Problem Set 4 Remediation of a Leaking Landfill
Problem Set # 4 Remediation of a Leaking Landfill Site river • 3 layers • MODFLOW’s River Package • transient flow • remediation design municipal water supply well In layer 3
Objectives 1. Determine the impacts of contamination from the leaking landfill (shown in light blue) at the river and the municipal well. 2. Design a strategy to mitigate the effects of the contamination.
Review from Geology 724 Head Dependent Boundaries in MODFLOW Q = C h • • River Package Drain Package General Head Boundary (GHB) Package ET Package
River Package h. R = head in the river hijk is the head at the node below the river Q = C (h. R – hijk) where C = (Kv/m) L w
River Package h. R = head in the river Typically the width of the river is smaller than the width of the grid cell. hijk is the head at the node below the river Q = C (h. R – hijk) where C = (Kv/m) L w Length of the river within each cell also may vary. Areal view of the river
Q = C (h. R – hijk) hijk m RBOT w Gaining River Cell
Q = C (h. R – hijk) RBOT Losing River Cell
Q = C (h. R – hijk) RBOT Losing River Cell
Q = C (h. R – RBOT) RBOT Percolating River Cell
Definitions Riverbed Conductance = (Kv/m) w. L Leakance = Kv/m Resistance = m/Kv Kv = vertical hydraulic conductivity of riverbed sediments m = thickness of riverbed sediments w = width of the river L = length of the river within the cell
Resistance River with sandy bottom = 1 day Small stream with silty bottom = 1 - 10 days Stream/lake in till = 100 days
In PS 4, we consider the alternative to “do nothing” as a remediation strategy. This is called “natural attenuation”. Recommended groundwater monitoring network for demonstrating natural attenuation. Source: EPA circular
Initial conditions In Part 3 A of PS 4, We will use I. C. of the type shown in Figure a. This is done in the initial concentrations window of GWV. Zheng & Bennett
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