Number 239 of the General Instruction on the Roman Missal (in front of the Sacramentary) states, "If any of the precious blood spills, the area should be washed and the water poured into the sacrarium." So, too, should the purificators used to cleanse chalices, patens and ciboria be washed in the sacrarium and the water drained into the earth.
The sacrarium is special because it drains directly into the soil underneath the church rather than into a common drain. If there should be no sacrarium, water from these washings may be poured on clean earth in the garden where it will not be stepped on. After the first washing these cloths may be allowed to dry and then washed in a normal way.
For more about what to do in the case of accidents with the eucharistic elements, see the Appendix in Ceremonies of the Modern Roman Rite, by Msgr. Peter J. Elliot (Ignatius Press).