To the amazement of practically everybody except Bailey, the dam complex was working. By May 6, the water held by the dam had risen 4 feet. By May 8, the water level was up 5 feet 4 inches. Three of the lighter vessels even crossed the upper rapids and now waited behind the dam for the heavier gunboats. As the soldiers worked to finish the dam, the water continued to build until the pressure against the dam became tremendous. General Banks feared the pressure would soon burst the dam, and the next day, at around 5:30 in the morning, one officer "heard a great crashing in the direction of the dam. Jumping out of the blankets and slipping on my coat, cap, and boots, I ran down to the bank. The water was rushing through at a great rate" (Tyson May 9, 1864).
Two of the barges used in the dam had broken loose, and the water was gushing through. Porter, seeing the crisis, quickly ordered the gunboat Lexington to run the gap:
The Lexington succeeded in getting over the falls and then steered directly for the opening in the dam, through which the water was dashing so furiously that it seemed as if certain destruction would be her fate. Ten thousand spectators breathlessly awaited the result. She entered the gap with a full head of steam; passed down the roaring, rushing torrent; made several spasmodic rolls; hung for a moment, with a harsh, grating sound, on the rocks below; was then swept into deep water and rounded to by the bank of the river. Such a cheer arose from that vast multitude of sailors and soldiers, when the noble vessel was seen in safety below the falls, as we had never heard before, and certainly have not heard since (Moore 1868:12).
Porter's fleet passing through Colonel Bailey's Dam above Alexandria, May 1864. From Frank Leslie's Illustrated Newspaper, July 16, 1864. Courtesy of Library of Congress.
The Lexington's run was followed by the three gunboats waiting behind the dam. Had the rest of the fleet been prepared, all of the boats might have escaped at that time. However, the navy's lack of confidence in the dam had given way to apathy, and as the released water rushed through the break, valuable time was wasted as the fleet gathered steam to attempt the run. Eventually, the water behind the dam fell and six gunboats still remained trapped.
But the Lexington's adventure had proven that the dam could work, and troops confidently went back to work. Bailey worried that the dam would break again and decided to leave the 70-foot gap in the dam as it was. But this time he added smaller, lighter dams near the upper rapids. Like the dam sections at the lower rapids, both crib and tree dam methods were employed. These dams helped channel the water while reducing the pressure on the main dam. Thus, instead of relying on one dam to hold back the water until another run could be made, a series of dams were built to create a deep channel of water along the whole course of the shoals in that part of the Red River.
Unfortunately, during Coastal Environments's archaeological excavations, this dam complex at the upper rapids was believed to be destroyed by modern development. Later, the U.S. Army Corps of Engineers conducted an underwater survey, locating what clearly appear to be parts of these upper works. If so, these submerged dam sections are preserved so that perhaps someday archaeologists may have an opportunity to investigate more of Bailey's engineering feat.
While the army labored to build the upper dam, the navy, more confident of rescue, worked to lighten the loads on the trapped gunboats. From May 10 through 12, the remaining gunboats above the rapids struggled through the upper shoals to the pool behind the main dam. Yet another dam had to be built to refloat a gunboat that got stuck during this passage. Then on the twelfth of May, the Mound City, the largest gunboat of the fleet, ran for the gap in the main dam. The previous scene was repeated, with thousands lining the banks to watch the excitement. Marching bands played the "Star Spangled Banner" and the 'Battle Cry for Freedom" Like the Lexington before it, as the Mound City hit the gap, it ground against the rocky river bottom, and then shot through. The next day all of the trapped vessels lay safely below the rapids.
While Federal troops labored to build the dam, Taylor's Confederate army was not idle. Some rebels continued to harass the outposts around Alexandria, while others destroyed bridges and blocked roads in an attempt to entrap the Union forces. Federal boats already below the rapids were constantly ambushed along the lower Red River as they attempted to supply the army. In fact, the Confederate soldiers were able to cut off all navigation on the river for a while, isolating the Yankees.
Admiral Porter's fleet on the Red River. From \ Harper's Pictorial History of the Civil War, March 1864. Courtesy of Library of Congress.
On May 13, with all the gunboats now safely below the rapids, Union forces moved out of Alexandria. The Union soldiers left with mixed feelings. They had been beaten in battle, harassed, and almost completely destroyed. They were exhausted. Still, they had accomplished a magnificent feat in building the dam and rescuing the fleet, and some had even made friends among the townsfolk.
Alexandria, May 1864. Courtesy of State Library of Louisiana.
But for the local population this was a critical time. Rumors spread that the town would be torched when the army left. Banks ordered a detail of 500 men to be left behind to protect the town from arson. But fires quickly broke out as soon as the main army was out of town. It is unclear who started the fires, as some accounts describe soldiers looting and setting fires, while other accounts note that army guards shot looters. Probably, both Union troops and local looters were involved. One detachment, the 92nd Colored Infantry who also helped build the dams, was known to have fought a fire for many hours, until the building was doomed and the troops were forced to continue their retreat. One Yankee soldier described the scene:
Cows ran bellowing through the streets. Chickens flew out from yards and fell in the streets with their feathers scorching them.... Crowds of people, men, women, children and soldiers, were running with all they could carry, when the heat would become unbearable and dropping all, they would flee for their lives, leaving everything but their bodies to burn. Over the levee the sights and sounds were harrowing. Thousands of people, mostly women, children and old men, were wringing their hands as they stood by the little piles of what was left of all their worldly possessions (Van Alstyne 1910:320-321).As the expedition retreated south down the Red River, Confederate cavalry did what it could to badger the Union forces at every opportunity. However, no matter how courageously the men fought, the rebel army was too small to seriously oppose the retreat of the entire expedition. At Mansura, Louisiana, Taylor attempted to stand against the Federals, but after a four-hour artillery duel, he had to withdraw.
Though the campaign seemed about at an end, Banks found that he had to call on the services of Lieutenant Colonel Bailey once more. At the Atchafalaya River, Bailey directed the construction of a bridge which he promptly fashioned out of transport vessels. Around 24 transports were placed across the river and held together with large timbers. Then, long planks were laid across the prows of the transports to form a temporary bridge. Banks's army was able to cross the river quickly and safely and continue the retreat south to Baton Rouge. By that time, every soldier knew and appreciated the frontier engineer from Wisconsin.