Q: What are the state and federal regulations governing pipe safety? A:
Federal Pipeline Safety Regulations, Title 49 of the Code of Federal Regulations
Pipeline Safety Improvement Act of 2002, Public Law 107-355
CPUC General Order 112-E
CPUC Gas Safety Program Requirements are codified in Public Utilities Code Sections
315, 768, 4351-4361 and 4451-4465
Q: How big are the backbone pipes vs. distribution pipes? A:
Smallest distribution piping: 1/2 inch
Most distribution piping: 2, 4, and 6 inches
Largest transmission piping: 42 inches
Most transmission piping: 24, 30, and 36 inches
Q: What is the percentage of lines that cannot be inspected with a pig? (System wide transmission and Line 132) A: According to its 2004 Baseline Assessment Plan, PG&E has 5,777 miles of transmission pipelines. Within this, PG&E has stated that it has 944 miles of PG&E and 28 miles of StanPac (a line PG&E co-owns with an another party, but is operated by PG&E) that are HCA miles. From among the total 972 HCA miles, PG&E provided an estimate that approximately 25 percent is piggable (this includes PG&E’s plans to make pipelines piggable that are not already piggable). For the remaining 75 percent of HCA mileage, PG&E has assessed, or intends to assess, using External Corrosion Direct Assessment.
Q: What does an external inspection of a pipeline entail? A: External inspection of a pipeline consists of routinely monitoring cathodic protection levels on a pipeline as well as a more detailed external inspection known as External Corrosion Direct Assessment (ECDA).
Cathodic protection (CP) is applied, on a continual basis, to steel pipelines to reduce the potential for external corrosion on these lines. CP levels must be monitored, at various locations in the vicinity of the pipeline, and actions taken to remediate any readings that do not comply with those specified by gas safety regulations. Line 132 was cathodically protected.
ECDA is a more specialized inspection process performed on a pipeline to look for external corrosion issues including low cathodic protection levels, as well as pipeline coating issues. Unlike routine CP monitoring performed at select locations, ECDA is performed over the entire length of the line being inspected.
ECDA is a four step process that combines pre-assessment, indirect inspections, direct examinations, and post assessment to evaluate the impact of external corrosion on the integrity of a pipeline. The pre-assessment step consists of collecting pipeline data, determining whether ECDA is feasible for the pipeline to be evaluated, selecting indirect inspection tools, and identifying ECDA regions. The indirect inspection step consists of using two or more indirect inspection tools with the objective to identify and define the severity of coating faults, other