Pipeline maintenance season is over. Unplanned outages aren't.

The summer pipeline maintenance season is over. Enercast’s notice archive counted 18 planned maintenance outages starting in August across U.S. interstate pipelines; by October that was down to 5, and only one has started so far in November. Unplanned outages — force majeures, compressor failures and capacity constraints — did not follow: October had 28, matching September as the most of any month since June.

The pattern is the usual one. Pipelines do their heavy work — pigging, compressor overhauls, valve and line replacements — between the spring and fall shoulder seasons, when demand is low and lost capacity costs the least. Unplanned events don’t follow a calendar, and as the system runs harder into winter, each one matters more.

How much capacity is offline now

Since mid-October, Enercast’s Capacity Offline page has published a daily total of interstate pipeline capacity out of service. It peaked at 4.18 Bcf/d on October 28, when Gulf South had cut scheduling into Freeport LNG at Stratton Ridge and ANR’s Greenville compressor unit was down (an estimated 1.03 and 0.89 Bcf/d), and fell as low as 0.63 Bcf/d on November 2. It has been about 1.67 Bcf/d since November 5: 0.39 Bcf/d planned, from Columbia Gulf’s Hampshire compressor station work, and about 1.28 Bcf/d unplanned, most of it Transwestern’s force majeure on its Thoreau West system.

Those totals count only outages where the pipeline posted a volume or one can be derived from the notice and recent flows. Several current outages post a capacity limit but no lost volume — Gas Transmission Northwest’s flow past Kingsgate is capped at 2.8 Bcf/d after a compressor failure at Wallula, and Colorado Interstate Gas has Segment 164 Cheyenne West limited to 0.347 Bcf/d through year-end — so the daily figure is a floor, not the full picture.

Still in effect

Largest and longest-running outages from the Capacity Offline ledger; the page lists every one. “est.” = derived from recent flow; Transwestern’s Thoreau West notice states no reduced limit, so the full recent flow through the segment is counted as at risk.

What’s scheduled

Very little. As of November 9, pipelines have posted only a handful of planned outages for the rest of the year:

As posted on pipeline bulletin boards by November 9. Pipelines can add maintenance at short notice.

What it means heading into winter

With most maintenance finished, pipeline capacity is not the constraint it was in August, just as heating demand starts to build. That does not by itself mean more gas will flow: supply depends on producers, and early November has gone the other way, with Appalachian and Haynesville receipts down after month-turn curtailments (see that story). And winter brings its own outages — compressor trips and freeze-offs — so the unplanned count is the one to watch.

How we count: an outage is one event in Enercast’s capacity-offline ledger, which groups a pipeline’s original notice, updates and lift into a single record and assigns it to the month it started. Planned = maintenance notices; unplanned = force majeure, compressor failures and capacity constraints (two September events and one October event were hurricane-related and are counted as unplanned). Volumes are shown from October 15, the first full day after Enercast began quantifying each outage daily (October 14); volumes marked est. are derived from recent flow and the posted limit.

Sources: Enercast critical-notice archive (interstate pipeline bulletin boards) · Enercast Capacity Offline ledger. Not investment advice; see the disclaimer.