Methods of Mold Investigation and

Remediation: A Case Study

Dawn Bolstad-Johnson, MPH, CIH

Christopher Hansen, CIHMichael Jimenez

City of Phoenix

Background Info…

Municipal Courts employees complained of non-specific health effects and requested an indoor air quality investigation.

A walk-through of the building revealed additional information:

There was a severe water leak about three weeks prior to the complaint

Background Info

The water leak was a result of a pipe that had burst while being repaired.Several thousand gallons of water were released in a short time.

The leak occurred in the basement area.Everyone was evacuated and a contractor was contacted to remove inches of standing water found throughout the basement.

Reported Health Effects

The initial health effects reported included a municipal judge who reported that he had lost his voice while he was on the bench.

Others reported non-specific symptoms and/or building conditions such as “feeling yucky”, “stuffy air”, not enough circulation, etc.

Indoor Air Quality Investigation

A walk through of the building revealed no visual evidence of mold growth on any of the affected wall systems.

Our hypothesis: If there was mold growth it may be contained within the wall cavities in the affected areas.

Sampling Plan

Both non-viable and viable area samples were collected simultaneously within areas where the health complaints originated.Additionally, 6 wall cavity samples were collected.

14 non-viable samples were collected utilizing Zefon Air-O-Cells 8 viable samples were collected utilizing an Andersen single stage impactor equipped with a malt extract agar (MEA).

Sampling MethodsNon-invasive wall cavity samples were collected by removing an electrical outlet plate and placing the Zefon cassette near the existing hole in the wall.The wall was tapped intermittently during the 3-4 minute sampling time.

Preliminary Sampling ResultsSample ID Viable

(CFU/M3)

Non-Viable(Spores/M3)

Alcove to 16/17 12 95

Courtroom 17 12 24

Judge Taylor 8,221 28,976

Judge Taylor - wall cavity

--- 60,038

Courtroom Pod-14/15 530 1,895

Courtroom 14 <12 95

Judge Doug 36 475

Judge Doug- wall cavity --- 100,667

Outside 189 2,523

Schematic Drawing

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STORAGEW M

Water Leak Source

The Dilemma

The sample results proved that we had mold growth in the wall cavities.We had employees experiencing health effects.

This building is scheduled for demolition within the next 9–12 mos.A $12M new courts facility is under the final stages of construction.

The Dilemma

We needed to remedy the problem:

Using the least amount of $$$, andThe least impact on the municipal courts system. (At least 4 courtrooms were shut down.)

Proposed Solution No. 1

Our insurance adjuster recommended a contractor to come in to:

Clean/wet-wipe all wallsApply a biocide to all surfacesFollowed by a chlorine dioxide bomb

This solution appeared to be the best at the time as it would minimize down time and overall disruption of court activities.

Problems…

Management witnessed the contractor training his staff on our job site.

Apparently, he had gotten his crew from a labor pool.

We gave the contractor an opportunity to supply us with minimal OSHA compliance training documentation.

They could not.

Additional Sampling

In the interim, additional sampling had been accomplished to determine the extent of the mold contamination.

An additional eighty-one (81) samples were collected in the remaining occupied areas of the basement which had not been previously tested.

Sampling Methods

Air Samples for viable and non-viable spores were collected simultaneously from the air delivery vent and the ambient room air.

A tent was constructed around the air diffuser to accomplish this task.

Sampling Methods

Additional non-invasive wall cavity samples were collected using a Zefon cassette and an existing hole in the wall as previously discussed.

Sampling ResultsSample ID Viable

(CFU/M3)

AmbientNon-

Viable(Spores/M3)

Wall CavityNon-

Viable(Spores/M3)

Courtroom 15 24 <25 684

Courtroom 16 <12 50 333

Courtroom 10 <12 500 2,073

Judge Garry’s Chambers 106 4,000 583,519

Courtroom 12 177 1,600 171,074

Courtroom 12 Inside Tent <12 300 ---

Women’s Restroom 24 675 11,814

Outside 495 15,575 ---

Schematic Drawing

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STORAGEW M

Water Leak Source

Solution No. 2

Additional sampling allowed us to clearly define affected areas.

In order to control the potential hazard, we elected to complete remediation in a limited number of areas.

All other areas were to be thoroughly cleaned with a 10% bleach and water solution.

Seal the walls above the ceiling with poly and expandable foam and all existing wall holes (e-outlets, phone jacks, etc.) with 6 mil poly.

Findings

Visible mold was found on drywall within the office during cleaning.The wall cavity samples in these areas were also high.

Strategy change:Remove sections of drywall with visible mold in office areas.

Solution No. 2 Addendum

We hired a mold remediation firm to removed mold contaminated walls and do the plumbing repairs.

Total Cost of Remediation:

$57,165.00

RemediationWalls were cut about 4’ or at least 1’ above visible mold contamination.

All work was accomplished under filtered negative air.

Remediation

RemediationVisible mold was found in the wall cavity.

RemediationClearance sampling was accomplished after remediation and cleaning were completed with non-viable spore traps.

Sample Results

Sample IDWall

CavityNon-Viable(Spores/M3)

Before Cleaning

Non-Viable

(Spores/M3)

After Cleaning

Non-Viable(Spores/M3)

Courtroom 12 171,074 1,600 25

Courtroom 13 11,927 75 25

Courtroom 15 684 <25 120

Courtroom 16 333 50 50

Eddie’s office 68,222 2,875 24

Angie’s office 2,444 2,375 120

Outside --- 15,575 8,548

ConclusionsAll walls around courtrooms 12, 13, 14, 15, 16 and 17 were sealed using an expandable foam and plastic sheeting over holes.

The wall between the men’s and women’s RR was removed as were areas within selected Judge’s chambers where visible mold growth was discovered.

Schematic Drawing

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STORAGEW M

Water Leak Source

Lessons Learned

Building tents around air diffusers while taking simultaneous room samples will quickly show whether the HVAC system is contributing to the mold count in the room.

There are non-invasive ways to check mold growth within wall cavity areas.While these samples cannot be compared to outside air, they will give you more info.