Overview

The Liquids HCA Tool is a part of G2-IS’s comprehensive pipeline integrity management software suite that helps operators manage risk, ensure compliance, and optimize performance. The Liquids HCA Tool is designed to meet all the requirements for “could affect” segment determination for hazardous liquids pipelines, as specified in 49 CFR §195.452   Pipeline integrity management in high consequence areas. The Liquids HCA Tool performs hydrocarbon plume transport simulations that support the following product transport mechanisms:

• Overland flow – simulation of the hydrocarbon release plume over the surface of the earth, taking topography into account
• Hydrographic transport – simulation of the downstream transport of a hydrocarbon release plume that has entered a stream/river network

To facilitate overland flow release plume simulations, The Liquids HCA Tool uses a customized version of an open source Computational Fluid Dynamics (CFD) modeling package called GeoClaw to perform overland flow plume simulations. GeoClaw uses high-resolution, Godunov-type, shock-capturing finite volume methods and Riemann solvers to solve the shallow water equations, a simplified, depth-integrated version of the general Navier-Stokes equations for incompressible, viscous fluid flow. Of particular importance to modeling pipeline releases and storage tank ruptures, dry states in the model space are handled automatically by GeoClaw. Unlike many CFD tools, the use of shock-capturing methods allows dry portions of the model space to be handled implicitly and accurately. GeoClaw also incorporates Adaptive Mesh Refinement (AMR) to facilitate efficient and stable simulation of the highly transient flows typical of pipeline releases and storage tank ruptures.

G2-IS has modified the GeoClaw kernel to allow for the incorporation of fluid density and viscosity terms. Unlike many other offerings, this enhancement enables GeoClaw to be legitimately used in modeling fluids other than water, e.g., hydrocarbons. This refined simulation capability is extremely important when the working fluid is a hydrocarbon product whose density differs from water, and whose viscosity may differ from water by multiple orders of magnitude.

The use of GeoClaw in the overland transport modeling portion of the Liquids HCA Tool enables the effective use of the high-resolution digital elevation data now available via the USGS 3D Elevation Program (3DEP) and the Esri Living Atlas. In many parts of the United States, 3DEP data is now available at 1-meter horizontal resolution. To allow the Liquids HCA Tool to take advantage of the ever increasing resolution of elevation data, G2-IS has enabled the GeoClaw engine to be run in the Microsoft Azure® virtualized computing environment. This enables nearly unlimited performance scalability in the Liquids HCA Tool, either on premises or in the cloud, a facilitates processing performance that far outstrips tools limited to desktop computing.

The hydrographic transport module of the Liquids HCA Tool utilizes the latest version of the National Hydrography Dataset (NHD), NHDPlus High Resolution (NHDPlus HR). Stream flow rate data is incorporated directly into the NHDPlus HR dataset, facilitating more accurate assessment of stream flow velocity, which is critical to determining the extent of the downstream transport of the release plume. The hydrographic transport engine of the Liquids HCA Tool makes use of Esri Network Analyst extension technology in performing downstream trace calculations.

The combination of Liquids HCA Tool simulation algorithms together with the extreme resolution of the USGS 3DEP and NHDPlusHR datasets facilitates more accurate and detailed release plume modeling than ever before possible. The output of both the overland flow and hydrographic transport modules of the Liquids HCA Tool is fully time aware. This facilitates the user’s ability to visualize the evolution of both overland and hydrographic transport plumes through time, using the ArcGIS Pro time slider. This capability enables Liquids HCA Tool output to be used as an aid in emergency response plans and exercises.