To conform to a tight construction schedule, the owner of the 400 MW Koteshwar project on the Bhagirathi River (a tributary of the Ganges River) in India scrapped many of its previous plans and used a hands-on managerial approach. This innovation enabled the plant to be commissioned ahead of schedule.
By R.S.T. Sai and D.V. Singh
|Photo (above): The reservoir for the Koteshwar project is a vital component of the larger Tehri Hydropower Complex, which will have a capacity of 2,400 MW when complete in 2017.|
In an industry often marked by slow progress and long struggles for project authorization, the 400 MW Koteshwar Hydroelectric Project in India can provide a model of effective and efficient construction and operation. First proposed in 2000, the project was under construction in early 2007. Two of the four generating units were commissioned just four years later. The progress of the facility can be credited in large part to hands-on management practices and construction methodology used by the plant’s owner, THDC India Limited.
To overcome a construction delay and finish the Koteshwar project in a timely manner, THDC implemented a unique management methodology that placed decision-making ability in the hands of a small committee and those working directly on the project. This eliminated much of the red tape that often halts hydropower development. Additionally, innovative construction techniques were used to shorten building time and make more efficient use of available resoures and manpower. Completing side-by-side construction activities simultaneously with the help of innovative organization was one method used to finish the project ahead of schedule. Many of these innovations and managerial strategies could be applied to other hydropower projects.
The Koteshwar project is a vital component of the larger 2,400 MW Tehri Hydropower Complex, the first major attempt to harness the potential of the Ganges River.
Koteshwar is the most quickly-implemented hydro project of its type in the nation, according to sources within the Ministry of Power, which commended the project and its owners and contractors. Contractor PCL-Intertech LenHydro Consortium began construction work in April 2007, the first two units were commissioned in March 2011, and the third and fourth units were commissioned in January 2012 and March 2012, respectively.
The Koteshwar project is comprised of a 97.5 meter-high concrete gravity dam on the Bhagirathi River, a tributary of the Ganges River, and a powerhouse at the toe of the dam on the right bank that houses four 100 MW turbine-generating units. Each generator is a vertical shaft, semi-umbrella type and is coupled to a Francis turbine. The turbines, generators, transformers and balance of plant equipment were provided by Bharat Heavy Electricals Ltd. of New Delhi, India.
Power generated at this plant contributes considerably to the ability of the Tehri Hydro Complex to provide a combined peak capacity of 2,400 MW to the local grid once the final phase is completed. The complex is operating at a capacity of 1,400 MW. The third component of the project, the 1,000 MW Tehri Pumped Storage Plant, is under construction and is expected to be commissioned by2017. Annual energy generation from Koteshwar is 1,155 GWh based on 90% water availability.
Water released from the Tehri Reservoir, situated 20 km upstream of Koteshwar Dam, is being regulated by the Koteshwar powerhouse for irrigation purposes. Also, the reservoir impounded by Koteshwar Dam functions as a balancing reservoir for the pumped storage plant.
Complex prevailing conditions and issues
Despite its considerably fast construction and implementation time (3.5 years as opposed to the nation’s average of six to 10 years), the Koteshwar project faced a number of complex issues that temporarily impeded progress. The innovations that enabled the project to be completed early were developed and implemented as a response to the issues faced.
Major work on the project began on August 31, 2002, when a US$66 million contract was awarded to PCL-Intertech LenHydro, with a scheduled completion date of May 31, 2006. The first river diversion milestone was achieved on December 28, 2003, only 28 days behind schedule. Thereafter, the pace of work was sluggish, largely due to the resettlement of families affected and repeated geological failures on both river banks.
|The powerhouse at the 400 MW Koteshwar hydropower project is located on the toe of the dam on the right bank and was fully operational in March 2012.|
The village Pendaras, where all the major structures were to be constructed, was to be completely vacated in March 2005. However, those vacating the land disturbed the construction activities by organizing sporadic agitations with various motivations, such as seeking employment with the contracting company. Officers and contractors were often man-handled and physically attacked.
Apart from this, two of the quarries being used to supply materials for the dam were in the villages of Mulani and Gairogisera. The state government relinquished control of the last one in 2007, substantially delaying construction work.
Further, soaring prices of raw materials also created a problem. For example, the price of steel started increasing, from US$547 per unit in 2007 to US$948 in 2008. As the prices increased, the project contractors did not receive adequate compensation as per the price adjustment formula in the contract agreement. The resulting cash-flow problem made it difficult for the contractor to procure materials. Additionally, payments to suppliers and for salaries were not made on time, promoting an attitude of distrust toward the project and its development team. As a result, work progressed very slowly up to February 2007, delaying all other development work past the initially scheduled completion date.
THDC management had two options: terminate the work and seek a fresh tender, or take some innovative management action to streamline the finances and resources of the contractor and get the work done through this company.
Termination was not an ideal option, as the owner would have to terminate a signed contract and risk a stay order, and progress up to that point would be lost through demobilization of the site. The project would essentially have to be restarted from scratch, creating an additional delay in completion of 18 months to two years. In addition, THDC would face a revenue loss of US$80 million per year.
Moreover, delay in completing this project would jeopardize development of the pumped-storage project, as the Koteshwar Reservoir was designed to be the lower reservoir. In addition, the delay would result in lost revenue from the Tehri plant, as it would not be able to function as a peaking station in the true sense. Currently, the Koteshwar plant fulfills the needed water requirement in the river by running one unit in base mode. If Koteshwar had not been implemented, Tehri would have to meet this need by running one unit in base mode around the clock. This means instead of getting peaking revenue, THDC would receive normal revenue. With all these factors considered, THDC management chose the second option.
Implementation of effective management
The value of work completed by the civil works contractor up to March 2007 was about US$20 million, as compared to a total contract price of US$66 million. At this stage, THDC felt that if the availability of required equipment, material and workforce could be ensured, the project could be completed within a minimal time frame by taking advantage of the resources/equipment already mobilized by the contractor. Accordingly, the THDC management board decided to carry out work at the project by “risk and cost” methodology. This meant making decisions at the site and making payments to manufacturers, suppliers, transporters and piece rate workers directly at the behest of the contractor and on that contractor’s written requests.
THDC’s management team empowered the project team with the decision-making abilities to cut short the procedural delays. The managing engineer for civil works was redesignated chief project officer (CPO) and was authorized to procure material, manpower, specialized work force and spares for maintenance of tools and equipment. He was also authorized to induct labor gangs/piece rate workers and fix their rates, if the contractor failed to do so. Finally, the CPO was authorized to set targets and directly distribute incentives to work gangs to accelerate the pace of work.
To speed progress of the project as a whole, an “empowered committee” was established in March 2007 to ensure there were plentiful resources available. The committee was comprised of the CPO and one member each from the design and engineering and corporate finance departments. Decisions made by the committee were recorded as meeting minutes and were deemed to have standing approval of the CMD (Chairman Managing Director). Such vast powers were vested with the committee to make administrative, technical and financial decisions required for bringing the project on track and to develop infrastructure so the project could be commissioned. The actions of the empowered committee drastically reduced the procedural and regulatory hang-ups that could slow progress.
Work proceeded quickly. The organizational set-up of the work site was restructured to increase efficiency. Executives with proven track records with the Tehri project were inducted into the new management team. Four independent sections were created within the civil works team, divided by the section each team would work on (dam, powerhouse, power intake and switchyard), each headed by an experienced senior manager.
All of the construction activities at site were planned and handled by THDC engineers. Incentives were distributed to the laborers directly by THDC as they achieved locally set targets. This ignited stiff competition between labor groups deployed at different locations on site, thus stimulating the pace of work. The uninterrupted cash flow and timely payment also boosted morale and confidence among contractors, workmen and suppliers and resulted in accelerated progress.
The hands-on management strategy adopted at Koteshwar was an unprecedented move in the history of Indian hydro. When the plant was commissioned, the efforts were lauded by the government of India.
The unusual delay and later innovative methodology adopted for managing the project required a shift in approach toward innovative construction techniques to catch up on the tight schedule. The engineers at the project site dared to think out of the box and adopt innovative techniques to replace conventional construction methods. The empowered committee stood behind these innovations and encouraged more unique developments.
Some of the innovations used at the site are described below:
Erection of turbines using a crawler crane
Conventionally, the erection of turbine parts is achieved with the assistance of an electrical overhead traveling crane, which travels on the crane beam cast on the walls on either side of the machine hall. The same methodology was planned for Koteshwar. However, based on the project requirements, a hydraulic crawler crane with a maximum lifting capacity of 250 MT was used. The crane was kept on the downstream side of the powerhouse in the tailrace channel area.
Erection of such turbine parts as the draft tube, stay rings and spiral casings was achieved using a mobile crane while the other parts were being constructed simultaneously. Use of this mobile tower crane enabled the project to engage in both civil and electromechanical activities, saving time and setting a new precedent for efficient development.
Using trusses to support the powerhouse
The above-ground powerhouse was constructed using roller-compacted-concrete columns, walls and beam structures. Conventionally, in a surface powerhouse, the roof slab is cast after raising the walls and columns to roof level. Thereafter, scaffolding erected from ground to roof level provides support and shuttering for the slab. In such a case, erection of electromechanical equipment is delayed until the scaffolding and shuttering material can be cleared from around the units.
To construct the powerhouse and install the units simultaneously, steel trusses of 21 meter span were constructed to support the shuttering of the slab. This made the entire unit area accessible, saving four months of construction time.
Alternative approach during excavation
Excavation for the penstocks was originally planned from the downstream side of the dam near the powerhouse. The excavated muck would be dumped into the powerhouse pit for disposal. To work on both tasks simultaneously, a methodology was developed to forego the interdependence of both the structures. Initially, construction of a partition wall between the powerhouse and stilling basin was suspended in this area to enable access from the stilling basin side. Later, the partition wall was raised, leaving an opening 8 meters wide by 8 meters tall at an elevation of 529 meters for carrying out activities in the powerhouse.
Alternative approach to service bay area
The only approach to the service bay and powerhouse area was through a 376 meter-long main access tunnel, with an inlet at Elevation 570 meters on the right bank. This area of the right bank had very unsteady geology, marked by repeated slope failures. Consequently, excavation of the tunnel was delayed until June 2007.
To move forward with work despite this delay, THDC chose to take an alternative approach from the downstream side, through the tailrace channel up to the service bay area of the powerhouse. Excavation of the tailrace channel would be connected with the downstream main approach of the stilling basin.
Although the main access tunnel was not fully operational until July 2009 because of the slope failures, service bay work began in early 2008. This approach not only helped keep the project ahead of schedule and provided access for both men and materials, it also provided a means for an electrical overhead traveling crane to be transported to the service bay, where it was erected in early 2009.
Concreting of generator barrel
Concreting of the generator barrel of Unit 1 was a challenge because there was not sufficient time to complete the task conventionally. To shorten the length of time required, THDC decided the discharge ring, which was to be placed in the turbine pit after hydraulic testing of the spiral casing, would be placed after completion of the concreting, which would shave 15 to 20 days off the schedule.
For this to happen, a temporary gallery nearly 1 meter wide was left around the stay ring pedestals below the spiral casing. Once the discharge ring was lowered, concrete work around it was completed from this gallery. Meanwhile, the turbine was erected alongside this work.
As a result, concreting of the Unit 1 generator barrel was completed on September 26, 2009, in only 57 days as compared to the planned 75. This was a great achievement because this activity conventionally takes as much as five months. Nearly one month was saved as per the schedule and nearly 2.5 months if it had been completed conventionally.
Arrangement for erection of steel liners
Construction of the steel liners for the penstocks was to be carried out through the lower horizontal penstocks, but due to rock ledge failure and further delay in excavation of the lower horizontal penstocks, this could not be achieved. To facilitate the erection of penstocks from the upper side, the contractor built cement concrete buttresses between all four penstocks. The contractor also installed a track-mounted gantry crane with the rail track at Elevation 590 meters up to Penstock 4. The steel liners were constructed with the help of this arrangement, which prevented a possible construction delay.
Arrangement of canopy for simultaneous work
Conventionally, hydromechanical/electromechanical construction work is completed once the civil works have been completely finished, which takes a considerable amount of time. To save time, erection work of the electromechanical/hydromechanical equipment began after completing the civil works up to mid-level only. To do this, workers created a canopy of steel to facilitate simultaneous working.
Substantial time was saved in the construction of the power intake and draft tube gates of the powerhouse, which were ready to house gates even before completion of the civil works up to the top level.
Accelerated reservoir filling and commissioning of Units 1 and 2
A geological event occurred on December 17, 2010, above the underground diversion tunnel of the project. As a result, the excavated muck found its way into the diversion tunnel, blocking the flow of water. As soon as the blockade was noticed, all four units of the Tehri plant located upstream were immediately shut down to avoid sending any more water into the Koteshwar powerhouse.
The balance of the civil and hydromechanial works that were pre-requisites to reservoir impoundment had to be completed so that water could be passed downstream through the spillway. The diversion tunnel gate at Koteshwar was lowered on January 23, 2011, and water passed through the spillway on the 27th.
At the time of reservoir impoundment, the penstocks of Units 1 and 2 were complete; however, the penstocks of Units 3 and 4 were not connected to their spiral casings and were expected to take more time. This would delay filling the reservoir and, consequently, could have delayed commissioning of Units 1 and 2.
To allow for filling the reservoir, the water flowing through the incomplete inlet pipes of Units 3 and 4 would have to be rerouted. Leakage water was routed to a draft tube by erecting a barrier of steel plates with stiffeners inside the penstock, with pipes and gate valves to discharge the accumulated water behind the plate.
This arrangement made it possible to fill the reservoir even though the Unit 3 and 4 penstocks were not entirely complete.
Fully operational since March 2012, the Koteshwar project can be seen as a model for hydro plant development in India due to the effective management techniques that were put into practice. However, success could not have been achieved without the innovation in construction techniques mentioned above.
R.S.T. Sai is chairman and managing director and D.V. Singh is technical director and former chief project officer of the 400 MW Koteshwar project with THDC India Limited.