Underground Singapore 2011 tion drawings. Barriers, walkway details, plant routes and limiting surcharges were identified on the design drawings for this project. The wider adoption of observational design approaches should be promoted for deep excavations. Observational approaches, when correctly applied, provide a rational means to remove often inherent conservatism in design parameters without compromising robustness. A further benefit is that observational approaches tend to advance understanding of soil-structure interaction by making designers monitor the actual performance of their designs against predictions. Consideration of the removal of earthwork supports requires an equal emphasis to the installation. On this project temporary concrete walings were used and they required demolition. The designer working closely with the site team introduced slots, void formers and reinforcement breaks to aid removal. Similarly, lifting eyes and cut locations for earthwork support installation and removal should be pre-planned and shown on design drawings. 3.2 Communicating design information Temporary works for deep excavations are often shown as "wished-in-place" on design drawings. Generally there is no information provided on how earthwork supports such as struts and walings or temporary access decks are to be installed, used or dismantled. This is usually left to "trade practice" and described in generic method statements that are generally of low value for risk management. A desired position would be for every step in the construction cycle to be clearly identified on design drawings, including access provisions for site workers and material delivery. If for operational reasons it is necessary to depart from the drawings, changes will be agreed with the designer to allow construction to progress safely. It is not always possible to mitigate all risks through design. Residual risks should be identified on design drawings as "Designers Notes" and highlighted, through the use of colour or a text box, so that they stand-out above general notes that tend to be fairly generic. On this project the designer highlighted in “Designers Notes� that temporary cut slopes inside the cofferdam required particular care to avoid oversteepening and prevent slips. When presenting information on design drawings it is favoured to use more images and fewer words. Plans, sections and developed elevations are typically shown on deep excavation drawings. Adding isometric views can be effective to show spatial arrangements and connection details for earthwork support systems. Including images of people and plant on design drawings is also a favoured practice since it can trigger designers and planners to re-evaluate working space provided. Animations showing the steps in seawall removal, prepared by the designer, proved useful to improve communication of the design intent on this project. Designers must encourage feedback on buildability from those engaged in the construction of their designs. Ideally dialogue should start during the early stages of design development and continue through the entire construction cycle. Traditional procurement approaches, where designs are produced with little or no contractor engagement, competitively tendered and awarded shortly before site works commence do not drive safer construction. Designs produced by designers integrated within construction teams tend to be more efficient and easier to build safely as was the case for this project. During the construction of deep excavations, design changes are often necessary due to unexpected ground conditions, utilities and because of differences between as-built conditions and construction drawings. Changes must be referred back to the designers to ensure that appropriate checks are conducted so that the work can proceed safely. Internet based systems, such as Gammon's GEMS, used on this project, allow the electronic issue and endorsement of all design changes as part of broader platform for temporary works control. Systems that rely upon paper "change requests" tend to be less effective because they often suffer communication lags and changes are difficult to track. 3.3 Harnessing technology There have been major advances in instrumentation for ground and structure monitoring, particularly during the last decade, with the development of ever more powerful microelectronics and communication
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