All sorts of crud can grow in wet holes like that one. I used to have to clean out sump holes under some large outdoor machines that I helped to maintain, and we had to suit up with respirators and shoulder long rubber gloves, and if we got wet, we had to change our clothes, and shower with detergent. Those holes collected rainwater runoff, and had solvents, oils, and "who-knows-what-else" in them - dead critters, once in a while. It's not too surprising to hear that Boyd and his crew are ill.