Groundwater and Surface Water Modeling
Fate & Transport
Deep Alluvial Aquifer Basin, Southern California:
A very large, deep alluvial groundwater basin in southern California is used extensively for municipal water supplies, including the use of native groundwater as well as non-native water that is brought into the basin and recharged. Industrial activities in the basin have caused significant water quality issues which is necessitating the need for a new water treatment facility. The client wants to identify potentially responsible parties (PRPs) to recoup some of the cost of the new treatment plant. LWS has developed a steady-state and transient surface water/ground water hydraulic interaction numerical flow model of the 175 mi2 basin in Southern California using MODFLOW. An initial 3-dimensional geologic model of the sediments in the basin was developed with RockWare to assist with the discretization and layering of the groundwater flow model. Once the groundwater flow model was constructed and calibrated, using over 7,00 calibration points, the ultimate objective of the numerical model was 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.
Gasoline Tank Spill, Eastern Colorado:
LWS was requested to model the fate and transport of a gasoline spill of 4,000 gallons from an above-ground tank. Geologic logs and water quality data were provided to set up the model. LWS worked with RockWare to develop 3-dimensional images of the geologic and hydrogeologic conditions at the site, plus the magnitude and direction of the plume in the local groundwater table. As a result of the development of the 3-dimensional model the client was able to better understand the fate of the plume due to areas of low permeability between the overlying colluvial material and the underlying bedrock versus areas where the colluvial materials were underlain by sandstones that promoted more vertical movement of the plume. The client is providing the LWS 3-dimensional model to prospective remediation contractors to more efficiently deal with cleanup of the plume.
San Luis Gold Project, Southern Colorado:
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 downgradient 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 groundwater flow models related to assessing the fate and transport of fertilizer materials released to local groundwater aquifers through operations and, in some cases, spills. Initial groundwater investigations, including the installation of monitoring wells and collection of water quality data, have been conducted to develop the necessary information to then prepare groundwater 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.
Industrial Site In The Central Valley, California:
Surface water transport modeling was necessary to assess the ability of an ephemeral stream to transport contaminants across an industrial site. Regional watershed characteristics, in conjunction with localized climatic data and surface channel properties, were used to estimate flow runoff from various storm events which were then modeled relative to flow duration across the site. These data were used in a civil lawsuit to demonstrate that contaminants generated on the eastern side of the property have historically been transported across the property in the storm water flow events.