CHAPTER 2

STATEMENT ON EXISTING INFORMATION

Table of Contents of Chapter 2

2. STATEMENT ON EXISTING INFORMATION ...... 1 2.1. CHARACTERISTICS OF THE AREA ...... 1 2.2. DEMOGRAPHY AND INFRASTRUCTURE ...... 1 2.3. HISTORY AND MINING ACTIVITIES ...... 3 2.4. GEOLOGY...... 7 2.4.1 Regional Geological Framework...... 7 2.4.2 Geology of the Mailuu-Suu Uranium Mining District ...... 12 2.5. HYDROGEOLOGY...... 14 2.6. HYDROLOGY OF MAILUU-SUU AND TRIBUTARIES ...... 15 2.7. CLIMATE ...... 19 2.8. LANDSLIDES/MUDFLOWS ...... 21 2.8.1 Previous work on the landslide problem in the Mailuu-Suu area...... 24 2.8.2 Landslides Databank...... 25 2.9. SEISMICITY ...... 25 2.9.1 Seismic data ...... 26 2.9.2 Influence of Seismicity on landslides and tailings stability...... 27 2.9.3 Seismicity in the Mailuu-Suu Region ...... 28 2.9.4 Results of recent Research ...... 28 2.9.5 Maximal seismic accelerations ...... 33 2.10. TAILINGS: DIMENSIONS, RADIOACTIVITY, CHEMO-PHYSICAL PARAMETERS ...... 33 2.10.1 Physico-chemical characteristics of the residues ...... 35 2.11. DESCRIPTION OF A SELECTED NUMBER OF TAILINGS (ACCORDING TO 9, 10) ...... 42 2.11.1 History and physical characteristics...... 42 2.11.2 Radiological situation...... 46

2. Statement on existing information

2.1. Characteristics of the area The Mailuu-Suu District of uranium ore mining and milling is located at approximately 41.13 North latitude and 72.51 East longitude, about 60 km north-west of Jalal-Abad and about 25 km from the border with Uzbekistan. Uranium mining and milling industrial activities started 1946 and lasted until 1968. The associated deposition of tailings (residues from ore processing) and of low-grade ore and waste rocks from mining, covering an area of approximately 44 hectares and with an estimated volume of 3 million m³, was carried out in a moderate mountainous terrain and in gently sloping alluvial areas, often in close proximity to the Mailuu- Suu-, Kara Agash-, Kulmensai and Ailampa-Sai Rivers. During the time of mine and mill operations, the tailing impoundments, processing plants, underground mine workings, waste rock depositories were connected with various configurations of roads, tailing delivery pipelines, return water collection-, settling and conveyance systems. Due to the mountainous topography especially in the upper reaches of the regional drainage pattern, the rivers and adjacent areas are subject to major flood conditions, primarily during spring run-off. Therefore significant damage evidence for high water erosion potential can be observed all along the river banks. Also evidence for significant landslide activities and of slope instability and movement can easily be observed throughout the area causing damage of roads, power lines, pipelines and housing and in some cases of tailings impoundments . In several cases this has resulted in the relocation of infrastructure and population. 2.2. Demography and infrastructure The town of Mailuu-Suu (25000 inhabitants) is located in the project area in proximity to the tailing impoundments and mine waste rock depositories. Smallest distance from city limits of Mailuu-Suu to tailings or waste rock depositories from uranium mining is 300 m. Smaller settlements are located in the valleys of the Mailuu-Suu, Kara Agach and Ailampa-Sai rivers. In most cases the tailings and waste rock dumps are upstream of the communities, sometimes not more than 500 m from houses. An exception forms the settlement of Kara Agach where waste rock dumps are located in the centre of the settlement. The communication infrastructure of the district is comparatively well developed. The highway Osh - Bishkek goes through the general region. The distance between Mailuu-Suu and Bishkek is 550 km. The main road Mailuu-Suu –Madaniyat – Andijan (Uzbekistan) – Osh (130 km) starts along the valley of the Mailuu-Suu river. Along the rivers, and stream valleys loose gravel roads and a network of earth roads lead to summer pastures and grasslands. The two coalmines and the uranium mines are connected with main and automobile roads. The town of Mailuu-Suu is connected with Andijan city by an asphalt coated road.

Chapter 2 pa ge 1

Water-supply The upper reaches of the Sary-Bee River (a tributary to the Mailuu-Suu River) 12 km upstream from Mailuu-Suu are used for water supply. Waters fed by glaciers and some springs are collected 3 km upstream from Sary Bee settlement and conducted downstream by 3 water pipes (diameter 350 mm). Their daily production amounts to 40 000 cbm with a maximum of 60 000 cbm. The population served is 23,000 inhabitants and that of the city itself is 17 to 18,000 These water pipes are buried for partial stretches along the right side of the Mailuu- Suu River valley and reportedly may have suffered some damage due to active slope movements and recent landslide activity. Downstream facilities for water purification with the planned production capacity 5.000 m³/day have been built and are hardly operational. However, at the present time up to 80 000 m³/day of water are fed into these plants, and therefore the quality of water purification is unsatisfactory. Reconstruction of the waste disposal plant is required. It can be said that at present, water is distributed from the river without treatment. Following excessive rainfall, it is highly charged with suspended matter and is not fit for domestic use. Since water is taken upstream from tailings, there is thus no risk to this water from radioactive contamination from the tailings. Since 1971 some wells are operating in the valley of the Mailuu-Suu river which produce uncovered underground pressure waters from zones of open fissuring. The total capacity of this water supply is 144 l/sec. Water supply of the villages Kugai and Sary Bee is realized with this water. It is also used for the need of the oil industry and the heat-electric generating plant of the electric bulb plant. These waterworks are under the jurisdiction of the electric bulb plant and are considered satisfactory . The last village served downstream is Kok-Tach where several distribution points connected to the conduct were recently installed. Before this, the residents took their water directly downstream from city rejections. In the best case, the water was used after decanting, explaining the occurrence of various diseases. Residents downstream from Kok-Tach continue to take domestic water directly from the river. A study conducted by the Hydraulic Service showed that extending the conduct downstream was financially impossible in current local economic conditions. No water for domestic or irrigation use is obtained by pumping wells in the water table of the Mailuu-Suu River. Plots of land bordering the river are irrigated by pumping its water. City gardens are watered from the conduit. Radioactive contamination of the river in the case of an accident at one of the tailings would thus affect the "drinkable" water supply (in fact already certainly not drinkable from a bacteriological standpoint) of only villages downstream from Kok-Tach and up to the border with Uzbekistan.

Chapter 2 pa ge 2 The water supplies along the river in Uzbekistan, in particular at Izbaskan, the first city downstream, is not within the scope of our study and is not within our possibilities of field surveys. There are no groundwater resources confirmed by exploration in the project area. A detailed exploration programme of groundwater resources of the area was outlined by the Geological Agency of the Kyrgyz SSR (see appendix 30) in the 90-ties. Its realization however came to end with Soviet time. Thus, since sovereignty, water supply of the town of Mailuu-Suu is not actualized and inadequate. Villages located downstream Mailuu extract the water directly from the Mailuu-Suu river, often without filtration, sometimes after sedimentation, for drinking water, water for animals or for irrigation. 2.3. History and Mining activities First discoveries of uranium mineralization were made by the geologist Ya.K. Pisarchik during the exploration for sulphur deposits in 1933. Traces of yellow and greenish minerals (which were determined to be Carnotite by Yu.M. Golubokova in 1934) were observed in the faults and fractures in Paleogene lime stones of the Mailuu-Suu River valley During the same year uranium mineralization were discovered by E.Ya. Orlovski in the area of exposure of rock layer "L1" in the periclinal extension of the Main Anticline (section "Svod") and also on the river banks of the Kara-Agach-Sai. These discoveries led to the beginning of investigations of the geological structure and radioactivity of the Paleogene sediments in this area. During the first period of exploration from 1934 to 1941 geological maps at the following scales were completed : • 1:100.000 (E.Ya. Orlovski, 1934), • 1:25.000 (A.A. Danilyants, A.S. Fyodorenko, 1935) and • 1:50.000 (S.S. Shults, N.V. Ognev, O.I. Nekrasova, 1940) A.S. Fyodorenko and A.A. Danilyants discovered economic Carnotite- and Tyuyamunite ore accumulations in exposures of rock layer "L1" on the flanks of the Northern Anticline in 1935. Like those of the "Svod" section, these ore occurrence were defined by surface trenching, by aditing and by minor drilling during the years 1938-1941 (A.A. Danilyants, B.M.Biryukov) and during 1943 (A.A. Danilyants, N.V. Ushmakov) . At that time the size of the until then discovered uranium deposit was considered to be insignificant and included only those ore bearing horizons which cropped out at surface . Smaller exploration activities continued 1943-1944. Gold exploitation started at the same time A significant increase of exploration efforts for uranium, however started in 1945. The responsibility for further exploration and exploitation of the deposit was transferred to branch N° 13 of the Combinat N° 6 which was changed into Combinat N° 5 in 1954.

Chapter 2 pa ge 3 The uranium ore section at the southern flank of the Main Anticline on the right bank of the Mailuu-Suu, in Horizon "L1" was discovered in 1946 and the ore occurrence on the left bank of the Mailuu-Suu River, in Horizon "L2" in 1948. Underground Mine N° 1 was sunk at this location which operated until the end of 1965. The ores in the Central Syncline were exploited by Underground Mine N° 2 during the years 1947-1957. In 1947 the mined uranium ores were milled (processed) in the Leninabad (Ferghansky) processing–plant of the Mining and Chemical Combinat in Leninabad, Republic of Tajikistan (built in 1947) which took the ores from Mailuu-Suu and from the older Teo–Moyunsky radium-uranium mine located 30 km South–West from Osh. These mines were part of the industrial complex, that started production of the first soviet uranium for the military industry. The enterprises of this complex including the later built hydrometallurgical ore processing plant in Mailuu Suu until the middle of 1950ties also received and processed uranium ore from Eastern Europe, Czechoslovakia (Yakhimov), Bulgaria (Bukhovo) and also from Tajikistan (Taboshar, Adrasman). In 1949 exploration-drilling in the SE section of the ore zone discovered the economic uranium ore deposit in Horizon "m" (Section “Kulmen”). It was exploited by Underground Mine N° 6 which operated until 1962 (see geological map). The uranium ore in the northern flank of the Northern Syncline (Section „Kara- Agach“), which is associated to Horizons "L1" and "L2" was exploited during the period from 1946 to 1958 by Underground Mine N° 3. After “conservation” of its shaft the Bedre Section was discovered and defined by drilling (1958-1961) further to the south east of the already exploited deposit. Here the most essential part of the reserves is associated to Horizon "L1" and the smaller part with Horizon "m". On the basis of these newly discovered reserves, Underground Mine N° 3 was re- opened and operated until 1968. Exploitation of the Mailuu-Suu deposit lasted more than 22 years from 1946 to 1967(68) by the West Mining Chemical Plant; Approximately • 45 % of the Resources of the deposit are associated to Horizon "L1", • 36 % to Horizon "m" and • 19 % to "L2" The possibilities to further increase the economic reserves of the Mailuu-Suu deposit at surface and down to a depth of 500 m (still considered to be economic) are now completely exhausted. The uranium ores from the deposit were processed on site by ion exchange and ?acid leach in two hydrometallurgical factories. The resulting product was uranium oxide which was first sent to the Mining and Chemical Combinat in Leninabad (Republic of Tajikistan) for processing.

Chapter 2 pa ge 4 Altogether more than 10.000 t of uranium were extracted from the Mailuu-Suu uranium ore deposit. (Aleshin, Torgoev, Losev 2000). After completion of mining the West Mining Chemical Plant was dissolved but its industrial establishments were transferred to the Leninabad Mining and Chemical Plant ( Industrial Association "Vostokredmet"). During the periods from 1966 to 1968 all 23 tailings have been “conserved” (recultivated) within the project P/J No. 200. This included: - Grading and covering the surface of the tailings with soil - Construction of the water –collection and drainage system - Installation of fences and warning signs - Stabilization of the dam–base applying a gravel cover for erosion protection - Channeling and fortification of the Aylampasay river riverbed with installation of gabions . The 13 mine waste dumps, however, have not been recultivated (as originally foreseen according to a method for their conservation, which was created by the Ukrainian Design Institute in Zheltye Vody, Ukraine). Subsequent observations of the condition of tailings and mine waste dumps have been carried out by the Hydro technical Exploitation Service of the Industrial Association Vostokredmet. Since 1992 these observations have been discontinued ( because of the break up of the Soviet Union) . Later in 1994 responsibility for the 23 tailings and 13 mine waste dumps passed to State Concern "Kyrghyzaltyn". Due to the absence of maintenance since 1992, reconstruction and repairs of the 1966- 68 conservation work were considered to be necessary in 1994 and partially carried out since then. At that time the gabions designed for strengthening the tailings dam adjoining to the Aylampasay river channel had already been destroyed as a result of the sand / gravel mining in the river bed (dry during the summertime) which lowered the erosional basis by 5,0 meters. This caused the washing away of the gabion strengthening during flood water periods. Also, already in 1994, water collecting systems, drainage channels and ditches had been washed out and destroyed almost everywhere as well as fences and signs had been broken off . The same destructions were observed at tailings depositories #3,5,6,7,8,9,10,17,18,19,20,21,22 located on the Mailuu-Suu river terrace. Reconstruction and repair work carried out in 1994/1995 is summarized as follows : [1] Reinforcement of the lower slope of the tailings against flood water volumes of 18 m³/sec. Reinforcement of the apron and crest was done by two methods: gabion baskets and monolithic concrete blocks. [2] Construction of a mudslide protection Dam ( tailings No. 3). [3] Repair of the water-collecting and drainage constructions (tailing No.7). [4] Filling in of swamp areas on ( tailings No.5, 14, 16). [5] Construction highland ditches ( tailings No.1, 4).

Chapter 2 pa ge 5 [6] Trenching of the water-collecting ditches (Tailings 1,2,3,4,13,8,20,21,5,6,7). [7] Fortification and widening of various areas of the Aylampasay river channel. Remedial works were not foreseen for tailings No. 11, 12, 15, 17 and 23, due to their satisfactory condition. The history of Mailuu-Suu uranium mining and milling and of subsequent events (- seismic events, slope movements-) affecting its legacies are summarized below (also see Figure 2.3 ) : • Mailuu-Suu History in Summary : • Uranium mining and processing. Production of appr. 10 000 t U • Underground mine workings in 5 areas, construction of 2 processing facilities, • waste deposits: 13 mine waste dumps, 23 tailings depositories • Infrastructure: Power Plant, schools, residential buildings • April 1958 : Dam rupture of tailings Nr. 7, (causing spills of 6000 cbm resulting in contamination of river Mailuu-Suu for 25 km downstream ) • mine workings abandoned, destruction (blasting) of Plant Nr. 7 • 1966 to 1968 “Conservation” of all 23 tailings • “Industrial Conversion”: Construction of light bulb factory ISOLIT • Aug. 1992 : Earthquake 7.3 Richter Scale, epicenter at 60 km distance (Susamir valley) in Mailuu-Suu town Richter Scale 7 triggering numerous land slides or slope movements • Slope movements both valley sides in the area of ISOLIT Plant old mine workings causing Mailuu-Suu River blockage, water level rising 6-10m, causing flooding and destruction of houses and connecting road, rupture of supply lines etc . Blockage was opened by blasting. • Re-activation of land slides and slope movements (by a tectonic event), destruction of Tailings depository Nr. 17, river erosion of Tailings depository Nr. 18 • 1994/95 : Reconstruction and repair work on tailings dams • Earthquake Richter scale 4,5 (Epicenter in Koktash) at 10 km distance from Mailuu-Suu town, damages at mine next to Tailing 3. First appearance of ruptures or subsidence above old mine workings announcing big slope movement. • Installation of Geo-monitoring measurement stations and early warning system by the German Geological Survey in the framework of ECHO • May 2002 : Re-activation of Tectonic Landslide, 100 m upstream from Tailings No 3, causing initially Mailuu-Suu River blockage and subsequent partial destruction of the ISOLIT Plant

Chapter 2 pa ge 6 2.4. Geology

2.4.1 Regional Geological Framework Most of the Kyrgyz territory is occupied by the Tien Shan Mountains. This 2500 km long and 500 km broad intra-continental mountain belt consists in a series of E-W trending sub-parallel mountain Ranges (4000 – 7000 m altitude), separated by intra- montane Basins (1000-2000 m altitude). The Tien Shan developed mainly during the Neogene and Quaternary, between the Kazakh platform in the North and the Tarim Basin in the Southeast.

Eurasian Plate

Tien Shan Fergana Basin Tarim Pamir

Indian Plate

India/Eurasia- Suture and related thrust- and fold belts

Figure 2.1 : Tectonic deformation north of the India/Eurasia suture zone The Pamir- Tienshan region in Central Asia is part of the active collision zone between the Eurasian and the Indian Plates (Figure 2.1 and 2.2 ). This collision and the resulting active development of the Pamir - Tienshan orogeny is one of the most interesting geo-scientific problem. In this connection earthquakes and mass movements (landslides, rock falls) are expressions of ongoing tectonic activity. The occurrence of landslides is concentrated at the eastern rim of the Ferghana Basin which is inhabited by about five million people (Kyrgyzstan and Uzbekistan) (Figure2.2 and Figure 2.3). After collision tectonics in the Carboniferous – Permian, tectonic activity resumed in Palaeogene times in relation with India-Eurasia collision. It culminated in the Miocene, and again at the Pliocene-Quaternary transition. The stress field during these periods was principally compressive and oriented NS. Recent tectonic activity is recorded in high-accuracy geodetic GPS measurements [6] which have been carried out in Central Asia by the GFZ in 1992, 1994, 1996 and 1998 [7, 8, 31]. They show regionally differing movement directions of plate subunits. Highest movement rates of 1.4 cm/a were obtained in NNE-direction at the Pamir- Tien Shan collision front. They are modified in the area of the Talas-Fergana Fau1t into a NE-oriented direction. This indicates a change in the horizontal stress field in this region leading to complicated interactions between active tectonic structures and consolidated older blocks as one factor controlling landslide activity in this area (Wetzel et al. 2000 [20], Figure 2.3 and 2.4). Present rates of deformation defined by GPS works have been indicated by Abdrakhmatov, 1996; Reigber et al., 1997 to amount to 20 mm per year. This

Chapter 2 pa ge 7 deformation is accompanied by a high seismic activity that affects all of the Tien Shan area (Figure 2.1, 2.2 and 2.6). This is supported by modern space-geodetic investigations including the GPS and radar interferometry. Results from repeated measurements across the 90 sites of the GFZ - CATS GPS network (Reigber et al., 2001 [33]) have provided direct evidence of current high rates of tectonic deformation far north of the India/Eurasia suture zone. These data help to quantify both the partitioning of deformation within the seismically active Tien Shan and Northern Pamirs, as well as the ongoing rotation of virtually undeformed blocks such as the Tarim with respect to stable Eurasia. The NNW to SSE shortening rates derived from the computations reach values of 23±3 mm per year over the ranges studied, suggesting that regional deformation rates have increased considerably within the study area since the onset of the Cenozoic shortening 20-25 Mio ago. Additional results suggest that a major portion of the ongoing shortening in the area is accommodated by earthquake faulting advocating for high probabilities of large earthquakes in this intraplate setting (Michel et al.,submitted) [32]. Much of ongoing northwardly directed convergence between India and Eurasia is taken up within the seismically active ranges to the north. In this segment overall average motions trend to the N but directly west of the Talas- Fergana fault within the Fergana Block and Chatkal Range, vectors are deflected from the average N-S trend and show a more north-westerly direction (Figure 2.2) Within the Alai Range to the S of the Fergana Basin, site velocities increase from the south- western extremities of the basin to the Talas Fergana fault. Site velocities tend also to increase from the western central part of the Chatkal range to the Talas- Fergana Fault. This coincides with a block rotation model, suggesting that the Alai range, Fergana valley, and Chatkal Range display counter clockwise rotation (schematically indicated in Figure 2.2). The assumption that faults are fully coupled seismically, is derived from the record of earthquakes in the last 30 years. The results of these recent investigations suggest that space geodetic and seismic strain rates roughly coincide and that a major portion of the current geodetic deformation in the area is accommodated by seismogenic faulting (Reigber et al., 2001) [33]. Using GPS results and information from seismic records along with information from the regional geology and remote sensing provided a fault-block model for the Tien Shan and adjacent areas with new information on the distribution of slip along major faults (Michel et al., submitted) (32). A particular feature of the Tien Shan is the NW-SE trending Talas-Ferghana fault (Figure 2) that accounts for a total dextral displacement of 200 km since Permian times (Havenith et al. 2002) [21]. This fault has a horizontal relative displacement of 7-8 mm/year and a vertical one of 6-5 mm/year. The tectonic activity of the Talas-Fergana fault is reflected on the territory of Mailuu-Suu, where major faults are present. The Tertiary/Cretaceous sequence in the Mailuu-Suu area is intersected by a complex system of associated faults, that are related to the major movement of the regional Talas-Fergana fault.

Chapter 2 pa ge 8

Figure 2.2 : Schematic structural framework and current high rate of tectonic deformation around the Chatkal-Fergana Block after Reigber et al. 2001 and Roessner et al. 2001 [31] The Mailuu-Suu area is situated in the transitional zone between the Variscian consolidated basement block in the north (Arslanbob) and the Ferghana Basin in the south. In the area of the town of Mailuu-Suu the northern rim of the Ferghana Basin is formed by an anticline consisting of weakly consolidated sediments (Upper Cretaceous up to Palaeogene) which is folded along an E-W axis. This fold structure of the older Alpidic structural phase forms a morphological saddle. In the northwest this structure interlocks with a NE-SW syncline which developed during the later

Chapter 2 pa ge 9 Alpidic structural phase. A shear zone separates the older consolidated basement from the younger structure of the Ferghana Basin. In this shear zone young NW - SE structures have been developed which can be interpreted as extensional elements. The perspective view based on the DEM derived from the MOMS-2P data. Wetzel et al. [20] demonstrate the spatial connection of these extensional elements with landslides which developed further downhill (Figure 2.3 and 2.3a).

Figure 2.3 : Simplified geological model (above) derived from structural interpretation based on MOMS-2P data (see Figure 2.3 a). Wetzel, Roessner, Sarnagoev, 2000 [20] Approximate location of Tailing 3

Chapter 2 page 10

Figure 2.3a : Perspective view based on MOMS-2P to demonstrate structural control of the landslide regime (orientation of the view see right) Wetzel, et al. 2002. Approximate location of Tailings depository No. 3

Chapter 2 page 11 2.4.2 Geology of the Mailuu-Suu Uranium Mining District The Mailuu-Suu Uranium deposit is located within the Mailuu-Suu River Valley and in the adjoining areas to the East and West (see map in Figure 2.4 ). The deposit is situated within the pericline of the Angrek-Sarybee Uplift. The uranium ore zones are associated with the Carboniferous horizons "L1" and "L2" of the Alai Sequence and the Palaeogene horizon "m" of the Turkestan-Sequence. The Shaidansk Overthrust limits the deposit to the north where strata of the Palaeozoic basement are overthrusted on Mesozoic and Cenozoic sediments . This tectonic lineament extends over a distance of 60 km. The tectonic movements along this line continue till recent times and are still active. The geological structure to the south is called Dzhurek-Akbalyksk Syncline. This depression extends to the SW with a length of 6 – 7 and a width of 4 km. The periclinal termination of the Angrek-Sarybi Uplift in the areas underlain by Meso- and Cenozoic sediments is complicated by 2nd order fold structures. In this area the Northern (Kara-Agach-) and the Main- (Mailuu-Suu-) Anticline, are interrupted by the Central Syncline. The axis of these anticlines are arching to the SW and W forming the Bedre-Coupola which limits the Central Syncline to the west. The southern limb of the main synclines do not exhibit any (structural) complications. The northern Anticline is an asymmetric fold with a less inclined north-western limb (25-30°) and a steeply dipping south-eastern limb (up to 90°) . At the location where the Mailuu-Suu River Valley intersects this limb is a fault intersecting Cretaceous and Palaeogene sediments. In WSW direction the profile intersecting the Main Anticline exhibits an asymmetric arch. This anticline is approx. 4 km long and at maximum 700 m wide The depression is underlain by Palaeogene and Neogene sediments. The tectonic zone of the Central over thrust runs along this depression and determines the structural differences between the northern and southern limbs (or boundaries of the syncline. The former being steeply inclined (becoming steeper with depth), the latter being lees steeply inclined (35-40°), with a decreasing angle at depth. Within the zone of the Central Fault the south-eastern limb of the Northern Anticline over thrusts the western limb of the Main Anticline. The total amplitude of the displacement does not exceed several hundred meters at this location. The Bedre-Coupola (or dome ) is an isometric positive structure with softly inclined strata (15-20°) in the S of the western pericline. Cretaceous sediments are exposed in the centre of the Coupola. The limbs consist of Palaeogene and Neogene sediments. The northern limb of this domal structure is straddled by a flexure-fault zone. A 2nd zone of this type, which limits the Bedre-Coupola to the S, extends in NW direction from the Mailuu-Suu River valley. Here a sudden change of dip angles in Cenozoic strata to the south can be observed – from 15-65° to 12-15°. An extended tectonic zone strikes more or less N-S along the Mailuu-Suu River valley (Mailuu- Suu-Faults). East of the Mailuu-Suu-Faults (Section Kulmen) the southern limb of the Main Anticline is complicated by numerous fractures or faults which represent old landfalls

Chapter 2 page 12 or rock-falls of blocks of Palaeozoic limestone according to the opinion of some geologists.

GEOLOGICAL MAP OF THE MAILUU SUU AREA

VIII VIII Pz S a

20° r y

80° b v. i

R Ri i v h . s

ga II Pg A - a

r Upper Town

Cr a Pz 22°

K Mailuu Suu 50° N2+Q1 30° I Cr

30° 25° 5.p3 CT J III 1.p3 HOB Kara Agash XI 25° 10°

IX IV 60° Kurgai Riv. 30° 60° Pg 10° VI 60° Cr 4.p - 2 Pg3+N1 V 50°

24° 4.p - 2 55°

N2+Q1 X 2.p -1 Oil Field Mailuu Suu III Pg3+N1 VII XII

Oil Field Mailuu Suu IV KAZAKHSTAN VII

3.p - 6 KYRGYZSTAN Town of UZBEKISTAN Mailuu Suu CHINA 01 2 3km TAJIKISTAN

GEOLOGICAL MAP OF THE MAILUU SUU AREA - LEGEND :

N2+Q1 Baktriski Sequence 1.p3 HOB Uranium Ore zones

Pg3+N1 Massagetski Sequence U-ore horizon „L1“

Pg Marine Paleogene U-ore horizon „m“

Cr Cretacious Sediments U-ore horizon „L2“

Outline of former J Jurassic Sediments mine workings

Pz Paleozoic basement Oil fields

Faults 20° Strike and dip

„old“ landslides

Major geological structures : Uranium-Ore Mines :

I Angrek-Sarybi Uplift II Dzhurek-Akbalyksk Syncline 1.p3 HOB Bedre (Mine No3-New Mine) III North. Kara Agash Anticline IV Central Syncline 2.p - 1 Southern Syncline (Mine No1) V Main (Mailuu-Suu) Anticline VI Bedre Coupola VII South. Syncline 3.p - 6 Kulmen (Mine No 6) (part of Naryn Monocline) VIII Shaidansk Overthrust Centr. Syncline and Svod 4.p - 2 IX North Bedre Fault Zone ( Mine No 2) X South Bedre Flexure-Fault Zone Kara Agash (Mine No 3 XI Central Fault 5.p3 CT -Old Mine) XII Mailuu Suu Fault

Figure 2.4 : Geological map of the Mailuu-Suu area The uranium ore deposit of Mailuu-Suu is located to the north of oil and gas containing structures. Those belong to the oil and gas deposits of Izbaskent, Mailuu-

Chapter 2 page 13 Suu-IV (Koktash), Mailuu-Suu-III und Mailuu-Suu-II. Within the confines of the latter uranium ore bodies and oil occurrences are mixed. The outline of the oil occurrence has a "T"-form. The essential part of the reserves are associated to carbonate horizons of the Palaeogene and in the first place with horizon "m" of the Turkestan-sequence. Less significant quantities of oil are contained in the sandy layers of the Neogene. The gas occurrences, however are associated to Cretaceous sediments. Gas occurrences where also discovered in Jurassic sediments . The majority of experts assumed a near surface hyper gene origin for the Mailuu-Suu uranium deposit. This theory was criticized by Ya.D. Gotman in 1944-1945. His view is that the known carnotite enrichments represent only the oxidation zone of original syngenetic ores of sedimentary origin Ya.D. Gotman`s opinion was confirmed by observations in deep adits in the underground mine sections Kara-Agach und "Svod", but also from deep drill holes which exhibited the transition of carnotite mineralization into the original rich “nasturanium” (pitchblende) ores which extend as a continuous horizon (without interruption) over the Central Syncline. This increased the reserves of the Mailuu-Suu deposit by several times. The deposit was then classified as an important industrial object (uranium reserves – more then 10.000 t). Ore grades in the Mailuu-Suu deposit vary within a great margin. The ores are classified in : • poor – low grade (0,03-0,1%), - 45 % of total reserves • average grade (0,1-0,2%), - 30 % of total reserves • rich (0,2-0,5%), - 20% of total reserves • very rich (0,5% und more) - 5 % of total reserves The depth of ore bodies in the Mailuu-Suu deposit is very variable: Ore cropped out at surface in mine sections "Svod", Kara-Agach and also in the northern limb of the Central Syncline. In the western flank of the Bedre-section, in the southern part of the Mine No.1 territory and in the south-western part of the Kulmen section the ore veins are plunging down to depths of up to 500 m . The possibilities to further increase economic reserves (for industrial use) of the Mailuu-Suu uranium deposit within depth that are still considered to be economic (from the surface down to 500 m depth ) are considered to be totally exhausted. 2.5. Hydrogeology Regional Hydrogeology data are compiled from the report of S. Jerohin (sub contract report from State Agency on Geology).

Chapter 2 page 14 Aquifers in the Mailuu-Suu area 1.) In the Mailuu-Suu River valley a widely distributed water bearing horizon is present in alluvial, proluvial younger deposits of upper Quaternary ( QIII-IV) age : This layer has a band like distribution along the valley and a down valley inclination and is overlain by boulders, detritus and gravel deposits with a matrix of clayey sandstone. These latter deposits have a maximum thickness of about 30 m. The (average) depth of this aquifer ranges between 1-20 m. The flow rate is 2-39 m/d. The groundwater has a mineral content of 0,2-0,7 g/l. Its chemical composition resulting from surface water infiltration is hydrocarbonatic-sulphatic and sulphatic-hydrocarbonatic. The water resource of this deposit is described as approximately 27 l/s (2.556 m³/d). 2.) The aquifer (water bearing horizons ) in the deposits of the Lower Baktriski Sequence ( N2 BK1): Aquifers are boulder detritus and boulder conglomerates of variable composition on the basis of a clay carbonate matrix. Water intake results from infiltration of atmospheric precipitation in quaternary deposits . The yield of drilled wells is 3-5 l/s, the flow rate is 0,3-11 m/d, mineralization is 0,3-3,4 g/l, average approx. 1 g/l. 3.) A weak aquifer in the deposits of the Massagetski Sequence (P3 -N1 ms):.This aquifer is not very widely distributed. Surface outcrops exist in the erosion channels of rivers and streams. Sediments consist of sandstone and gravel deposits and to a lesser extent of conglomerates. Water yields are extremely variable. In the Mailuu-Suu River valley ( altitude 2547 m a.s.l.) the yield is approx. 0,6 l/s, the yield of springs at 141 m lower elevations is 0,2 l/s. The chemistry is not very well investigated. Different zones are observed with increasing depth. The mineralization increases from 0,5 g/l to 3 g/l; the components contain sulphate- and sulphate chloride. 2.6. Hydrology of Mailuu-Suu and Tributaries Within the land-slide risk area the main hydro graphic element is the Mailuu-Suu river, where the Bedre, Kara-Agach, Kugai, Car-Baya, and Kulmen inflow. The rivers are fed by snow and springs. The water discharge is varying depending on the amount of atmospheric precipitation and the intensity of snow melting. So, the water flowing is the highest in May-June. The density of hydro graphic network is 0.66 km/km². The Mailuu-Suu River belongs to the North-Ferghana-area of the Syr-Darya-Basin. The topographic relief of the area is characterized by a system of hills and mountains which belong to the north-western extensions of the south-western slope of the Ferghana-Mountain Range. The Mailuu-Suu Basin is surrounded at three sides by these topographic features. The average altitude of inflows to the Mailuu-Suu Basin does not surpass 2.000-2.600 m. At the upper reaches of the Mailuu-Suu there are 9 glaciers with a total surface of 3,2 km², which do not have an essential impact on the inflow and outflow regime. Precipitation on the western slopes of the Ferghana-Mountain range is relatively high especially during the cold season . Because of this a 1 to 3m thick snow cover accumulates in this area. This corresponds to a water reservoir in the order of 200-500

Chapter 2 page 15 mm. The annual precipitation rate in 1.000 m altitude a.s.l. amounts to 500 mm, and to 1.000-1.100 mm in 2.500-3.000 m altitude. The Mailuu-Suu River during his course from the NE to the SW collects 169 tributaries. There are 4 lakes in the basin. At its outflow from the mountainous area the Mailuu-Suu River builds a delta and fans out in numerous channels and forks . The recharge area of the Mailuu-Suu is 530 km². The biggest tributaries are the rivers Davansai, Semendyk-Sai, Kurgai, Sarybee and Kara-Agach. The area of investigation is crossed by the river Kara-Agach and the stream Kulmensai. The Kara-Agach is the right tributary of the Mailuu-Suu and starts at the altitude of 2.100 m a.s.l. on the eastern slopes of the Kelmtau mountain range. It `s recharge area is 36,9 km² at 14,6 km river length. The averaged, balanced slope angle of the river bed is 114 %o, and 191 %o for the recharge area. The Kulmensai stream is 8,1 km long with a recharge area of 13,7 km². The Mailuu-Suu River belongs to the rivers fed by snow and glaciers. The run-off regime is characterized by three periods : 1.) Period of snow high water regime (March to May ) when the runoff is mainly fed by melt water from the lower and medium altitude mountain regions 2.) May to August, snow–glacier decharge period, thawing period of snow and glaciers in higher altitudes. The mean duration of high water periods is 176 days, with a maximum of 221 days and a minimum of 118 days. On average, 77 % of the entire annual rate are discharged during these high-water periods. 3.) From the end of August to the beginning of March is the period of normal water levels. Rivers are recharged by ground-waters. During some years minor high- water periods occur in the autumn caused by autumn rain falls. The highest water levels are observed during the spring and summer high water periods ; the lowest water levels during the autumn and winter time. The highest water level was recorded 16th of April 1958 when because of a rupture of tailings pond No. 7 the water level increased to 636 cm. The lowest water level was measured 11th of February 1956 with 29 cm. In humid years (1959, 1969) the water level rose to the marks of 213 cm and 192 cm. During the course of the warm season variations of the water-level throughout a single day can be observed depending on the time of the day. This is explained by the variation in intensity of thawing of snow and ice in the higher altitudes. The flow in Kara-Agach River is determined by snow melt and strong rain falls. Until now, there is no systematic observation of this rivers flow regime. Therefore the description is analogous to that of the Kurgai River which joins the Mailuu-Suu River further upstream. The flow regime is characterized by a stepwise increase of the water level from November to March due to the melting of the instable snow cover. A sudden increase of water levels takes place from April to March due to seasonal snow melt and rainfalls. This increase terminates end of May. After that there is a continuous decrease of water levels until June when the normal water level prevails .

Chapter 2 page 16 The flow in Kulmensai River is relatively regular and is fed by groundwater. During the period of seasonal snow-melt a slight increase of river-flow is observed. Significant and short periods of increased flow are recorded during rainfalls. The Mailuu-Suu River flows through the western and north-western sides of the Boo- Bash-Ata mountains. It reaches the border with Uzbekistan near the village of Izbaskent. The river then flows into the Kara-Darya, which in turn flows into the Naryn River, which becomes the Syr-Darya. The Mailuu-Suu River is 87 km long with a catchment area of 530 km². The Mailuu-Suu River is fed by glaciers, snow and rainfall. Glaciers, with an elevation above 4,000 m, cover an area of about 3.2 km². There are also four lakes in the river basin, with outlets into the river. The largest lake is Kutmankul, with a surface area of 0,6 km² and catchment area of 38 km². Less than 20 percent of the catchment area is covered by trees and bushes. The river flows in the investigated area from the north to the south. Where it enters the Ferghana valley, a part of it is divided and deviated for irrigation. The river feeds water-bearing horizon in the valley of the Karaungur river. The Kara-Darya river takes its beginning far beyond the area of investigation and is formed by the confluence of the several rivers (Tar, Karakuldja, Kurshab, Kugart) that have snow and spring feeding. Water discharge of the Mailuu-Suu river (Tables 2.2), varies from 1.8 m³/s (October- January) to 38 m³/s (April-June) depending on season. So many springs are dried out by the end of summer in the south part of the area. The discharge data of the river are given in Table 2.4. The normal flow rate of the Mailuu-Suu River during the time of systematic observation is recorded as 9,01 m³/s. Average annual long-term water discharge is 10.83 m³/sec. The average flow rate of the Kara Agach river is 0.61 m³/s according to calculations. The maximum annual mean flow-rate was measured in 1969 with 19 m³/s, and the minimum annual mean in 1938 with 4,58 m³/s. The minimal discharges are observed generally in January and February and amount to on average 3.7 m³/sec (the least average monthly discharge is 2.17 m³/sec). Minimum flow is observed towards the end of the period with normal water-levels. The mean minimum flow volume is 2,08 m³/s. Maximum discharge in the Mailuu-Suu River occurs normally during May and June, i.e. in the months of intensive snow-melting. Based on a 58 year observation period, it can be seen that the maximum peak discharges take place when rainfall coincides with peak snow melting. During high water season in May the discharge is on average 30.8 m³/sec (the greatest average monthly discharge is 47.20 m³/sec). The highest recorded volume of flow during the period of observation was measured in 1969 with 108 m³/s, the lowest flow volume in 1974 with 17,4 m³/s. The average maximum discharge of the Mailuu-Suu River for a period of 58 years has been recorded as 51.5 m³/s. The estimates of the 1 in 100 year flood event discharge are rather variable and range between 130 and 170 m³/s (Table 2.1).

Chapter 2 page 17 Table 2.1 : Estimates of discharge rates in the Mailuu-Suu River for the 1 in 100 year flood event

Estimated by Catchment. Years Average Max Estimated Discharge area Max Discharge km² (m³/s) (m³/s) (m³/s) Once/100 y Once/10 y Design Inst. Norms 530 58 51.5 108 131 83.1 2.0114-83 World Bank 2002 710 169 103 Estimate* * Estimation of Temelsu – Gibb for Irrigation Rehabilitation Project – design of Mailuu-Suu headworks rehabilitation

Table 2.2 : Within-year Distribution of Flow in the Mailuu-Suu River, m³/s [22]

Characteris- Jan. Feb. March Apr. May June July Aug. Sept. Oct. Nov. Dec. Average Annual tics

Mailuu-Suu River in the Range of Kara-Agach River Creek Water Station

Average 2.47 2.51 4.76 24.7 24.7 16.7 8.03 4.46 3.57 3.24 3.31 3.41 8.49 (1980)

Maximum 2.69 2.66 17.3 34.8 60.1 47.5 23.9 11.2 6.36 8.91 8.35 4.26 19.0 (1969)

Minimum 2.51 2.50 3.54 8.36 10.8 6.40 4.18 3.25 3.16 5.03 10.9 5.50 5.51 (1965)

Mailuu-Suu River in the Range of Water Scoop

Average 1.96 1.99 3.78 19.6 19.6 13.2 6.50 3.61 2.89 2.62 2.68 2.76 6.75

Kugai River

Average 0.38 0.39 0.67 3.57 3.15 1.31 0.65 0.44 0.38 0.41 0.45 0.39 1.04

Sarybie River

Average 0.22 0.23 0.51 2.1 1.8 0.77 0.38 0.25 0.22 0.24 0.26 0.23 0.609

Kara-Agach River

Average 0.22 0.23 0.51 2.1 1.8 0.77 0.38 0.25 0.22 0.24 0.26 0.23 0.612

Table 2.3 : Discharge Rate of Weighted Alluviums and Turbidity of Water in the Mailuu-Suu River at Hydro post – Mouth of Kara Agach River during the observation period 1974 to 1983 [22]

Characteristics Jan Feb Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec Average . . . Average, kg/s - - - 19.8 5.7 3.3 1.05 - - - - - 4.13 Average, g/m³ - - - 846 283 221 124 - - - - - 459

Chapter 2 page 18

In terms of mineralization the Mailuu-Suu belongs to the weakly mineralized rivers . Highest mineralization is observed during the period of normal water levels with 290 - 450 mg/l. Lowest mineralization with 190-215 mg/l is recorded during the high water period when snow melt waters predominate in the flow volume. Table 2.4 : Water discharge of the Mailuu-Suu River at hydropost "North of the Kara-Agach River" Observation Average monthly discharges of water, m³/s Average Max. Min. period 1 2 3 4 5 6 7 8 9 10 11 12 annual discharge, discharge, discharge, m³/s m³/s m³/s 1985 2.86 3.80 6.95 31.1 31.5 21.3 10.7 5.14 4.06 4.03 3.8 3.7 10.7 31.5 2.86 1986 2.52 2.48 2.83 9.23 14.2 11.7 7.99 4.85 3.64 4.57 3.58 4.25 6.0 14.2 2.43 1987 3.9 4.73 12.2 34.2 42.0 32.1 22.5 13.8 7.53 8.2 9.6 5.9 16.3 42.0 3.9 1988 6.16 5.0 8.12 24.7 47.2 37.5 17.5 7.38 5.26 4.76 4.5 3.5 14.3 47.2 3.5 1989 3.26 2.17 5.14 11.5 18.87 14.3 9.2 4.92 3.19 3.37 3.04 2.97 6.83 18.87 2.19 Average 3.74 3.64 7.05 22.15 30.75 23.38 13.6 7.22 4.74 4.39 4.9 4.06 10.83 30.75 2.9 monthly The chemical composition of river waters is hydro-carbonatic - and calcium bearing. The waters are soft with a degree of hardness not exceeding 2-3,5 mg/l. The water in the river is fresh with mineralization of 0.27 g/l, hydrocarbonatic. Information on solid particle transport exists only for the Mailuu-Suu River. The mean quantity of transported solid particle matter is 4,13 kg/s, and the mean annual degree of turbidity (due to suspended solids) (Trübungsgrad) is 459 g/m³. The calculated norm for solid particle transport is with 4,57 kg/s close to the actual value During the passage of mud-flows the degree of turbidity (due to suspended solids) can reach more than 10.000 g/m³ . During the period of systematic observation the highest (Trübungsgrad) degree of turbidity was measured May 2, 1980 with 12.000 g/m³. The highest volume of transported solids was observed May 23, 1979 amounting to 650 kg/s at a degree of turbidity of 9.500 g/m³.. More than 90 % of total suspended solids are transported during the warm period of the year. The highest mean monthly volumes are recorded during the periods of maximum flow . For the Kara-Agach River the norm for solid particle transport was determined in a modular way according to the Mailuu-Suu River and it amounts to 0,32 kg/s. According to the character of the ice regime the Mailuu-Suu and its tributaries belong to those rivers which are episodically covered by ice. Ice formation starts end of December. Total destruction of the ice cover occurs mid February. 2.7. Climate The regional climate is continental with long, dry and hot summers and relatively short moderate winters. Frequent periods of thawing and high precipitations (snow and rain) are characteristic for the winter climate.

Chapter 2 page 19 Maximum temperature is +38,5 °C, minimum -8,5 °C, annual mean temperature is +13,1 °C. The period of stable temperatures above 0 °C starts beginning of April, the frost- period starts second half of October. Climatic characteristics are given on data of meteo station “Lenin Jol” located at the altitude of 706 m in the village with the same name. The minimal average monthly temperatures of the air are observed in December January and amount to on average – 0.6 °C. Average long term snow coverage is 0.37 m within valley part of the studied territory. Freezing depth of the soil is 15 cm. The greatest amount of precipitation is observed from November to May, the least amount is in summer. In particular years there is no precipitations in summer. Mean annual precipitation in the area is 447 to 578 mm (200 mm as snow).. The maximum is 815 mm and the minimum 225 mm. Over the year precipitation is distributed as follows: spring - 40%, winter - 27%, autumn - 23%, summer - 10%. The greatest amount of precipitation is observed in spring, in March, April and May minimal in August. Generally, the studied territory is located in the zone of insufficient humidity where the annual total amount of precipitation is less than value of evaporation from surface. This fact adversely affects feeding conditions of the ground water. The conditions are most favorable in autumn-winter period, when atmospheric precipitation is most intensive, and the evaporation is minimal. The snows fall in period of from 15 October to 13 December and melt in period of from 15 March to 16 April. The total amount of days with snow coverage varies from 100 to 205. This climate is typical within 800-1400 altitudes. At remote places microclimatic conditions can exist: dry and hot 20 km down the Mailuu-Suu river and wet and colder 20 km up the stream. These climatic conditions favor the intensive water saturation of loose clayish sediments at mountain slopes. This results in the change of soil properties: the soil gains plastic properties. Main wind directions are NNE and S mainly resulting from the course of the Mailuu- Suu-River valley. Mean wind velocity varies between 2 – 5 m/sec . The highest registered wind velocity was registered in January 1995 with 17 m/s from the North. Flora of the region with the exception of high mountain areas is very rich and varied. Walnut, pistachio and fruits are cultivated. Mean daily temperature-, precipitation- and depth of snow cover data are presented in relation to extensometer measurements displacement data continuously from Nov. 1996 to July 2001 These data originate from the Lenin Jol meteo station located 30 km northeast of Mailuu-Suu altitude 721 m a.s.l (Tables 2.5-2.6).

Chapter 2 page 20

Table 2.5: Air temperature at meteostation Lenin Jol

Year123456789101112 1979 -1.1 2.9 7.8 14.6 17 24.5 27.8 25.9 21 15.5 4.1 4.3 1980 -1.3 -1.6 6.5 17.1 21 24.9 28.1 25.2 21.5 18.9 6.4 4.5 1981 2.4 3.5 10.6 14.9 21.1 23.7 25.9 24.7 20.5 15 10.6 4.2 1982 0.7 1.1 7.6 17.6 22.2 25.3 26.6 25.4 20 12.8 8.2 2.9 1983 -1.2 4.7 7.3 15.3 20.3 24.1 27.7 27 20.9 13.3 2.7 -0.1 1984 -1.8 -5.5 6.1 15.2 20.3 26 29.1 28.1 20.6 14 8.8 -0.5 1985 -3.4 1.6 5.2 17 19.9 26.1 27.9 25 22.2 14.4 9.2 -8.7 1986 1.4 3.7 5.4 15 20.4 24.1 27.5 25.7 22.5 13.2 6 1.4 1987 2 3.9 10 12.8 20 22.5 25 26.8 20.5 14.9 6 -0.8 1988 0.2 2.7 7.7 17.1 18.1 25.9 28.1 25.2 20.9 10.1 5.3 3.1 1989 -3.2 -2.3 9 13.2 17.7 24.5 27.1 27 20.6 13.6 10.2 4.4 1990 -2.1 2.8 8.1 14.2 21.5 27.4 25.7 26.6 22.3 16.2 5.1 3.5 1991 -2.4 0.7 6.6 16.2 19.9 24.2 26.7 25.1 21.1 14.2 8.3 1.7 1992 0.3 3.9 5.1 15.2 16.9 24 26.7 23.6 20 15 7.6 2.08 1993 0.1 2.8 7.6 17 17.3 25.9 28.1 25.2 20.9 14 9.7 3.6 1994 -3.2 -3.4 -9 13.2 17.7 24.5 27.1 27 20.6 13.6 10.2 4.4 1995 1.4 3.7 5.6 14.9 20.3 24 27.5 25.7 22.5 16.2 5.1 3.5 1996 1.4 0.7 6.6 12.6 18.6 25.2 26.4 25.3 22.5 14.9 6 -0.8 1997 1.5 1.2 8.1 15.9 18.7 25.4 28.2 25.4 22.3 14.7 5.1 3.3 1998 -2.3 -2 2.2 10.8 11.6 16.2 20.3 19.8 17 19 6 2.2 1999 -0.7 3 1.6 7.6 14.3 16.5 17.9 20.8 16.4 11 6.9 3 2000 1.4 -1.4 3.1 11.3 16.1 18 20.4 20.4 16.6 11.5 2.8 3.1 2001 -0.4 0.2 6.5 22.3 27.8 19.1 20.1 20.9 19 7.5 2.8 -1

Table 2.6: Precipitation at meteostation Lenin Jol (mm)

Year123456789101112 1979 95 41 27 160 72 11 2 0 18 2 89 53 1980 66 106 88 56 42 1380193721 1981 20 69 39 102 65 30 16 25 12 9 61 9 1982 19 50 58 14 12 5 3 22 26 24 39 2 1983 68 18 54 101 63 10 1 7 27 91 71 12 1984 15 86 80 29 11800875046 1985 42 78 83 53 74 108303712054 1986 7 5.33 13.66 20 12 13.33 0 2.33 2.66 42 52 27 1987 16.66 23.33 31.66 47 7.33 21.33 14.66 2.33 2.66 14.66 23.66 34.33 1988 22.33 12.66 29 9 31 3.66300808.6621.66 1989 1.34 1.52 0.57 1.23 1.29 0.23 0.21 0 0.35 0.08 1.79 1990 27 18.66 36.33 26.33 6.33 1 10.66 2 0.33 4 28.66 13.66 1991 45 30 28 103 90 83 48 6 4 22.66 9.66 13.66 1992 39 56 71 80 61 107 25 50 0 10 0 17 1993 25 109 88 35 63 36 55 27 0 23 3 58 1994 47 53 113 31 64 13 4 10 10 18 45 52 1995 41 62 29 50 506702672713 1996 73.3 97.6 96.7 98.2 35.2 1.8 46.9 0 11.4 12 86 50 1997 62.2 42.6 60.1 177.8 79.3 31.9 5.4 4 0 15.8 27 7.4 1998 128.6 139.9 103.4 135.3 333 194.6 69 54.1 31.2 0.01 0.48 1.75 1999 77.8 42.5 149.1 177 121.6 82.9 102.5 28.3 47.6 44 121 143 2000 57 57.5 67.3 141.8 18.1 62.9 48.5 49.2 44.9 49 225.1 5.7 2001 66.8 89 29.3 40.6 51.4 20 1.6 0 6 84.2 99 52 2.8. Landslides/mudflows Large landslides (up to more than one million cubic meters per event) are widespread at the eastern rim of the Ferghana basin (forelands of Tien-Shan mountains ). As outlined in Chapter 2.4 this region is situated in an area of an active plate boundary (collision of Indian and Eurasian plates) [20].

Chapter 2 page 21

Figure 2.5 : Main structural units of the Pamir- Tien-Shan region (after Gubin 1986 and Chedia 1986) and landslides areas investigated by GFZ Potsdam, [20] Every year landslide activity in this part of Kyrgyzstan cause significant damage of settlements and infrastructure and also to loss of human lives. These landslides and slope instability are caused by complex interactions between a number of endogenic and exogenic factors within the general geological setting including : - relief - nature of surficial deposits - structural geology - engineering geology, - meteorology and climate, - vegetation and land use - specifics of the regional geological context In general, landslides may occur in the elevation range between about 700 and 2000 meters representing the weakly consolidated sediments of the topographically rising rim of the Ferghana basin below its transition into the high mountains. Three geologically determined main groups of landslides can be distinguished : - Landslides developing in loess units of the Lower, Middle and Upper Quaternary (Q1-Q3) - Landslides developing in weakly consolidated Meso- and Cenozoic sediments (Jura up to Paleogene) consisting of sand- and siltstones with intercalated clays, loams, carbonates and sulfates - Landslides developing in older and younger sedimentary units at the same time and event

Chapter 2 page 22 In case of the first type of landslides (Q1-Q3) the actual mass movement can happen within minutes and hours and affect thousands up to more than one million cubic meters in a very short period of time. In case of the other two types, active mass movement takes place in the range of days up to several weeks. Sediments of the Upper Neogene (N2) are rarely affected by landslides. These units mainly consist of conglomerates and weakly consolidated gravels with interbedded loess-like loams. High porosity and permeability of these units seem to prevent engineering-geological conditions which are critical to slope failure. In the same area phases of landslides activity can alternate with inactive phases over longer periods of time. Landslide activity has been documented by local authorities for many years based on topographic and geological mapping, engineering-geological investigations and aerial photography. (These data are administered by the Kyrgyz Ministry of Ecology and Emergency Situations). Because of the local character of these investigations these information only partially allowed landslide-oriented geological interpretations in a regional scale. Scientific investigations of landslide-causing factors have been subject of a collaboration between the Remote Sensing Section of the GFZ Potsdam and the Ministry of Ecology and Emergency Situations in Kyrgyzstan using a detailed assessment of geological structures as an important landslide-causing factor based on remote sensing and GIS techniques. (Wetzel, Roessner, Sarnogoev, 2000) [20]. The Mailuu-Suu Basin belongs to the areas with a high degree of risk from land- and mudslides in the high mountain part and in the hill-country part of the basin. More than 150 landslides are known in the general area almost 40 % of which are considered unstable. During the last 10 years an increase of landslide activity has been observed in this region. Several hundred buildings have reportedly been damaged or destroyed and nine people died. Three quarters of all watercourses in the basin represent dangerous conditions for existing and projected construction or cultivation in the lower reaches of the river valleys due to the fact that many or all factors responsible for the occurrence of mud- or landslides are very strongly developed in the respective catchment basins. These factors include : - the existence of easily erodable sediments and - the strongly structured relief, - the thinning steppe vegetation, - the dry and hot summers, which all support the formation of significant slope movements as well as major mud- and landslides.

Chapter 2 page 23 However, rainfalls are the main reason for the formation of mudslides. Up to 98% of the observed mudslides on the slopes of the Ferghana Mountain Range are directly associated to rainfalls or rainfalls during the period of snow-melt. The frequency of mudslides in the Mailuu-Suu basin is at average 1 - 1,5 mud-or landslides/year. The mudslide-activity starts in April and ends in August . The maximum of mudslides fall in May when 33% of all observed mud-or landslides are registered. The highest mudslide-activity was registered during the years from 1929 to 1958 when 5 mud- or landslides occurred per year . The flow rate of the slides ranges between 8,4 m³/s to 60 m³/s. According to the type of slides they are to be classified as muddy to stony or rocky.

2.8.1 Previous work on the landslide problem in the Mailuu-Suu area German Federal Institute for Geosciences and Natural Resources 1996 [4 and 6] The German Federal Institute for Geoscience and Natural Resources (BGR), Hannover, Germany September 1996 initiated the intended to create a computer data- base on landslides in Kyrgyzstan and started introducing prevention measures on selected slides. This included the installation of a local geo-monitoring network for land slide risk in Mailuu-Suu. Due to the short duration of the project some technical problems the electronic data-base installation could not be finished in time. But both partners intended to complete the task in the near future [6]. BGR checked a Kyrgyz- made notification system which provides both measurement of' movement and integrated radio-controlled warning instrumentation. Three sites were equipped with those instruments. Later in 1996, a warning system was installed within the in the framework of an ECHO project. The installation included 5 position sensors placed in potential landslide masses threatening the Tailings 3 and 9, 17, 5, 7 and Tailing 8. Evaluations performed with sensor data and precipitation rates have shown that in case of heavy rainfalls rock masses are notably displaced. The largest displacement within two and a half years after installation in 1996 has been 4 m on the landslide-prone slope above Tektonik with a total precipitation during that time of about 2000 liters per square meter. Of course, it is completely open, how much additional rain may have to fall before the landslide starts to move down the slope all by itself. Collaboration between the Remote Sensing Section of the GFZ Potsdam and the Ministry of Emergency and Civil Defence in Kyrgyzstan). Since 1992 Geodetic GPS Measurements and Structural Evaluation and Interpretation of Remote Sensing Data resulted in the recognition of the significance of young tectonics on slope movements. This is especially true for the major shear zone that separates the older consolidated basement from the younger structure of the Ferghana Basin. In this shear zone young NW - SE structures have been developed which can be interpreted as extensional elements. A special example for this mechanism is the Kashgarta landslide which developed in spring of 1994. The width of its upper part amounts to about 800 meters where the detached material consists of weakly consolidated Tertiary sediments. In the lower parts of the valley Mid-Quaternary losses were affected by the mass movement. Until the end of June 1998 a total mass of about 10 million tons had been moved downhill along a distance of 4 km in a

Chapter 2 page 24 glacier-type way. A determination of the position of the lowest part of the landslide in the field in July 1999 resulted in an increase of this distance up to 5.5 km. (Wetzel, Roessner, Sarnogoev, 2000) [20]. Geophysical prospecting as monitoring tool of landslides and Uranium waste dumps in Maily-Say, Kyrgyzstan (Torgoev et al., 2001) Almost fifty percent of the slopes in the Mailuu-Suu valley were reported to present instabilities and small failures that already developed into landslides or are likely to produce some in near future. Most of the large landslides are monitored since 1996, four years after the occurrence of the catastrophic landslide “Tektonik" that destroyed roads and bridges across the Mailuu-Suu river. Many landslides are still active and show seasonal increase of displacements along ruptures. Besides the climatic factor, regional tectonics and former mining activity are reported to significantly influences slope stability. Locally, ground failures also are thought to be related to seismic activity . GEOPRIBOR teams and Havenith [21] investigated slope instabilities in the Mailuu- Suu valley by using seismic and electrical sounding and geo-electrical profiles as well as TEM (transient electromagnetics ). Seismic and resistivity data were interpreted as 1 D models and geo-electrical profiles as 2D electrical tomography. TEM data were processed as 2D pseudo section and as l D soundings. In addition, these two data sets were also analysed by combined inversion. As result, the campaign of geophysical prospecting has shown that instabilities are generally linked to low ground resistivity zones that may extend over the entire area of the slope. Geophysical and borehole data obtained on two of the uranium tailings along the Mailuu-Suu river hint at the imminent risk of pollution by infiltration of ground water through the protection layers. Beyond the risk of pollution, investigations of slopes surrounding the waste dumps have detected instabilities likely to trigger landslides that might destabilize the tailings. Such a scenario has already occurred in the Mailuu- Suu valley and is actually predicted by slope stability calculation tailing No3 in the vicinity of the town.

2.8.2 Landslides Databank Available data on unstable slope sections and landslides that are essential for the physical security of tailings depositories from uranium ore processing are compiled in the Annex 2-1 of this chapter. 2.9. Seismicity Each year thousands of seismic events occur in Kyrgyzstan and about 10 events per year can be considered as hazardous. In the last century, Kyrgyzstan has been affected by a series of seismic disasters, the strongest being the Ms = 8.2 Kemin earthquake in 1911 (Bogdanovitch et al., 1914, Delvaux et al., 2002). Figure 2.5 shows historical and instrumental seismicity in Kyrgyzstan and bordering regions based on the data of the Kyrgyz (and world) seismic catalogue from 250 BC to 2000. Largest earthquakes in the last 150 years were:

Chapter 2 page 25 - Belovodsk (Ms1=6,9 in 1885) - Verny (or Alma-Ata, Ms=7.3, 1887), - Chilik (Ms=8.3, 1889), - Kemin (Ms=8.2, 1911), - Chatkal (Ms=7.5, 1946) and - Suusamyr (Ms=7.3, 1992) earthquakes. These events were generally accompanied by large surface ruptures, such as the Kemin earthquake that activated fault segments with surface ruptures over a cumulated length of more than 250 km (Delvaux et al., Abdrakmatov and Havenith et al. 2002) [21] .

2.9.1 Seismic data Information about strong earthquakes in Central Asia was collected since 1885, when the Belovodsk event happened (40 km West of Bishkek, Ms = 6.9) and was based on macro-seismic observation. In 1927, the first Kyrgyz seismic station was installed at Bishkek (formerly Frunze). Since then, instrumental data were used to determine earthquake characteristics, precision of epicenter localization being within 50 km. Currently, 12 analogue and 10 digital stations are working inside the Kyrgyz network; most of them were installed between 1960 and 1970. Precision of epicenter localization is now estimated at ±3 km. The Kyrgyz catalogue has been updated till 1996. From then to the present time i.e. 2001, (Abdrakmatov and Havenith et al. 2002 [21]) completed the database by using events Ms>4 from the world seismic catalogue of the USGS – NEIC (National earthquake Information Centre). Previous Intensity maps In former Soviet Union countries and for the evaluation of the intensity of seismicity in the Kyrgyz Republic, seismic hazard was generally expressed in terms of "ballovs". This scale was elaborated by the Institute of Earth Physics of the Academy of Sciences of the USSR in 1952 . It is an intensity scale and ranges from 0 to 11. Especially steps 6 to 9 (ballovs) are of practical importance. Using this scale, Djanuzakov et al. (1995) compiled a deterministic seismic hazard map of Kyrgyzstan principally based on macro-seismic observations. The map by Djanuzakov et al. (1996) (see Annex 2-2) shows three types of ballov-zones : 7-ballovs, 8 ballovs and 9- ballovs zones. Inside the highest seismic hazard zone with 9-ballovs, areas are delimited, where events with magnitudes larger than 7.5 Ms (Richter scale) can be expected. The large ballovs-intensity zone exists along the Talas-Ferghana fault among the central Ferghana Range.

1 Ms = surface wave magnitude (Gutenberg – Richter scale ; International Committee on Magnitude 1956 and 1967) For the evaluation of damages and for construction purposes only the surface wave magnitude is of significance as opposed to the body wave magnitude – Mb.

Chapter 2 page 26 In terms of seismic risk - the town of Mailuu-Suu belongs to the areas which are classified as belonging to step 8 or 9 of this scale with the related intensity of seismic events (and magnitudes larger than 7 Ms Richter scale). Earthquakes of this intensity could cause very strong deformations at surface, triggering rock-falls, landslides, mudflows resulting in considerable losses and destructions of objects of human activity. Abdrakmatov and Havenith et al. 2002 [21] used this map and compared it with the probabilistic Arias Intensity map. In the frame of the global seismic hazard program (GSHAP), Ulomov et al. (1999) and Zhang et al. (1999) have studied, among others, seismic hazard of Central Asia. Both groups considered most parts of Kyrgyzstan at the highest risk level, i.e. above 0.48m/s² for a return period of 475 years.

2.9.2 Influence of Seismicity on landslides and tailings stability The Kemin earthquake of 1911 had direct or indirect effects as mudflows or landslides. In 1992, the Ms=7.3 Suusamyr earthquake affected the Northern and central Tien-Shan mountain regions. The giant Toluk rock avalanche was triggered by the earthquake inside the Southern Suusamyr Range (Ghose et al., 1997). Observations made in regions affected by large earthquakes during the last 120 years support the observed relationship between seismicity and slope movements : - rock avalanches in the Kyrgyz Range triggered by the Belovodsk earthquake in 1885; - rock avalanches in the Chon Kemin and Chon Aksu valleys triggered by the Kemin-Chilik earthquake in 1911; - debris slumps in the Suusamyr valley and rock avalanches in the Aramsu and Suusamyr Ranges triggered by the Suusamyr earthquake in 1992; - slope instabilities regularly triggered in the Mailuu-Suu valley (Northern Ferghana Basin). The geological and tectonic framework for the seismicity of Kyrgyzstan was described above in Chapter 2.4. The situation in the Mailuu-Suu area is exacerbated by the fact that tailings depositories and waste rock dumps are situated along riverbanks and on slopes above. These deposits in the course of the above mentioned events and destructions with their stability at compromise could than become an additional risk factor . Some of the landslide areas (Tektonik and Ko-etash) or underlain by and some waste storages sites are situated just near the active fault zones. Such zones are characterized by high extent of fracturing, anomalous state of stress field, high water-content and other features favorable to the formation of landslides and rock falls. On the other hand active faults are considered as the potential zones of seismicity. The source areas of numerous strong earthquakes that create surface rupturing and slope failure coincide with active faults. This points to the general geodynamic hazard of active fault zones. Both intensive seismic events and geological effects of strong earthquakes (rupturing, slope failure, etc.) can affect waste storage sites and produce catastrophic environmental pollution.

Chapter 2 page 27 2.9.3 Seismicity in the Mailuu-Suu Region According to the map of seismic zoning by Djanuzokov et al. 1995 (Annex 2-2 ) the Mailuu-Suu region belongs to the zone with a seismicity of 9 points, which is equivalent to possible magnitudes according to the Richter scale of M>7,5 and probability of re-occurrence of such earthquake-intensity of once in more than 500 years. Another map of seismic risk in Kyrgyzstan (Annex 2-2) is based on a 1997 probability assessment of strong earthquake potential. According to this map the Mailuu-Suu region is located on the boundary between high and average seismic danger. Strong earthquakes in the wider vicinity of Mailuu-Suu took place near towns or villages such as Isfara, Namangan, Andizhan, Baitok, Osh, Yar-Tene, Leninabad, Tashkent, along the Suusamyr and Kosh-Deve valleys. The Mailuu-Suu region is located not far west from the active Talas-Fergana fault which was the source zone of the 1946, Ms 7.6 Chatka1 earthquake. In Mailuu-Suu this event had the intensity of about 7-8 points of the ?Mercalli scale. Several smaller events that occurred in the region nearby also had the same intensity. The last earthquakes in a 100 km radius zone around Mailuu-Suu are compiled in table in Appendix 2-3 (USGS Earthquake Database; TORGOEV, Communic.May 2002) The strongest earthquake (? Epicenter 450 km SE of Mailuu-Suu) happened on December 16, 1902 (up to 9 ballovs). According to the data obtained at Andozhan seismic station (60 km from Mailuu-Suu) the periodicity of 7-ballov and 9-ballov earthquakes since 1929 is 0.1 eq./year and 0.01 eq./year, respectively. The Mailuu-Suu area is thus regarded as a high seismic area. The seismicity of this area is characterized by high magnitude/intensity earthquakes (6.9 to 7.2 on the Richter Scale or 9 MSK2). The latest earthquake occurred in the Mailuu-Suu territory on May 15, 1992. It had a magnitude of 6.2 Richter and an Intensity of 8.2 MKS. On July 7 of the same year the landslide named “Tektonik” was mobilized.

2.9.4 Results of recent Research The recent study by (K. Abdrakhmatov, H-B. Havenith, D. Delvaux, D. Jongmans & P. Trefois, 2002) defined probabilistic seismic hazard at regional scale by developing new probabilistic seismic hazard and Arias Intensity maps for the territory of the Kyrgyz Republic and bordering regions. For long-term prediction, 100 year maps with 90% probability of non-exceedance have been developed. The procedure used for seismic hazard prediction in terms of PGA (Peak Ground Acceleration) was also applied to Arias intensities in order to be able to define regional seismogenic landslide hazard maps.

2 MSK stands for "Medvedev-Spoonheuer-Karmik" intensity scale, which is used in central and eastern Europe. The intensity is a qualitative description of an earthquake at a particular location, as evidenced by observed damage and human reactions at that location.

Chapter 2 page 28 Both PGA and Arias intensity mapping implied that largest hazards are expected along the Southern Tien-Shan border, around the Ferghana Basin, among the Chatkal, Ugam and Suusamyr Ranges as well as in the Kemin-Chilik region. Seismic hazards computed for specific large towns indicate that Kashgar and Alma-Ata are most at risk with maximum predictions of 0.66g and 0.47g, respectively, for a period of 50 years with 90%-probability of non-exceedance. [21]. Results of seismic hazard prediction for 10 towns in Kyrgyzstan and surrounding regions are displayed in Table 2.6 on the basis of 90% probability of non-exceedance periods of 50 and 100 years. Out of this table, it clearly appears that Kashgar is the town with highest hazard, but Alma-Ata, Osh and Balykchy also show high hazard evaluations.[21] Seismic zoning The complete seismic data set was combined with information concerning tectonics and active faulting in order to define seismic zones over the study area. Figure 2.6 shows the zoning with regard to topography and tectonics. For each zone Abdrakhmatov, Havenith et al. 2002 [21] calculated the magnitude for a recurrence period of 475 years that can be estimated by both the mean Gutenberg-Richter law and the upper 90% prediction limit (see table below). According to this map the Mailuu-Suu area belongs to zone 16 - Central Fergana Range with active Arslanbob fault (Figure 2.6).

Chapter 2 page 29 Table 2.7: Results of seismic hazard prediction for 10 towns in Kyrgyzstan

mean upper 90%- Mmax - Mmax - upper Historical Zone n° law prediction b-value R mean law prediction law Magnitude a-value law a-value 475 years 475 years Mmax Background 4.00 4.00 0.90 / 7.4 7.4 6.4 Zone 1 2.71 2.94 0.84 -0.97 6.4 6.7 5.3 Zone 2 2.60 2.90 0.75 -0.98 7.0 7.4 6.9 Zone 3 2.06 2.43 0.75 -0.96 6.3 6.8 5.8 Zone 4 2.70 2.90 1.01 -0.96 5.3 5.5 4.3 Zone 5 2.87 3.12 0.70 -0.99 7.9 8.3 8.3 Zone 6 2.78 3.03 0.80 -0.98 6.8 7.1 7.5 Zone 7 2.82 3.01 0.76 -0.99 7.2 7.5 6.7 Zone 8 3.13 3.64 0.80 -0.98 7.3 7.9 7.6 Zone 9 3.33 3.92 0.86 -0.95 7.0 7.7 7.3 Zone 10 2.90 3.11 0.90 -0.97 6.2 6.4 4.9 Zone 11 3.89 4.20 1.30 -0.97 5.1 5.3 4.2 Zone 12 3.22 3.45 0.80 -0.99 7.4 7.7 6.8 Zone 13 4.39 4.59 0.98 -0.99 7.2 7.4 6.4 Zone 14 3.52 4.03 1.00 -0.88 6.2 6.7 5.1 Zone 15 3.64 3.84 0.85 -0.99 7.4 7.7 6.5 Zone 16 4.10 4.47 1.03 -0.97 6.6 6.9 5.5 Zone 17 2.91 3.03 0.79 -1.00 7.1 7.2 6.2 Zone 18 3.44 3.59 1.00 -0.99 6.1 6.3 5.3 Zone 19 3.46 3.74 0.90 -0.99 6.8 7.1 6.7 Zone 20 4.15 4.38 1.01 -0.99 6.8 7.0 6.4 Zone 21 4.09 4.40 0.96 -0.98 7.1 7.4 6.7 Zone 22 4.09 4.28 0.91 -0.99 7.4 7.6 6.6 Zone 23 4.55 4.67 0.85 -1.00 8.5 8.6 7.4 Zone 24 4.44 4.66 0.87 -0.99 8.2 8.4 7.8 Description of zones in Fig . 2.6 and Table 2.7 : - Zone 1 : The Talas Basin and Southern Karatau mountains. - Zone 2 : The Kyrgyz Range bordered in the North by several active faults (e.g. Chonkurchak (a) and Issyk-Ata (b) faults). - Zone 3 : The Chu Basin. - Zone 4 : The Kindl-Tas Range. - Zone 5 : Chon Kemin – Chilik zone composed of Zaili, Sugety and Kungei Ranges including seismically active faults, that produced events of M>8: Chon Kemin-Chilik (strike-slip, a) and Chon Aksu (thrusting, b). - Zone 6 : Ketmen Range. - Zone 7 : Ugam mountains with Range bordering active faults. - Zone 8 : Chatkal Range with Range bordering active faults.

Chapter 2 page 30 - Zone 9 : Suusamyr region including Suusamyr Basin and Range. The Ms=7.3 Suusamyr earthquake occurred on the Aramsu fault (a). - Zone 10 : Kochkor and Djumgal Basins. - Zone 11 : Issyk Kul Basin. - Zone 12 : Teskey Range with active PredTeskey (a) fault. - Zone 13 : Northern Fergana Basin. - Zone 14 : Central Fergana Basin. - Zone 15 : Southern Fergana Basin. - Zone 16 : Central Fergana Range with active Arslanbob fault (a). - Zone 17 : Naryn Basin. - Zone 18 : Atbashi Basin and Range. - Zone 19 : Saryaz Range. - Zone 20 : Alay and Turkesten Ranges including. - Zone 21 : Kokshal Range. - Zone 22 : Akesu Basin with western extension of seismically active Baicheng- Kuche thrust system (a). - Zone 23 : Alay Basin bordered in the North in the South by the seismically active Northern Pamir thrust (a). - Zone 24 : Kipintage thrust zone delimited in the South by the active Kipintage thrust fault (a) and including the active Piqiang (b) fault. Out of all tectonic maps used, the main structural feature appeared to be the Talas- Ferghana fault. Therefore, the territory was first divided into a north-eastern and south-western Tien-Shan region to both sides of this fault. During a second step 24 individual zones were outlined according to the Basin-Range structure, which seems to strongly constrain the distribution of seismic activity. A relatively large number of zones were defined in order to highlight local variations of seismicity. (Figure 2.6 ) (K. Abdrakhmatov, H-B. Havenith, D. Delvaux, D. Jongmans & P. Trefois, 2002) [21].

Chapter 2 page 31 Mailuu Suu

Verny Chilik Belovodsk Kemin

Chatkal Suusamyr

M7,8 1902 M 6,4 2003 M-7.4, 1949 24th of Febr. ,S-Xinjiang M-7,3 1974 Talas-Fergana Fault

Figure 2.6 : Seismo-tectonic map of Kyrgyzstan and surrounding regions with a) seismic zone names, principal towns, location of Mailuu-Suu b) historical seismicity and several active faults. After Abdrakmatov et al. 2002 [21].

Chapter 2 page 32 2.9.5 Maximal seismic accelerations According to Kyrgyz construction norms and rules (CH – P 11-7-81) construction should allow for maximal amplitudes of vertical and horizontal accelerations in Kyrgyzstan equal and not less than 200 cm/s² (0,2 g). In accordance with the map of potential peak accelerations which was recently made up by Belgian and Kyrgyz geophysicists [21] the maximum values of seismic acceleration rates calculated for the Mailuu-Suu Region can reach the amount of 0,25 g (Fig 2.7). (Torgoev, Pers; Communic. May 2002).

Mailuu Suu

Figure 2.7 : Probabilistic PGA - Map of Kyrgyzstan (after K. Abdrakhmatov, H-B. Havenith, D. Delvaux, D. Jongmans & P. Trefois, 2002 [21]. (PGA – Peak Ground Acceleration) : Position of Southern Xinjiang Earthquake, 24th of February, 2003, Magnitude 6,4 Richter scale, depth 33 km (USGS). Abdrakhmatov et al., (2002) note that the choice of the prediction period is depending on the engineering project. For example seismic hazards of the Toktogul dam should include all maximum hazard components and this implies a PGA value of 0.5g for upper prediction G-R, Pe85, and 10% probability of exceedance in 100 years. They conclude that for this kind of large construction, a 250-year period with a 10% probability of exceedance may even be more adequate, which implies a maximum PGA of 0.7g, all other parameters kept identical 2.10. Tailings: dimensions, radioactivity, chemo-physical parameters The mine works were active from 1946 until 1968, and 23 tailings deposits and 13 mine waste dumps were developed. The entire volume of these deposits is approximately 3 million m³ and their total activity was reported with 50 000 Ci3 [14]. Supervision and maintenance of the tailings areas were conducted by the staff of the mining industrial complex until 1991. This involved inspection of the sites, controlled security access to the industrial area, along with maintenance of the site fencing,

3 1 Ci (Curie) equals 3,7E+10 Bq

Chapter 2 page 33 tailings integrity containment structures and the surface drainage system. This work was stopped in 1991 with the collapse of the Soviet Union. Tailings depositories and mine waste rock dumps in ecologically most critical positions concentrate along he Mailuu-Suu river valley between the northern end of the town of Mailuu-Suu and the village of Kara Agash (Figure 2.8). Tailing depository N° 3 is located on the left bank of the Mailuu-Suu River, in a small depression opposite of the "Isolit" Factory (former ” Plant N° 3 “). Tailing N° 9 is located approximately 45-50 m to the south on the slopes of a little hill. Tailings N° 10 is located 30m further up the slope towards the SE and still further up 250 m to the S along the watershed is tailings N° 11. Tailings N° 8 is located on the right river bank opposite to N° 9 and borders directly to the territory of the "Isolit" Factory. Of these tailings depositories only N° 3 is constructed in a somewhat organized manner. The others are unorganized stockpiles of processing residues on the slopes of the Mailuu-Suu River valley as opposed to constructed or even engineered tailings depositories. In 1961 because of lacking dams or confinement structures in tailings deposits N° 8, 9, 10, their surfaces were reportedly strongly eroded by floods and rainfalls. The processing residues spilled down slope as a result and were partly discharged into the Mailuu-Suu River at only 1-100 m distance from these tailings deposits (8). Originally only some tailings (like Tp.8) had a fence, locked gates, and protective ground screen. Now most of the dumps are out of proper control and timely repairs. Therefore, many tailings depositories (No. 3, 5, 6, 7, 9, 10) are accessible for people and domestic animals. A road, providing bus communication, is passing over tailing No.18. The tailings No. 20 and 21 were used as an area for gardens, country houses, livestock pasture etc. 13 Mine waste rock dumps with sub-balance ore piles are located mainly in the Mailuu-Suu, Aylampasai, Kulmensai and Kara Agash Sai river valleys. They contain low grade ore and uranium mineralized rocks frequently cut by streams (as No. I and II in the Kulmensai river valley ) which transport and disperse low radioactive materials further downstream. In most cases these dumps are not stabilized or recultivated, but used as dumps for municipal wastes (as for instance in the Aylampasai river valley). An overview on location, type of deposit and radioactivity is provided in the following tables and on Figure 2.8 and a databank on available data on tailings from uranium ore processing in the Annex 2-2 of this chapter. The environmentally most critical depositories are described in more detail below.

Chapter 2 page 34 (Comp.H.Quarch, 04/01) Former Mill, blasted Kara A gash Sai Ri Location of Mill Tailings v. VII M1 N6 . iv and Waste Rock Dumps IX R VIII Suu N7 luu in the Mailuu Suu Area ai X M M2 N5 VI Legend: XII XI

a b Mill Tailings a)“organized“- b)“wild“ deposits KARA AGASH SETTLEMENT Mining Spoils V

M1 Mine Shafts Isolit Factory (former Mill) N17 N18 N3 N15 N8 N20 N9 N21 N19 N10 XIII N22 III N11

N14 N16 M4 I M3 II Kul IV Ayl mens ampa ai R sai iv. Ri v.

MAILUU SUU TOWN N1 N23

N4 N2

N13 1 km

N12 Figure 2.8: Location of mill tailings and mining heaps at Mailuu-Suu

2.10.1 Physico-chemical characteristics of the residues Grain size Thinly crushed and mineralized rocks that underwent a chemical processing circuit (tailings) consist of mud, silt and sand, limy sandy loams, partially in a paste-like (fluid) consistency: particle size 0,05-0,15 mm in diameter (data of GRP "Kiziltepageologia") [9]. The finer grained slime part of the tailings makes up from 60 up to 80 % of the so-called “pulp” materials or processing residues. For Tailing N°3 characteristics are shown in Table 2.8.

Chapter 2 page 35

Table 2.8: Average physico-mechanical properties of tailing 3 [9] Range Mean Value Type of material loam, sandy loam Grain Size Fraction (mm) fine (d < 0,1mm) Specific Gravity (g/cm³) 2,68 -2,71

Dry Volumetric weight in the zone of aeration ps (g/cm³) 1,45 - 1,84 1,62 (non-consolidated zone) (t/m³) Dry Volumetric weight in water saturated (g/cm³) 1,49 - 1,61 1,56 condition (below groundwater level) (t/m³) Volumetric weight in humid state (g/cm³) 1,89 (t/m³) Volumetric weight in the water saturated zone (g/cm³) 1,93 (t/m³) Moisture content in the zone of aeration (non- W (%) 15+5,5 21 consolidated zone) Moisture content in saturated condition (below (%) not less than 24 groundwater level) Angle of internal friction (degree) 11 to 35 Cohesion C (tc/m²) 0,0 to 3,0 Permeability coefficient (coefficient of kf (m/d) 0,03 to 0,86 0,005-0,01 l/d filtration) Porosity (void ratio) n (%) 33,7 + 7,4 Average density of solid material (kg/m³) 1600 Mass of the solid material (kg) 1768 x 10E8 General composition and radioactivity The composition of the solid part corresponds to the composition of the natural uranium ore. Out of this material about 90 % of the initial quantity of uranium has been chemically leached during the uranium ore processing technology applied. Therefore the radio-activity of the tailings is mainly caused by the radioactive decay products (uranium-thorium radioactive decay chains) i.e. the presence of radium -226 226 (Ra ) with a half-life period of Т1/2 = 1600 years. In the hydro-metallurgical processing of uranium ores the greater part of (more than 99 %) of the initial radium content in the ore is thus left in the solid wastes. Radium is thus the main radio nuclide in the tailings. The chemical composition of the radioactive residues reflects the original composition of the uranium ore, namely: increased calcium content and decreased content of silica, nickel, copper, chromium and other elements. Moreover, there is an increased manganese content (up to 500 to 2000 g/t) which is a technogenic waste product of the oxidizer (permanganate) used in the processing circuit [9]. Most radioactivity is contained in the finer grained slime part of the tailings. The average specific activity of tailings from Mailuu-Suu ores has been reported to range from 1100 up to 27300 Bq/kg ; the specific activity of tailings processing from the Eastern -European ores was reported to reach the value of 52600 Bq/kg [9]. General information on the tailings and the waste rock heaps is given in Tables 2.9 and 2.10 (We found an average of 230 Bq/g: see Table 3.8).

Chapter 2 page 36 Table 2.9: Inventory of mill tailings and mine waste rock dumps in the Mailuu-Suu District No. Location Ty- Thick- Surface Waste Max. Main Work to be done Long term measures for tailings Dates pe ness – Volume Exposure Peculia- immediately (Ministry 2) (m) area (m³) (µR/h) rities recomm. 2000) Proposed techn. Solut. for wast d. (m²) 3) N1 right riv.bank of 9 24150 84000 40-60 Conservat. none Enclosures 2003 Aylampa Sai Riv. Warning signs N2 left riv.bank of 5 26400 65000 40-60 --“ -- Precise outline of Enclos. restor. 2003 Aylampa Sai Riv. boundaries Warning signs Fortif. of left riv. bank Clear riv. bed to facilit. drainage Into a drain. Channel N3 left riv.bank of 8 (34) 8700 110500 30-60 Landslide and Loc. monit. of landsl. Evaluate dam stability against 2001 Mailuu-Suu Riv. 80000 (130- flood risk threats vibro-seismic impact earthquakes SE of Isolit Fact. Both 360) Fill surf. eros. trench of Richter 7. Adopt appropr. values w. soil meas. appear Re-til ext. slope 400 m² 2003 plan + prep. stabil. Enclos. restor., warmning signs landslide block "Tectonic" Implement work to relieve "Tectonic" N4 right riv.bank of 3 25000 115000 40-50 --“ -- Re-till surf. 500 m² Restore enclos. + warning signs 2003 Aylampa Sai Riv. (140- 380) N5 right riv.bank of 2,6 10000 111000 25-80 Landslide and Loc. monit. of landsl. Evaluate dam stability against 99/2000 Mailuu-Suu Riv. (18,6) (100- flood risk threats prob. descent of "Koytash" N of Kara Agash 125) Re-till destroyed landsl. with form. of support lake aft. basis village sections of drain. Dev. techn. meas. on "Koytash" 2003 chann. desc. Clear sump for mud Restore enclos. + warning signs slide and drain chann. N6 right riv.bank of 9,5 14300 80000 15-30 Conservat. none

Chapter 2 page 37 Mailuu-Suu Riv. N of Kara Agash Restore enclos. + warning signs 2003 vill. N7 right riv.bank of 27 108000 600000 15-25 --”-- Loc. monit. of landsl. Evaluate dam stability against 99/2000 Mailuu-Suu Riv. threats prob. descent of "Koytash" N of Kara Agash Re-till destroyed landsl. with form. of support lake aft.basis village sections of drain. Dev. techn. meas. on "Koytash" 2003 chann. desc. Clear sump for mud Restore enclos. + warning signs slide and drain. chann. N8 right riv.bank of w 12600 90000 15-25 --”-- Loc. monit. of landsl. Evaluate dam stab. against prob. 2000 Mailuu-Suu Riv. threats descent of "Isolit" landsl. S of Isolit factory Restore enclos. + warning signs 2003 Reinforce lower slope of dam along 30 m N9 left riv.bank of w 24200 115000 40-60 --”-- Loc. monit. of landsl. Evaluate probab. of "Technikum" 2000 Mailuu-Suu Riv. (600) threats landsl. 2003 Precise outline of Restore enclos. + warning signs boundaries N10 left riv.bank of w 11500 50000 60-70 --”-- Loc. monit. of landsl. Evaluate probab. of "Technikum" 2003 Mailuu-Suu Riv. threats landsl. Restore enclos. + warning signs N11 Hillslope betw. w 13750 70000 40-80 --”-- Determ. precise loc. + Restore enclos. + warning signs 2003 Mailuu-Suu + draw outline Kulmensai rivers, NE of Mailuu-Suu town N12 right riv.bank of 18000 2000 60-80 --”— Determ. precise loc. + Restore enclos. + warning signs 2003 Aylampa Sai Riv. Is covered draw outline near suburbs of Mailuu-Suu town N13 left riv.bank of 6,5 13950 40000 60-80 Flood risk Reinforce 80 m of Restore enclos. + warning signs 2003 Aylampa Sai Riv. coastline along dam W of datschas N14 N of Aylampa Sai 7 14300 99000 150-300 Conservat. Planning and re-tilling Restore enclos. + warning signs 2003 Riv. (360) of surface (500 m²)

Chapter 2 page 38 N15 Hillsides NE of 4 68000 47000 20-30 --”-- Mailuu-Suu town N16 N of Ashbaz riv. 21 29640 303000 15-20 --”-- none Restore enclos. + warning signs 2003 (90) N17 left riv.bank of w 1050 1000 16-20 covered by determine loc. and Restore enclos. + warning signs 2003 Mailuu-Suu Riv. landslide outline under NE of Isolit Factory landslide Reinforce 100 m of coastline along tailings dump N18 left riv.bank of w 1760 3000 20-70 --”-- Outline and enclose Re-burial 2000/01 Mailuu-Suu Riv. (90-360) below N 3 dam Provide basis for re- burial N19 left riv.bank of w 1755 6000 25-30 --”-- Mailuu-Suu Riv. (90) below N 10 dam N20 right riv.bank of w 900 5000 15-25 --”-- Precise outline of Restore enclos. + warning signs 2003 Mailuu-Suu Riv. boundaries SW of N 8 N21 right riv.bank of w 1750 2000 30-80 --”-- Precise outline of Restore enclos. + warning signs 2003 Mailuu-Suu Riv. boundaries SW of N 20 N22 left riv.bank of w 2240 2000 18-25 --”-- Determ. precise loc. + Restore enclos. + warning signs 2003 Mailuu-Suu Riv. (80) draw outline N of Mailuu-Suu town N23 left riv.bank of w 60-80 --”— Aylampa Sai Riv. covered by glass E of N 1 (carwashing station) 431945 2000500 w = "wild" or “unorganized” deposits (without engineered containment structures)

Chapter 2 page 39 Table 2.10: Inventory of mining heaps (waste rock dumps) in the Mailuu-Suu District

No Location Thickness Surface Waste Maxim. Main Peculiarities Long Term measures for (m) area Volume Exposure tailings 2) (m²) (m³) (µR/h) Proposed techn. Solut. for waste 3) I right riv.bank of Kulmensai 15 9900 9900 13-110 land slide risk; re- Transfer to pile N4 cultivation necessary; eroded by Kulmensai Riv. II left riv.bank of Kulmensai 21 13800 13800 13-85 --“ – Transfer to pile N4 eroded by Kulmen- sai Riv. 1km distance to dwellings III east of settlement 5 5000 5000 15-120 --“ – Surface contouring 0,2 km distance cover with recultiv. layer to dwellings IV right riv.bank of Kulmensai 23 7200 7200 15-85 --“ – Use as deposit. for 1+2, surf. above flood level 1 km distance contour., stabilise deposit., to dwellings intrus.-prevention V slope near Kara Agash-Sai Riv. 7 7600 7600 15-105 --“ – transfer waste + 1 m of within settlement substratum into area of N 8- limits 10, replace by clean soil VI Kara Agash-Sai Riv.-valley 10 5200 5200 16-65 eroded by Kara transfer into area of piles N 8- Agash-Sai Riv. 10 0,4 km distance to dwellings VII Kara Agash-Sai Riv.-valley 10 2900 2900 14-40 eroded by Kara clean valley floor, flatten + Agash-Sai Riv. stabil. slopes fortify base of 0,1 km distance to slopes towards river dwellings VIII W right riv.bank of Kara Agash-Sai Riv. 4 13500 13500 30-60 --“ -- recontour and stabilize surface (VII) cover with recultiv. layer

Chapter 2 page 40 VIII E included included 30-60 --“ -- prevent. intrus. + unauthorized in N VIII W in N VIII W use of wastes IX 0,4 km west of N. 8 4 4600 4600 15-105 --“ – Surface contouring (flattering, 0,25 km distance to "Planierung") dwellings cover with recultiv. layer X 0,3 km sw of N. 9 5 28400 28400 15-85 --“ – Surface contouring (flattering, 0,4 km distance to "Planierung") dwellings cover with recultiv. layer XI right riv.bank of Kara Agash-Sai Riv. 30 4400 4400 3-105 --“ -- terracing, partial transfer of waste rock cover with recultiv. layer XII right riv.bank of Kara Agash-Sai Riv. 30 2800 2800 30-180 eroded by Kara transfer waste + 1 m of sub- Agash-Sai Riv. stratum into area of N 8-10, replace by clean soil XIII right riv.bank of Mailuu-Suu Riv. 3900 3900 35-95 contours not well transfer waste + 1 m of sub- contam. part of slope defined stratum into area of N 4, 0,2 km distance to replace by clean soil dwellings 109200 1033900

Chapter 2 page 41 2.11. Description of a selected number of tailings (according to 9, 10)

2.11.1 History and physical characteristics Tailing deposit 3 Tailing 3 is located at the foot of a steep slope (close to 45°) which overhangs the tailing 400 m to the East. It is restricted to the North and to the South by two small 20 m high spurs which are perpendicular to the slope foothills of which they are made of. The tailing’s surface presents a top platform of variable width (between 70 and 100 m) and a 100 m length; to the West, the tailing presents a sloping downhill embankment towards a road which travels at the slopes’ foot and which was set up on the high bank of the Mailuu-Suu river. The average altitude of the tailings beach surface is 1012 m a.s.l. The actual volume of stored processing residues is 110.500 m³. The structure can hardly be termed a “valley dam impoundment” because there is only a pioneer dam at the base of the pile of residues. The rest of the embankment slope up to the mudslide barrier which confines the beach area to the West has been contoured at operations end and then covered by a layer of alluvial gravel deposits. The processing residues consist essentially of clayey to sandy grain-size fractions with a specific gravity of 2,68-2,71 g/cm³. The sandy fraction dominates in the deeper parts of the depository but becomes more and more replaced by the silt and clay fraction in the middle part of the section. The clay fraction is dominant in the upper part (75 - 80%). [9][10]. Dry volumetric weight is 1,45-1,84 g/cm³ in the non-consolidated zone, with a mean of 1,62 g/cm³ and 1,49-1,61 g/cm³ below groundwater level, with a mean of 1,56 g/cm³. The volumetric weight in humid state is 1,89 g/cm³, but 1,93 g/cm³ in the water saturated zone. The coefficient of permeability is 0,03-0.96 m/d. The moisture content of the processing residues is 21% in the non consolidated zone and 24% below groundwater level. Operation of the tailings dam began in March, 1954 and lasted till February, 1958. During this period 150 thousand m³ of processing residues were deposited in Tp. No. 3 including the residues from the processing of uranium ore concentrates from various uranium mines in Eastern Europe [8]. In May, 1958 i.e. right after the termination of operating on Tp. No. 3 (as waste disposal site for uranium ore processing residues), seepage of contaminated waters from the (hydraulic) waste deposits was observed in the middle part of its inclined embankment. As a “preventive” measure, 2/3 of the surface of the embankment slope was covered by a layer of 0,5-0,8 m thick gravel deposits. In 1960, even though no additional sludges or liquids were deposited in the former tailings pond (except the natural accumulation of diluvial sediments from the adjoining slopes) the seepage water level in the hydraulically deposited dike kept on being rather high. Seepage waters were still leaking in the middle part of the embankment slope (depth of 0.5 m in piezometer wells ), and also from the ridge of the pioneer dike. This had caused fears concerning the stability of the tailing depository already at that time. Leakage of seepage waters was observed annually during the spring period from 1958 to 1965 in the middle and lower part of the embankment slope and at the bottom of the pioneer dike.

Chapter 2 page 42 During 7-8 months annually a small well was observed (and small stream ) at the northern edge of the tailings depository. These waters regularly saturated the base of the tailing mass. Accumulation of moisture in the tailing mass has resulted in the fact that in 1960-61 an elevation of the seepage line was registered in the tailings body in spite of continued leakages observed from its sides. Regular observations of the water level showed little change meaning the expected consolidation of the tailings had not happened. To the contrary the seepage line level had increased. In order to maintain the tailing dam's stability, the mill (processing plant) operating at that time (1960-62 ) undertook a number of measures including slope stabilization of the pioneer dam and covering the embankment slope of the hydraulically deposited processing residues by gravel deposits. Also periodic drainage of underground waters both in the body of the tailing dam and cleaning of the drainage system were performed. However the works to provide drainage of the water saturated tailings were inefficient, and the expected natural consolidation and increase of stability not occur. The stability calculations executed in 1961 by MIBI showed, that the coefficient of stability did not exceed the value of K = 0,945 taking into account seismic influences, and that the stability required according to the norms (К > 1,5) was not provided. Therefore in order to increase the stability of tailing depository No.3 it was decided to reduce the volume of the tailings by subjecting part of the residues to repeated processing and by depositing other parts on to other tailing dams. This was carried out in 1964 with the application of the scraper winch which was fixed on the left (southern) edge of the impoundment at the elevation of 1016 m asl. [8]. The tailings were delivered from the northern edge to the southern descent tray (drain chute ). At the bottom the impoundment the tailings were then (by means of another scraper winch) transported on a wooden descent tray to a bunker. From there were delivered for re-processing by motor vehicles. Any measures for their encapsulation or covering were not provided [8]. As a result, of these “conservation” procedures of tailings dam No.3 in 1965 its volume was reduced by one third of its original volume to 110500 m³ .At this volume and the average density of 1600 kg/m³ of the dry solid matter (“skeleton”), the weight of the solid matter of the tailings is calculated to amount to 1.77-108 kg with a general activity of contained radio-nuclides of 1,86-1014 Bq, including an alpha –activity of 9.29-1013 Bq. 1965-67 “conservation” work on Tp. No.3 included [8]: • reshaping, recontouring and covering the surface protection against erosion (gravel cover) • terracing the embankment slope • construction of a ? waste water collection pond and building of a fence • construction of a temporary motorway (for transport of cover materials) starting from Tp.No. 9 tailings dam traversing the saddle to the south descending on T.3 • Constructions located in the tailings dam and the used equipment were cemented. The drainage pipes for the dewatering of the slimes (diameter of 213 mm) were plugged by clay.

Chapter 2 page 43 • Two thirds of its eastern embankment starting from the position of the starter dam towards the pond (beach) was covered with a 0,75-1,0 m thick layer of alluvial (rounded) gravel and pebbles. The protective coat on the embankment slope was composed of two layers: - bottom gravel layer of 0.25 m thickness - top – layer of larger components (diameter 7 to 10 cm). - These cover materials were applied starting from the pioneer dam and continued upslope. The materials were brought by trucks and distributed across the slope the slope by bulldozers. Existing berms on the slope were maintained. The average thickness of the gravel fill on the lower part of the slope was 1.6 to 1,8 m. After reshaping by bulldozer, the new tailings surface was covered by a layer of clay (0,2 m thickness) which was moistened by water and subsequently roller-compacted. This clay layer was then covered by a protective gravel- layer (0,8 m thickness). The resulting dry volumetric weight (in the zone of aeration) amounted to 1,65 to 1,70 t/m³. During this conservation work on Tp. No 3 the total amount of cover materials applied are summarized as follows : 1550 m³ polluted (?soils, debris and ?other materials ) used for reburial of the tailings 400 m³ gravel materials (diameter 15 – 20 cm ) applied down slope of the pioneer dam as a protective coat on the embankment (slope): 875 m³ small gravel materials 875 m³ larger gravel materials (diameter of 7 to 10 cm) and as cover on the tailings surface : 800 m³ clay 3200 m³ protective gravel on top of the clay layer Until 1991 the ”Service of Hydraulic Engineering Constructions” of the “Leninabad Mountain - Chemical Plant”, who was responsible for Tp. No.3 and the other disposal areas in Mailuu-Suu region, did observations, repair, maintenance and undertook preventive measures to keep the depositories and their protective constructions in safe condition. With the end of the USSR and due to organizational, technical and financial problems these works practically ceased. This had a negative effect on the long-term stability and ecological safety of the tailing depositories. Since 1994 the situation has become aggravated due to the continuing saturation of the highly radioactive wastes, and increasing sediment load that accumulated on the tailings surface of Tp.3 and due to creep processes which directly or indirectly began to threaten the integrity and stability of the tailings impoundment.

Chapter 2 page 44

Tailing deposit 10 Tailings deposit N° 10 [9] [10] is a non-organized stockpile of processing residues which means it was accumulated without preparation of an engineered impoundment concept. It is situated 80m to the SE of tailings depository N° 3. As already mentioned above, the surface was strongly eroded in 1961 and the processing residues were spread down slope into the valley. The site is 215 m long, 50 m wide, and has a surface area of 10.750 m²; the volume is 50.000 m³, the average altitude of the surface is 965 m a.s.l. The basin or settling pond is filled with homogeneous material consisting of mostly silty particles (d<0,05 mm). The admixture of sandy components is 20-40%. These materials have (?partly) consolidated and dried out from the surface down to a depth of 2-3 m. Moisture remained in deeper levels which were water saturated in some sections. A (? water table) was not encountered. There is no information on the physical and chemical properties of processing residues stored in basin N° 10. However, such data exist for non-organised wild tailing deposits in storage sites N°17 – 22 (Grain size distribition: gravel/silt,sand/clay: 1.35/51.8/12.2 %; Specific weight: 2.67 g/cm³; dry volumetric weight: 1.84 g/cm³; moisture content: 26%] Tailing deposit 7 Tailing deposit 7 was in operation until 1958. It is located near the territory of former plant N° 7 and it belongs to the wet or “swampy”-type of tailings basins (unthickened or low slurry density tailings placed through spigots onto wide beaches). It is 400 m long and 280 m wide, its volume is 600.000 m³. The mean average altitude of its surface is 1.050 m. Tailings depository N° 5 is at distance of 50 m and has a volume of 80.000 m³. In April 1958, in Mailuu-Suu after an earthquake and a week of heavy rains, a breach in the containment dam of tailing No.7 occurred, at 30 m distance from the Mailuu- Suu river (Figure 2.2). The cause is not known but reportedly an estimated 60 000 t of the tailings were dispersed by the river. The resulting mudflow containing the radioactive residues destroyed a lot of objects in the town of Mailuu-Suu and contaminated the flood plains downstream (for 40 km down by the river, to the territory of Uzbekistan [3]Reportedly also people were killed (14). The necessary cleanup of agricultural fields was going on for many years. (Torgoev, Aleshyn 2001). In 1961 the dam of tailings depository N° 7 was partly destroyed; due to water- saturation and –erosion 0,5-13m deep channels were cut into its surface. These wash- outs broadened into breakthroughs. This caused discharge and dissemination of processing residues out of the tailings basins by rain water and flooding into the Mailuu-Suu River which is only at 30-40 m distance from the lowermost dam of the depository. The original distribution of the materials in depository N° 7 was disturbed by the failure . This original distribution in the basin was characterized by the dominance of silty particles (d<0,05 mm). Only at the bottom and at the surface of the peripheral sections sandy components predominate as a result of slope erosion . Subsequently the damaged dam sections were eventually repaired. In 1996 the dams of the depository N° 7 were reported to be in satisfactory condition. The surface of the depository was reported to be smooth and plane, erosion channels and wash-outs were not observed. This situation has not changed very much until 2002.

Chapter 2 page 45 2.11.2 Radiological situation Investigations on the tailings depositories near the town of Mailuu-Suu were first carried out in 1989 on tailings in order to evaluate the quality of “conservation” (?) recultivation work which was done until that time (Soroka and Molchanov, 1993) „Conservation“ of part of the tailings depositories at that time was usually carried out by covering the surface with a layer of (alluvial) sand and gravel with a total thickness of 0,5 m. Depositories N° 7 (and 12) were an exception, insofar as the processing residues were first covered with a layer of pink colored Sumsar clay (0,2 m) and then with an alluvial sand /gravel mixture of 0,5 m thickness. For this reason depositories N° 2 and 7 were selected as objects of investigation because of their differences in terms of structure and thickness of the cover (Soroka and Molchanov, 1993). Results of the investigations showed that the gamma dose rate at the uncovered surface of the processing residues was 6,0-8,2 µSv/h, whereas the surface of the covered side of the tailings pond exhibited only 0,15- 0,20 µSv/h which corresponds to the level of the (geogene) background of the area. Analyses of cover materials used for recultivation showed some increased concentrations in 238U, 226Ra and 210Po. 80 Bq/kg (or 5 ppm) as observed for 238U represents twice the world’s average. The 238U and 226Ra contaminations in the (cover materials) of depository N° 7 were explained by the capillary rise of moisture which was also the carrier of this contamination. This form of radionuclide migration was also observed in the cover materials in depository N° 2. The clay cover layer in tailings pond N° 7 was found to reduce the penetration of 222Rn and hence also the concentration of 210Po in the cover material (see Figure 2.9).

Chapter 2 page 46 Tailings Pond N° 2

Tailings Pond N° 7

Figure 2.9: Distribution of natural radionuclides in the cover materials of tailings ponds N° 7 and N° 2 Mailuu-Suu (Soroka and Molchanov 1993)

Chapter 2 page 48 The major part of contamination in the cover materials was contributed to the radon progeny due to diffusion of radon of the tailings materials. During the months of October to December 1994 the Uzbek State Geological Agency "Kiziltepageologiya" conducted a survey of the radio-ecological situation around tailings ponds N° 3, 7 and 10. At that time tailings pond N° 17 on the left bank of the Mailuu-Suu, was already destroyed and covered or washed into the river due to a mudslide that had occurred. Tailings ponds N° 3, 9 and 10 at that time were considered not affected by mudslides. Tailings pond N° 11, located a little bit further to the south was considered to be most likely already buried by landslide debris. Its position could only be determined on the basis of a slight elevation of the gamma dose rate (up to 150 µR/h4) at the suspected location. They performed spiral augering and drill hole measurements at tailings pond N° 7. Tailings ponds N° 3 and 10 turned out to be not accessible for vehicles by them. The surface areas of tailings ponds N° 3, 7 and 10 were surveyed on foot for external gamma exposure5 (Figure 2.10). As a result it was established that the surface of tailings pond N° 3 is characterized by a relatively low average gamma dose rate of 25-75 µR/h, which reaches 400- 550 µR/h in some spots, (however 1000-2000 µR/h in one spot below the dam) . In the central part of tailings pond N° 7 measurements of the gamma-dose-rate were not very high with 15-20 µR/h (almost geogene background). Very different measurement results for the gamma dose rate were recorded from the outer sides of the dams and from the areas adjacent to the dams of tailings ponds N° 3, 7 and 10. The highest gamma dose rates were measured in the areas directly adjacent to tailings pond N° 3 (35-2200 µR/h) and also adjacent to N° 7 (45-500 µR/h) .-The lowest result was recorded from tailings pond N° 10 (35-170 µR/h). These facts point to a higher permeability of dams of tailings ponds N° 3 and 7 in comparison with those of tailings pond N° 10. This is also supported by measurement results of the total alpha- activity of soil samples which were taken from the outer sides of the dams and their confinements (Table 1, 4a, 4b in Annex 2.3). Altogether these facts are testifying to the permeability of the dams for radionuclides, whereby the tailings pile No. 3 is characterized by the greatest permeability of the depositories investigated. Also “Atmo-geochemical” investigations (including Radon) and results obtained in measurement profiles between the Mailuu-Suu River and tailings pond N° 7; at the left river bank along tailings ponds N° 3, 9, 10, 11 and 17. These data are not discussed here because results from radon measurements are very time depended. The slightest change in parameter (e.g. moisture content of sample, wind speed) affects the figure obtained. In large, the evolution of radon emanation results corresponded to the evolution of the gamma monitoring data. It was stressed that the insufficient sealing capacity of the cover emplacement on the tailings allows exhalation of Radon and its dispersion into the atmosphere. of the environment .

4 1 µR/h= 10 nSv/h 5 Results of surface gamma measurements were recorded with different types of instruments with variable sensibilities and therefore have only relative significance. The type of instrumentation used, their sensibilities and the methodologies of measurements are rarely indicated in the available source materials .

Chapter 2 page 49

Figure 2.10 : Results of a surface gamma scintillometry survey on tailings ponds N° 3 and 10 (source: Uzbek State Geological Agency "Kiziltepageologiya"- Report 1995 of fieldwork 1994) [9].

Chapter 2 page 50

Measurement results from drill holes in the periphery of tailings pond N° 7: Spiral augering measurement results on the site of tailings pond N° 7 registered the highest concentrations of radionuclides and radon in a drill profile close to the northern edge of tailings pond N° 7. In the central and southern parts of the tailings pond, a slight decline in the concentration of radionuclides and radon was registered. Close to the southern edge the Rn- concentration rose again. According to measurement results from drill holes, elevated Rn- concentrations in drill holes correlate with elevated Ra-concentrations in the upper layers of the tailings pond. In drill holes located close to the tailings pond along its southern, eastern and northern edges, gamma-anomalies of 50-70µR/h were recorded. Drill results indicated that in the majority of drill holes at the central part of tailings pond N° 7, radioactive releases were associated to a semi-liquid, pasty substance of white to light grey color which consists of carbonates: gamma dose rate was 500-1.500µR/h. Two additional drill holes were sunk close to the road which passes along tailings pond N° 3 with the objective to detect releases from this tailings pond. However these two drill holes encountered tailings belonging to tailings pond N° 18, from which no location marks existed any more . Moreover this tailings deposit is crossed and covered by the road tarmac. Also a bus stop is located directly on the tailings with a radioactivity at surface of 200 µR/h. In addition drill hole measurements recorded a Rn exhalation of up to 160 Eman. The most important radionuclide in the tailings is Ra. Its concentration in tailings pond N° 7 ranges from 407*10E-4 % U equ. to 1.091*10E-4 % U equ., which corresponds to 1,4*10E-8 % - 3,7*10E-8 % Ra. Residual U-concentrations in this tailings pond are 72-137 mg/kg. The Th- concentration is 1-4 g/t. Measurement results from drill holes in the periphery of tailings pond N° 3: Thirteen 1-3 m deep manual drill holes were sunk within the boundaries of tailings pond N° 3. Some of these drill holes reached the upper layer of the radioactive residues. None of those succeeded in penetrating the full sequence of processing residues. Detected anomalous sections in manual drilling ranged from 80 µR/h up to 1.100 µR/h. CHU Ecological Laboratory (19) reported specific alpha-activities of samples, taken from the outer side of the dams and adjacent territories at Tailing 3, that vary between 1600 Bq/kg and 24800 Bq/kg. The lowest mean values of the specific activity are observed on the dam of Tp. No. 10 the highest values in Tp. No. 3. These facts are again testifying to the permeability of the dams for radionuclides, whereby the tailings pile No. 3 is characterized by the greatest permeability of the depositories investigated. Some results from radionuclide-analysis from soil-(and stream-sediment) samples Results indicated a dispersion of the contamination in surroundings of tailing ponds N° 3, 7 and others. A sampling programme was carried out all along the Mailuu-Suu river downstream of the area of these tailings deposits in order to determine the spread and range of radionuclide dispersion. The results are summarized in the Table 2.11.

Chapter 2 page 51

Table 2.11 : Results of stream sediment sampling in 1997 in vicinity of the tailings depositories for determining seapage from tailings

In sediments In water

Stream sediment sample location : from U Ra Th U Ra 10E-4 % (10E-4 % (10E-4 %) (10E-5 g/l) (10E-10 (g/t) U-equiv.) g/l) Distance T7 4d) North flank of the Tp.No.7, near the Mailuu-Suu 0 2 6 8 1,2 <0,001 right river bank 2d) Bottom of clear water spring below the Tp. 19 80 9 18 <0,001 Size: 3 by 4 metres. Discharge: 15 l/min. Inflows into Mailuu-Suu river in 20 metres. Soil radioactivity near the spring 40 to 80 µR/h.

1d) Boggy ground, soil gamma activity is 20 µR/h. 80 11 4 46 <0,001 Size: 1 by 4 metres. Films of salts near the spring. Very poor discharge. 3d) Clear water spring sediments. Discharge: 5 l/min. 20 85 3 2,5 <0,001 Inflows into Mailuu-Suu river in 20 m. . Green grass around the spring. Soil radioactivity 20 µR/h 5d) sample from the bottom of Mailuu-Suu river in 0,2 2 10 9 0,92 <0,001 front of central part of Tp. #7 6d) sample from the bottom of Mailuu-Suu river in 0,4 1 29 8 1,2 <0,001 front of south flank of the Tp. #7 9d) Boggy ground located in front of Tp. #3 (within 12 37 4 4,5 <0,001 Tp. #18). Water of the bog flows into Mailuu-Suu river in 15 m distance. 7d) sample from bottom sediments of Mailuu-Suu 1,7 1 8 3 1,3 <0,001 river a little downstream from plant "lzolit” in front of the Tp. #3 (and Tp. #18). 8d) Bottom sediments of Mailuu-Suu river in front of 1,8 3 12 4 1700 <0,001 Tp.#3 (Tp. #18), near its south flank 10d) Bottom of Mailuu-Suu river at northern town 3,3 2 7 8 1,4 0,330 limit of Mailuu-Suu 11d) Bottom of Mailuu-Suu river 3.5 km downstream 8,5 4 11 9 2,1 <0,001 from the town (near the road police check point) 12d) Bottom of Mailuu-Suu river near Madaniyat town 30 1 3 6 1,9 <0,001 entrance Background U = 1 to 3 g/t In summary the results indicate elevated Ra in stream sediments near Tp. 7 and 3 and also downstream in Mailuu-Suu town. Sample 2d and 1d indicate seepage from tailings dam and also sediments taken from springs in the vicinity of Tp. 3, 18 and 7 are elevated in U and Ra indicating seepage from the tailings. (samples 3d and 9d ). The authors (19) concluded that the radium content in bottom sediments decreases almost 10 times and reaches background (3*10- 4% uranium equivalent) after 8,5 km and before 30 kilometers distance and downstream from the tailings . The thorium content does not change significantly, and the uranium content is close to background at a shorter distance from the tailings . In water, the radium content is mostly less than 10E-13 g/l (0.037 Bq/L). The average uranium concentration is about 1.5*10-5 g/l which is 10 times more then background but below the exemption limits. Only sample #8d taken near Tp. No.3 and 18 has a high uranium content which can be explained by seepage from Tp. No.3 . Authors estimated that the migration distance of radium, which is the main radionuclide of the tailings is between 8,5 and 30 km. A dam constructed downstream in the Mailuu-Suu river to the catch radionuclide fraction migrating in bottom sediments was therefore suggested (9). The

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preliminary assumption in (9) was that increased uranium concentrations will decrease to background level after inflow into Syr-Darya river and that radioactive residues getting into the Mailuu-Suu river, are not dangerous for the Ferghana valley as far as most of them are locked in bottom sediments along the mid stream section of the Mailuu-Suu river.

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