Determination of Clearance Criteria Following Mercury Decontamination Projects

Transcription

1 Determination of Clearance Criteria Following Mercury Decontamination Projects PO-115 American Industrial Hygiene Conference and Exposition May 13-16, 2006 David Regelbrugge, CIH, CSP Gary N. Crawford, CIH Brad Caddick Win Williams PH: Chicago, Illinois 1

2 Background How do you go about clearing a mercury clean-up site? Few established methods for identification, decontamination and/or clearance of remediated areas. 2

3 Background 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. 3

4 Exposure Values Occupational Exposure Values OSHA Ceiling limit of 100 µg/m 3 ACGIH TLV of 25 µg/m 3 Also carries a Skin notation 4

5 Exposure Values Environmental Values Values vary between agencies EPA Reference Concentration 0.3 µg/m 3 Agency for Toxic Substances and Disease Registry (ATSDR) 0.2 µg/m 3 minimal risk level 3 µg/m 3 for Industrial/commercial clearance» For an 8 hr day <1µg/m 3 for residential clearance» For a 24 hr day Which value should be used? 5

6 Exposure 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 6

7 Exposure Values Illinois environmental values Illinois Department of Public Health (IDPH), the ATSDR, EPA and other local agencies agreed upon acceptable environmental levels. 7

8 Illinois Re-occupancy Environmental Levels Level Acceptable for Re-occupancy Indoor Air Concentration Residential <1 µg/m 3 Industrial-Commercial 3 µg/m 3 8

9 Exposure 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/m 3. 9

10 Assessment 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/m 3 Instrument B Detection minimum detection level of µg/m 3 Instrument B was used due to the increased sensitivity. 10

11 Assessment Strategy Any area with visible mercury or measurements above the Illinois industrial/commercial clearance levels (3 µg/m 3 ) was considered contaminated. Contour map developed or highlighted photograph used to identify where contamination was found. 11

12 Remediation Strategy All contaminated areas were cleaned by a contractor with mercury remediation experience. 12

13 Case Study 1 Mercury Contamination in Laboratory 13

14 Case 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. 14

15 Case Study 1 Initial assessment: Mercury concentrations ranged from 0.3 µg/m 3 to >260 µg/m 3 Highest concentrations near a fume hood Elevated concentrations also observed above asbestos floor tile located near the fume hood. 15

16 Case Study 1 Asbestos and mercury remediation was recommended Contractor with asbestos and mercury abatement experience was hired to perform the remediation. 16

17 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. 17

18 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 18

19 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 19

20 Case Study 1 Multiple cleanings were conducted Cleaning process repeated for mercury until area measurements indicated that airborne mercury concentrations were below 3 µg/m 3 (ATSDR commercial level) Cleanings performed 6 times over four days 20

21 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. 21

22 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. 22

23 Case Study 1 Final mercury air samples (continued) When direct reading instrument indicated that mercury concentrations in the remediated area were below 3 ug/m 3 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 75 o F during collection 23

24 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/m 3. 24

25 Case Study 2 Mercury Contaminated Science Hall 25

26 Case 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. 26

27 Case 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. 27

28 Case Study 2 Highlighted digital photographs used to identify contaminated areas 28

29 Case 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. 29

30 Case 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 30

31 Case 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. 31

32 Case 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. 32

33 Case 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/m 3. 33

34 Case Study 2 Visible mercury found underneath baseboard & cabinet 34

35 Case Study 2 Bottom of cabinet and floor tile removed to access mercury contamination. 35

36 Case Study 2 Catch basin being cleaned 36

37 Case Study 2 Final air samples (continued) When direct reading instrument indicated that mercury concentrations were below 3 µg/m 3 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 75 o F during collection 37

38 Case 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/m 3. 38

39 Lessons Learned 1. 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/m 3 was achievable. 39

40 Speaker Contact Information: David C. Regelbrugge, CIH, CSP Director, Environmental Health & Safety Boelter & Yates, Inc. 847/