ASBESTOS IN SOIL CASE STUDY HOBMOOR SCHOOL, BIRMINGHAM. Dr Phil Studds Ramboll

Transcription

1 ASBESTOS IN SOIL CASE STUDY HOBMOOR SCHOOL, BIRMINGHAM Dr Phil Studds Ramboll Case study - Introduction New School site at Yardley Client Balfour Beatty Construction Limited, PFI Contractor for 10 Birmingham Schools New Hobmoor School Site Context Soft landscaping, sports areas, significant cut and fill Previously developed land - industrial Historic review and site visit established significant volumes of demolition rubble from prefabricated buildings across the site Surrounding residential area 1

2 Initial Assessments Significant demolition rubble across the site Asbestos Containing Materials (ACM) encountered during site clearance Specialist Survey (Specialist Contractor) undertaken - sampling, perimeter air monitoring Asbestos cement chrysotile Asbestos insulating board -amosite ACM located in the top mm of top soil 2

3 Regulations Most Relevant Reports The Health and Safety at Work Act 1974 The Asbestos Licensing Regulations 1983 (as amended) The Asbestos (Prohibition) Regulations 1992 (as amended) The Control of Asbestos at Work Regulations 2002 The Control of Asbestos Regulations 2006 Construction (Design and Management) Regulations 2007 UK Guidance No definitive guidance for concentrations in soil. ICRCL Guidance Note 64/85 Asbestos on Contaminated Sites published 1990 If obvious ACM present treat as contaminated Addison et al, HSE Contract Report 83/96 Introduce idea of testing for free fibres Hazardous Waste Regulations 0.10%wt asbestos in soil threshold for hazardous waste 3

4 Source Available Numbers No Standard SGV - CL:AIRE, CIRIA, IOM, EIC + others working on this. 0.1% w/w = UK Hazardous waste threshold; Australian Dept. of Health bounded 0.01% w/w unbound 0.001%; Dutch intervention limit: bounded 0.1% w/w unbound 0.01%; The US EPA (2003) - action level > 1% w/w must be remediated; UK HSE - Council Directive 83/477/EEC 7 Workplace Exposure Limit fibres/ml for all types airborne asbestos over a 4hr period. RIVM (2003) data: dry soil with a fibre concentration of 0.001% = airborne fibre concentrations equivalent to a lung cancer risk of 10-5 for lifetime exposure; WHO set a lifetime exposure to f.ml -1 associated with 10-5 cancer risk Assessment Difficulties Over time ACMs degrade in soil, perhaps increasing the amount of fibres there were initially assessed. Assessment of fibre release is therefore essential Typical background asbestos fibre counts in outdoor urban air f/ml HPA advise on an unofficial environmental limit of f/ml But standard air fibre monitoring equipment gives a 0.01f/ml detection limit! (SEM f/ml) Test methods for fibre release dustiness tests (meaningful tests required). Modelling Tools once site specific exposure data is gathered, how are the risks evaluated? There is currently no public available modelling to assess soil source asbestos exposure 4

5 Assessing Risk - Summary Impact from asbestos should be assessed like any other soil contaminant (i.e. S-P-R), except; Impact occurs as discrete fragments Potential for exposure increases with time as material breaks down with time Hazard assessment based on % w/w crude and does not relate to concentration of air borne fibres, the real risk Risk from exposure to airborne asbestos from soil dependent on: Asbestos content in soil; Type of asbestos present; Matrix of soil (clay or sand dominated), moisture content Site use and exposure duration/behaviour of receptor RISK MANAGEMENT PHASE 1 Pollutant linkages identified during construction and operation of the site Free fibres, friable materials (asbestos cement, AIB) Remedial Options Appraisal 1. Dig & dump (vegetation strip) - > Handpick ACMs and cap and with imported top soil (300mm) + marker layer ~ 0.5M 3. Assess risks of reusing top soil in situ Developed a bespoke methodology Comprehensive worldwide review of asbestos legislation & guidelines 5

6 BESPOKE ASSESSMENTS ARE TOP SOILS SUITABLE FOR REUSE ON SITE? I OBJECTIVES All ACM has been removed from the top soil as far as reasonably practicable. II There is no significant amount of residual free fibres within the top soil. OBJECTIVE TESTING III Vigorous disturbance of the soil, greater than the worst case envisaged during school operation, will not generate detectable levels of asbestos fibres in outdoor air. Soil Screening Soil Fibre Analysis Air Monitoring I, III, IV, V II III, V IV Vigorous disturbance of the soil, greater than the worst case envisaged during school operation, will not generate detectable levels of asbestos fibres in indoor air. Indoor Air Experiment IV, V V There will be no significant load of asbestos fibres into the environment during future school operations. 6

7 INDOOR AIR EXPERIMENT Estimate potential air fibre release during school operation e.g. soil derived indoor dust Simulate realistic and real time situation worst case Purpose built 12m 3 sealed enclosure with air lock entry Vigorous disturbance of soil (5mins for every 15mins over a 1h period) generate dust Air monitoring and testing Phase Contrast Optical Microscopy (PCOM) analyses ACM impacted soils generating dust in a school building SOIL FIBRE ANALYSIS Analysis of screened soils for free fibres Samples sent to specialist lab - Institute of Occupational Medicine (IOM) in Edinburgh Qualitative analysis binocular & Polarised Light Microscopy (PLM) Quantitative analysis (% w/w) Quantitative Phase Contrast Microscopy No detection of free fibres Vigorous disturbance of soils does not generate secondary asbestos fibres Specific to conditions on the Hobmoor site soil type, asbestos type etc. 7

8 SOIL SCREENING Hand picking of asbestos cement and AIB fragments Licensed contractor, HSE approved methodology Trommel sieving (14mm mesh) Air monitoring across the perimeter of the site & in Control Zone RISK COMMUNICATION Asbestos is an emotive subject Perceived hazards and risks Stakeholder Management was key to the success of this project Balfour Beatty Health & Safety Executive Environment Agency Birmingham City Council Contaminated Land Officer Environmental Health Departments School Board of Governors Complex air monitoring confidence to neighbours 8

9 CONCLUSIONS Screened top soil fit for purpose Reused in soft landscape without capping layer Site Specific & Bespoke risk assessment methods developed and implemented Worst case activities simulated and tested No residual fibres detected Concluded residual risks Low Risk Communication undertaken Conclusions cont. In total 80 soil samples were analysed and 14 were identified with visible ACM debris, all of which recorded <0.01% asbestos by weight of the sample. No free fibres were detected in any of the soil samples tested. Results of all air monitoring - below detection limit of the standard HSE method i.e. <0.01 f/ml during the earthworks. Air testing experiment samples repeatedly disturbed did not generate airborne fibre concentrations above limit of detection of the standard HSE method (<0.01 f/ml). 9

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