Umiray-Angat Transbasin Tunnel Rehabilitation Project
I. BACKGROUND:
The Umiray River contributes about 20 – 30% of the raw water for Metro Manila. The diversion facilities which was constructed under the Umiray-Angat Transbasin Project (UATP) became operational on June 2000. The intake facilities is located at Umiray, General Nakar, Quezon, while the outlet facilities is located in Macua, Dona Remedios Trinidad, Bulacan. The water from Umiray River to Macua River is conveyed through a 13 km tunnel (4.30 m. diameter) across Sierra Madre mountains.
On November 29, 2004, typhoon “Winnie” has caused severe damages to our Umiray-Angat Transbasin Tunnel and its facilities resulting to the complete stoppage of operation particularly the conveyance of raw water from the Umiray River to the Angat Reservoir thru Macua River. Among the damages incurred are as follows:
1. Various MWSS and military equipment were washed out / lost due to flood;
2. Conveyance channel at the Tunnel Intake is covered with big boulders, logs and other debris;
3. The 13 km tunnel is clogged with boulders, logs and other debris;
4. The 5.50 km access road is not passable due to 31 landslides;
5. All bunkhouses were washed out; and
6. The concrete bridge (5 m. width x 30 m. length) leading to the tunnel outlet was totally washed out.
On November 29, 2004, typhoon “Winnie” has caused severe damages to our Umiray-Angat Transbasin Tunnel and its facilities resulting to the complete stoppage of operation particularly the conveyance of raw water from the Umiray River to the Angat Reservoir thru Macua River. Among the damages incurred are as follows:
1. Various MWSS and military equipment were washed out / lost due to flood;
2. Conveyance channel at the Tunnel Intake is covered with big boulders, logs and other debris;
3. The 13 km tunnel is clogged with boulders, logs and other debris;
4. The 5.50 km access road is not passable due to 31 landslides;
5. All bunkhouses were washed out; and
6. The concrete bridge (5 m. width x 30 m. length) leading to the tunnel outlet was totally washed out.
II. Rehabilitation Works:
A. Immediate Works (Phase 1):
Due to the clogging of the tunnel, the flow of raw water from the Umiray River to the Macua River was completely stopped resulting to a decrease in the volume of raw water available at Angat Reservoir and would mean a water shortage come dry season supplemented by the forecasted occurrence of El Nino by July 2005. To mitigate this water shortage, urgent works were done only to let the raw water flow again through the tunnel which is considered as Phase 1 of the rehabilitation works. Thus, MWSS together with its Concessionaires immediately undertook the following activities:
1. Hired the services of laborers consisting of local settlers in the area and the Dumagats for the manual clearing operation at the tunnel;
2. Contracted three (3) contractors of known experience in tunneling and access roads;
3. Hired the services of consultants to serve as Works Engineer and later to undertake the study/design of the permanent rehabilitation works;
4. Hired the services of one (1) Heavy Lift Helicopter for the airlifting of equipment at Umiray (inlet side). The Umiray area which is the inlet side of the tunnel could only be reached through the tunnel and since the tunnel is presently clogged, the only possible way is through the use of a helicopter; and
5. Requested for Approval/Clearance from the Office of the President to allow MWSS to undertake the immediate repair/rehabilitation works through “Negotiated Procurement” citing Section 53(b) of the Implementing Rules and Regulations of Republic Act 9184.
On March 17, 2005, after about three and a half (3.5) months of de-clogging works, the Umiray-Angat Transbasin Tunnel was finally cleared of logs and debris allowing the flow of raw water again from the Umiray River to the Macua River thru the tunnel, contributing additional 9 cms or approximately 780 million liters per day to the Angat Reservoir. Works done is only clearing of tunnel and stockpiling of silt, rocks, logs and debris on the river bank to let the water flow.
Due to the clogging of the tunnel, the flow of raw water from the Umiray River to the Macua River was completely stopped resulting to a decrease in the volume of raw water available at Angat Reservoir and would mean a water shortage come dry season supplemented by the forecasted occurrence of El Nino by July 2005. To mitigate this water shortage, urgent works were done only to let the raw water flow again through the tunnel which is considered as Phase 1 of the rehabilitation works. Thus, MWSS together with its Concessionaires immediately undertook the following activities:
1. Hired the services of laborers consisting of local settlers in the area and the Dumagats for the manual clearing operation at the tunnel;
2. Contracted three (3) contractors of known experience in tunneling and access roads;
3. Hired the services of consultants to serve as Works Engineer and later to undertake the study/design of the permanent rehabilitation works;
4. Hired the services of one (1) Heavy Lift Helicopter for the airlifting of equipment at Umiray (inlet side). The Umiray area which is the inlet side of the tunnel could only be reached through the tunnel and since the tunnel is presently clogged, the only possible way is through the use of a helicopter; and
5. Requested for Approval/Clearance from the Office of the President to allow MWSS to undertake the immediate repair/rehabilitation works through “Negotiated Procurement” citing Section 53(b) of the Implementing Rules and Regulations of Republic Act 9184.
On March 17, 2005, after about three and a half (3.5) months of de-clogging works, the Umiray-Angat Transbasin Tunnel was finally cleared of logs and debris allowing the flow of raw water again from the Umiray River to the Macua River thru the tunnel, contributing additional 9 cms or approximately 780 million liters per day to the Angat Reservoir. Works done is only clearing of tunnel and stockpiling of silt, rocks, logs and debris on the river bank to let the water flow.
B. Permanent Works (Phase2):
Since the immediate works done is only for the purpose of allowing the flow of raw water again into the tunnel, a permanent rehabilitation works has to be done to strengthen the stability of the structures to withstand future flood and typhoons. A Consultant was hired therefore to study and evaluate the existing structure including the hydrological component, and to undertake the detailed design for the complete rehabilitation works, as follows:
1. Complete restoration of the access road to tunnel outlet;
2. Construction of permanent RCDG Bridge for the tunnel outlet;
3. Widening of oxbow channel at the tunnel outlet;
4. Intake structures such as the various mechanical gates; trash rack, waterway protection works, retaining wall, ogee dam, etc;
5. Rehabilitation of mini-hydro plant;
6. Construction of log arresters;
7. Installation of power/communication cables inside the tunnel; and
8. Village/Housing relocation.
Since the immediate works done is only for the purpose of allowing the flow of raw water again into the tunnel, a permanent rehabilitation works has to be done to strengthen the stability of the structures to withstand future flood and typhoons. A Consultant was hired therefore to study and evaluate the existing structure including the hydrological component, and to undertake the detailed design for the complete rehabilitation works, as follows:
1. Complete restoration of the access road to tunnel outlet;
2. Construction of permanent RCDG Bridge for the tunnel outlet;
3. Widening of oxbow channel at the tunnel outlet;
4. Intake structures such as the various mechanical gates; trash rack, waterway protection works, retaining wall, ogee dam, etc;
5. Rehabilitation of mini-hydro plant;
6. Construction of log arresters;
7. Installation of power/communication cables inside the tunnel; and
8. Village/Housing relocation.
C. Project Cost: US$ 30 Million
D. Schedule of Detailed Design & Construction: 2009 – 2010
E. Project Update (as of May 31, 2008):
- FS and Preliminary Design already completed.
- Technical Proposal submitted by a private proponent, San Lorenzo Ruiz Builders (SLRB), is still being evaluated by MWSS.
- This Project is proposed to be implemented through BOT scheme.
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