Sgt Elisha Butt replaced Sgt James Simpson (co. A) in charge of the brigade pioneer corps on 13 or 15 August 1863, because Co. A had too few sergeants. This took a large number of orders and letters: see the letter on 13 August and various letters and orders on 15 August.
On 24 June 63 the pioneers were ordered to turn over all arms and accoutrements in their possession. On 13 Aug 63, the regiment received a letter asking why requested pioneers hadn't been sent. On 14 Aug 63, they received an order from brigade hq about the reorganization of the pioneer corps. They received another letter on 15 Aug about the reorganization of the brigade pioneer corps. See the orders on 15 August 1863 for personnel changes.
Sinex issued orders relating to pioneers on 15 August. This describes some of their duties and their equipment, and clarifies command responsibilities for them (perhaps this is a response to the letter received on that date).
On 15 April 1864, Sinex ordered that the regimental pioneer corps was to consist of the following 7 men, and any excess pioneers were to be returned to their companies: corp Robert Fletcher (I), and pvts Robert Gray (A), Samuel Edwards (B), John McCoy (D) (still there Sep (?) 64), George B. Tomlin (E), Peter McCollough (F), Patrick Costello (I) (general order 8, HQ 91st PA, 15 Apr 64
They were apparently entitled to bear arms (circular, HQ 91st PA, 10 April 1864).
see details and detachments for other details to the pioneer brigades