SHE in the field
The 20-hectare Riversway Docksides site, located between the River Ribble to the south and Preston town centre to the north, has been used for oil storage and distribution since the 1920's, resulting in extensive contamination. James Baldock, hydrogeologist and Health & Safety co-ordinator for The IT Group, examines the inherent risks of remediation.
The IT Group (IT) was commissioned to design, install, operate, and monitor an in situ soil and groundwater treatment system employing pump and treat methods to remove free-phase, and reduce dissolved-phase contamination beneath the site. The system was enhanced by Soil Vapour Extraction (SVE), used to reduce absorbed-phase contamination.
Prior to commencing work all health and safety considerations were assessed and integrated into a site-specific Health, Safety and Environmental Plan. The plan documented topics such as air monitoring protocols, chemical handling requirements, Personal Protective Equipment (PPE) requirements, decontamination and site control procedures.
The plan also included Job Safety Analysis (JSA) sheets, which described in detail the specific tasks for each step of the project and defined the safety implications and how to best mitigate them. This method allowed the resident engineer supervising the tasks on site to evaluate safety risks and devise contingency plans to avoid them before commencement of site work, rather than getting onto site and discovering problems at a later stage.
It was important that everyone working on site was made aware of, read and signed the document before work commenced. The IT Group briefed subcontractors on the levels of PPE required and the safety standards expected, as past experience has shown that if these issues are raised before the project begins the subcontractor cannot then claim retrospectively that they didn't understand the importance of safety.
Site staff working for IT undergo 40 hours of training with OSHA (the American equivalent to the UK Health and Safety Executive) to ensure competence. Any unsafe activities, no matter how minor, were documented on site, to improve the focus of the post-project safety assessment.
The groundwater and product recovery wells were installed using cable percussion drilling rigs. Typically, the biggest problems are ensuring subcontractors are wearing the appropriate PPE and in some cases are mindful of the no smoking policy when drilling boreholes into petroleum contaminated soil. Other issues may entail the lack of supporting bars on rigs leading to instability during drilling, and / or frayed wire ropes (a serious issue if these break as the cable will rapidly detach itself from the rig at speed and would cause serious injury if a person was hit). The selection of competent and safe subcontractors, a pre-work safety briefing and examination of the drilling equipment generally alleviated these concerns. Other issues, such as buried services, were also considered and minimised by using cable avoidance tool scanning and by digging an inspection pit to a depth of 1.0m at each borehole location as extra verification.
The highest safety risks for the installation of remedial equipment were evaluated as electrical risks, flooding of the water treatment plant, and cranage of equipment onto site. To negate these, approved and vetted electrical subcontractors were employed to make electrical connections for all equipment. The groundwater treatment plant was located within a bunded area draining to a sump. If a serious failure did occur, causing the sump to fill, a float switch would be triggered to shut down the groundwater pumps and treatment plant.
Lifting assessments were performed based on the capacity of the crane and the weight of equipment.
Visual safety checks of the plant were made on a daily basis and recorded on a log sheet to ensure continued safe operation. Where required, items on the plant were labelled to ensure no works were carried out on the plant without the correct lock out/tag out practises.
The IT Group placed warning signs within the system area to highlight the areas of greatest potential risk. Of particular note was the air stripping tower which needed to be climbed for various maintenance tasks. All staff undertaking this used harnesses to prevent serious injury in the event of a fall. Similar factors were taken into account for refilling the activated carbon drum vessels.
Generally the safety performance of both subcontractors and IT was good, but can always be improved on the next project. With this aim in mind, a review was to see what lessons could be learnt, do we need to use different subcontractors next time? Has our own performance been sufficient? How can we improve?
In 1997, The Health and Safety Executive published a document titled Managing Contractors - a guide for employers, suggesting that a five step plan should be used to manage subcontractors, as follows: planning; choosing a competent contractor; check contractors are aware of site main contractor procedures; monitor performance; and review the work.
It is generally acknowledged that the Health and Safety challenges to be addressed for a project of this nature are far greater than those needed for, say, a traditional site investigation, mainly due to the wide variety of tasks undertaken during the course of such a project.
A balance that always has to be attained is that which exists between financial constraints and health & safety concerns, as health and safety costs money. PPE is generally very expensive in the UK, but in the view of the author the expense is always justified if it can improve safety.