The 85Kr activity of well No. 9 is (2.1 ± 0.3) mBq/cm 3 STP ofKr or ≈0.3% of the modern atmospheric activity indicating that no young water component is present in this groundwater and that no contamination occurred in extracting a Kr gas sample for 81Kr analysis. The 81Kr concentration was measured by laser resonance ionization spectroscopy to be 82 ± 18% of the modern atmospheric concentration. Only 5000 atoms of 81Kr were used in the final analytical step which represent ≈7% of the initial number present in a water sample of 50 1. An upper limit of 140 ka is calculated for the age of the water from a simple 81Kr decay model. Of key importance for the future use of a 81Kr dating technique is the conclusion that subsurface production of 81Kr appears to be unimportant.