Cleaning up legacy contamination at steelworks’ site

Enviropacific Services’ (EPS) main role during the BHP Remediation works was the practical implementation of the Material Management Plan (MMP) (Maunsell, 1999). This involved the classification and management of contaminated material identified in preliminary investigations and encountered during earthworks.

The former use of the site as a steelworks left a legacy of contamination which included asbestos, coal tar, hydrocarbons and heavy metals. The practical application of the MMP to the contamination involved identification of the specific contaminant and development of a management strategy. Material was identified by EPS using visual and olfactory indicators to classify the material into one of three broad levels of contamination. The movement of each type of material was tracked from source location to placement area. For each specific type of contamination, particularly friable asbestos and free-flowing separate phase hydrocarbons (SPHs), detailed management plans were created to ensure that the material was managed appropriately and in accordance with the relevant standards and legislation. A large volume of SPH contamination was encountered during works.

The material present was described by the EPA environmental auditor to be the worst he’d seen in NSW. It consisted of free-flowing coal tar and oil-impacted soil with the impacted area which covered 3600 m² and ranged at depths up to 5 m below the design sub-grade level. EPS conducted a delineation investigation of the contamination and identified a number of target locations where material was encountered above the water table. Removal works consisted of excavating these target locations, classification of material load by load, segregating clean overburden from the target contamination and material tracking to the practicable extents. In total, approximately 5000 m³ of contaminated material was removed over a one-month period. EPS was also responsible for atmospheric monitoring of volatile hydrocarbons and odours.

EPS developed an air-quality monitoring plan that delineated personal protective equipment (PPE) response levels for personnel on site. On several occasions, works in the most contaminated areas was required to be undertaken using half-face respirators, Tyvek suits and gloves.

At other areas of the site, several types of asbestos material were encountered, including bonded sheeting, friable asbestos in soil and friable asbestos pipe lagging. Enviropacific was responsible for the control and management of this material during removal. During all works, a nominated NATA-accredited occupational hygienist conducted air monitoring to ensure that the concentration of fibres in the ambient air did not exceed 0.01 fibres/mL of air. This limit was not breached at any stage during the following removal works on this site, indicating that the control measures implemented were both adequate and effective.

Difficult areas on the project

EPS ensured that the required controls were implemented to prevent cross contamination and potential exposure of on-site personnel, and the environment to the contaminants.

Events at the time of works, such as the NCIG asbestos and Orica gas-release incidents, meant that public focus of environmental contaminants was elevated during works. Consequently, it was necessary to ensure that the relevant stakeholders were consulted during the process. This involved conducting additional boundary monitoring for airborne asbestos fibres, odour and volatile organic compounds (VOCs) depending on the type of works being undertaken. By liaising with the stakeholders prior to commencing works potential difficulties were avoided.

The removal of the SPH material required both environmental and personnel monitoring to be conducted. EPS monitored and recorded readings at several locations at 30-minute intervals to ensure that the volatile gas concentrations and odour levels in the ambient atmosphere were maintained at a low level for the duration of works. Operators and ground personnel in the contamination zone were required to wear Tyvek suits and gloves. The action limits were not reached during removal works.

New techniques on the project

EPS has worked on multiple stages of the BHP Remediation Project, however job-specific procedures continued to be developed throughout this stage of works to manage gross contamination on a case-by-case basis. This involved inducting site personnel into each system of work, outlining the risks and safe work practices depending on the material.

Project-specific procedures were developed for the on-site management of grossly contaminated materials including:

• Personnel monitoring: Plant operating within the SPH contamination zone were fitted with monitors and carbon filters to ensure that personnel were not exposed to levels exceeding the TWA. Operators were in constant contact with EPS but were aware of the specific trigger levels and the actions required.
• Atmospheric monitoring program: EPS monitored and recorded readings at several locations during the gross SPH material removal in 30-minute intervals to ensure that the volatile gas concentrations and odour levels in the ambient atmosphere were maintained at a low level for the duration of works. This regime was designed specifically for the SPH removal and the additional data provided a greater understanding of the behaviour of this type of contaminant for future works.
• Decontamination procedures: The importance of decontamination procedures for both plant and personnel was emphasised throughout the works. Site personnel were conscious of maintaining ‘clean’ and ‘dirty’ areas and ensured that plant did not cross between the two without being washed down prior. This extended to ensuring that refuelling the ‘dirty’ machines was completed in a way that was not going to contaminate the fuel tanker.