Simulation of zones of contribution to wells at site GM–38, Naval Weapons Industrial Reserve Plant, Bethpage, New York

• DOI: 10.3133/sir20145036
• Publication Date: 2014-03-29T00:41:35Z
• Authors: Paul Misut
• Keywords: Particle (ecology); Water well; Aquifer properties; Tracking (education)

A three-dimensional groundwater-flow model is coupled with the particle-tracking program MODPATH to delineate zones of contribution wells pumping from Magothy aquifer and supplying water a chlorinated volatile organic compound removal plant at site GM–38, Naval Weapons Industrial Reserve Plant, Bethpage, New York. By use driller’s logs, transitional probability approach generated three alternative realizations heterogeneity within assess uncertainty in representation. Finer-grained sediments low hydraulic conductivity were realized as laterally discontinuous, thickening towards south, comprising about 17 percent total volume. Particle-tracking evaluations steady state present conditions used develop remedial wells. Because high rates advection coarse-grained sediments, transport by dispersion (or) diffusion was assumed be negligible. Resulting existing are complex shapes, influenced each realization other nearby hydrologic stresses. The two particle tracking techniques helped identify Backtracking observations points intersection backward-tracked particles shells GM–38 Hot Spot, defined surfaces equal concentration, identified source Spot simulated Forward-tracking fate including well capture discharge constant head drain boundaries. percentage particles, started that sourced varied 72.0 98.2, depending on delineation (present A). forward-tracked captured 81.1 94.6, used, remainder primarily Bethpage Water District Plant 4 production Less than 1 ultimately differences between forward- ranges due some not being wells, intersecting specific regions Spot. During 2013, an test detailed time series corresponding water-level responses recorded numerous locations. These data verify demonstrate sensitivity results transient-state changes.