Why is the horizontal section of the Deep Isolation concept necessary?

The horizontal section (the disposal section) of the drillhole allows waste to be placed end-to-end (with some spacing between the waste canisters). This end-to-end placement results in a lower thermal heat load than a mined repository or vertical borehole and placing the canisters horizontally provides more support for the waste canisters. The horizontal aspect also allows for less disturbed rock directly over the waste. An 18” drillhole will have approximately 9” of disturbed rock around the drillhole, but the remainder of the thousands of feet of rock between the waste and the surface will remain undisturbed.