A newly released investigation from a submarine mishap in 2015 that caused some $1 million worth of damage shows that an inexperienced crew was given the go-ahead to complete a tricky return-to-port mission in the dark, despite warnings from the commanding officer that they weren't ready.

The Ohio-class submarine Georgia ran aground in the predawn hours of Nov. 25, 2015, the day before Thanksgiving, as it prepared to return to port at Kings Bay, Georgia, to replace a failed towed array sonar. While conducting a scheduled pick-up of a new pilot at Fort Clinch, Florida, near the entrance to St. Marys River, which approaches the base, the sub inadvertently exited the channel, then collided with a buoy amid the crew's efforts to re-orient. The grounding occurred as the crew worked to get clear of the buoy, the investigation shows.

Ultimately, the sub was able to return to port to assess damages, which were mostly cosmetic, save for the ship's screw propeller, an acoustic tracking device and an electromagnetic log meter that measured the sub's speed. The Georgia was taken into dry dock in December 2015 for assessment and the costly repairs.

The investigation, which was completed in March 2016 but just released to Military.com this month through a public records request, found that the "excessive speed" of the sub as it approached the pilot pick-up made it more difficult for the crew to control the ship, and that the tugboat carrying the pilot was positioned poorly, making the maneuver more complex.

Ultimately, though, blame for running aground is laid at the feet of the commanding officer. In the wake of the incident, the commander of Georgia's blue crew, Capt. David Adams, was relieved of his post due to a loss of confidence in his ability to command. Like all submarines in its class, Georgia has two identical crews -- a blue and a gold -- that alternate manning and patrols.

"His inability to effectively manage the complexity of the situation and failure to respond to the circumstances in a manner sufficient to protect the safety of the ship and crew is beneath my expectations for any CO," an investigation endorsement by Rear Adm. Randy Crites, then-commander of Submarine Group 10, reads.

In his detailed and thorough endorsement of findings, Crites also dismisses the notion that maneuvering in the dark and with a green crew was what led to the sub's disastrous mishap.

"Ultimately, had this crew (and the Pilot) executed the same plan in the same manner during broad daylight, there is nothing in the ship's planning effort, demonstrated seamanship, or response to tripwires that indicates the outcome would be any different," he said.

While coming in for the brunt of the blame, Adams was not alone in being designated for punishment. Crites indicated his intent to take administrative action against the sub's executive officer; chief of boat; navigation/operations officer; weapons officer, who was the officer of the deck; and assistant navigator. He also said he'd issue non-punitive letters of caution to the commander of Submarine Squadron 16 and his own chief of staff and director of operations -- all Navy captains -- for failure to take appropriate action toward resolution regarding Adams' concerns around the sub's transit into port.

The 475-page investigation, which includes witness statements, logs and other supporting documentation, offers insight into what those concerns were. In a Nov. 24 email to the commodore of Squadron 16 marked "confidential," Adams, the Georgia blue crew commander, lays out his qualms about the plan he has been ordered to execute, particularly the predawn return to port for a brief one-day stop with a crew that had spent just three weeks underway together on a new ship.

"CO/XO/NAV have not piloted into Kings Bay in the last 20 years. All of the untoward [incidents] I know of occurred between [St. Marys] and Fort Clinch," he wrote. "My assessment is that this is not a prudent plan for [return to port] ... Having just been at sea for a few weeks, I have not built enough depth. I am concerned about the fatigue level of my command element.

"Given an all day evolution and subsequent [underway], we will have spent the majority of 36 hours awake and are set to pilot out and submerge on the mid-watch at 0330."

The two-page memo, it appears, was never received and read by Submarine Squadron 16's commodore, Capt. John Spencer. But Adams testified he had relayed the same concerns face-to-face with Spencer days before, on Nov. 22. He also discussed the same issues, he said, in a follow-up phone call.

This much is clear: the plan wasn't called off, and the mission was cleared to proceed. But murky communication dogged the lead-up to the operation, and later the mission itself.

Spencer and others testified that Adams had been given leeway to "slow things down a little" if he felt uncomfortable. Adams said he believed any delay would have been viewed as insubordination.

On the day of the mishap, communication was also flawed, in ways that underscore the crew's unfamiliarity with each other, and possibly the sleep deprivation that had left some members running on just two to three hours of rest.

According to the investigation, as the Georgia approached the point at which it was to meet with the tug and pick up the pilot -- the navigation expert who would drive the ship into port -- it became clear that the tug was well west of its expected position. The sub, meanwhile, was approaching too fast and slowing too gradually. The investigation found it was still making 15 knots, or about 17 miles per hour, when it passed the set "all stop" point. That speed and positioning would make every maneuver that followed more risky and difficult.

Initial attempts to communicate with the tug and the pilot aboard via radio were unsuccessful, and the planned transfer happened late. Adams did not want to scrap the transfer and proceed into port without the pilot, the investigation found, because of the challenges of pulling into port without one.

When the sub exited the channel at the west end of the Fort Clinch basin, the crew's communication skills faced a major test. The assistant navigator recommended to the navigator that the sub go to "all back emergency," a call the navigator then passed to the bridge. The officer of the deck seemed to agree, but said nothing, the investigation found. Adams, however, overrode the order, believing it would not work, and ordered "all ahead full" instead. He started directing the officer of the deck, but did not fully take control of the sub or give direct orders to the helm, the report states.

Despite a series of maneuvers -- right hard rudder, left hard rudder, all ahead full, right hard rudder -- the sub collided with Buoy 23 in the channel. But the worst was still to come.

"When [Adams] asked [the lookout] if the ship hit buoy 23, [the lookout] informed the CO that he did not care about the buoy, but thought the ship was going to run aground on the beach forward of the ship," the investigation states.

As grounding looked imminent, the Georgia asked the driver of the C-tractor tugboat if the tug could cross in front of the sub on the starboard, or right, side, and push the bow around. The tug master refused, according to the investigation, worried that the water was too shallow.

The sub ended up, as the lookout put it, "hitting Fort Clinch."

The mishap, and the misgivings that preceded it, came against the backdrop of a Navy grappling with a culture in which overworked and unready crews were regularly put underway in service of operational needs. After two separate deadly destroyer collisions in 2017, service leaders found, among other things, that a "'can-do' culture" had undermined safety and led to unduly high operational tempo and fatigue.

"The can-do culture becomes a barrier to success only when directed from the top down or when feedback is limited or missed," the Navy's comprehensive review of the destroyer mishaps, released in October 2017, found.

Whether these factors came into play with the Georgia is more difficult to say.

In a statement for the investigation, Adams emphasized that he took full responsibility for what had transpired.

"Despite my significant reservation - expressed face-to-face, on the phone, and In emails with staff and leadership ... concerning the risks of proceeding Into Kings Bay In the dark with an inexperienced team, when my requests to delay [return to port] one hour later were denied, I failed in my command responsibilities by driving to achieve mission success at the expense of appropriately acting to mitigate risks to increase our margin of safety," he said.

"In retrospect, I should have loitered at [St. Marys] until I was satisfied that the risks were commensurate with the mission gain."

Reached for comment by Military.com, Adams, who retired in 2016, referred to a public statement he had released at the time of his relief, in which he called the actions that caused the grounding "mine alone."

"I ask that my lapses not be used to denigrate the terrific service of the Sailors and families of GEORGIA BLUE," he said at the time "After thirty years of serving in the world's finest Navy, my only regret is that I will miss sailing with them again to stand against our nation's enemies."

But the fact that some above Adams were also warned offers insight into how the higher command viewed the incident.

Crites faulted Spencer, the Squadron 16 commodore, with "failure to provide his ship a plan with adequate margin to safety, specifically in not providing sufficient guidance and training to his staff that developed the plan in his absence and not aggressively pursuing complete resolution of the ship's requested arriva through personal intervention with the Type Commander staff."

The chief of staff and director of operations for Submarine Group 10, Crites said in the report, had failed to "pursue acceptable resolution to the concerns they had with the plan for the ship's arrival."

Holly Carey, deputy public affairs officer for Submarine Force Atlantic, declined to say whether all administrative actions recommended by the investigation were carried out.

"What I can tell you is that the Navy is confident that leadership took appropriate corrective actions against several personnel assigned to the squadron and submarine based on the findings of the investigation," she said.

"Following the investigation, which concluded in 2016, leadership took appropriate accountability measures and has taken all necessary steps to prevent a recurrence in the future. USS Georgia, and her current crew, serve proudly today among the U.S. Submarine Force and has leadership's full confidence to protect the interest of the United State and allies."

-- Hope Hodge Seck can be reached at hope.seck@military.com. Follow her on Twitter at @HopeSeck.