DIGGING UNDER FIRE AT DUTCH GAP 1864True enough. One of the photos on that wiki is the exact same location as the above pic, but they are very different, I can't tell which one was taken first.
The caption references Butlers canal, but I can't find that name anywhere else associated with Dutch gap.
Here for a moment the Engineering corps of General Benjamin F. Butler's army paused while the camera of the army photographer was focussed upon it. In August, 1864, Butler. with his army then bottled up in Bermuda Hundred, began to dig a canal at Dutch Gap to save a circuit of six miles in the bend of the James River and thus avoid the batteries. torpedoes, and obstructions which the Confederates had placed to prevent the passage of the Federal fleet up the river toward Richmond. The difficulties of this engineering feat are here seen plainly in the photograph. It took Butler's men all the rest of the year (1864) to cut through this canal, exposed as they were to the fire of the Confederate batteries above. One of the last acts of General Butler was an unsuccessful effort to blow up the dam at the mouth of this canal, and by thus admitting water to it, render it navigable.
Here are some more construction photos "under fire"