Continuous Plume Monitoring Using Wireless Sensors: Proof of Concept in Intermediate Scale Tank

The current practice for monitoring of subsurface plumes involves the collection of water samples from sparsely distributed monitoring wells and laboratory analysis to determine chemical concentrations. In most field situations, cost and time constraints limit the number of samples that could be collected and analyzed for continuous monitoring of large, transient plumes. With the development of wireless sensor networks WSNs , that allow sensors to be incorporated into a distributed wireless communication and processing system, the potential exists to develop new, efficient, economical, large-scale subsurface data collection and monitoring methods. This paper presents a proof-of-concept study conducted in a two-dimensional synthetic aquifer constructed in an intermediate scale test tank to demonstrate the feasibility of using WSN for subsurface plume monitoring. The tank was packed to represent a heterogeneous aquifer, and a sodium bromide tracer was used to create a plume. A set of ten wireless sensor nodes motes equipped with conductivity probes to measure electrical conductivity formed the network. Software for automated data acquisition was developed and tested. Results of two experiments conducted using this test system are presented. The lessons learned from the first experiment were used to make modifications to the way the sensors were placed, how they were calibrated and how the sensors were interfaced with the data acquisition system. The findings are used to identify future research directions and issues that need to be addressed before field implementations of a WSN based data collection system for plume monitoring. DOI: 10.1061/ ASCE EE.1943-7870.0000045 CE Database subject headings: Groundwater quality; Groundwater pollution; Monitoring; Sampling; Probe instruments; Plumes. Introduction and Background Maintaining a reliable supply of potable water with acceptable quality is of primary interest to water managers and planners. Groundwater monitoring is an important component in the design of strategies for site remediation and subsequent performance assessment. Data gathered during site characterization is used to build and calibrate groundwater flow and transport models to predict plume behavior in the subsurface. Subsurface characterization presents numerous challenges. Heterogeneity in the subsurface resulting from the spatial variGraduate Student, Center for Experimental Study of Subsurface Environmental Processes CESEP , Div. of Environmental Science and Engineering, Colorado School of Mines, Golden, CO 80401; presently, Water Resources Engineer, CH2M HILL, Sacramento, CA 95814 corresponding author . E-mail: [email protected] Professor, Center for Experimental Study of Subsurface Environmental Processes CESEP , Div. of Environmental Science and Engineering, Colorado School of Mines, Golden, CO 80401. E-mail: [email protected] Undergraduate Student, Dept. of Mathematical and Computer Sciences, Colorado School of Mines, Golden, CO 80401. E-mail: ploden@ mines.edu Assistant Professor, Dept. of Mathematical and Computer Sciences, Colorado School of Mines, Golden, CO 80401. E-mail: [email protected] Professor, Dept. of Electrical and Computer Engineering, Colorado State Univ., Fort Collins, CO 80523. E-mail: Anura.Jayasumana@ Colostate.edu Note. This manuscript was submitted on April 25, 2008; approved on January 12, 2009; published online on August 14, 2009. Discussion period open until February 1, 2010; separate discussions must be submitted for individual papers. This paper is part of the Journal of Environmental Engineering, Vol. 135, No. 9, September 1, 2009. ©ASCE, ISSN 07339372/2009/9-831–838/$25.00.