<P> The summit tunnel (Number 6), 1,660 feet (510 m), was started in late 1865, well ahead of the railhead . Through solid granite, the summit tunnel progressed at a rate of only about 0.98 feet (0.30 m) per day per face as it was being worked by three eight - hour shifts of workers, hand drilling holes with a rock drill and hammer, filling them with black powder and trying to blast the granite loose . One crew worked drilling holes on the faces and another crew collected and removed the loosened rock after each explosion . The workers were pulled off the summit tunnel and the track grading east of Donner Pass in the winter of 1865--66 as there was no way to supply them, nor quarters they could have lived in . The crews were transferred to work on bridges and track grading on the Truckee River canyon . </P> <P> In 1866 they put in a 125 - foot (38 m) vertical shaft in the center of the summit tunnel and started work towards the east and west tunnel faces, giving four working faces on the summit tunnel to speed up progress . A steam engine off an old locomotive was brought up with much effort over the wagon road and used as a winch driver to help remove loosened rock from the vertical shaft and two working faces . By the winter of 1866--67, work had progressed sufficiently and a camp had been built for workers on the summit tunnel which allowed work to continue . The cross section of a tunnel face was a 16 - foot - wide (4.9 m), 16 - foot - high (4.9 m) oval with an 11 - foot (3.4 m) vertical wall . Progress on the tunnel sped up to over 1.5 feet (0.46 m) per day per face when they started using the newly invented nitroglycerin--manufactured near the tunnel . They used nitroglycerin to deepen the summit tunnel to the required 16 - foot (4.9 m) height after the four tunnel faces met, and made even faster progress . Nearly all other tunnels were worked on both tunnel faces and met in the middle . Depending on the material the tunnels penetrated, they were left unlined or lined with brick, rock walls or timber and post . Some tunnels were designed to bend in the middle to align with the track bed curvature . Despite this potential complication, nearly all the different tunnel center lines met within 2 inches (5.1 cm) or so . The detailed survey work that made these tunnel digs as precise as required were nearly all done by the Canadian born and trained Lewis Clement, the CPRR's Chief Assistant Engineer and Superintendent of Track, and his assistants . </P> <P> Hills or ridges in front of the railroad road bed would have to have a flat - bottomed, V shaped "cut" made to get the railroad through the ridge or hill . The type of material determined the slope of the V and how much material would have to be removed . Ideally, these cuts would be matched with valley fills that could use the dug out material to bring the road bed up to grade--cut and fill construction . In the 1860s there was no heavy equipment that could be used to make these cuts or haul it away to make the fills . The options were to dig it out by pick and shovel, haul the hillside material by wheelbarrow and / or horse or mule cart or blast it loose . To blast a V shaped cut out, they had to drill several holes up to 20 feet (6.1 m) deep in the material, fill them with black powder, and blast the material away . Since the Central Pacific was in a hurry, they were profligate users of black powder to blast their way though the hills . The only disadvantage came when a nearby valley needed fill to get across it . The explosive technique often blew most of the potential fill material down the hillside, making it unavailable for fill . Initially, many valleys were bridged by "temporary" trestles that could be rapidly built and were later replaced by much lower maintenance and permanent solid fill . The existing railroad made transporting and putting material in valleys much easier--load it on railway dump cars, haul where needed and dump it over the side of the trestle . </P> <P> The route down the eastern Sierras was done on the south side of Donner Lake with a series of switchbacks carved into the mountain . The Truckee River, which drains Lake Tahoe, had already found and scoured out the best route across the Carson Range of mountains east of the Sierras . The route down the rugged Truckee River Canyon, including required bridges, was done ahead of the main summit tunnel completion . To expedite the building of the railroad through the Truckee River canyon, the Central Pacific hauled two small locomotives, railcars, rails and other material on wagons and sleighs to what is now Truckee, California and worked the winter of 1867--68 on their way down Truckee canyon ahead of the tracks being completed to Truckee . In Truckee canyon, five Howe truss bridges had to be built . This gave them a head start on getting to the "easy" miles across Nevada . </P>

When did the transcontinental railroad start and end