What Happens When the Navy Loses One Drydock for a Year
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Take One Naval Drydock Offline for a Year. Watch the Fleet Backlog Spread.
Losing one dock does not simply delay the ship scheduled to use it. In a repair network already running close to capacity, the outage can create a maintenance queue that survives for years after the dock returns.
Consider a network with five interchangeable compatible drydocks. Each is assumed usable 85% of the calendar year after allowing for turnover, maintenance and other unavailable time.
At 95% normal network load, the five docks provide about 1,551 usable dock-days per year against approximately 1,474 dock-days of demand. There is only about 78 days of annual spare capacity.
Remove one dock for a year and usable capacity falls to about 1,241 dock-days. Demand does not disappear. The network ends the year approximately 233 dock-days behind.
Once all five docks are restored, the network again has only about 78 spare dock-days per year. A 233-day backlog therefore requires roughly three additional years to erase if demand remains unchanged.
Watch the outage move beyond the outage year
A few percentage points of normal load change everything
The table holds the same assumptions constant: five compatible docks, 85% usable calendar availability and one dock unavailable for 12 months.
| Normal Network Load | Load During Outage | Backlog Added | 240-Day Dock-Slot Equivalent | Recovery After Dock Returns |
|---|---|---|---|---|
| 80% | 100.0% | 0 days | 0.00 | No backlog |
| 85% | 106.3% | 78 days | 0.32 | About 4 months |
| 90% | 112.5% | 155 days | 0.65 | 1 year |
| 95% | 118.8% | 233 days | 0.97 | 3 years |
| 97% | 121.3% | 264 days | 1.10 | About 5.7 years |
| 99% | 123.8% | 295 days | 1.23 | About 19 years |
The Navy has already seen how quickly dock availability can change
After a seismic assessment, the Navy temporarily suspended submarine docking in Puget Sound Dry Docks 4, 5 and 6 and the Delta Pier drydock at Trident Refit Facility Bangor. Interim mitigation returned facilities to service during 2023, while Dry Dock 6 was later determined not to require immediate mitigation.
NAVFAC awarded a $377.7 million retrofit task order in September 2025. The Navy marked completion in August 2026, ultimately describing the project as delivering capacity back to the shipyard. Added work brought the reported contract value to $517 million.
The network is not starting from an empty queue
| Attack-Submarine Measure | GAO FY2016-2025 Finding | Why It Matters to an Outage |
|---|---|---|
| Active idle time | 8,906 days | Submarines already experienced periods waiting pierside to enter maintenance |
| Depot maintenance delay | 6,494 days | Existing availabilities have repeatedly occupied the system longer than planned |
| On-time depot completion | About 11% | Schedule recovery cannot be assumed automatically after infrastructure returns |
| Average depot period | 809 days in FY2021-2025 versus 744 days in FY2016-2020 | Longer maintenance periods increase pressure on the same infrastructure |
| Virginia-class daily O&S reference | $237,080 per delayed or idle day | Provides an order-of-magnitude reference for the cost of lost operational days |
Total drydock count can overstate usable capacity
The outage model deliberately uses the term compatible drydock. Naval drydocks are not interchangeable. Hull dimensions, structural strength, nuclear-support requirements, utilities and certification determine what work can move elsewhere.
Modernization itself has to be scheduled around maintenance
The Navy is rebuilding drydocks while simultaneously trying to maintain the fleet. Its Shipyard Infrastructure Optimization Program therefore has to coordinate construction windows with submarine and carrier availabilities.
Navy infrastructure leadership has publicly described the planning problem: modernization projects are synchronized with ship-maintenance schedules specifically to avoid taking too much capacity offline at once.
The 240-day dock-slot equivalent is a scenario value used to make backlog easier to visualize. GAO reports that complete attack-submarine depot maintenance periods are substantially longer, averaging 809 days during FY2021-2025, but a submarine is not necessarily physically in drydock for that entire maintenance period.
The modeled cost equivalent should not be interpreted as a forecast. It applies GAO's $237,080 Virginia-class daily operating-and-support reference only if modeled backlog days become active idle or otherwise delayed submarine days.
Public research base:
U.S. Government Accountability Office, GAO-26-109256, August 2026.
Congressional Budget Office, submarine shipyard capacity analysis.
Naval Sea Systems Command, public shipyard and SIOP materials.
U.S. Navy, Pacific Northwest seismic mitigation announcements, 2023.
NAVFAC, Puget Sound Dry Dock 4 modernization announcements, 2025-2026.
Naval Drydock Outage Backlog Simulator
Take capacity offline and see how many dock-days accumulate, how many maintenance slots that represents and how long the queue survives after the facility returns.
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