Despite this potential complication, nearly all the different tunnel center lines met within or so. The detailed survey work that made these tunnel digs as precise as required was nearly all done by the Canadian-born and -trained Lewis Clement, the CPRR's Chief Assistant Engineer and Superintendent of Track, and his assistants. 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 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 through 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. 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