Gas pipeline information

On Tuesday, June 14, 6:00-8:00 PM, we held a special event for all cluster residents: a meeting with Mr. Joe Marshall, District Manager for the Williams company, which operates the TRANSCO natural gas transmission pipeline that passes through our Cluster property.  The meeting with Mr. Marshall also included an informal potluck dinner with food provided by the many fabulous chefs within our Cluster. A summary of the points made during the presentation and during the ensuing discussion is listed below.– In case of any emergency regarding the gas pipeline, dial 911

– Four pipelines currently run through the Cluster: 2 x 30″ diameter, 1 x 36″ diameter, and 1 x 42″ diameter. To maintain the pressure, compressor stations are setup every 75 miles. The nearest compressor station is in Manassas; the next nearest is in Elkton City, Maryland.

– The pipes are buried about 4 feet undergound (originally 3.5 feet). If you see exposed pipe in Snakeden Creek where it crosses the pipeline, please notify Williams immediately (800-440-8475). Exposed pipe was observed in the creek last year, but was repaired.

– The gas in the main pipeline is NOT odorized–this occurs at the distribution point where the gas enters the supply lines of Washington Gas. For our Cluster, the point of distribution is in Herndon off Baron Cameron Road. It is at this point that the gas is odorized with mercaptan (or methanethiol), which imparts the pungent odor. The chemical formula of mercaptan is CH3SH, with the thiol group (SH) replacing one of the hydrogens in the methane (CH4) molecule (a little sulfur goes a long way!).

– Although the gas in Transco pipelines is not scented by mercaptan, it contains traces of machine oil, so it may be possible to detect a leak by its oily scent (similar to engine oil).

– The gas in the pipeline is at a pressure of either 780 psi or 650 psi, depending upon the diameter of the pipe and the current demand for gas. For comparison, the “bombs” of gas you might see on a distribution truck are at a pressure of 2500 psi, and water in your house is probably less than 80 psi. Mr. Marshall also mentioned that there are four classes of pipeline administration, A through D, from least developed to urban, respectively.  We are in Class C, which means a line pressure of as much as 780 psi is used.  In developed areas, such as the Reston Town Center, the high rise buildings cause a downgrading to Class D, with max pressure of 650 psi.  With more building, the entire stretch may well be downgraded to D one of these days.

– The pipelines are steel with composition coatings inside and out. A weak electrical current applied to the outside of the pipes actually helps prevent corrosion by conducting away electrons that cause rust, much like the sacrificial anode in your water heater attracts electrons and thus protects the metal housing of the heater from corrosion.

-The pipes were designed to sustain 500,000 cycles of testing and so far have undergone 25,000 cycles, so that the pipes have lived through 25 of its 500 lives, so to speak.

– Continuous and repetitive testing includes direct inspection by a “pig” which moves through the inner surface of the pipe and records its findings in a digital recorder which is then extracted and shipped to Houston for analysis. The “pig” last squealed through the pipes under the Cluster in 2010. It is not due for another 7 years, possibly earlier.

– Pounding of even non-hardened surface such as the Winterthur parking lot by dumpsters of garbage trucks is acceptable and poses no risk.

– There are strict separations of right-of-ways by various utilities. Any work that might impinge on the gas pipeline right of way must have a Transco rep on site; any deviation, if observed, should be reported to Transco ASAP. Williams requires a minimum of 24” of vertical clearance between their lines and any utilities that cross the Pipeline easement.

– The pipeline for the newly configured crossing at the Dulles Access and Toll Road and the Metro rail extension will be sheathed within an outer pipe for added protection.

-All in all, they request and urge that we be on the alert for any smell, wilting plants, transgressions, etc. and call them as soon as possible if anything suspicious is observed.

The number to call is: 800-440-8475

Failing to have their number handy, it is painted on the yellow marker posts above the pipelines. In case of an emergency, call 911.

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