Delay Doppler images of Mercury's polar regions showing enhanced radar backscatter have been interpreted as evidence for water ice in the polar craters and are consistent with pure water ice covered by about 20 cm of regolith. In this paper we assume that the volatile at the Hermean poles is water ice, and that it was initially deposited at one time in a clean layer. We constrain the time of such an impact by determining the rate of regolith emplacement. The rate of burial of ice deposits in polar craters on Mercury is estimated to be 0.43 cm/Myr. If the ice deposits in Hermean polar craters are both clean and buried by 20 cm of regolith, they must be relatively recently emplaced, <50 Myr ago. The predicted H concentration in the uppermost meter of regolith is calculated as a function of both time since emplacement of the ice and initial thickness of the ice layer. The combination of neutron data and radar data can provide additional insight into the size and age of ice deposits at Mercury.