The Bureau of Mines conducted water sampling with flow measurements at moraine state park to determine the long-term effectiveness of the deep mine sealing completed between 1969 and 1971. Data collection in 1979 and 1980 consisted of taking two samples per weir location from a group of mine entries. These data were compared with baseline data from before and 1 year after seal completion, utilizing standard statistical procedure. The total mean water discharge and total mean iron load increased, whereas the mean acid load decreased. The minimum water discharge, minimum acid, and total minimum iron load increased, and the maximum water discharge, maximum acid, and total maximum iron load decreased as a result of sealing. The acid load variance was reduced approximately 55 pct. The water discharge and water quality were more consistent than before sealing. In general, the water quality was better within a mine pool than at the discharge points; the development of a pool did not insure improvement at the discharge points. Overall, mine sealing improved the water quality in the Park's Lake Arthur.