Albania Dam Safety Monitoring

Michael Furrer, Max Osterried, Marialis Çelo, Hans-Jakob Becker

Abstract This article deals with the implementa- tion of geotechnical and geodetic mo- nitoring systems for five hydropower dams in Albania. The dams were equip- ped with different automatic and manual sensor systems to improve the safety of the dams by monitoring the behaviour of the structures and their surroundings. The topography and accessibility in this wild and beautiful country presented a very special challenge.

1. Introduction As a mountainous country with a large amount of precipitation during the winter months, Albania has a huge potential for hydro power which has been used for a long time. Spread across the country there are numerous dams, big and small. Most of these dams are used for irrigation during Figure 1. Geodetic Monitoring at Fierza HPP. the dry summer months. A number of dams are also used to produce electric power. owned. Hence KESH is responsible for the River Cascade (Fierze, Koman, Vau I Dejes) The dams are mostly embankment dams maintenance and the safety of these dams. and the two hydropower plants of the Mat with heights of up to 160 m. The three lar- River Cascade (Ulza, Shkopeti) in the gest dams are under the control of KESH 2. The Dam Safety Project north-eastern part of Albania (see Table 1) (Korporata Elektroenergjitike Shqiptar), a A survey of the present state of the safety financed by SECO (Swiss Federal Depart- joint-stock company which is 100% state- of the three hydropower plants of the Drin ment of Economic Affairs) was carried out.

Table 1. List of Hydropower Dams.

«Wasser Energie Luft» – 106. Jahrgang, 2014, Heft 3, CH-5401 Baden 231 strumental observations, periodic dam safety evaluations, etc.); • Operational safety and dam mainte- nance (reservoir rule curves, qualified staff, etc.); and • Emergency planning such as emer- gency action plans, alarm system, etc. The status of the structural safety of the dams built along the Drin and Mat riv- ers several decades ago was uncertain. Therefore, in the first step, the safety of these dams was assessed, and remedial actions were proposed, where necessary, to reduce the most urgent risks. As far as Dam safety monitoring is concerned, in- vestments such as successful finalisation of the implementation of geotechnical and geodetic monitoring systems for five hy- Figure 2. Automated rectangular Figure 3. Drilling works for inclino- dropower dams in Albania are discussed weir measuring seepage flow inside meters with sub-contractors Altea in this paper. Komani dam. Geostudio2000 at Porava. 3. Geotechnical Monitoring Geotechnical monitoring included the design, specification, manufacturing/ procurement and installation of sensors and the data acquisition systems. This included all cabling, drilling and injection grouting works and the setup of monitor- ing stations. Data handling and analysis software and measurement devices were provided and local and personnel at head- quarters were trained in using the meas- urement equipment and the data acquisi- tion and analysis software, respectively. Measurement intervals and equipment maintenance schedules were suggested based on both local conditions and the experience with the systems in use.

4. Instrumentation To monitor the structural integrity of the dams a three-pronged approach is used. Seepage through the dam body is moni- tored using automated piezometers be- hind the grout curtain and by collecting and measuring seepage run-off via automated V-notch weirs (see figure 2). Standpipe pi- ezometers are used on the downstream Figure 4. Geodetic Network for Vau I Dejes HPP (with Zadeje and Qyraq dams), dam face and the abutments to monitor reference points and lines of sight in red and green, object points and lines of water levels. And lastly, an automated sight in blue, levelling points and lines in purple. seismic network records vibrations in a background mode and seismic events. In this context, the dams and appurtenant Cascades represent about 85% of the total Other measurement points include structures were inspected to identify the electricity production in Albania, any loss inclinometers installed in landslide areas main hazards and the present conditions of power production will have a significant near the dams (Fierza HPP and Koman of the civil structures. negative impact on the economy and the HPP). An example is shown in figure 3 Dam safety is a fundamental pre- regional energy market as well. regarding the Porava landslide area near condition for sustainability of hydropower Dam safety as an integral concept includes HPP Fierza. Furthermore, jointmeters and generation. Without adequate safety, not the following items: pendulums are used inside Ulza dam to only are there large numbers of people • Structural safety of dam and technical monitor its deformations depending on the at risk, but the power production will be information and documentation; reservoir level. jeopardized. Since the Drin and Mat River • Dam safety monitoring (visual and in-

232 «Wasser Energie Luft» – 106. Jahrgang, 2014, Heft 3, CH-5401 Baden Figure 5. The construction steps of a double-wall pillar, foundation, concrete, finish.

Figure 6. Transport of construction material, Mules, improvised cable cars. Figure 7. Powerhouse in Koman with land slide area in the background.

5. Monitoring Measurements are taken automatically and also manually at specified intervals. Automatic data acquisition is achieved through a network of automated sensors, interfaces at the nodes and the Geomoni- tor software installed on a dedicated indus- trial PC inside the command centre where all the raw data streams come together at each hydropower plant. The Geomonitor software is very versatile in that it not only Figure 8. Improvised ferry service downstream of Shkopet HPP, Installation of collects data, but also allows supervisors object points at Ulza HPP. to monitor sensors in real-time, plot, view and interpret recorded data. Furthermore, 6. Geodetic Monitoring The reference points are properly and du- alarms can be set and, when triggered, The geodetic monitoring encompasses rably secured in stable ground outside the send event-specific information to super- the design, building, measurement and expected deformation area. visors via email, SMS or other pre-defined adjustment of a geodetic network of points In spring 2012 a first site visit of all methods. on and around the hydropower dams as the dams and land slide areas took place. Manual records and data down- well as in land slide areas in the sphere of Meanwhile the locations for the object loaded from the Geomonitor system is influence of the reservoirs. Furthermore, it points (on different levels of the down- then transferred to the Dam Department involves the commissioning and delivery of stream faces of the dams, on the intakes, at KESH, Tirana. Trained staff there uses all the specific equipment required to take on the spillways, on rocks in landslide area the WebDAVIS web-based data manage- the geodetic readings such as total sta- etc.) were set and stable locations for the ment and visualisation software to inter- tions, digital levels, adjustment software construction of reference points were eval- pret, store, plot, manage and share the and accessories as well as the training of uated with the support of a geologist. information. A periodical report is issued the personnel of the dam operator. The reference points were mainly based on the visualised data. The goal of a geodetic monitoring built as doublewall survey pillars with The installed systems provide both is to study the behaviour of the dam struc- centring plate and protective cover. The an early warning system for structural fail- ture and its surroundings and to derive the foundation of the pillars reaches up to ure as well as long term monitoring ca- structural health thereof. 1.5 m into the soil and is whereever pos- pability to ensure correct maintenance sible sounded in proper rock (see figure 5). procedures and enhance longevity of the 7. Instrumentation Additional reference points have been dams. Thus, the future of Albanian energy In every geodetic monitoring the reference mounted in the vicinity of the pillars as a production is secured and the safety of points are of greatest importance, since all back-up. Every network consists of ap- its people living downstream of the dams future readings will be based on the coor- prox. 10 pillars and 5 to 7 additional refer- guaranteed. dinates of the 0-reading of these points. ence points (see figure 4).

«Wasser Energie Luft» – 106. Jahrgang, 2014, Heft 3, CH-5401 Baden 233 Figure 9. Fierza HPP with horizontal displacement vectors and confidence ellipses 95%.

Figure 10. Ulza HPP with horizontal displacement vectors and confidence ellipses 95%.

The civil work for the reference we were happy to have the support of a meter pipes to connect the geotechnical points was carried out in the summer local subcontractor who had the experi- measurement systems with the geodetic months May to September 2012 and ence and creativity to make it happen. All network. Additionally to the 3d-deforma- proved to be difficult due to the topogra- the excavations were done manually (see tion measurements a number of levelling phy and accessibility. Most of the locations figure 6). points were installed on the dam crests. are in steep and rocky terrain and cannot The object points on the dams were In Koman the rock mass above be reached by car. The construction ma- either built as concrete foundations or se- the intake and the slope above the power terial such as cement, gravel, water, etc. cured directly into the rock or concrete of house proved to be very unstable and rep- had to be transported by mules or by pretty existing structures. Some of the points resents a serious hazard to the infrastruc- adventurous self-made cable cars. There were mounted directly onto the inclino- ture (see figure 7). To monitor the move-

234 «Wasser Energie Luft» – 106. Jahrgang, 2014, Heft 3, CH-5401 Baden Figure 11. Ulza HPP with vertical displacement vecotrs. ments and their velocity a number of object The analysis of the measurements (Fierza 40 m) and Mat-cascade (Ulza 12 m). points were installed. was done in the following week at the of- The lower levels of the Drin- (Koman, Vau I In total 45 pillars, 70 concrete foun- fices of the dam operator. All the meas- Dejes) and Mat-cascade (Shkopet) can ad- dations, 147 bolts, 27 target plates and urements of each dam were evaluated just their water levels only marginally. The 5 permanent reflectors were installed. and adjusted coordinates were calcu- results show that the embankment dams in lated. In a first step the data was verified in Koman, Vau I Dejes and the buttress dam 8. Measurement concept a free network adjustment. The networks in Shkopet are stable and hardly show All points (reference and object points) are were measured highly over-determined measurable deformations. The situation is measured and adjusted in one highly over- whereby single erroneous measurements different in Fierza and Ulza. determined network. Thus every point can be detected and eliminated. The refer- In Fierza significant horizontal within the network receives a coordinate ence frame for the adjustment was chosen shifts towards the downstream side are for its 0-reading position. The measure- locally so that the Y-axis is aligned with recognisable. However, the displace- ments are repeated in a slightly slimmed- the dam crest and the X-axis points into ments include a transversal component, down version at regular intervals. The net- the direction of the largest expected de- which indicates an opening and closing of work will be adjusted after every measure- formations. the valley cross section and a resulting in- ment and is referenced to the 0-reading fluence on the dam (see figure 9). coordinates of the stable reference points. 10. First Sequence Readings The valley cross section narrows With every measurement the stability of the The first sequence readings took place in in spring by about 8 mm at a distance of reference points is checked again. Only in early spring 2013 in the same constellation about 420 m, but the uncertainty with only this way the comparability of results can be as in autumn the year before. After the long one measurement is high. In the mean- guaranteed over a long time. precipitation period in winter and the snow time, the dam operator carried out a sec- melting in spring the reservoirs were filled ond sequence reading which confirmed 9. 0-Readings to their maximum level. All dams had to this effect. The «breathing of the valleys» The 0-readings for all dams took place in open their spillways to release water which was already observed in Switzerland dur- October 2012. Autumn holds the best con- caused flooding in the downstream areas. ing the permanent monitoring related to ditions for geodetic measurements: the The metrological conditions for the geo- AlpTransit Gotthard [1], [2]. There a con- reservoirs are almost empty after the long detic measurements were excellent and tinious series of measurements over sev- and dry summer; the weather is usually still the survey points had survived their first eral years is available and the validity of dry but not as hot as in summer anymore winter well. Only one pillar had been de- the results is much higher. It is interesting and the vegetation is getting lighter. stroyed by «human rock-fall». Once again that in Albania,this effect is evident only The measurements were taken by the measurements were also used to train in Fierza, which is probably related to the a team consisting of specialists from BSF the personnel of the dam operator in the geology and natural fluctuation in ground Swissphoto and KESH. Meanwhile on the handling of the equipment, the challenging water level in this area. Unfortunately the job training was given. The measurements logistic and the evaluation and interpreta- geotechnic lot had not yet been completed were completed within two days at each tion of the data. and therefore no data from geotechnical dam. Due to the difficult access and long sensors such as piezometers were avail- distances between the points we were 11. Results able for the period of the geodetic meas- happy to have additional personnel of the The analysis of the first Sequence reading urements. hydropower plants at our disposal (see data set allowed for a first interpretation of On the gravity dam in Ulza, signifi- figure 8). the deformation of the dams and the ve- cant deformations that resemble the shape On every pillar at least two to three locity of the land slides. The differences of of a folding motion, occur (see figure 10). sets of angles were measured. Every point the waterlevels of the reservoirs between The settlements along the dam crest are within the network was observed from at the two measurements can be regarded significant with up to 5 mm over the entire least three positions. as maximal for the first Levels of the Drin- crest (see figure 11). Again, the uncertainty

«Wasser Energie Luft» – 106. Jahrgang, 2014, Heft 3, CH-5401 Baden 235 with only one measurement is high and the 12. Conclusions Bibliografie behavior of the dam can not be conclu- Within the Dam Safety Project a geodetic [1] Studer, Salvini; «Automatic Monitoring of sively determined. However, it is conceiv- and geotechnical network has success- large Dams in the Swiss Alps during Construc- able that the additional applied load due fully been implemented for the five larg- tion of the Gotthard Base Tunnel» (57 km), Geo- to the higher water level (+12 m) causes est hydropwer dams in Albania. The local matik Schweiz 12/2010. a settlement and vertical tilting. Although staff was trained thoroughly and is now [2] Hansmann, Loew Evans; «Reversible rock- the settlements are at their maximum in able to carry out the measurements inde- slope deformations caused by cyclic water- the middle of the dam, the largest horizon- pendently which they have already dem- table fluctuations in mountain slopes of the tal displacement or tilting can be found onstrated. The project was a success Central Alps, Switzerland», Hydrology Journal towards the left abutment. This might be from the perspective of the entrepreneurs (online) 8.11.2011. caused by either topography/geologie or involved. structural unstabilities. The downstream The dam operator must collect Adress of the Authors: tilting/displacement seems to effect the further data through periodical measure- Michael Furrer, BSF Swissphoto AG whole structure by pulling the right abut- ments within the next two years, to re-eval- [email protected] ment towards the left abutment. uate the stability of the dams. After com- Max Osterried, Solexperts AG Basically, the deformations in Fi- pletion of the geotechnical part more data [email protected] erza and Ulza are large. The dams are al- from inclinometers, piezometers, pendu- Marialis Çelo, KESH, [email protected] ready 35 respectively 56 years old. Unfor- lums, etc. will be available with which a Hans-Jakob Becker, Solexperts AG tunately no previous measurements are more detailed assessment of the behavior [email protected] available. Before a series of at least four of the dams will be possible. measurements over two years is present, The maintenance of the measuring it can not be determined whether the de- equipment and devices will constitute a formations only represent a special event further challenge. Due to the large defor- or a normal behavior and how these move- mations in Fierza and Ulza a permanent ments influence the stability of the dams. automatic monitoring would be desirable.

Die nächste Ausgabe von «Wasser Energie Luft» erscheint am Donnerstag, 4. Dezember 2014

Foto: MMi

236 «Wasser Energie Luft» – 106. Jahrgang, 2014, Heft 3, CH-5401 Baden