BET2492/BPS3413 CONSTRUCTION SAFETY Lecture 8 : Demolition works

LEARNING OUTCOMES Upon completion of the class, it is expected that student will be able to: LO1: Identify hazards on demolition works LO2: Determine suitable controls when performing demolition works

INTRODUCTION Demolition is one of the most hazardous construction operations - responsible for more deaths and major injuries than any other activity If a demolition project is well planned the risks of injury and death can be minimized The planning and execution of a demolition project should only be done by appropriately competent persons The work should be supervised by someone with sufficient knowledge of the particular structure being dismantled Expert advice from structural engineers will be necessary

Demolition in progress

PRINCIPAL HAZARDS OF DEMOLITION WORK noise and vibration from heavy plant and equipment falls from height or on the same level falling debris electric shock premature collapse of the structure being demolished fires and explosions from the use of flammable and explosive substances dust and fumes smoke from burning waste timber the silting up of drainage systems by dust pneumatic drills and power tools the problems arising from spilt fuel oils the existence of services, such as electricity, gas and water manual handling collision with heavy plant presence of asbestos and other hazardous substances plant and vehicles overturning

PRE-DEMOLITION INVESTIGATION & SURVEY The owner of a property is required to provide the demolition contractor with a pre-demolition investigation and survey A full site investigation must be made by a competent person – determine the hazards and associated risks which may affect the demolition workers and the public Competent person - a specialist structural engineer who will also advise on the temporary support of adjacent buildings and the correct method of dismantling or demolition

ASPECTS UNDER INVESTIGATION The construction details of the structures or buildings to be demolished (including the materials used, fragile roofs, rot, the presence of cantilevered structures and any general weaknesses) The location of any underground or overhead services (water, electricity, gas and sewage) The location of any underground cellars, storage tanks, chimneys, balconies or bunkers particularly if flammable or explosive substances were previously stored Neighboring structures or buildings The previous use of the premises The means of access to the site The load carrying capacity of adjoining land including The removal of waste The presence of underground culverts The details of any traffic or pedestrian routes through the site The need for possible temporary support structures for the building being demolished and adjoining buildings The provision of welfare facilities Falls of materials and people The proximity of neighbors The location of any dangerous machinery The location of any public thoroughfares adjacent to the structure or building The presence of asbestos, lead or other hazardous or radioactive substances and any associated health risks The name of the planning supervisor. Environmental issues, such as dust, water pollution and noise Public safety including the provision of high fencing or hoardings Manual handling issues

PRE-DEMOLITION INVESTIGATION & SURVEY Details of the construction structure of building to be demolished would include whether it was built of brick, pre-stressed concrete, reinforced concrete or steel Important to consult with legal advisers to ensure that there are no legal covenants or disputes which could affect operations on the site The planning supervisor must notify the Health and Safety Executive of the proposed demolition work- a written risk assessment of the structure to be demolished

PRE-DEMOLITION INVESTIGATION & SURVEY The site manager should arrange for suitable plant and equipment to be provided so that the work can be executed to the standards required by health and safety legislation Issues of public protection, local traffic management and possible road closures – avoid by notifying the local authority The provision of temporary access roads, welfare facilities, office accommodation, fuel storage and plant maintenance facilities on site - considered at the planning stage.

ENVIRONMENTAL MONITORING Environmental monitoring may need to be carried out in certain situations Some of the most common hazardous substances in demolition work include: lead – is most dangerous when it is in the air as a fume or dust (e.g. cutting steelwork coated with lead-based paint or dismantling of tanks containing lead-based petrol) asbestos – where possible it should be removed before any other demolition work starts and must always be removed by a licensed contractor. Asbestos may be found in sprayed coatings, thermal and acoustic insulation materials, fire resistant walls/partitions, asbestos cement sheets or flooring materials PCBs – a toxic substance found in electric transformers and capacitors, refrigeration and heating equipment silica – occurs in stone, some bricks and concrete aggregate. Any demolition of structures constructed from these materials will give rise to dust containing silica.

ENVIRONMENTAL MONITORING Residues of hazardous substances may also create a hazard to demolition workers Storage tanks, vessels, pipes and other confined spaces may contain flammable vapours or toxic sludges – formerly used in industrial or chemical processes

DEMOLITION METHOD STATEMENT There are two forms of demolition: piecemeal – where the demolition is done using hand and mechanical tools such as pneumatic drills, cranes and demolition balls, hydraulic pusher arms or heavy duty grabs deliberate controlled collapse – where explosives are used to demolish the structure. This technique should only be used by trained, specialist competent persons. This is the most economic form of demolition but it is the most hazardous and everyone must be at a safe distance at the time of the collapse A risk assessment should be made by the contractor undertaking the demolition This risk assessment will be used to draw up a method statement for inclusion in the health and safety plan.

DEMOLITION METHOD STATEMENT Content of method statement: details of the method of demolition to be used - the means of preventing premature collapse or the collapse of adjacent buildings, and the safe removal of debris from upper levels to prevent overloading due to the debris details of site access and security details of the location of any underground or overhead services details of protection from falling materials arrangements details of equipment, including access equipment, required and any hazardous substances to be used arrangements for the protection of the public and the construction workforce against noise and whether hazardous substances, such as asbestos or other dust, are likely to be released details of the isolation methods for any services which may have been supplied to the site and any temporary services required on the site

PRIOR TO DEMOLITION.. The isolation of all services (gas, electricity and water) which feed the site is essential before any demolition takes place Proper arrangements must be made with a reputable waste disposal contractor for the disposal of demolition waste The site should be made secure with relevant signs posted to warn members of the public of the dangers Asbestos containing material requires special care and will only be dismantled by a licensed contractor A safe system of work is developed for demolition which ensures that people are distanced as far as possible from the demolition area. Glass must be removed from all windows before demolition starts

CONSTRUCTION PHASE HEALTH & SAFETY PLAN Should include the following: the co-ordination of and provision of information to other contractors risk assessments and other statutory assessments emergency procedures health and safety monitoring arrangements site rules welfare arrangements the provision of information and training to the workforce consultation arrangements with the workforce.

DEMOLITION USING EXPLOSIVES An exclusion zone must be established at a distance from and surrounding the structure to be demolished An exclusion zone comprises four areas: 1. the plan area of the structure to be demolished 2. the designed drop area where the bulk of the structure is designed to drop 3. the predicted debris area which is beyond the design drop area and where the rest of the debris is predicted to drop 4. the buffer area between the predicted debris area and the boundary of the exclusion zone.

MANAGEMENT OF THE DEMOLITION AND GENERAL CONTROLS Demolition hazard control involves implementing measures which reduce the risk at the demolition site Elimination is the most effective control measure. This involves removing the hazard or hazardous work practice from the site, by the following actions: disconnecting services to the demolition site ensuring there are no sparks or ignition sources, where a risk of fire or explosion exists ensuring separation between the public and demolition activities excluding unauthorized persons from the site

MANAGEMENT OF THE DEMOLITION AND GENERAL CONTROLS Substituting or replacing a hazard or hazardous work practice with a less hazardous one could include the following: using a controlled collapse technique, in place of people working at heights using power shears in place of grinding or oxyacetylene cutting, where a risk of fire exists Isolating or separating the hazard or hazardous work practice from workers and others involved in the demolition area by the following: installing screens on plant to protect from dust and noise installing barriers and fences marking off hazardous areas

SPECIFIC ISSUES IN DEMOLITION WORKS Premature collapse - one of the main causes of serious injury resulting from demolition work due to ineffective planning Protection from falls and falling material Noise Dust Siting and use of machinery – applicable to competent person only Environment – contamination needs to be identified Competence and training