As part of my job, I will probably have to clean out a basement together with another intern, who is female, which presents a shaila of yichud. There are other people in the actual building, but in terms of the basement, it will be only the two of us. May I rely on telling the goyishe security guard to check in on us from time to time? May I rely on leaving the door open or unlocked, even though no one will actually come in, unless I request, and even then who knows if the goy will want to come in?
The best thing is to keep the door open and request one of the Jewish neighbors to drop in unexpectedly.
E:H 22:5 & 9, 148:2 Ramo, Pischei Teshuvah E:H 178:15, Makneh Kiddushin 91, Teshuvas Maharil Diskin Kuntras Acharon 206, Teshuvas Dovev Meshorim 5,