Table 3.6 shows the sources of supply of the proposed project and indicates the range of flows coming from each throughout the year. However, operation of this project will be greatly influenced by the operation of the Joun Hydro Electric Power plant (HEP) system and by the season. These factors will also affect the water quality.
Upstream Joun Lake, the Karaoun Lake collects water from the Litani River impounding a total volume 220 Mm3 of water. Priority of allocation of this water is given to irrigation and drinking purposes. 30 Mm3 are used for irrigation in Tyre, Saida and other southern villages whereas a volume of 40Mm3 is to be maintained for the Lake. The remaining 150 Mm3 are used for generating hydroelectric power at the stations shown in Table 3 -26.
Table 3 26 Hydroelectric Power Plant Chracteristics
In the dry season, the main source of water will be the Karaoun Lake. Water will be drawn from the Karaoun Reservoir (capacity 220 Mm3).
In the wet season, the source may be both the Karaoun Lake and the Awali River. The Awali River is a mountain stream on the western side of the Mount Lebanon range. Upstream of the Joun Lake and the Awali HEP, the catchment area is about 300 Km2.
The flow of Awali is seasonal and highly variable, averaging 3.0 m3/s, but varying from 0.1 m3/s in late summer to 30 m3/s and over during spring runoff.
Some of the flow from Litani and most of the flow from the Awali are combined in Joun Lake (also known as the Awali compensation basin). This is located immediately downstream of the Awali HEP, before up to 30 m3/s of flow is passed through the existing Joun tunnel to the Joun HEP. Residual flow from the Awali River is passed along the natural river channel.
Figure 3 6 Schematic Drawing of Water Resources
The existing HEP system is operated as a power peaking system for approximately four hours per day. During periods of high flow in the Awali River (December to April), the final stage of the system (Joun HEP) may be operated 24 hours per day. Under these conditions, the maximum flow which can be diverted to the Awali project may have to be limited to 2.5m3/s for part of the 4 hour peak period of power generation. Table 3 -27 summarizes key factors determining source of water.
Table 3 27 Key Factors Determining the Source of Water
The raw water flow will be self-regulated at the Joun Regulation Structure by means of a level control valve.
The velocity limiting valves upstream are also designed to close in the event of failure of the level control valve.
This structure will normally be unmanned. It will be inspected for maintenance every month.
Tunnel and Pipelines
There is a risk of build-up of deposits at the low points in the tunnel system in the Joun – Ouardaniye inverted siphon and to a much lesser extent in the Nahr Damour inverted siphon. Slight opening of the washout valves at Wadi Abou Yabes and Nahr Damour every 6 (six) months will be sufficient to scour out any deposits.
It is recommended that the whole tunnel and pipeline system be emptied every 5 (five) years for an overall internal inspection. It can be partially drained by allowing the water level to be lowered by normal usage except for the Joun-Ouardaniye WTW section which would be drained from the 700mm washout at Wadi Abou Yabes, the 900mm washout at Nahr Damour inverted siphon and a number of washouts on the Khalde to Hadath/Hazmieh pipelines.
Air valves and 250 – 400mm diameter washouts will be provided at high and low points respectively along the proposed pipelines from Khalde to Hadath and Hazmieh. Washouts will discharge water to dry stream beds. Air valves will result in only occasional discharges of air which has come out of solution or entered the pipeline during maintenance, whilst the washouts will operate only during emergency or planned maintenance.
The tunnel system will also be inspected in the event of significant seismic activity.
The Ouardaniye WTW will be operated by a staff of 25 to 30 persons. It will operate automatically for 16 hours per day, with a shift system of staff covering operation outside normal working hours. The overall system control will be from a Central Control Room including monitoring and control of raw and treated water quality. Works throughput will be set daily to satisfy anticipated demand and the water levels in the Hadath and Hazmieh Reservoirs. In the event of the reservoirs and tunnel being full, the rising water level at the WTW outlet will be used to control throttling of the inlet flow at Joun.
The treatment plant is designed to have the capacity of treatment of 9m3/s flow of water if additional water resources are supplied in the future.
Table 3 -28 and 3 -29 summarize respectively the inputs and outputs arising during normal operation of the works and indicate the vehicular movements required. These are subject to modifications after final stage design.
Overflows capable of discharging a fraction of the WTW’s capacity (up to about 1000 l/s) during operational changes will be removed by a 600mm diameter pipeline following the route of the WTW access road and discharged to a dry stream bed and thence into the sea. Emergency drainage from the flocculators, clarifiers, rapid gravity filters and filter wash water will follow the same route.
During commissioning of the WTW and the conveyor system, production water will be discharged through the emergency outfall or through the washouts. Chlorinated water will be de-chlorinated prior to discharge.
Surface water drainage from the WTW will be designed for a storm with a 1 in 20 year return period and will be routed to Wadi Baraz to the north of the WTW site. At the lower end, the wadi will require improvement by the construction of a concrete channel to direct flow to the culverts under the coastal road and railway, and an outfall structure under the beach. Petrol/oil will be provided where appropriate and drainage from the area in front of the Chemical House will be separated and routed to a chemical drain system which serves the chemical loading and handling areas. The system will discharge to the sludge thickening plant for disposal to landfill with the sludge.
Foul sewage from the WTW will be collected and treated in accordance with accepted local technology. In the absence of a local sewer system, a properly designed septic tank or small treatment works will be installed.
Khalde Surge Structure
The Khalde Surge Structure will be unmanned. It will be inspected for maintenance annually. Detailed surge analysis will be used in the design process to ensure that the surge shaft structure will not overflow and flood adjoining land. The shaft and its compound will be equipped with appropriate safety measures to prevent the ingress of foreign bodies into the treated water.
The Khalde Measurement and Sampling Chamber will also be unmanned. However, as it is the point at which the Contractor will be contractually required to deliver treated water, it will be visited daily for water sampling. Upkeep and maintenance will be the responsibility of the Contractor.
Immediately downstream of this Chamber will be velocity limiting valves which will close in the event of catastrophic failure of the downstream pipelines.
Khalde Distribution Chamber
The operation of the unmanned Khalde Distribution Chamber will be the responsibility of the BMLWE, which will operate the distribution valves manually.
Hadath 90 and 125 and Hazmieh 90 Reservoirs
The Hadath and Hazmieh Reservoirs will be unmanned structures and also the responsibility of the BMLWWA. Information on water level and water quality will be transmitted to the Central Control Room at the Ouardaniye WTW. Emergency re-chlorination will be provided at the reservoirs using mobile facilities.