The document summarizes rehabilitation works for the urban water supply and sewer system in Derventa, Bosnia and Herzegovina. It describes the existing combined sewer system that collects wastewater, stormwater, and industrial wastewater, of which only around 50% of the city is connected. The proposed works include constructing a new sewer collector network (Lot B1 and B2) and upgrading existing pumping stations PS1, PS2, PS3 and building new pumping stations PS4 and PS5 to improve wastewater management and prevent pollution of nearby waterways. Equipment is also procured to support maintenance and operation of the rehabilitated system.

2. Rehabilitation of the Urban Water Supply & Sanitation in Sava River Basin (BMZ ID 2002 65 876)
CURRENT SITUATION AND THE EXISTING PROBLEM
The existing sewer system is a combined system, which collects the wastewater produced in households, industrial wastewater, and small companies as well as storm water. At the moment, approximate between 50% and 55% of the water consumers in the city of Derventa are connected to the sewer system, while the rest 45% discharge their wastewater into septic tanks and open pits.
The pipe network consists of the pipes with the materials of PVC and concrete.
The existing sewer system has the following defects to be improved through the works to being tendered:
· The existing sewer system is insufficient to collect the wastewater produced in the city of Derventa. The piping system is in poor condition due to the poor maintenance and improper connections.
· The discharge of the untreated wastewater without authorisation into the oxbow lake of the Ukrina river and other tributaries of the Ukrina river as well as the Ukrine river has caused not only the serious pollution in the Ukrina river but also in the downstream of the Sava river.
· The hydraulic overload has caused the blockage of the collector in the Gakovac settlement, which has lead to a frequent overflow of the wastewater onto the ground surface.
· The dimension of the existing collector on the left bank of the Ukrine river is not sufficient as to allow any more connection of sewerage pipe. Thus, a new collector is required to be constructed to collect and discharge the wastewater collected in the
new settlement “Lug” on the left bank.
· There are several “weak points”, which have insufficient hydraulic capacity due to the inadequate dimensions or gradients, in the existing sewage system.

3. Description of the Works:
Lot B1 – In the northern part of the Derventa city, a new HDPE collector with diameters of DN 400-DN800 and length of ~2,000 m shall be laid along the road from the “Banja Luka”, in order to transport the wastewater collected by the existing branches to the future WWTP.
The dimension of this new collector shall be calculated under consideration of the future development along the road “Banja Luka”.
Under the new bridge, because the existing pumping station (PS 2) is out of the operation, the new collector shall be connected to the existing overflow structure (SWO 4). In this phase, the wastewater collected by the new collector will be discharged into the Ukraine River through the SWO4.
The sewerage pipe (DN 300 – DN 500, concrete) which is laid in the northern part and connected to the Pump Station “PS3” shall be disconnected from the PS3 and connected to the new collector.
Lot B2 - In order to collect the wastewater produced in the area along the road to “Banja Luka” and the refugee settlement “Lug” as well as the areas in the southern part of the Derventa City, the new sewerage networks which consists of ~ 2,400 m DN300-DN400 HDPE pipes shall be laid and the house connection shall be constructed.
The wastewater collected by this new network will be discharged into the new main collector which shall be constructed in Lot B-1 by a new pump stations PS 4 & PS5 (LOT B-3)
Lot B3:
PS 1 and SWO 2 - Regarding to the Pumping Station PS 1, the investigation shall be carried out by the Contractor through pipe flushing and camera inspection (250 m from the starting point) to make clear if there is sewerage in the pipes, which should be connected to the pumps,
and where the sewerage is discharged.
2. PS 2 and SWO 4 - The Pumping Station PS 2 will not be in operation and therefore not be rehabilitated in this phase. The Pumping Station PS 2 will not be connected with the new sewage pipe within this project. The new sewage pipe will pass the PS 2 and will divert the sewage directly into Ukrina River. Future Project foresees operation of PS2 and downstream collector up to the Treatment Plant.
3. PS 4 - In order to lift the wastewater collected by the new sewer network and the existing sewerage pipe (DN 300) to the new main collector, new pumping station PS 4 using submersible non-clog pumps shall be constructed. The two pumps will operate on an on- duty/stand-by basis. Each pump shall provide a capacity of 72 m³/h
4. PS 5 – In order to lift the wastewater collected by new PS4, connection of existing collectors at abandoned PS3, new pumping station PS5 using 4nr submersible non-clog pumps shall be constructed. 2nr pumps will provide a capacity of 2x540m3/h and 2nr small pumps - 2x180m3/h.

4. CORRUGATED HDPE SN8 PIPES REHAU RAUVIA
U-PVC SN8 PIPES REHAU

5. PREFABRICATED MANHOLES BINIS
PREFABRICATED MANHOLES BINIS

6. MANHOLE COVERS – PAM REXESS
DIRT CATCHERS

7. GEOTEXTILE: M-PROINTEX
GRUNDFOS PUMPS (S, SE & SEV SERIES)

8. Lot B1 Collector Line
DN800 – L=598m;
DN600 – L=761m;
DN400 – L=523m;
DN300 – L=220m
In total – 2.102,00m collector installed;
38nr of prefabricated manholes

9. EXCAVATION WORKS
TRENCH BRACING

10. USE OF PIPE LASER

12. MAGISTERIAL ROAD CROSSING 1 / UNDERGROUND DRILLING
MAGISTERIAL ROAD CROSSING 2 / UNDERGROUND DRILLING

13. USE OF GEO-TEXTING ON HIGH UNDERGROUND WATER TRENCH SECTIONS
INSPECTION MANHOLES ON EACH COLLECTOR DIRECTION CHANGE POINTS. MANHOLES PRODUCED BASED ON DETAILED DESIGN WITH SPECIFIED DIAMETERS AND ANGLES

14. SURVEY CONTROL

15. EXTENSION OF LOT B1 – DN300 COLLECTOR
INSPECTION MANHOLE

16. INSPECTION MANHOLE “DIRT TRAP”
MANHOLE COVER

17. TIGHTNESS TESTING AS PER EN1610

18. CCTV INSPECTION AS PER ATV M 14, PART 2

19. CCTV INSPECTION AS PER ATV M 14, PART 2

20. PLATE LOAD TEST ON ROAD CROSSINGS
REINSTATEMENT OF SURFACES - ASPHALTING

21. Lot B2 Sewage Network
DN400 – L=274m
DN300 – L=1,844m
In total: 2,118m of collector installed;
House connections – 126nr;
Prefabricated manholes – 61nr

22. COLLECTOR DN400 TRENCH EXCAVATION
INSPECTION MANHOLE INSTALLATION

23. INSPECTION MANHOLE INSTALLATION
PIPE LASER GUIDED INSTALLATION

24. PIPE LASER GUIDED INSTALLATION
COLLECTOR DN300 TRENCH BRACING

25. INSPECTION MANHOLE INSTALLATION
INSPECTION MANHOLE INSTALLATION

26. COLLECTION MANHOLES INSTALLATION

27. COLLECTION MANHOLES DRILLING FOR U-PVC HOUSE CONNECTION PIPE

28. U-PVC PIPE HOUSE CONNECTION TO THE COLLECTION MANHOLE

29. COLLECTION MANHOLE – U-PVC HOUSE CONNECTIONS
COLLECTION MANHOLE INSTALLATION

30. Lot B3 Pumping Stations
PS1 – Cleaning, rehabilitation of Pumps and inclusion into the SCADA System;
PS2 – Connection of new B1 Collector to existing PS2, discharging into Ukrina River over SWO4 structure. Future development foresees engagement of PS2 to pump the waste water downstream further from the City until the new Treatment Plant
PS3 – Existing PS3 is to be abandoned, belonging Collectors to be connected to new B1 collector, existing pumps to be rehabilitated and transferred to new PS4;
PS4 – new PS to be built for lifting the collector B2 elevation, 2nr pumps to be installed (2x20l/s, Hmax=12.4m); water level sensors, control and power cabinet to be installed, inclusion into SCADA System
PS5 – new PS was to be built lifting the elevation of B1 collector, 2+2 pumps (2x150l/s + 2x50l/s) with lifting heights of 7.72m & 7.15m to be installed, water level sensors, control and power cabinet to be installed, inclusion into SCADA System

31. EXISTING PUMPING STATION PS-1

32. EXISTING PUMPING STATION PS-1

33. EXISTING PUMPING STATION PS2 (CURRENTLY OUT OF FUNCTION)
FUTURE PROJECT FORESEES OPERATION OF PS-2 AND TRANSPORT OF SEWAGE TO THE PLANNED DOWNSTREAM TREATMENT PLANT

34. EXISTING PUMPING STATION PS-2 TABLE VALVE ON SWO STRUCTURE
EXISTING PS-2 / SWO4 OUTLET TO RIVER “UKRINA”

35. EXISTING PUMPING STATION PS-3, PLACED OUT OF OPERATION UNDER THE PROJECT
ABANDONED PS3, PUMP REHABILITATED AND TRANSFERRED TO NEW PS4

37. NEW PUMPING STATION PS-4

38. PS-4 PENETRATING 1ST WALL ELEMENT

39. 1ST WALL ELEMENT
LOWERING OF 1ST ELEMENT

42. STORM WATER OVERFLOW STEEL DN400 PIPE

43. INLET HDPE DN400 PIPE – FROM LOT B2 NETWORK
OVERFLOW STEEL DN300 PIPE

44. ROOF SLAB

45. PRESSURE PIPES 2NR SWING CHECK VALVES DN150
TRANSITION DN300/150 WITH SWING CHECK VALVES

46. INSTALLED 2NR SUBMERSIBLE NON-CLOG
GRUNDFOS “SEV” PUMPS
(2X23.30L/S, H=12.4M, 50HZ)
PS-4 OUTLET CHAMBER

47. PS-4 TIGHTNESS TESTING (AS PER EN1610), PLUGGING BALONS

49. LOCATION OF NEW PUMPING STATION PS-5

50. SEGMENTAL LOWERING – 1ST WALL’S SEGMENT

51. SEGMENTAL LOWERING – 1ST WALL’S SEGMENT

52. SEGMENTAL LOWERING – 1ST WALL’S SEGMENT
LOWERING BY EXCAVATION

53. SEGMENTAL LOWERING – 1ST WALL’S SEGMENT
SEGMENTAL LOWERING – 2ND WALL’S SEGMENT

54. SEGMENTAL LOWERING – 2ND WALL’S SEGMENT
(INLET HDPE DN600 PIPE VISIBLE)
UNDERGROUND LOWERING OF THE 2ND WALL’S SEGMENT

55. PREPARATION FOR UNDERWATER BASE PLUG CONCRETE INSTALLATION
PREPARATION FOR BASE PLUG CONCRETE INSTALLATION

56. BASE PLUG CONCRETE INSTALLATION
BASE SLAB REINFORCEMENT WORKS – OVER THE BASE PLUG CONCRETE SLAB

57. MIDDLE SLAB CONSTRUCTION
(OUTLET DN800 PIPE VISIBLE)

58. TOP WALLS CONSTRUCTION
INNER WALL – PRESSURE PIPES NOZZLE’S PENETRATIONS

59. OUTLET CHAMBER (PRESSURE PIPES AND HDPE DN800 OUTLET PIPE)
TOP WALLS VIEW, DN500 OVERFLOW PIPE VISIBLE

60. INNER WALL, PRESSURE PIPE NOZZLES
OUTLET DN800 PIPE

61. PS-5 ROOF SLAB REINFORCEMENT
ROOF SLAB CONCRETE POURING

63. TIGHTNESS TESTING AS PER EN1610
OVERFLOW DN500 PIPE

64. TIGHTNESS TESTING AS PER EN1610, PLUGGING BALLOONS

65. TIGHTNESS TESTING AS PER EN1610, PLUGGING BALLOONS
TIGHTNESS TESTING AS PER EN1610,
CALCULATED ADDING WATER
(ABSORPTION OF CONCRETE SURFACES)

66. PRESSURE PIPES, SWING CHECK VALVES INSTALLATION
PRESSURE PIPE PLINTH

68. CONTROL CABINET, SCADA SYSTEM
VENTILATION PIPES AND ACCESS HATCHES

69. 2NR SUBMERSIBLE NON-CLOG GRUNDFOS “S2” PUMPS
(2X150L/S, H=7.72M, 50HZ)

70. WATER LEVEL SIGNALING PROBES;
2NR SUBMERSIBLE NON-CLOG GRUNDFOS “SE” PUMPS
(2X50L/S, H=7.15M, 50HZ)

71. OUTLET CHAMBER:
PRESSURE PIPES, OUTLET DN800 HDPE PIPE

72. CONTROL CABINET
PUMP / SYSTEM TEST

73. PUMP / SYSTEM TEST
PUMP / SYSTEM TEST

74. PUMP / SYSTEM TEST
PUMP / SYSTEM TEST

75. Lot A10 “Delivery of equipment for maintenance and proper operation”:
Lot A10 “Delivery of equipment for maintenance and proper operation”:
Pick-up vehicle 4WD:
NISSAN NAVARA DC 2.5 DCI LE
Backhoe Loader:
KOMATSU WB97S-5
Pipe Cutting Saw:
STIHL TS420
Flat Bed Vehicle:
RENAULT MASTER 2.5 DCI 150
Vibratory Rammer:
WACKER BS 60-2i
Asphalt Cutter:
WACKER NEUSON BFS 1350 AL