title: Measurement of LNAPL flow using single-well tracer dilution techniques.
abstract: This paper describes the use of single-well tracer dilution techniques to resolve the rate of light nonaqueous phase liquid (LNAPL) flow through wells and the adjacent geologic formation. Laboratory studies are presented in which a fluorescing tracer is added to LNAPL in wells. An in-well mixer keeps the tracer well mixed in the LNAPL. Tracer concentrations in LNAPL are measured through time using a fiber optic cable and a spectrometer. Results indicate that the rate of tracer depletion is proportional to the rate of LNAPL flow through the well and the adjacent formation. Tracer dilution methods are demonstrated for vertically averaged LNAPL Darcy velocities of 0.00048 to 0.11 m/d and LNAPL thicknesses of 9 to 24 cm. Over the range of conditions studied, results agree closely with steady-state LNAPL flow rates imposed by pumping. A key parameter for estimating LNAPL flow rates in the formation is the flow convergence factor alpha. Measured convergence factors for 0.030-inch wire wrap, 0.030-inch-slotted polyvinyl chloride (PVC), and 0.010-inch-slotted PVC are 1.7, 0.91, and 0.79, respectively. In addition, methods for using tracer dilution data to determine formation transmissivity to LNAPL are presented. Results suggest that single-well tracer dilution techniques are a viable approach for measuring in situ LNAPL flow and formation transmissivity to LNAPL.
authors.affiliation: Department of Civil and Environmental Engineering, Colorado State University, 1320 Campus Delivery, Fort Collins, CO 08526-1320, USA. tsale@engr.colostate.edu
authors.forename: Tom
authors.initials: T
authors.lastname: Sale
authors.forename: Geoffrey Ryan
authors.initials: GR
authors.lastname: Taylor
authors.forename: Gabriel
authors.initials: G
authors.lastname: Iltis
authors.forename: Mark
authors.initials: M
authors.lastname: Lyverse
mesh_terms: D004784:Environmental Monitoring; D005456:Fluorescent Dyes; D014872:Water Movements; D014874:Water Pollutants, Chemical; D014881:Water Supply
chemical_list: D005456:Fluorescent Dyes; D014874:Water Pollutants, Chemical