T85 Advances in Characterization of Groundwater Flow Processes

Monday, 10 October 2011
8:00 AM - 12:00 PM
Room M101AB

THE COMBINATION OF DIRECT PUSH INJECTION LOGGING AND HEAT TRACER TEST FOR THE INVESTIGATION OF CONNECTIVITY IN HETEROGENEOUS AQUIFERS

Paper number: T85-7
Program: Technical Sessions
Time: 9:25 AM – 9:45 AM

Authors

Abstract

Transport and mixing processes in aquifers are strongly influenced by their heterogeneity, namely the spatial variability of the hydraulic conductivity K. Understanding and quantification of these processes was and is the object of intensive research, which has been carried out frequently by stochastic modeling. In latter, K is modeled as random to account for its seemingly erratic spatial distribution and for scarcity of field data. It is common to characterize conductivity Y = lnK by a few statistical moments: mean, variance, horizontal and vertical correlations scales. But observations during tracer tests at well investigated tests site like the MAcro Dispersion Experiment (MADE) site and Lauswiesen showed effects which cannot be described with these statistical moments alone. The observed effects are tracer breakthroughs limited to vertical small zones. A possible explanation for these observations is a connectivity of hydraulic conductive zones. Such connectivity would have a great importance for the transport of contaminants as well as for the efficiency of remediation measures.

A promising tool for the characterization of the heterogeneity of aquifers is the direct push injection logger DPIL. The DPIL can be used to rapidly characterize relative variations in K at a vertical resolution of decimeters. If these DPIL profiles show a high variability in K over short distances then it is necessary to evaluate the lateral connectivity of high conductive zones. For this purpose a heat tracer test can be used. In contrast with salt and colour tracers, heat tracer tests can be carried out with cost efficiency over longer periods by injecting water of significantly different temperature than that of the groundwater. Furthermore, the spreading of the heat tracer can be monitored relatively easy by an adaptive placement of direct push wells and temperature sensors. The feasibility of the heat tracer test concept was tested in May 2010 at the Lauswiesen site. 165 m3 of water with a temperature of approx. 20°C were injected over a period of 43 hours followed by the injection of 116 m3 water with groundwater temperature. The process was observed with temperature measurements at selected points. The results clearly demonstrate the suitability of the heat tracer test for the investigation of connectivity in heterogeneous aquifers.