Mold Remediation

[rlewistx]

I am a structural engineer, not a mechanical engineer, but this seemed to be the appropriate forum for the question. I was called out to an existing office building, located in NE TX, that had mold in the basement. There is a high ground water table, near the floor line. There are at least 2 large sump pits with pumps. They have had leaking in the basement, not large amounts, but persistent enough over the years to grow mold. They have cleaned up the mold and would now like to reoccupy the basement.

The basement wall is concrete. In front of the concrete wall is a small chase. The built a trough in the floor slab about 8 " wide by putting a curb in the floor slab. They built the stud wall on the curb so there was a cavity behind the studs. The trough emptied into the sump pits. This cavity is where the mold grew. The leaking occurred in isolated spots, not all around the basement, and it appeared to be small when it happened so the water sat on the wall or in the trough and never made it to the sump.

The owner doesn't want to dig up the outside of the building and re-apply a water proofing material to the foundation. I was wondering if there was a system whereby dry air could be circulated in this wall cavity and exhausted outside to dry up the moisture as soon as it occurs and prevent mold from growing. Would this be a typical response to this type of situation? Any other suggestions would be greatly appreciated.


Thanks.

Rich

 

[rlewistx]

I haven't gotten anyone to bite on this yet and it is getting buried deep in the list so I thought I would try sending it to the top again.

Thanks.

 

[ccw]

I just attended a brief seminar by a microbiologist on the subject. Here are some salient points which might be applicable.

Mold needs food and water. Deprive either or both and you are OK. Keep the space dry and clean and there will be no mold problem.

Follow ASHRAE 1047 recommendations where possible, which basically says "keep it dry".

Keep the annular space air moisture below 17% or below 60% RH and mold probably will not grow. Your idea of pushing through dry air in the annular space is good in this regard. However, this air should not be recirculated.

There currently are no TLD, PEL's by NIOSH, OSHA, etc. for acceptable exposure. There are &quot;unofficial&quot; guidelines now for bio-aerosol based sampling of < 300CFU/M**2 being safe. Field test kits and labs should be available in the DFW area.

Having said that, one might consider rebuilding the false wall using galvanized metal studding and sheeting, (mold cannot eat metal but love cellulose products) use only metal ductwork in the HVAC. Instrument the 8&quot; annular space for humidity sensors. Of course, fix the troughs so each drains dry.

Before repairs make sure the area is cleaned up thoroughly. The mold critters - stachybotrys, etc. are not irritants but the toxins they may produce and leave behind are irritants: trichothecene, satratoxin. After repairs make sure there is a commissioning phase to test the efficacy of the remediation before taking occupancy. Do periodic field bioaerosol sampling during occupancy.

Lastly, be careful because engineers, contractors, and owners are easy targets for litiguous minded &quot;mold sensitive&quot; occupants.

 

[ccw]

One final thought on the subject, used induced draft fans for the annular space, ie. keep the occupancy space under positive pressure, so biotoxins from the annular space cannot be pulled in through any false wall/ceiling penetrations such as electrical boxes, leaky duct work, etc.

 

[kenvlach]

Pretty much agree with ccw's advice, and want to emphasize the lawsuit liability. Also, there are waterproofing masonry paints which might cut your costs.

See TOXIC MOLD NEWS ONLINE

http://www.toxic-mold-news.com/toxic_mold/stach.html

&quot;Stachybotrys Chartarum (atras) is a greenish-black fungus that is found throughout the world and is typically wet and slimy to the touch. There are somewhere in the neighborhood of 15 different species that grow in surroundings where the humidity exceeds 50%. Stachybotrys Chartarum thrives on materials high in cellulose and low in nitrogen content. Examples include wet leaves, straw, carpet, wallpaper, thermal insulation, fiberboard, dry wall, gypsum board, paper, dust, and hay. What these examples have in common is their propensity to become chronically moist or water logged due to excessive humidity, water leaks, flooding, etc...&quot;
&quot;Stachybotrys chartarum (SC) is dangerous to humans because it can, given the proper environmental conditions, create multiple toxic chemicals called mycotoxins. These toxic byproducts exist in the spores of the mold, as well as in the tiny fragments that can become airborne...&quot;

To get action out of your property owner, just print out results of a web search for 'black mold lawsuit.'
There are many lawyers out there looking to make a buck; see

http://www.moldlawyer.com/