Q: My wife and I live in a house that was built in 1939. About a month or so ago, we discovered that the original galvanized pipe that drained the kitchen sink and the washing machine into the main drain line had a large hole rusted in the bottom of it and that upwards of six months of kitchen sink waste had been draining into the crawlspace. There was a large area (about 15 inches by 15 inches) covered in standing water that contained a great deal of organic matter. We ran fans under there for a while once the pipe was fixed, and I pulled out all the plastic moisture barrier that was keeping the water from seeping into the soil. At last, all the standing water is gone, but I think because of the organic content of the water, the area which was covered by water is now covered by mold. Most of the mold is white, some looks dark gray. I'm unsure how to proceed from here in order to ensure that this mold does not come back to haunt me. Any advice on what my next steps should be? If I hire someone to take care of this, what sort of things should I make sure they plan to do? One company planned to sprinkle lime and sand over the area and then lay down new moisture barrier on top of that. Is that good enough to deal with this problem in a healthy way?

A: From your description of the problem in your basement, it sounds like the organic matter/waste water was contained within the vapor barrier which you removed and disposed. If the vapor barrier's integrity was compromised, however, some of the waste water/organic matter may have gotten into the soil beneath it. It sounds like the area is unoccupied and is not a mixing chamber for your heating system.

I'd recommend that the soil in that area be removed only if there is visible organic matter present in the soil from the opening in the drain line. Since soil is composed of organic matter, I wouldn't be overly concerned with the mold on the soil. If the mold is associated with organic waste matter, it should be removed along with the visible organic waste from the drains. A vapor barrier can then be installed and I would maintain the crawlspace free from standing water in the future.

You did not describe the exact location of the rusted opening. From your description it sounds as if the rusted opening was in the basement below the floor joists. If the opening is at or above the sub floor level, you should check the floor boards for signs of water damage and/or microbial contamination. If water damage and/or microbial contamination is identified, the wood may need to be treated or otherwise remediated.

This question was answered by Mary Biagiotti, a certified industrial hygienist with EFI Global.

QA archive >>

If you have a question for a mold expert, please send it to Brett Lyon, senior editor of construction.com at brett_lyon@mcgraw-hill.com.