Stephen R. Radocha, treasurer of the Coaldale School Board and mining employee of the Lehigh Navigation Coal Company at its No. 8 colliery, was killed instantly at 10 a.m. today by a delayed explosion of dynamite which he and his mine buddy, Raymond Hoffman, also of Coaldale, had placed a few minutes earlier. A native of Czecho Slovakia, he immigrated to this country in 1906. Surviving are his widow and four children.