PIPELINE SAFETY ADVISORY BULLETIN
(Expanded to Nationwide Coverage)
Advisory Bulletin: ADB-97-03 DATE: 03/4/97

To: Owners and Operators of Hazardous Liquid and Natural Gas Pipelines

Subject: Potential Soil Subsidence on Pipeline Facilities.

Purpose:

Inform system owners and operators of possible hazards relating to soil subsidence on pipeline facilities, and to monitor the potential impact of flooding and soil subsidence on those facilities .

Advisory:

Heavy rainfall and flooding have increased the potential for damage to pipeline facilities. Several accidents have occurred on natural gas transmission facilities that appear to be related to the stress of soil movement on the facilities. Accordingly, the Department of Transportation's Pipeline and Hazardous Materials Safety Administration (PHMSA) is advising operators of pipeline facilities, regardless whether those facilities are regulated by PHMSA, of the need for caution associated with excessive flooding and soil movement. In particular, pipeline operators should conduct training, and patrol their rights-of-way to identify areas of potential soil subsidence that could adversely affect the safe operation of their pipelines. Additionally, emergency plans should be reviewed to assure they adequately address conditions possible in areas of soil subsidence.

In conducting patrolling and reviewing emergency plans and procedures for natural disasters, operators should consider, as appropriate to their pipeline systems, each of the actions outlined below:

Be alert to weather patterns and conditions that are precursors to soil movement/subsidence and have personnel available for patrolling, preventative maintenance activities, and emergency response actions such as shutdown, isolation, and containment in case of a pipeline failure.

Conduct training of personnel responsible for patrolling the pipeline right-of-ways to identify areas that are potentially susceptible to soil movement/subsidence that could be detrimental to the safe operation of a pipeline.

Perform frequent patrols, by methods designed to effectively evaluate right-of-way conditions, in areas susceptible to soil movement/subsidence that might jeopardize the operation of the pipeline.

Evaluate the accessibility of pipeline facilities, such as valves, needed to isolate pipeline segments or sections of pipelines that might be jeopardized by soil movement/subsidence.

Evaluate areas of potential soil movement/subsidence and, as appropriate, monitor soil movement/subsidence and take preventative actions to assure the safe operation of the pipeline.

Background:

Damage to a pipeline may occur as a result of additional stresses imposed on piping by soil movement/subsidence. Record rains resulting in saturated soil conditions may result in soil movement/subsidence in some areas. Training of pipeline patrol personnel and using effective patrolling methods are essential elements for success in identifying areas of potential movement/subsidence. The impact of moving soil against buried pipeline may result in forces sufficient to cause a failure. Soil movement/subsidence has been identified as the primary contributor to two recent failures of a pipeline in the State of Washington.

Issued in Washington, DC on March 4, 1997.

Richard B. Felder, Associate Administrator

Office of Pipeline Safety

Pipeline and Hazardous Materials Safety Administration