remediation system out of the range of this sensors' capacities to effectively monitor the performance of that system. In that case, a second sensor may be required whose position is dictated by the first sensors results. The second sensor will be used to monitor the performance of that system over time and track contaminant movement over time. It will be also be used in conjunction with the first probe to evaluate how ground water movement under the entire site has changed over the course of the project. Install VECTOR system(s) and establish ground water flow directions and magnitudes and observe periodic influences that will affect treatment capture zones (i.e. nearby pumping schedules, seasonal effects, surface water body fluctuations, etc.); collect lithology and chemistry samples Select optimum locations for piezometric analysis: Establishing a hydraulic conductivity will require at least one head measurement in addition to that within the VECTOR location that lies in line with the ground water direction Establish hydraulic conductivities and anisotropies: Use multiple head measurements from a suite of piezometers downstream and upstream of the VECTOR to obtain a range of conductivity values . Obtaining core samples form those locations may help establish the correlation between facies and conductivity.

Contaminant Characterization:

• Constrain source age, location, and likely contaminant distribution based on VECTOR resultsPrecisely establish optimum (qualitative) chemistry sampling locations for delineating plume extent.
• Conduct chemistry sampling using qualitative methods. Refine calculation of age and contaminant areal extent, if necessary.
• Establish optimum locations for quantitative chemical analysis of plume.
• Obtain quantitative chemistry results and further constrain contaminant degradation rates and, with multiple-depth VECTOR results, the 3-D positioning of density-dependent species within the aquifer.
• Use VECTOR ground water velocity and direction measurements and qualitatively calculate the future position of specific chemistries over time using a simple spreadsheet program.

Select remediation or containment technology:

Select intrinsic bioremediation or monitored natural attenuation: Use VECTOR locations with screened interval as both chemistry and vector sampling point. No one will argue with the statement, "Ground water sampled at this location and depth came from there, and is heading over there at this velocity. Furthermore, by the time it gets (there), contaminants will have (or not) degraded into a harmless substance." In addition, VECTORs will allow you to select the best sampling points to monitor the progress of natural attenuation.Select some manner of pump & treat system (i.e. air sparging or circulation well system): Using existing VECTORs at your site and a cleverly designed limited aquifer test you can establish modeling constraints for determining zones of influence for your pump and treat system. Customize the system by applying flow vector corrections to account for anomalous influences to the circulation cell. An additional VECTOR in a key location will provide unambiguous (physical) performance assessment of the remediation system. A screened VECTOR will also act as a chemical sampling point. Select enhanced bioremediation: Use VECTOR results to determine injection effectiveness by quantitatively observing induced changes to the flow vector. Monitor pore space reduction (from biofouling) by directly observing directional changes and in-situ flow rate reductions. Use head measurements and VECTOR data to readily calculate temporal changes in hydraulic conductivities. Monitor corrective actions in the same way. Select reactive barrier technology: Use a suite of VECTORs to resolve flow patterns within the barrier area. Monitor barrier permeability over time by watching flow vector changes. Use with a linear array of piezometers perpendicular to barrier to monitor changes in barrier hydraulic conductivity over time. Select inert barrier technology: Monitor ground water flow patterns around contained area or impermeable ground water diversions. Improve quantification of subsurface stresses on system due to extreme climatic events.

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