|Official name||Angat Dam|
|Location||Barangay San Lorenzo, Norzagaray, Bulacan, Philippines|
|Construction began||November 1961|
|Opening date||October 16, 1967|
|Construction cost||Php 315.344 Million|
|Dam and spillways|
|Base width||550 meters|
|Capacity||850 million cubic meters|
|Turbines||10 Vertical shaft, Francis turbine (Includes turbines from the main powerhouse and the auxiliary powerhouse)|
|Installed capacity||256,000 kW^1|
Angat Dam is a concrete water reservoir embankment hydroelectric dam that supplies the Manila metropolitan area water. It was a part of the Angat-Ipo-La Mesa water system. The reservoir supplies about 90 percent of raw water requirements for Metro Manila through the facilities of the Metropolitan Waterworks and Sewerage System and it irrigates about 28,000 hectares of farmland in the provinces of Bulacan and Pampanga.
Among the 2.5-meter high, six-span dam’s main features are easily deflatable and inflatable rubber body, resistance to sedimentation, economical and having auto-deflation system.
Angat dam has a normal high water level of 210 meters, according to the Philippine Atmospheric, Geophysical and Astronomical Services Administration (Pagasa).
It has three gates opening a total of 1.5 meters to gradually release water that had accumulated due to incessant rains during typhoons.
In comparison, Ipo Dam, which is downstream from Angat dam, has three gates and the 100.8 meters is its normal high water level. Ambuklao dam on the other hand, has two gates with the normal high water level (NHWL) of 752 meters. Binga dam which sits downstream from Ambuklao has three gates and the NHWL of 575 meters. San Roque dam, which was receiving water from Ambuklao and Binga, has the NHWL of 280 meters.
Built in 1926, 50 kilometers upstream from the Bustos Dam as a fixed type river weir without gates, the AARD, Angat Afterbay Regulator Dam (commonly known as Bustos Dam) is the longest rubber dam in Asia at 79 meters and the second largest in the world.. It has coordinates of 14°57'25"N 120°57'15"E serving nearby cities: Real, Quezon, Rodriguez (Montalban), Rizal, Antipolo City, Rizal.
In 1967, steel sector gates were installed on top of the regulator dam for the purpose of generating irrigation water, power supply and domestic water supply.
Emma hit Central Luzon in 1967, passing through the Angat Hydro-Electric Project and Dam of the National Power Corporation (NPC or Napocor) in Norzagaray, Bulacan. The heavy downpour caused the water in the Angat Dam reservoir to rise perilously to a danger height of 212 meters above sea level. Napocor caused the opening of the spillway gates to prevent an overflow of water from the dam.
The Engineering Construction, Inc. (ECI), which had been doing construction work also in Norzagaray, suffered losses to its equipment and properties when the extraordinary large volume of water rushed out of the spillway gates and hit ECI’s installations and construction works. National Power Corporation vs. Court of Appeals (G.R. No. L-47379, 16 May 1988).
At about 2100 hours on October 26, 1978, during the height of that infamous typhoon "KADING", NAPOCOR opened simultaneously all the three floodgates of the Angat Dam.
NPC started to open the three floodgates simultaneously from 1 meter to 8 meters at 0100 hours of October 27, 1978, until all floodgates were opened to the maximum of 14 to 14.5 meters by 0600 hours of the same day.
These acts of NPC resulted in the inundation of several towns in Bulacan near Angat Dam. Hardest-hit was Norzagaray, Bulacan. About 100 Garayenos died and million of pesos worth of properties (houses, farms, plants, working animals) were destroyed.
11 civil suits were filed against the electric corporation in the Regional Trial Court of Malolos.
NPC countered that there was very little opening of the spillways, ranging from 1 meter to 2 meters. But from midnight or from the first hours of October 27, 1978 the opening of all the three (3) spillways started at 5 meters and swiftly went as far up as 14 meters. The court noted that had the opening of all the three (3) spillways been made earlier and gradually, there would have been no need to open the same suddenly: "What made the situation worse was that the opening of the spillways was made at the unholy hours when residents were asleep. The plaintiffs all testified that they were never given any warning that the spillways would be opened to that extent. x x x” 
With its construction, the Bustos Dam’s height was increased by 2.5 meters and later renamed Angat Afterbay Regulator Dam, increasing the service area of the Angat-Maasim Rivers Irrigation System (AMRIS), which operates the AARD from 25,000 hectares in 1927 to 31,485 hectares in 20 towns in Bulacan and Pampanga benefitting 20,562 farmers.
The series of typhoons from 1968 to the early part of 1980 was damaging to the dam whose Bay 1 sector gate finally gave way in September 1990 after typhoon "Iriang" carried away the structure 250 meters downstream from its original post. The agency has undertaken temporary rehab works in the dam using their own budget and through funding assistance from the World Bank.
The present dam was rehabilitated by Kurimoto, LTD., Osaka, Japan , manufacturing date, as of May, 1997.
It has Washed Out, Intake, Sluice and Roller Gates sets. It's clear spans are 4.6% 1.53 meters. It's gate (opening) heights are 4.5 and 1.0 meters. The weight of the leafs are 5.4 and 1.0 tons. The operating speeds is 0.3 m./ min.
In 2001, The Japan International Cooperation Agency (JICA) has approved a P500-million grant-in aid to the government for the repair and improvement of the Angat Afterbay Regulatory Dam (AARD) in Bustos, Bulacan, the National Irrigation Administration (NIA) said here over the weekend.
^ The sum of both installed capacity. The main powerhouse has 200,000 kW (4 X 50,000 kW) installed capacity while the auxiliary powerhouse has 46,000 kW (3 X 6,000 kW, 1 x 10,000 kW, 1 x 18,000 kW) installed capacity.
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