1

Determination of Clearance Determination of Clearance

Criteria Following Mercury Criteria Following Mercury

Decontamination ProjectsDecontamination ProjectsPOPO--115115

American Industrial Hygiene Conference and Exposition

May 13-16, 2006

Chicago, IllinoisDavid Regelbrugge, CIH, CSPGary N. Crawford, CIHBrad Caddick Win WilliamsPH: 847-692-4700E-Mail: dcr@boelter-yates.com

2

BackgroundBackground• How do you go about clearing a

mercury clean-up site?– Few established methods for

identification, decontamination and/or clearance of remediated areas.

3

BackgroundBackground• Spills & Releases

– Most often seen in educational facilities and hospitals.

• Spills may be from years of abuse or a single careless incident

– For example, laboratory use vs. a student finding or bring mercury from home to school to show to fellow students.

– Rare but occasionally seen in homes.

4

Exposure ValuesExposure Values

• Occupational Exposure Values– OSHA

• Ceiling limit of 100 µg/m3

– ACGIH®

• TLV® of 25 µg/m3

• Also carries a “Skin” notation

5

Exposure ValuesExposure Values• Environmental Values

– Values vary between agencies• EPA Reference Concentration 0.3 µg/m3

• Agency for Toxic Substances and Disease Registry (ATSDR)

– 0.2 µg/m3 minimal risk level– 3 µg/m3 for Industrial/commercial clearance

» For an 8 hr day – <1 µg/m3 for residential clearance

» For a 24 hr day

– Which value should be used?

6

Exposure ValuesExposure Values• Environmental Values

– Illinois gas regulators spills• Began in July of 2000• Older gas regulators (installed prior to

1961) contained approximately 135 grams (two teaspoons) of liquid mercury.

• Located inside homes• Mercury was spilled during replacement• Approximately 200,000 homes affected

7

Exposure ValuesExposure Values

• Illinois environmental values– Illinois Department of Public Health

(IDPH), the ATSDR, EPA and other local agencies agreed upon acceptable environmental levels.

8

Illinois ReIllinois Re--occupancy occupancy Environmental LevelsEnvironmental Levels

3 µg/m3Industrial-Commercial

<1 µg/m3Residential

Indoor Air Concentration

Level Acceptable for Re-occupancy

9

Exposure ValuesExposure Values

• Since there had been a consensus between the IDPH, ATSDR, EPA and other agencies in the Illinois case, we decided to used the ATSDR industrial-commercial clearance level of 3 µg/m3.

10

Assessment StrategyAssessment Strategy• Use direct reading instrument to survey

areas and identify potential areas of concern.

– Two instruments available • Instrument “A”

– Detection minimum detection level of 3 µg/m3

• Instrument “B”– Detection minimum detection level of 0.002 µg/m3

– Instrument “B” was used due to the increased sensitivity.

11

Assessment StrategyAssessment Strategy• Any area with visible mercury or

measurements above the Illinois industrial/commercial clearance levels (3 µg/m3) was considered contaminated.– Contour map developed or highlighted

photograph used to identify where contamination was found.

12

Remediation StrategyRemediation Strategy

• All contaminated areas were cleaned by a contractor with mercury remediation experience.

13

Case Study 1Case Study 1Mercury Contamination in Laboratory

14

Case StudiesCase Studies•• Case 1:Case 1:

Laboratory where mercury had been used in experiments for years. Lab was scheduled for a major renovation. Lab officials wanted the area checked for asbestos and mercury prior to demolition/renovation.

15

Case Study 1Case Study 1• Initial assessment:

– Mercury concentrations ranged from 0.3 µg/m3 to >260 µg/m3

– Highest concentrations near a fume hood

– Elevated concentrations also observed above asbestos floor tile located near the fume hood.

16

Case Study 1 Case Study 1 • Asbestos and mercury remediation

was recommended• Contractor with asbestos and

mercury abatement experience was hired to perform the remediation.

17

Case Study 1 Case Study 1 • Removal techniques

– Containment with decontamination chamber (DCU)

– Workers wore disposable clothing and respirators equipped with HEPA/mercury filters.

– Vacuums and negative air machine equipped with HEPA/mercury filters.

18

Case Study 1 Case Study 1 • Remediation techniques

– Asbestos materials removed first• Increase in airborne mercury (Hg) vapors

seen when tile was removed– Possible contamination under the tile?

– Following the asbestos removal• Hg Sorb®, a mercury absorbent was used

on floor and other contaminated areas. This was followed by a through cleaning of the areas with Red Devil TSP/90®

19

Case Study 1 Case Study 1 • Air samples collected during

remediation– Samples for both asbestos and mercury

collected during removal.– Asbestos samples collected in

accordance with NIOSH 7400– Mercury concentrations measured with

the direct reading instrument

20

Case Study 1Case Study 1• Multiple cleanings were conducted

– Cleaning process repeated for mercury until area measurements indicated that airborne mercury concentrations were below 3 µg/m3 (ATSDR commercial level)

• Cleanings performed 6 times over four days

21

Case Study 1 Case Study 1 • Waste

– All asbestos waste double bagged– All waste bags tested for mercury

contamination prior to disposal with the direct reading instrument

• Waste > 1 µg/m3 (the residential clearance criteria) considered potentially contaminated and TCLP analysis performed.

• If TCLP analysis indicated levels > 0.2 mg/L (EPA limit) the material was disposed of as mercury waste.

22

Case Study 1 Case Study 1 • Waste (Continued)

– Any elemental mercury or known mercury contaminated wastes were placed into plastic drums or buckets.

– This waste was sent to a licensed metal disposal/recycling facility.

23

Case Study 1 Case Study 1 • Final mercury air samples (continued)

– When direct reading instrument indicated that mercury concentrations in the remediated area were below 3 ug/m3 final air samples were collected.

– Final air sampling methodology • Five (5) samples collected throughout the lab• NIOSH Method 6005 on SKC® Hydrar® sorbent

tubes• seven to eight hours sampling duration • Ambient temperature kept above 75oF during

collection

24

Case Study 1 Case Study 1 • Final mercury air samples (continued)

– Area was released when air samples indicated the mercury concentrations were at or below the ATSDR industrial/commercial level of 3 µg/m3.

25

Case Study 2Case Study 2Mercury Contaminated Science Hall

26

Case Study 2Case Study 2•• Case 2:Case 2:

Three story college science hall scheduled for sale and possible demolition. Mercury use in building was unknown but suspected. Limited visible mercury observed in a couple of areas.

27

Case Study 2Case Study 2• Mercury survey completed with the

direct reading instrument• Same criteria used as in Case 1• Isolated areas of mercury

contamination identified.• Highlighted digital photographs used

to indicate contaminated areas.

28

Case Study 2Case Study 2Highlighted digital photographs used

to identify contaminated areas

29

Case Study 2Case Study 2• Mercury remediation of contaminated

areas recommended.• Remediation performed, similar to

that used in Case 1.– Regulated areas were used instead of

full containment.• Limiting access to contaminated areas• Full PPE for remediation crew.• Disposable foot coverings used to prevent

potential tracking of mercury.

30

Case Study 2Case Study 2• Direct reading instrument used to evaluate

remediation progress.• Findings during remediation

– Visible mercury found underneath cabinets and ceramic tiles near cabinets.

– Mercury detected in some of the drain pipes.• Horizontal pipes removed• Vertical pipes flushed with mercury surfactant

31

Case Study 2Case Study 2• Main catch basin for the building was

tested for mercury.– Water & sludge tested

• Water results compared Local Sanitary Districts discharge limits for mercury

• Sludge sent for TCLP analysis.– Water and sludge were contaminated.– Test performed prior to pipe cleaning.

32

Case Study 2Case Study 2• On-site sewer system tested

– Same environmental criteria applied to manholes as the catch basin.

– Mixed results• Sludge contaminated in three of the four

manholes tested.• Water in most manholes was not

contaminated.

33

Case Study 2Case Study 2• On-site sewer system cleaned

– Cleaning performed by a licensed hazardous waste/remediation

• Sewer vacuum/cleaning truck utilized.• All sludge & water removed

– Direct reading instrument was used to evaluate sewer cleaning

• Considered clean when measurements below the ATSDR level of 3 µg/m3.

34

Case Study 2Case Study 2Visible mercury found underneath baseboard & cabinet

35

Case Study 2Case Study 2Bottom of cabinet and floor tile removed to access

mercury contamination.

36

Case Study 2Case Study 2Catch basin being cleaned

37

Case Study 2Case Study 2• Final air samples (continued)

– When direct reading instrument indicated that mercury concentrations were below 3 µg/m3

final air samples were collected.– Final air sampling methodology

• Eight (8) samples collected on each floor of the building.

• NIOSH Method 6005 on SKC® Hydrar® sorbent tubes.

• Seven to eight hour sample duration. • Ambient temperature kept above 75oF during

collection

38

Case Study 2Case Study 2• Final air samples (continued)

– Area was released when air samples indicated the mercury levels were at or below the ATSDR industrial/commercial clearance level of 3 µg/m3.

39

Lessons LearnedLessons Learned1. Instrument “B” was an excellent instrument

to use for the initial inspection, monitoring of remediation and for use prior to final air sampling.

2. Mercury contamination can be worse than it originally appears.

3. The ATSDR’s recommended industrial/commercial clearance level of 3 ug/m3 was achievable.

40

Speaker Contact Information:Speaker Contact Information:

David C. Regelbrugge, CIH, CSPDirector, Environmental Health & SafetyBoelter & Yates, Inc.847/685-9276dcr@boelter-yates.com