Complex Radon Mitigation of a Large Building

"Home Plate", a combination bar, grill, and recreation center, is an 8000 ft2 single-story slab-ongrade building with a partial basement. Radon testing of each ground-contact room found elevated radon levels in seven of eight rooms (5.6 pCi/L to 13.4 pCi/L). Mitigation diagnostics determined that the installation of three active soil depressurization (ASD) systems would reduce the levels to <4 pCVL if the (-) 80 Pa shell differential pressure (DP) caused by the building's exhaust systems could be reduced to 5 8 Pa. In 2002, a phased approach to reduce the significant DP was implemented. This approach included installation of passive louvers and a prototype 5-ton supplemental air-makeup system. The approach was successful, with postmitigation results ranging from < 0.5 pCi/L to 2.0 pCVL.