Ground Water Flow Modeling
Deep Alluvial Aquifer Basin in Southern California:
LWS has developed a surface water/ground water hydraulic interaction numerical model of a basin in Southern California using MODFLOW. The numerical model was developed after completing an extensive geologic model of the sediments in the basin. There is a concern related to contamination of municipal production wells by potentially responsible parties (PRPs) and, therefore, one of the objectives of the numerical model is to assess the fate and transport of constituents of concern in the aquifer from their source. Given that these are historical sources, they have been identified through the use of reverse particle tracking, using MODPATH.
Front Range Resources ASR Project:
LWS constructed both a steady-state and a transient numerical ground water model of the Lost Creek Basin on the Eastern Plains of Colorado, using MODFLOW. The purpose of the ground water model was to evaluate a proposed aquifer storage and recovery (ASR) project whereby water would be recharged into the Lost Creek alluvial aquifer using three separate rapid infiltration basins (RIBs) and the recharged water would subsequently be recovered through a series of 33 alluvial aquifer wells located down gradient of the RIBs. Parametric studies were conducted using the results from the MODFLOW model to demonstrate not only whether the water could be efficiently recovered by the down gradient wells but also whether the proposed operation prevents injury to other existing wells in the Basin.
Cherry Creek Alluvial Modeling Project:
There are a number of water supply entities in the Upper Cherry Creek Basin in the Denver metropolitan area (upstream of Cherry Creek Reservoir) that compete for relatively small renewable water supplies on Cherry Creek. These entities decided to evaluate regional cooperation possibilities through the use of a numerical surface water/ground water hydraulic interaction flow model, as well as a water rights assessment tool. LWS developed the numerical surface water/ground water model using MODFLOW. The model simulates the alluvial pumping points for each water supply entity, as well as the surface diversion for Rueter-Hess Reservoir, and discharge points associated with water reclamation facilities. The model has been used to evaluate multiple water use, and water sharing, scenarios to evaluate optimizing the beneficial use of limited Cherry Creek water supplies.
Timnath Landing Dewatering:
LWS developed a numerical ground water flow model using MODFLOW to evaluate the most efficient means to dewater the alluvial aquifer underlying the proposed residential and commercial development. The proposed dewatering methodology was the construction of three ponds that would drain adjacent alluvial aquifer water by gravity, with the ponds being maintained at constant elevations that would facilitate permanent dewatering. The results of the LWS MODFLOW model have been used by the civil engineering firm that is preparing the development plan, as it demonstrates the means to dewater the site to allow foundation and basement construction.
Energy Fuels Sheep Mountain Project:
As part of the permitting process, the proposed open pit uranium mine in Fremont County, Wyoming had to demonstrate that it would not impact flows on Crooks Creek, a tributary to the Sweetwater River, which is then a tributary to the North Platte River. LWS developed a MODFLOW model of the pit to assess changes in ground water flow patterns due to dewatering and subsequent mining of the open pit, which was to be completed in phases. The results of the LWS modeling were used by Energy Fuels to obtain a mine permit from the Division of Environmental Quality.
Sustainable Water Resources Water Supply Development Project:
LWS has use the existing Rio Grande Decision Support Systems (RGDSS) numerical ground water flow model, developed in MODFLOW, to evaluate both the ability to develop a 35,000 ac-ft/yr water supply project as well as assess potential injury to other water rights within the basin. Given the need for an augmentation plan to offset depletions associated with the proposed water supply project, multiple analyses were completed to assess the most efficient means to develop an augmentation water supply.
Spear T Ranch:
The Ranch is located in Morrill County, Nebraska and it has two surface water permits for diversions from Pumpkin Creek. However, over the years ground water use has increased upgradient from the Ranch such that surface flows have continued to diminish due to the hydraulic interaction between the local ground water table and the surface flows and Pumpkin Creek. LWS was requested to develop a numerical surface water/ground water model of Pumpkin Creek and the associated alluvial ground water system, using MODFLOW, to assess the magnitude of injury to the Spear T Ranch water rights. This case was pursued in Nebraska District Court (CI03-16).
San Luis Gold Project:
As part of the permitting process related to the Tailings Storage Facility (TSF) LWS personnel used a MODFLOW model with MT3DMS to assess potential water quality issues should any water escape the TSF. The model was designed to specifically evaluate the attenuation of both flow and constituents of concern downstream as any theoretical release of water would exit an unnamed tributary of Culebra Creek where the TSF was located and flow into the Valley Fill aquifer. The Town of San Luis has two municipal production wells completed in the Valley Fill aquifer a few miles down gradient of where any theoretical release of water would enter the Valley Fill aquifer from the TSF. The model demonstrated that there would be no impact to the Town’s municipal production wells.
CF Industries Manufacturing and Distribution Facilities:
LWS personnel have prepared a number of ground water flow models related to assessing the fate and transport of fertilizer materials released to local ground water aquifers through operations and, in some cases, spills. Initial ground water investigations, including the installation of monitoring wells and collection of water quality data, have been conducted to develop the necessary information to then prepare ground water models to assess not only the fate and transport of constituents of concern (COCs) but also to identify issues related to regulatory agencies, e.g., containment of COCs within the property, attenuation of COC concentrations, and development of remediation actions. LWS personnel have assisted at sites in Tennessee, New York, Indiana, Illinois, Missouri, and Nebraska.