QES has used a range of analytical and numerical models to simulate the fate and transport of contaminants in vadose zone soil and in groundwater, for negotiating site-specific cleanup goals, aiding the design and enhancement of groundwater pump and treat systems, and managing groundwater basin operation, including for drought protection.
Modelling is only worth what its calibration is worth, so we benchmark independently where the stakes justify it.
For several sites including a former Unocal chemical storage terminal and Air Force Plant 42, QES used fate and transport modelling to develop soil screening and cleanup values higher than the conservative levels in RWQCB Los Angeles Region guidance, without posing a risk to groundwater. The agencies agreed to the approach, which used the VLEACH model, at substantial cost saving for the clients.
As senior hydrogeologist on behalf of US EPA Region IX, QES reviewed input data and calibration results of a model prepared by the steering committee’s consultant and prepared an independent model using CFEST to benchmark the results. The benchmarked model let US EPA and the steering committee work closely together in refining alternative remediation strategies.
As lead hydrogeologist, QES refined the basin-wide San Gabriel numerical CFEST model to assess groundwater flow and solute transport in the South El Monte operable unit and Whittier Narrows, and designed an extraction well network to intercept contamination migrating toward the Central Basin. Wells were installed using model-derived location, production capacity and construction specifications.
QES critiqued the production performance of a 2,000 gallon per minute extraction well remediation system and evaluated its effectiveness in containing trichloroethylene and tetrachloroethylene contamination. The evaluation included development of a hydrologic budget, design of aquifer testing, and capture zone and drawdown modelling, together with the effect of lower water levels on extraction well capacity.
Using MODFLOW, QES developed a three-dimensional flow model to evaluate remedial alternatives, interpreting lithologic, geophysical, piezometric pressure and groundwater chemistry data from hundreds of wells. Particle tracking was performed to evaluate vertical flow rates and to develop shallow extraction scenarios balanced with deep groundwater production.
As task manager of hydrogeology, QES developed conceptual basin operational schemes and a basin-wide groundwater flow model using CFEST to simulate and compare artificial recharge and recovery scenarios for drought protection. Geologic properties, historical hydrogeologic patterns and well capacity information were assimilated into a three-dimensional finite element model by interfacing GIS data.
Call or write and you will speak with the people who will do the work. We will tell you plainly what a defensible path forward looks like.