Preparatory Survey for Greater Yangon Water Supply Improvement Project (Phase II) FINAL REPORT CHAPTER 7 DISTRIBUTION FACILITIES OF ZONE 1 7.1 Outline of Planning The water supply area of Zone 1 consists of CBD and IUR (see the Figure 3-8). These areas were initially developed by the British rulers along with the existing water supply systems in this zone. This water supply system has been used for long and is most likely in deteriorated condition with high leakage rate. Therefore, rehabilitation/renewal of the water supply system is required and study has been conducted keeping this in mind. 7.1.1 Review of Master Plan and Existing Condition In the MP, construction of Kokkowa WTP, and related transmission facilities are proposed considering the increasing water demand and use of river water as alternative water source. Also, reconstruction of Central SR along with new pumping station is proposed for High subzone. For Low subzone, use of existing Kokine SR is suggested. Distribution pipes are also proposed to be constructed both in High as well as Low subzones. Existing distribution system including SRs is illustrated in the following Figure. Presently, water distributed to Zone 1 is coming from Hlawga, Gyobyu and Ngamoeyeik reservoirs through the Yegu booster PS. According to the MP, in 2025 also, a part of this water (reduced amount) will be used for distribution to Kokine sub-Zone along with water from Kokkowa water supply system to be developed. The Yegu PS will be demolished when the Kokkowa water is available for Zones 1 and 3 by 2030. 7-1 Preparatory Survey for Greater Yangon Water Supply Improvement Project (Phase II) FINAL REPORT Source: METI Study Figure 7-1 Existing SRs of Zone 1 7.1.2 Existing Condition of Yegu PS Yegu PS receives raw water from Gyobyu and Hlawga (gravity) reservoirs and Nyaughnapin WTP and water from all these sources are mixed at Yegu PS before sending it to Kokine SR. Yegu PS consists of 2 systems: old and new systems/ There are 4 new pumps (installed in 2007) in the new system and all of them are in working condition. Of these, 2 pumps are duty and the other 2 are stand by), sending 20 MGD of water to existing Kokine SR through 1400 mm pipe. Water from Kokine SR is distributed via Shwedagon SR to entire southern and western areas of zone 1 excluding some eastern areas to which water goes directly from Yegu PS. There are 7 old pumps (initially installed in 1964 and changed in 1990) in the old system, of which only 4 pumps are in good condition. The old pumps are used to pump small amount of water to downtown area through 1050 mm pipe. 7-2 Preparatory Survey for Greater Yangon Water Supply Improvement Project (Phase II) FINAL REPORT Source: JICA study team Figure 7-2 Schematic Diagram Showing Water Distribution from Yegu PS Data on water quality in 2015 at Yegu PS is given in Table below. Water quality data indicates that despite mixing of water from three water sources, the maximum turbidity is 5.80 NTU and average turbidity is 2.71 NTU. In general, the water supplied is within the water quality standard. 7-3 Preparatory Survey for Greater Yangon Water Supply Improvement Project (Phase II) FINAL REPORT Table 7-1 Water Quality Data at Yegu PS in 2015 Source: YCDC 7.1.3 Existing Condition of Kokine SR (1) Outline The Kokine SR was constructed in 1926 for supplying water to high area at that time. The condition of structure itself is not known; however, based on discussion with YCDC no leakage is reported. Concrete test of the structure was carried out in May 2016 and it is observed that compressive strength of existing concrete is about 36 MPa, which indicates that concrete structure is strong enough. On the other hand, in 2007 about 1.5 m (5 feet) high deposition of silt was reported, resulting in decrease of its effective storage volume. It was once desilted in 2007; however, the silt could be again accumulated and therefore, periodical cleaning of this SR is required. More fundamentally, turbidity needs to be removed from the raw water in the WTPs. Table 7-2 Existing Characteristics of Kokine SR Item Specification Construction Year 1925 to 1926 Site Size 559 feet x 286 feet Structure Underground RC 7-4 Preparatory Survey for Greater Yangon Water Supply Improvement Project (Phase II) FINAL REPORT Item Specification Volume 90,920 m3 (20MG) Water Level HWL +42.7 m (140 feet), LWL +36.6 m (120 feet) Water Depth 6.1 m Inlet Pipe 1400 mm Steel Pipe from Yegu PS Existing Outlet Pipe 1050 mm Iron Pipe for Shwedagon SR 1050 mm Iron Pipe for north townships 1050 mm Iron Pipe for southwest townships Source: JICA Study Team (2) Retention Time Retention time of the Kokine SR (excluding small 1 MG capacity Shwedagon Pagoda SR, constructed in 1894) to the total demand of Zone 1 is given in the following Table. Retention time is more than 8 hours up to 2025, which is the minimum retention time for diurnal demand fluctuation. However, after 2025, additional SR capacities are required to maintain the retention time of 8 hours. Table 7-3 Forecast of Retention Time of The Kokine SR Item 2014 2025 2030 2035 2040 Daily Maximum Demand of 44 MGD 54 MGD 60 MGD 65 MGD 71 MGD total Zone 1 Retention Time* 11.0 hr 8.9 hr 8.0 hr 7.4 hr 6.8 hr *Retention time is calculated as 20 MG divided by daily maximum demand. Source: JICA Study Team (3) Leakage from the Reservoir In this Study, a survey was conducted to understand the situation of leakage in Kokine reservoir. At Kokine SR, the water level in reservoir was measured in order to check if there is reduction in water level even after stopping all the inflow to and outflow from this SR. For this purpose, the operation of Yegu PS was stopped and two inlet valves to Kokine SR were closed completely. Also, three outlet valves were closed completely. After closing all valves, the water level in Kokine SR was measured every 15 minutes. Two measurements were recorded, one of the water level gauge installed at reservoir and another measured manually. The change in water in Kokine SR for two cases is shown in Figure below. The brown line represents water level measured by gauge installed at SR, and blue line indicates the water level measured manually. It is observed that in both measurements, water level in SR reduces by about 8 cm/hr. Thus, the total drop in water level of Kokine SR at this rate would be about 192 cm/day which will result into loss of a large amount of water. 7-5 Preparatory Survey for Greater Yangon Water Supply Improvement Project (Phase II) FINAL REPORT Source: JICA Study Team Figure 7-3 Reduction in Water Level of Kokine SR Upon discussion with EDWS it was learnt that the bottom level of pipe connecting to check valve is at about 10 feet and if there is less than 4 feet of head over the check valve on SR side, the check valve does not close properly and may result into leakage through check valve. Considering the above explanation, the water level in SR was lowered (through supplying water) below the level of pipe connecting to check valve. Subsequently, after closing the outlet valves again, the reduction in water level was recorded to understand the situation of leakage in the SR without the influence of check valve leakage. The water level of Kokine SR thus recorded is shown in Figure below. In this case, the drop in water level of SR is observed as 6 cm/hr. Source: JICA Study Team Figure 7-4 Reduction in Water Level of Kokine SR without Influence of Check Valve 7-6 Preparatory Survey for Greater Yangon Water Supply Improvement Project (Phase II) FINAL REPORT (4) Reason of Leakage and Necessity of Reservoir Rehabilitation From above Figures, it is clear that the reduction in water level of SR is caused by leakage. However, it is not clear whether the leakage is through the valves or through the reservoir walls itself. It is possible that leakage occurs through inlet valves, check valve or outlet valves, as all of these structures are very old and may not be closing appropriately. It is also possible that there is leakage through the walls in reservoir itself. To confirm this, all the inlet and outlet valves will require to be changed first. Hence, it is proposed that during construction works, all the valves be changed first with new ones. Upon installation of new valves, the water level in SR needs to be monitored after closing all inlet and outlet valves. If the monitored data indicates reduction in water level of SR, then there is certainly leakage through the SR structure itself. In that case, the SR should be emptied, cleaned and checked for leakage areas. Locations of leakage need to be repaired necessarily to enable the use of this SR safely again. Depending on the leakage locations, repair methods shall be selected and repair be carried out. Available space is limited at Kokine SR, therefore attention need to be paid during construction works and required space need to be made available. Considering that concrete structure of Kokine SR is still strong enough, EDWS prefers to continue using this reservoir upon confirmation of leakage and rehabilitation (if required). 7.1.4 Existing Condition of Central SR and Shwedagon Pagoda SR It is located at the top of hill near the Shwedagon Pagoda.