This shape leaves ample room for the cars, and, by contracting the roof, is more secure than a semicircle of 16 feet diameter. Portions of the Brookville tunnel were lined with brick for added strength, with the brickwork originally contracted to Joseph Dettor, a local brickmaker. Because of the poor quality of Dettor's bricks, Crozet decided to use these bricks on the Greenwood Tunnel to the east, which was a stronger bore than Brookville. Crozet estimated in 1854 that the total number of bricks required for the entire tunnel would be upwards of 750,000. After examining the offers of multiple brickmakers, the Virginia Board of Public Works contracted Robert Harris to provide the bricks for the Brookville Tunnel. The resulting arch was between in thickness over the entire length of the tunnel, and formed an opening approximately high and, at the extreme, wide. During the construction, the timbers that were used to support the fragile sections of the tunnel to be arched were left in place after the arch was completed, as it was thought too hazardous to remove them. When the earth slip occurred during the Civil War, these remaining timbers acted as levers, furthering the cracking and structural instability of the tunnel. As the new arch was constructed, the old timbers were removed, and the space in between the new and old walls was filled with brick and cement. The original brick portals were replaced by the Chesapeake and Ohio Railway in 1928 with concrete portals, as part of a series of tunnel upgrades across the line beginning in the 1920s. The new portals no longer bore the distinctive elliptical design of Crozet's original, but had vertical sides and a semi-circular arch. The total cost to complete the Brookville Tunnel amounted to $114,600, with a cost per foot, at a length of , of $131.90. By comparison, the cost per foot of the Greenwood Tunnel was $138.30, the Little Rock Tunnel was $123.90, and the Blue Ridge Tunnel was $108.60. Costs at the Brookville Tunnel were greatly increased from the expected by the frail and insecure earth encountered, contrary to what originally appeared to be solid rock. Workers, both inside and outside laborers, were paid approximately $1.12 per day, while miners were paid $1.37 per day, equivalent to $ and $, respectively, today.