Safe Working Practices - Safety in Construction of Underground Structures in the Complex Geology of Tehri Pump Storage Project – A Case Study

Dr. Rakesh Kumar Khali, Vice President - Operations, (Tunnel, UG Structures & Hydro Power), G.R. Infraprojects Ltd. highlights the technology incorporated for safety in construction during the course of the Tehri Pump Storage Project and cites examples that illustrate the efficacy of safety measures in averting accidents.

Safety is central to the construction of any mega project; it ensures executing projects without any mishap or loss of life. The construction of underground tunnels, shafts, chambers, and passageways is indispensable yet fraught with dangers. Reduced light conditions, difficult or limited access and egress, or possibility of being exposed to air contaminants and the hazards of fire and explosion are the threats an underground construction worker may face.

To ensure the safety and health of underground workers, the Occupational Safety and Health Administration has been made operational at the prestigious Tehri Pumped Storage Project (PSP). Safety operations are not limited only to the permanent structures and persons working on it, they extend to the infra-structure and its users as well.

The paper seeks to establish that while it is difficult to maintain safety at construction site, it is even more challenging to maintain safety in the entire gamut of infrastructural framework which supports the construction of the main work. While there exist several codes and statutes for the safety of the main works and persons working on it, such guidelines are not well laid down for the infrastructural work. It is felt that more attention needs to be paid to frame the safety guidelines for infrastructural works per se and ensure zero accidents at project sites.

Introduction to Tehri Pump Storage Project

The Tehri PSP is located on the left bank of the Bhagirathi river in the district of Tehri, about 1.5 km downstream of its confluence with the Bhilangana river (now forming a part of Tehri Reservoir), falling between 78°30’ and 79°00’E longitudes and corresponding 30°30’ and 33°30’N latitudes. The nearest railhead is Rishikesh (Uttarakhand), located approximately at about 82 Km south of the project site. The construction of the Tehri PSP by HCC Ltd under progress, envisages an underground Machine Hall on the left bank of river Bhagirathi, housing 4 reversible pump turbine units, each of 250 MW capacity.

The reservoir of the Tehri dam will operate as the upper reservoir and the Koteshwar reservoir as the lower reservoir for this project. Two completed Head Race Tunnels (HRTs) (3 and 4) will be augmented by respective Surge Shafts at the end of each HRT. These HRTs will bifurcate into two steel lined penstocks at the base of the Surge Shaft to feed two turbines each. The water from the turbine units will discharge into two TRT’s which, in turn, will carry the water of all the four units into the downstream reservoir. The availability of water for the Tehri Pump Storage Project shall be governed by the mode of operation of the Tehri Power Complex. During non-peak hours, water from the lower reservoir will be pumped back to the upper reservoir by utilizing the surplus available power in the grid.

Interestingly, the underground Tehri PSP, which is in the advance stage of construction, is located in the same hillocks where the Tehri Hydro Power Project (HPP) is. The major project components of the PSP are:(a) 25.4m (W) X57.3m (H) X203m (L) size Machine Hall to accommodate 4 of turbines of 250 MW each, (b)22m dia. 02 nos. Upstream Surge Shafts with Surge Chambers, (c)77m (L) X24m (H) X10m (W) size BVC,(d) 81m (L) X20m (H) X13m (W) PAC and (e)18m dia 02 nos. downstream surge chambers. (f) 02 nos. of 1081m & 1176m TRTs.

For such a huge crucial project which is fully underground, ensuring safety is a challenging task. The challenge is further compounded by the complicated Himalayan geology which surprises us at every stage of construction.

Project Colony

Large projects, more so, hydropower projects, are located in remote areas where large infrastructure consisting of several components is required. The Project Colony including residential and non-residential buildings, is an integral part of such an infrastructure. The location of a colony has to be particularly chosen with utmost care to ensure that the area is not prone to slips, floods and other natural risks. In case such a location is not available, which usually is the case, necessary measures have to be taken to ensure the safety of the colony. The slopes cut to provide benches for the colony have to be stabilized. For this gabion walls or other structural and/or non-structural measures need to be carried out along with the construction of buildings. (Photo-1)


If it is a seismic zone, the buildings should be earthquake resistance. The engineering history reveals that buildings constructed with thick mud walls have collapsed and caused loss of human lives, while the conventional Assam type buildings were least damaged. If the area is prone to flash floods, proper warning measures have to be ensured. Some lead time provided with such warnings has proved to be of immense help in minimizing loss of life and to some extent of the property as well. A suitable flood warning site can usually be ratified through interaction with Central Agencies viz. Central Water Commission and the State Agencies viz. Irrigation Department and the District Administration. For an effective use of the warning system, the residents must also be educated how to respond to the warning system. Adoption of such a system instills a sense of security among workers and their families. The system gets further tested through periodic drills. Our past experience shows that in the absence of proper training, panic-stricken people start running in the wrong directions.

Fire is another potentially dangerous threat. Even though the buildings in the colony are of a temporary nature, foolproof electric installations must be put in place as per specifications. Installation of Earth Leakage Circuit Breakers (ELCBs) has proved to be an asset, ensuring the safety of human life in case of faults occurring in the insulation. The installation has meticulously to be fixed and monitored periodically to prevent tripping resulting from human contact with faulty appliances.

Sometimes, even well-designed buildings succumb to minor accidents. In a project, the CGI roof sheets were blown off the buildings during a storm for want of wind ties being fixed. The residents were injured and those surviving had to undergo nightmares until the buildings were repaired.

No borrow pit should be allowed to exist in the vicinity of a colony. They can be a potential health hazard due to collection and stagnation of water. In an extreme case a borrow pit left undressed had resulted in the death of an infant by drowning in the pit. Therefore, the filling up of the site after completion of the job should be made mandatory.

Road Infrastructure

Most of the dam sites are located in the interiors of the hills where the river valleys are very narrow. There is very little place available for the construction of roads. Hence, these roads have to be constructed by cutting benches and providing Zigs. The width, gradient, line of sight and stability of the road go a long way towards ensuring the safety of vehicles and human lives. Majority of lives lost on these projects are on account of accidents on these hill roads. More often than not, sufficient land is not available from the owner which also leads to construction of improper roads. Parapets on the outer side would prevent rolling down of vehicles. (Photo- 2). In case it is not possible to have a road on which two vehicles can cross, refuges should be provided at regular intervals. Proper road signs, preferably luminous, must be installed at the required places. More signs rather than less should be wished for.

Plant & Machinery

All plants and machinery on the Project have to be kept in very good working order to ensure that no accidents occur on account of their failure. The daily checking of plants before commencement of shift should be meticulously followed. Slings, wire ropes and hoist gears should be given special attention.

Accidents occur on account of faulty roads and human and mechanical errors. Moving away from road safety already discussed, let the vehicles plying on the road be repaired with the help of preventive and not breakdown maintenance. These allowances must take into account the roadworthiness of steering, brakes and transmission system. Although other provisions are equally significant, failure of brakes, steering and transmission system are fatal and have to be prevented.

Most accidents, as a matter of fact, occur entirely due to the fault of the drivers who in most of the cases are inexperienced and unlicensed helpers of the persons operating the vehicles. A common misconception is that the project area does not come under the traffic regulatory authority. The ground reality is that these roads require highly skilled drivers compared with other places. The ill practice of parking vehicles only in heavy gear, instead of applying parking brakes and/or wheel block, has resulted in rolling of vehicles into the valley. In a recent case, while a worker was attending to a vehicle from inside, it rolled off in the valley as it was parked without applying parking brakes or wheel block. This resulted in the injury to the worker. Inexperienced drivers have sometimes driven straight into the valley while turning around the vehicle. A close monitoring of the performance of drivers has to be carried out, and quick, stringent remedial measures taken to ensure safety.

Quarry

A quarry is the infrastructure that feeds the main construction material for the work. Usually, the quarry is located at a distance from the main work; site. The progress on the main work depends on the production of construction material from the quarry, yet the working at quarry usually does not get the desired attention. The job at the quarry is hazardous and has led to several accidents. As the quarrying operation involves removal of over-burden, blasting of rock, mucking and loading of blasted material by excavators-- both men and machines are used under extremely difficult situations. The labour force is preoccupied in turning out maximum output and is usually not careful in keeping an eye out for boulders which may slip, or the slopes may fail.

Alertness of dedicated persons has reduced the number of fatal accidents. Such a person should be indispensably posted on all quarries. The blasting operations at the quarry have to be strictly in accordance with the rules and have to be followed in letter and spirit. The person in charge of blasting should be fully aware of the rules on the subject. The inspection of misfired holes has to be carried out by a competent person whose competence ought to be monitored periodically. The quality of illumination should be very good to ensure full safety of the personnel and the plant. The timings of blasting should be well notified and also warned through powerful sirens. (Photo-3)

Medical Facilities

In the first place, the possibility of accidents at the site should be ruled out and prevaricated. However, the medical facilities both at the first aid level and at the hospital should be adequate for cases of injury or trauma as also for treatment of diseases. The level of facilities to be provided in the project hospital should depend upon the size of the project, nature of operations and the distance from the nearest well-equipped hospital. Ambulances should be provided and kept in working condition all the time. Attention has also to be paid for the prevention of diseases like malaria and diarrhoea etc. and to prevent the same, blood samples of labour and staff entering the project area should be examined. The water supply should be suitably treated and periodically checked to ensure that no water-borne disease spreads out in the area. The sanitary arrangements should be well planned and maintained.

HSE Management System -- Our Experience

Health, Safety and Environment play an important role for the development of any infra project. The purpose is to prevent job related accidents. The role of HSE management is to achieve construction safety and health, a purpose which is generally oversighted. This function does not supersede, override, or take precedence over the other assignments of the officers who are ultimately responsible for safety and health. The key function of HSE management, construction safety and health, has to be monitored with another standard system called Integrated Management System. This system covers all norms of ISO 9001 and 14001.

In the Tehri Pumped Storage Plant, the effectiveness of HSE is so calculated that we have maintained the Zero Incident goal. To ensure the status, each individual has been assigned the following chart of duty:-

• Enforce carefully and systematically the planning and implementation to avoid human injury, property damage, and loss of productivity.
• Create a safety culture by sensitizing the safety and environmental awareness of the employees through the Employee Safety Training Program, taking assistance from the management and the organized labor. The program includes orientation of all new employees, regular safety meetings, pre-task planning, and ongoing safety training.
• Minimize hazards/disruptions to the traveling public by controlling access to construction areas, following established safety procedures prescribed in the ‘airport operational systems’, and secure work areas adjacent to those spaces.
• Establish and maintain a system that promptly identifies and corrects unsafe practices.
• Establish emergency procedures to respond within a minimum time to fire accidents and eventual call up-for an ambulance.

Individual initiative and commitment are predominantly effective in the operations of safety. A healthy, safety culture has to be inculcated among all the employees, officers or workers. Having adopted the procedures of ISO 9001, the HSE department at our project has rigorously followed the specified parameters stated below:

Safety Induction Training and Premedical Test

Safety Induction Training and Premedical Tests are invariably carried out for all new joining officers, workers and sub contractors. The training schedule and content is dependent upon the kind of job and location the employees are likely to be given. The high indicators of the Occupational Safety and Health Ordinance (OSHO) in the company prove the degree of adherence to the norms cited in OSHO.

Toolbox Talk on daily basis

Safety meetings and toolbox menu is conducted on a regular basis to educate the workers and officers and also ensured through its compliance. The practice prevents workers from getting complacent and taking safety for granted. Toolbox talks are the essence and strategy to have officers and workers inspect the equipment, tools and PPE they will be working with. The mechanism creates a safety culture and thereby protects its employees. Toolbox meetings carried out regularly enhance the knowledge of safety awareness related to the job hazards. The status of Zero Accident level at our Project has been given in Photo-4.

Monthly Training for Safety Awareness

Training for safety awareness is conducted every month on safety norms related to mechanical and electrical operations. All persons engaged in the projects have to compulsorily possess adequate safety knowledge and have a high degree of safety awareness, and follow the following ready-reckoner:

• Recognize the importance of safety and assign sufficient resources to handle it
• Give proper consideration to safety during planning and design to eliminate/reduce prospective safety hazards.
• Avoid performing unsafe acts, creating unsafe conditions, identifying unsafe conditions and take initiative for rectification.

Under Section 6a of the Factories and Industrial Undertakings Ordinance and Section 6(c) of the Occupational Safety and Health Ordinance, it is mandatory to inform, instruct, train and supervise the workers on the operations involving safety. Our Site Safety Committee consists of 34 members, including workers and managers.

The Project Manager chairs the meetings and the HSE Manager functions as Secretary. Generating Minutes of meetings (based on all non-confirmatory issues of a whole month) with their photo documentation is assigned by the Secretary.

Hazard Identification, Risk Assessment and Controls

Hazards & risks are identified, and feasible control measures proposed to reduce potential hazards are stated at the planning stage by the Project Manager, the Project Construction Head, DPM- Planning & Controls, Project HSE Head. The risk assessment at project level will be carried out for every activity undertaken. When the project is in progress, risks and measures for control will be recorded in the risk- control documents by the operators in the prescribed format. The section in charge, site engineer and supervisors along with the Project HSE Head will review, the risks involved and propose appropriate measures.

Procedure for Hazard Monitoring and Action

The Site Safety Department will carry out regular inspections of the workplace. Reporting of safety deficiencies and/or violations will be done on the basis of the daily inspection report. The details of items requiring actions and the time limit for the same will be furnished. In a separate proforma, deficiencies’ will also be reported under the head ‘unsafe acts and unsafe conditions’. The reports will subsequently be distributed to all the sites concerned.

Mock Drill

Sensitization of employees through mock drills is essential for emergency situations including fire, chemical disaster, flood, cyclone, blast, etc.

Monitoring the Environment

Environmental monitoring is used in the preparation of Environmental Impact Assessment (EIA), as well as in many circumstances where human activities harm the natural environment. All the monitoring strategies and programmes are justified with facts of the current status of an environment and prescription of the parameters to be followed vis-a-viz the environment. Results of such monitoring have to be reviewed, analyzed statistically, and published.

Emergency Plan by our HSE Department

• Emergency Alarming System have been provided at all sites.
• Emergency Assembly points have been declared and sign boards also displayed at the locations.
• Emergency Ambulance facility is available for 24 hours (all working days & nights)
• First aid trained pharmacists are available on 24 hours basis at the Site Medical Dispensary.
• First aid boxes and treatment has been provided at all sites besides the one at the Medical Dispensary on 24 hours basis.
• Rescue teams have been formed.
• Half yearly mock drills are conducted to evaluate the entire Emergency System.

Celebration of Safety Week at Site

Every year, the Tehri PSP team celebrates a National Safety Week by conducting various safety awareness activities at site. The aim of this initiative is to inculcate a culture of safety and to seek inclusion of all the workers from all the project sites. During the week, workshops, training programmes, medical camps, screening of safety films, and seminars are held. Banners and posters at prominent places notifying the safety week theme are displayed.

The theme this year was “Reinforce positive behavior at workplace to achieve safety & health goals”. HCC Tehri PSP team introduced Proactive Safety Observation Programme (PSOP) in 2013 and Behaviour Based Safety Programme (BBS) in 2015.The PSOP programme analyses the cause of possible accidents which are then categorized into near misses, unsafe conditions and unsafe acts. Each of these causes is systematically reported and corresponding actions are taken to mitigate them. The BBS programme goes one step further by engaging every employee to take responsibility for his own safe or unsafe behavior. Then implementation of a data driven decision-making process is prepared.

Another interesting concept introduced was the “Best Safety Practice Competition”. The competition was conducted at all the projects sites. The purpose was to:

• Engage and motivate HSE staff to reduce safety risks in their work area.
• Set a benchmark of HSE practices for all projects.
• Provide an opportunity to explore the professional concepts.

The celebration concluded with the valedictory function during which winners of the safety competitions were awarded prizes and certificates. (Photo-6).

Conclusion

The pace of any enterprise depends on the efficiency of the human resource engaged in it. The leitmotiv of human efficiency lies in security of life and the wages earned. The first question the worker instinctively asks is ‘whether or not the working conditions are secured’. The question acquires magnitude when asked by a worker who has to work in an underground tunnel where loss of life may occur because of falls, incidents with site vehicles, collapsing materials, and contact with overhead power lines. The machines themselves (if ineptly handled) may add to the list of the causes of death.

Taking into consideration this human psychology, the first job of a manager is to make a workplace thoroughly secure with multiple security systems. We have adopted the ISO 9001: 2008, OHSAS 18001: 2007, ISO 14001: 2004,OSHS, PSOP and BBS system to ensure accidental and hygienic security of our workers. If a worker feels psychologically secure, his efficiency increases, which leads to speedy and higher production, which in turn paves the way to the growth of the company. And a prosperous, trustworthy company makes the nation strong.