Sean at Mojave Desert Blog did you the favor of crunching the numbers in the Assessment, though of course you can check them for yourself. Quoting highlights from his article:

Up to 700 non-adult tortoises during the 3 year construction phase are expected to die. Non-adult tortoises are difficult to spot and remove from burrows, resulting in an estimated 90% mortality rate due to construction.

BLM estimates up to 9 adult tortoises (160mm or larger) will be killed during the 3 year construction phase.

BLM anticipates harassing 1,025 adult tortoises, and 2,349 non-adult tortoises, bringing the total number to over 3,000.

As many as 700 tortoises killed directly by construction, and then handling 3,300 more with a shockingly high mortality rate just from handling — for relocation, the data from the Fort Irwin relocation in 2008 indicate mortality can be about 50% of tortoises moved, and about as high a rate among tortoises in the “host” population to which Ivanpah’s torts are relocated, if you monitor the tortoises for more than three or four months. Mortality rates for mere handling can be 5-10%. If the overall mortality rate for all harassed tortoises and host tortoises at the relocation sites is just 9%, that’s a thousand dead tortoises.