Introduction of the new Hazardous Liquid Pipeline Integrity Management Program compliance regulations in December 2000 includes the requirement to identify High Consequence Areas (HCA). These new compliance regulations have incited new maintenance challenges for pipeline operators. HCA identification tools, developed to determine potential release volumes and impact locations can now be utilized to minimize the HCA exposure potential as new pipelines are proposed and their routes planned. Simple planimetric information regarding proposed pipeline routes is translated into a spatial, or three-dimensional, digital model to simulate the potential release of product. In addition to the lateral translation of the pipeline centerline to avoid HCA features, further evaluations can be performed to simulate the placement of mainline valves, optimize SCADA response times, and evaluate the impact that elevation poses on drain-down volumes. Improved strategies for pipeline placement early in the design phase of construction can prove to be cost effective during the operating life of the pipeline.


The U.S. Department of Transportation Research and Special Programs Office of Pipeline Safety (OPS) has implemented new requirements for operators of hazardous liquid pipelines and proposed new rules for natural gas pipelines. The purpose of these new rules is to reduce the risk of pipeline incidents in areas defined to have high consequences to the public or environment. The new rule for hazardous liquid operators is located in 49 CFR 195.4521, and the characteristics of the proposed rule applicable to natural gas transmission pipeline operators is currently in the OPS draft Docket RSPA-00-7666. The intent of both rules is to require pipeline operators to validate the integrity of their pipelines in High Consequence Areas. In addition to requirements for the regular integrity assessment (i.e. an evaluation of the pipeline condition using inline inspection, hydrostatic testing, or other approved technologies) of the pipelines, standards for scheduling the repair of known pipeline anomalies have been established. Due to the nature of high consequence areas, these standards may be more stringent than current industry practices and may therefore increase operating costs significantly.

By identifying HCA?s on proposed pipeline routes during the design process, future impact to the public and the environment can be minimized through route changes and other impact limiting actions. Limiting impact to HCAs in this manner will also reduce future maintenance cost to the pipeline operator since non-HCA impacting pipeline may not require assessment as frequently and the speed of repairs of known anomalies may be less stringent. This practice is also consistent with the liquid rule 49 CFR 195.210.


HCA Definitions

In 49 CFR 195.450, High Consequence Areas for Hazardous Liquid Pipeline Operators are defined as: a High Population Area (HPA), which describes urbanized areas; an Other Populated Area (OPA), which is a place defined and delineated by the Census Bureau containing a concentrated population; a Commercially Navigable Waterway (NW); and Unusually Sensitive Areas (USA) which are defined in 49 CFR 195.6. Unusually Sensitive Areas include drinking water intakes (DW) and ecologically sensitive areas (ESA) that have imperiled or threatened species.

Natural gas transmission pipeline operators must comply with HCA definitions that are limited to impacts on populated or publicly occupied areas. These include class 3 and 4 locations as well as Identified Locations such as occupied buildings that have persons with limited or confined mobility, and loc

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