SSN-688 Los Angeles-class Engineered Refueling Overhaul (ERO)

At about 2/3 the way through its life, the submarine undergoes a large and comprehensive overhaul that includes periodic maintenance, system upgrades, and alteration. For the earliest built Los Angeles Class submarines, the work also includes refueling the ship's reactor plant. These availabilities are called Engineered Refueling Overhauls (EROs). For the later Los Angeles Class submarines, the reactor doesn't need to be refueled. For these vessels the overhaul is called an Engineered Overhaul.

Submarine Engineered Refueling Overhauls (EROs) are complex, short duration availabilities performed to extend the useful life of the vessel. Average duration of an ERO is 24 months with a production period of less than 15 months. Unlike ships under construction EROs are performed on assembled hulls with limited access. The unique sensitive and safety (SUBSAFE) nature of submarine repair and refueling efforts dictates that the availability must be thoroughly and carefully integrated in advance to minimize disruptions and delays. The production period at the beginning of the ERO is extraordinarily labor intensive.

Initially, the Navy planned to operate the SSN-688s for three 84-month cycles, perform major maintenance twice, and retire the submarines after 24 years. SSN-688 class submarines could operate for much longer than 30 years; one of the shipbuilders stated that 10 to 20 years of additional service would not be unreasonable. Past Navy actions indicated that extending a submarine's service life may be feasible. After a 5-year study was completed on the SSN-637 class submarine--the predecessor of the SSN-688 class--the design life was extended from 20 years to 30 years, with a possible extension to 33 years on a case-by-case basis. By the end of 1999 the Navy had determined that it could safely extend the service lives of all its Los Angeles and Improved Los Angeles class submarines by 3 years, to 33 years. This reduced somewhat the steady-state procurement rate needed to maintain an SSN force of a given size, and delayed the point at which the size of the SSN force might bottom out due to rapid retirements.

Between 1998 and 2001 the US retired 11 Los Angeles class submarines that had an average of 13 years left on their 30-year service lives. The 18 SSN-688 class submarines that will be refueled at their mid-life made good candidates for a service life extension because they could operate for nearly 30 years after the refueling. After these submarines serve for 30 years, they could undergo a 2-year overhaul and serve for one more 10-year operating cycle, for a total service life of 42 years. The cost for the additional overhaul of SSN-688 class submarines would be about $406 million per boat.

Eight older Los Angeles-class submarines, without a vertical launch system, could be refueled at a cost of $210 million more than it would cost to inactivate them.

• FY2000 - SSN 713 Houston
• FY2001 - SSN 698 Bremerton
• FY2001 - SSN 699 Jacksonville
• FY2001 - SSN 714 Norfolk
• FY2005 - SSN 716 Salt Lake City
• FY2006 - SSN 717 Olympia
• FY2007 - SSN 718 Honolulu
• FY2008 - SSN 710 Augusta

These submarines could still be used in strike missions, however, by firing Tomahawk land attack missiles through their torpedo tubes. But all had been inactivated by 2019.

In late 1999 the Clinton Administration decided to add $1.1 billion in funding to the shipbuilding plan in the period FY2002-FY2005 for submarine refuelings beyond those previously programmed. The money is to be used either for refuelings of 688-class submarines scheduled for early retirement, or conversion of Ohio-class Trident ballistic missile submarines into cruise missile submarines (SSGNs). A total of 7 older 688s would require refueling to avoid early retirement. Their refueling was not previously funded, and the $1.1 billion would be enough to refuel 4 of them. Alternately, the $1.1 billion would be enough to convert 2 older Trident SSBNs into SSGNs.

The Clinton Administration's DOD guidance called for a force of 50 attack submarines, although some studies called for raising the number of subs to as many as 72. Existing plans were sufficient to meet the goal of 50 boats, although higher numbers would require modification to these plans. According to Navy secretary Richard Danzig, as of October 1999 the Joint Chiefs of Staff were studying options for increasing the size and capability of the submarine force. The three options under review include by converting older Ohio-class SSBN submarines to so-called SSGNs at a cost of $420 million; refueling and extending by 12 years the service life of perhaps eight Los Angeles-class (SSN 688) subs at a cost per copy of $200 million; or building new Virginia-class (SSN 774) subs at a rate of at least four over the next five years, at a cost of roughly $2 billion per boat. The FY2000 Defense Authorization bill requires the Navy to study converting four of the oldest Tridents to the new SSGN configuration.

The JCS Submarine Force Structure Study, completed in November 1999, concluded that the optimal force structure would be 68 attack submarines by 2015 and 76 by 2025, with the minimum being at least 55 by 2015 and 62 by 2025. The first would be to refuel some Los Angeles-class submarines previously scheduled to be decommissioned.

The Portsmouth Naval Shipyard conducts maintenance and refueling of nuclear submarines at its facilities on the Piscataqua River. Depot modernization maintenance requires less than a year in port, and an engineered refueling overhaul is a 2-year operation. The Navy canceled two Engineered Refueling Overhaul projects that had been scheduled -- SSN 716 Salt Lake City and SSN 710 Augusta.

Engineered Overhaul (EO)

The Attack Submarine (SSN) Engineered Overhaul (EO) program modernizes, and upgrades SSNs for extended service in the fleet. SSN-719 USS Providence entered Portsmouth Naval Shipyard on 29 October 2003 for the Navy's first-ever Engineered Overhaul for an attack submarine. For these later Los Angeles Class submarines, the reactor doesn't need to be refueled. For these vessels the overhaul is called an Engineered Overhaul, versus the Engineered Refueling Overhaul (ERO) of earlier boats. This included maintenance and several system upgrades with an estimated total cost of $160 million.

The workload to capacity mismatch resulted in lower priority attack submarine (SSN) availabilities (as compared to ballistic missile submarines and nuclear-powered aircraft carriers) being delivered late and a bow-waving of workload from one fiscal year to the next that could not be executed. The workload backlog exacerbated the public shipyard workload-to-capacity mismatch and contributed to an increasing trend in late SSN [maintenance] deliveries.

The Navy originally scheduled the USS Boise to enter a shipyard for an extended maintenance period in 2013 but, due to heavy shipyard workload, the Navy delayed the start of the maintenance period. In June 2016, the USS Boise could no longer conduct normal operations and the boat remained idle, pierside for years thereafter waiting to enter a shipyard. GAO estimated that between fiscal year 2008 and 2018 the Navy spent more than $1.5 billion in fiscal year 2018 constant dollars to support attack submarines that provide no operational capability—those sitting idle while waiting to enter the shipyards, and those delayed in completing their maintenance at the shipyards.

By 2020 there had been significant delays in SSN deployments due to a backlog in SSN maintenance at the Navy’s four government-operated naval shipyards (NSYs). It had been five years since the attack submarine Boise returned from its last patrol, and the work under the overhaul contract awarded in September 2020 was scheduled to wrap up in May 2023, eight years after the sub left the operational fleet. The Navy initially hoped to get Boise into Newport News as early as 2018, but the private yard struggled with its first two Los Angeles-class SSN maintenance periods for USS Helena (SSN-725) and USS Columbus (SSN-762).

One of the main issues with assigning attack subs to private shipyards is that they are not set up as maintenance shops. They are built and organized as new construction yards. Naval Sea Systems Command attributed the delays of Columbus and Helena to the fact that the workforce was inexperienced in conducting submarine maintenance, which differs greatly from new construction.

The Navy’s four shipyards continued to face chronic and substantial delays in more than three-quarters of submarine maintenance periods, and the Navy experienced substantial growth in idle time for submarines awaiting the start of maintenance periods. The Navy continues to spend money to support submarines that have provided no operational capability — submarines sitting idle no longer certified to conduct normal operations — while waiting to enter the shipyards. In 2020 the Navy assessed that the submarine idle time would be eliminated by the end of FY 2023 and the submarine maintenance backlog would be worked off by the end of FY 2023.

The service life of SSN-688 boats is estimated at 33 years. These estimates include actual service with the operational fleet and regularly scheduled maintenance. To this number must be added however many years a given boat was pier-side awaiting delayed maintenance, a number which would vary from boat to boat. This may help explain why the 2021 Navy sip retirement plan called for SSN-756 Scranton and SSN757 Alexandria to retire in 2026, 35 years after they comissioned. And SSN-753 is expected to remain in service past 2026, serving at least 37 years in comission.