Radon Mitigation of Groundwater at a Commercial Fish Hatchery

Groundwater radon levels of 83 Bq/L (2240 PC&) generated indoor radon levels >3300 Bq/m3 (89 pCi/L) at a commercial fish hatchery. Passive and active mitigation strategies to reduce the waterborne radon levels included a packed column, a waterfall through perforated grates, surface aeration, and bottom bubblers. Though waterborne co~centrations were reduced up to 83% using a combination of mitigation procedures, a comparable reduction in indoor radon concentrations was not observed. Measurements by two continuous radon detectors agreed with those from grab flasks. A diurnal cycle showed that indoor radon levels peaked in early afternoon, probably as a result of wanner air being dissolved in the water during mitigation. Reduction of indoor radon levels below 148 Bq/m3 (4 pCi/L) was achieved by direct air ventilation at high flow rates.