 Up to three trains were operated at once, with a passing siding in the middle of the tunnel allowing for one trainload of supplies to be delivered every half-hour.Hazardous materials such as dynamite were not allowed inside the tunnel and had to be packed over the Santa Ynez Mountains on a primitive trail.The work was made even more difficult by the constant leakage of groundwater into the tunnel which formed "a continuous downpour from the roof in many places" and special care had to be taken to prevent contamination, since this water ultimately flowed into Santa Barbara's municipal supply.