RFETS, Golden CO – Integrated Hydro Systems, LLC

Integrated Hydro Systems, LLC

Specialization Areas - Numerical Modeling

Rocky Flats Environmental Technology Site - U.S.DOE

The U.S. Department of Energy (DOE) operated a nuclear weapons parts manufacturing facility at the Rocky Flats Environmental Technology Site (RFETS) in Golden, Colorado, for years.

Since 2000, IHS has provided substantial hydrologic and contaminant fate/transport modeling support to convert the DOE facility to a National Wildlife Refuge in 2005. We continue to support post-closure CERCLA evaluations.

The hydrologic conditions at RFETS are complex and complicated by the industrial surface and subsurface features of the site. To study effects of these changes on the site hydrology and water balance and to evaluate possible future water management scenarios, Integrated Hydro Systems, LLC developed a fully integrated hydrologic MIKE SHE/M11 model of the surface-subsurface flow system.

A fully-integrated flow model with this detail and complexity had not been previously developed in a semi-arid area. As a result IHS developed and coordinated a comprehensive MIKE SHE/MIKE11 code validation effort in conjunction with the code developers, the Danish Hydraulic Institute.

Click Here

Post-Closure Industrial Area Model Output

IHS, contracted through US DOE Legacy Management company Navarro Research & Engineering, developed a post-closure model to simulate long-term, hourly integrated flows and contaminant plume fate/transport. This was a unique opportunity to demonstrate that previous IHS predictions of post-closure hydrologic conditions and VOC fate/transport remained largely unchanged.

Results were presented to US DOE, SMStoller and state regulators.

Post closure evaluation of former landfill / slumping

IHS developed localized, high-resolution, integrated flow models of two former industrial landfills to understand existing coupled hydrologic dynamics and predict changes to future water levels and seepage given different barrier, gravel under-drain, topographic grading and surface drainage network configurations and climate regimes.

Utilizing recent field data, IHS revised existing integrated hydrologic conceptual flow models, illustrating key features influencing various integrated flow processes and flow paths. This formed the basis for further revisions/updates to the post-closure integrated hydrologic flow model.

Hourly simulated output of water levels in unconsolidated overburden and underlying weathered bedrock were used to identify areas prone to seepage, and therefore slumping. Various designs aimed at mitigating the slumping via subsurface water control were evaluated with the updated, localized integrated landfill model.

Localized, Integrated, Building Closure Models

Localized, high-resolution integrated MIKE SHE/M11 surface-groundwater flow models were developed for seven former deep-basement nuclear manufacturing structures to address concerns by state and federal agencies

Building Models provided needed understanding of coupled surface-groundwater dynamics for current and alternative closure configurations, for typical and extreme annual and event-level climate sequences.

Models predicted seep areas, discharge rates, groundwater levels and fate/transport of VOCs.

Fate & Transport of Volatile Organic Compounds - Risk Assessment

Complex subsurface utility corridors/piping, geology and a complicated history of multiple comingled free-phase DNAPL sources were some of the challenges in the modeling long-term fate and transport of the VOCs. Integrated flow modeling results from MIKESHE supported saturated zone modeling using the GMS MODFLOW flow and RT3D fate/transport codes.

IHS supported a site-wide Comprehensive Risk Assessment (CRA) of numerious reactive fate/transport of VOC parent and daughter product plumes throughout the industrialized area.

Select Projects