On the march to Harrison's Landing on the James River, he reconnoitered and selected positions for the Battle of Gaines Mill, the passage of White Oak Swamp and the Battle of Malvern Hill. After the conclusion of his work in that campaign, he again was engaged in working on the defenses of Washington as chief engineer of the Department of Washington until May 1864. He had certain additional special assignments such as devising the defenses of Pittsburgh, Pennsylvania, during this period.
He planned and selected locations for the Battle of Gaines Mill, the passage through White Oak Swamp, and the Battle of Malvern Hill on his way to Harrison's Landing on the James River, and afterwards worked on the defenses of Washington as chief engineer of the Department of Washington until May 1864. He also had special assignments such as designing the defenses of Pittsburgh, Pennsylvania.