G. The Horizontal Directional Drilling Technique
The HDD method is extremely protective towards the environment, causing no ecological damage at all. Several reasons also speak for the application of the directional technique in central town areas. These mainly concern the construction costs, construction periods, permission procedures, soil movement, surface restoration and the traffic, compared to open trenching methods.
A well planned HDD operation includes preliminary survey of the bore path area, concerning other existing external lines and the soil condition.
The choice of the drilling unit depends upon the bore length, the diameter of the pipe to be installed and the soil quality.
Keeping up a certain bore path is the main problem of the pilot bore, when the fluid assisted technique fails because of mechanical soil resistance. For these conditions, there are the TT drilling facilities with built-in impact unit, which can be switched on when the drilling progress becomes unsatisfactory due to problematic grounds.
Localisation is carried out following the transmitter-receiver principle. One operator follows the course of the bore head all the time. All measured values are taken to protocol, directional corrections are passed on to the machine operator via radiophone. It is also possible to directly store the data found in this way, printing them with the help of a PC or Laptop later on.
On arrival, the drilling head is replaced by an upsizing head. One or more intermediate reaming operations follow, or the pipe is pulled in at once.
Advantages of the HDD method:
- surfaces are neither broken up nor damaged (road surface, front gardens etc.),
- restoration and repair are not required,
- short drilling and construction period,
- wide spectrum of application.
Unit 6. Safety on Site
CONSTRUCTION HEALTH RISKS: KEY POINTS
There have been big improvements over recent years in reducing the number and rate of injuries to construction workers. Despite this, construction remains a high-risk industry and accounts for a high percentage of fatal and major injuries.
What is less recognised is that construction is a high-risk industry for health issues too. Below are some key points about these risks, why they are so significant and how to manage them.
The big picture.
Every year more working days are lost due to work-related illness compared to injuries. The statistics reveal that construction workers have a high risk of developing diseases from a number of health issues.
· Cancer – construction has the largest burden of occupational cancer amongst the industrial sectors. It accounts for over 40% of occupational cancer deaths and cancer registrations. It is estimated that past exposures in the construction sector annually cause over 5,000 occupational cancer cases and approximately 3,700 deaths. The most significant cause of these cancers is asbestos (70%) followed by silica (17%) working as a painter and diesel engine exhaust (6-7% each).
· Hazardous substances – dusts, chemicals and potentially harmful mixtures (e.g. in paints) are common in construction work. Some processes emit dusts, fumes, vapours or gases into the air and these can be significant causes of breathing problems and lung diseases. A number of construction – related occupations also have high rates of dermatitis from skin exposures to hazardous substances.
· Physical health risks – skilled construction and building trades are one of the occupations with the highest estimated prevalence of back injuries and upper limb disorders. Manual handling is the most commonly reported cause of over seven day injuries in the industry. Construction also has one of highest rates of ill health caused by noise and vibration.
Underlying causes.
There are many reasons why construction workers have a high risk of developing occupational disease. This includes:
· The construction site environment – unlike a factory, construction work takes place in many and varied environments. Different sites can present a range of health risks, including existing ones like asbestos. The extent of these risks can also vary between areas of the same site.
· The dynamic nature of the work – construction sites are constantly changing and a large number of trades may all be carrying out tasks potentially dangerous to their health and that of others.
· Risk appreciation – there is generally a low awareness of health risks and the controls needed. It can take many years for serious ill health conditions to develop and the immediate consequence of a harmful workplace exposure may often be dismissed as not significant compared to the immediate impact of injuries caused by accidents.
· Employment – many workers are either self-employed, work for small companies, or frequently change employers. Others work away from home. These situations can make it problematical for workers to easily look after their own health and they often have little or no contact with occupational health professionals.
Common principles.
The risks of ill health can be managed by following the simple steps. These steps follow a few essential common principles:
· ‘Ill-health can be prevented’ – it is possible and practical to carry out construction work without causing ill-health.
· ‘Treat health like safety’ – managing health risks is no different to managing safety risks.
· ‘Everyone has a role to play’ – everyone involved in construction has a responsibility in managing risks to health. Each must take ownership of their part of the process.
· ‘Control the risk, not the symptoms’ – monitoring and health surveillance programmes are not enough on their own. While they are an effective part of managing health risks, the first priority is to stop people being exposed to the risk in the first place.
· ‘Manage risk, not lifestyles’ – the law requires steps to be taken to prevent or adequately control work-related health risks. Helping workers tackle lifestyle issues like smoking or diet may be beneficial but is not a substitute for this.