| Popis: |
A systematic approach is presented for the design of a multiphase vadose zone monitoring system recognizing that, as in groundwater monitoring system design, complete subsurface coverage is not practical. The approach includes identification and prioritization of vulnerable areas, selection of cost-effective indirect monitoring methods which will provide early warning of contaminant migration, selection of direct monitoring methods for diagnostic confirmation, identification of background monitoring locations, and identification of an appropriate temporal monitoring plan. An example of a monitoring system designed for a solid waste landfill is presented and utilized to illustrate the approach and provide details of system implementation. The example design described incorporates the use of neutron moisture probes deployed in horizontal access tubes beneath the leachate recovery collection system of the landfill. Early warning of gaseous phase contaminant migration is monitored utilizing whole-air active soil gas sampling points deployed in gravel-filled trenches beneath the subgrade. Diagnostic confirmation of contaminant migration is provided utilizing pore-liquid samplers and conservative tracers. A discussion of background monitoring point location is also presented. |
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