04

Table 3.
1 Population Projection by City/Municipality Up to 2025 (1/2)
Average Annual
Historical Population Projected Population Growth Rate % to Region/Province
1995 2000 2000 2025
(Sep.) (May) 1995- 2000- 2010- Area Populatio Populatio
Census Census 2005 2010 2015 2020 2025 2000 2010 2025 2000 2025 (sq. km) n Density n Density
The Philippines 68,349 76,499 84,241 91,868 99,016 105,507 113,661 2.3% 1.8% 1.4% - - 294,454 260 386
Region IV 9,904 11,794 12,860 14,525 16,357 18,225 20,320 3.6% 2.1% 2.3% - - 46,844 252 434
NCR (MetroManila)
Cities
1) Las Pinas 413 473 609 759 953 1,114 1,290 2.8% 4.8% 3.6% 4.8% 9.8% 41.5 11,398 31,094
2) Manila 1655 1581 1,473 1,345 1,286 1,146 1,011 -0.9% -1.6% -1.9% 15.9% 7.7% 38.3 41,279 26,387
3) Makati 484 445 443 432 426 391 356 -1.7% -0.3% -1.3% 4.5% 2.7% 29.9 14,883 11,905
4) Mandaluyong 287 278 281 277 280 264 246 -0.6% -0.1% -0.8% 2.8% 1.9% 26 10,692 9,473
5) Marikina 357 391 436 472 530 556 576 1.8% 1.9% 1.3% 3.9% 4.4% 38.9 10,051 14,819
6) Muntinlupa 400 379 468 558 639 682 720 -1.1% 3.9% 1.7% 3.8% 5.5% 46.7 8,116 15,416
7) Paranaque 391 450 507 554 637 683 725 2.9% 2.1% 1.8% 4.5% 5.5% 38.3 11,749 18,930
8) Pasig 471 505 555 595 658 679 694 1.4% 1.6% 1.0% 5.1% 5.3% 13 38,846 53,379
9) Valenzuela 437 485 560 624 719 773 823 2.1% 2.5% 1.9% 4.9% 6.3% 47 10,319 17,507
10) Caloocan 1023 1178 1,339 1,471 1,701 1,833 1,956 2.9% 2.2% 1.9% 11.9% 14.9% 55.8 21,111 35,045
11) Pasay 409 355 359 353 344 313 282 -2.8% -0.1% -1.5% 3.6% 2.1% 13.9 25,540 20,276
12) Queｚon 1989 2174 2,285 2,343 2,533 2,554 2,549 1.8% 0.7% 0.6% 21.9% 19.4% 166.2 13,081 15,338
T3-1
Sub-Total 8316 8694 9,314 9,783 10,705 10,987 11,228 0.9% 1.2% 0.9% 87.5% 85.5% 555.5 15,651 20,212
Municipalities
1) Malabon 347 339 369 390 414 411 404 -0.5% 1.4% 0.2% 3.4% 3.1% 23.4 14,487 17,267
2) Navotas 229 230 244 253 267 264 258 0.1% 0.9% 0.1% 2.3% 2.0% 2.6 88,462 99,170
3) Pateros 55 57 57 56 57 55 52 0.7% -0.2% -0.4% 0.6% 0.4% 10.4 5,481 5,042
4) San Juan 124 118 109 98 93 82 71 -1.0% -1.9% -2.1% 1.2% 0.5% 10.4 11,346 6,866
5) Taguig 381 467 588 711 897 1,055 1,227 4.2% 4.3% 3.7% 4.7% 9.3% 33.7 13,858 36,419
Sub-Total 1136 1211 1,366 1,508 1,729 1,867 2,013 1.3% 2.2% 1.9% 12.2% 14.5% 80.5 15,043 25,007
Metro Manila Total 9452 9933 10,680 11,291 12,434 12,854 13,241 1.0% 1.3% 1.0% 100.0% 100.0% 636 15,574 20,652
Cavite Province
Cities
1) Cavite 93 99 97 94 92 89 85 1.3% -0.6% -0.6% 4.8% 2.6% 10.9 9,083 7,806
Municipalities
1) Bacoor 251 306 362 421 492 564 638 4.0% 3.2% 2.8% 14.8% 19.4% 25 12,240 25,504
2) Imus 177 195 240 289 334 379 424 2.0% 4.0% 2.6% 9.5% 12.9% 89 2,191 4,768
3) Kawit 57 63 67 71 75 79 80 2.0% 1.2% 0.8% 3.1% 2.4% 13.4 4,701 6,006
4) Noveleta 27 32 35 37 41 44 47 3.5% 1.5% 1.5% 1.6% 1.4% 5.6 5,714 8,304
5) Rosario 54 74 83 90 104 119 135 6.5% 1.9% 2.7% 3.6% 4.1% 3.6 20,556 37,366
Sub-Total 566 670 792 908 1,046 1,134 1,240 3.4% 3.1% 2.1% 32.5% 40.2% 136.6 4,905 9,077
Total 659 769 879 1,002 1,138 1,251 1,368 3.1% 2.7% 2.1% 37.3% 42.8% 147.5 5,214 9,273
Other Municip. 951 1294 1,478 1,409 1,577 1,736 1,882 62.7% 57.2%
Cavite Total 1610 2063 2,357 2,411 2,715 2,987 3,250 5.1% 1.6% 2.1% 100.0% 100.0% 1287.6 1,602 2,556
Table 3.1 Population Projection by City/Municipality Up to 2025 (2/2)
Average Annual
Historical Population Projected Population Growth Rate % to Region/Province
1995 2000 2000 2025
(Sep.) (May) 1995- 2000- 2010- Area Populatio Populatio
Census Census 2005 2010 2015 2020 2025 2000 2010 2025 2000 2025 (sq. km) n Density n Density
Rizal Province
Cities
1) Antipolo 346 471 692 984 1,376 1,860 2,453 6.4% 7.6% 6.3% 27.6% 47.8% 306.1 1,539 8,015
Municipalities
1) Angono 59 75 90 104 124 142 160 4.9% 3.3% 2.9% 4.4% 3.1% 26 2,885 6,149
2) Baras 20 25 28 31 35 39 41 4.6% 2.1% 2.0% 1.5% 0.8% 23.4 1,068 1,773
3) Binangonan 141 188 209 228 264 296 323 5.9% 1.9% 2.4% 11.0% 6.3% 72.7 2,586 4,445
4) Cainta 202 243 338 454 587 733 894 3.8% 6.4% 4.6% 14.2% 17.4% 10.2 23,824 87,634
5) Cardona 36 39 41 42 44 44 43 1.6% 0.7% 0.1% 2.3% 0.8% 31.2 1,250 1,378
6) Jala-Jala 20 23 25 27 30 31 32 2.8% 1.7% 1.2% 1.3% 0.6% 49.3 467 658
7) Rodriguez(Montalb 80 115 130 144 173 201 228 7.5% 2.3% 3.1% 6.7% 4.4% 312.8 368 730
8) Morong 36 42 43 44 47 48 47 3.1% 0.5% 0.5% 2.5% 0.9% 37.6 1,117 1,261
9) Pililla 37 45 48 51 57 60 63 4.0% 1.3% 1.3% 2.6% 1.2% 74 608 847
10) San Mateo 99 136 159 181 218 255 290 6.6% 2.9% 3.2% 8.0% 5.6% 64.9 2,096 4,467
11) Tanay 69 78 89 99 111 119 125 2.5% 2.4% 1.6% 4.6% 2.4% 243.4 320 515
12) Taytay 145 198 226 255 303 349 392 6.4% 2.5% 2.9% 11.6% 7.6% 38.8 5,103 10,101
13) Teresa 24 30 33 36 40 44 46 4.6% 1.7% 1.8% 1.8% 0.9% 18.6 1,613 2,498
T3-2
Sub-Total 968 1237 1,460 1,697 2,032 2,362 2,686 5.0% 3.2% 3.1% 72.5% 52.3% 1002.9 1,233 2,678
Rizal Total 1314 1707 2,152 2,681 3,409 4,222 5,139 5.4% 4.6% 4.4% 100.0% 100.0% 1309 1,305 3,924
Quezon Province
Cities
1) Infanta 40 51 57 62 69 77 85 5.0% 1.9% 2.2% 3.0% 3.8% 134.6 379 631
Municipalities
1) General Nakar 21 24 28 31 34 38 41 2.7% 2.6% 1.9% 1.4% 1.8% 1343.3 18 31
2) Real (out of Basin) 28 31 37 42 47 52 57 2.1% 3.1% 2.0% 1.8% 2.5% 563.8 55 101
Sub-Total 49 55 65 73 82 90 98 2.3% 2.9% 2.0% 3.3% 4.4% 1907.1 29 52
Total 89 106 121 135 151 149 154 3.6% 2.4% 0.9% 6.3% 8.1% 2041.7 52 75
Other Municip. 1,937 2,011 2,073 93.7% 91.9%
Quezon Total 1551 1679 1,848 1,974 2,087 2,178 2,255 1.6% 1.6% 0.9% 100.0% 100.0% 8706.6 193 259
Source: (1) "1995 Census-based City/Municipal Population Projections" NSO, December 1999
(2) "1995 Census-based National, Regional and Provincial Population Projections" NSO, June 1999
Note: (1) Population projection by city/municipality up to 2010 was adopted from Source (1) after replacing 2000 figures with Population Census 2000.
For this replacement, average annual growth rates projected by NSO were applied up to 2010.
(2) For Population in 2015 and 2020, the Region/Province population projection of the Source (2) was adopted.
For the projection of City/Municipality level in 2015, 2020 and 2025, the ratios of City/Municipality to each region/province were projected
and applied. In this computation, the aggregate of the ratios of City/Municipality was adjusted to be 100% in total.
This was based on the observation that these ratios of City/Municipality to Region/Province are stable in the long term.
(3) Projection of 2025 population :
Philippines: Growth rate of 1.5% per annum shown in LTPDP 2025 was applied to 2020 projected population.
Region: Growth rates of 2015-2020 were applied.
City/Municipality: As stated above (2).
Table 3.2 GDP/GRDP Projections for 2000-2025
Growth
2000 2005 2010 2015 2020 2025 2000-
The Philippineｓ
Agriculture, Fishery and Forestry 189,826 209,478 220,164 231,394 243,198 255,603 1.2%
Industrial Sector 332,483 448,251 617,032 849,364 1,169,175 1,609,406 6.5%
Service Sector 439,443 578,664 767,105 1,016,911 1,348,067 1,787,062 5.8%
Total GDP 961,752 1,236,393 1,604,300 2,097,669 2,760,440 3,652,072 5.5%
Average growth (% p.a.) 4.8% 5.2% 5.3% 5.5% 5.6% 5.8%
NCR (Metro Manila)
Agriculture, Fishery and Forestry 0 0 0 0 0 0 0
Industrial Sector 111,669 144,337 191,828 254,943 338,825 450,307 5.7%
% share to the nation 33.4% 32.2% 31.1% 30.0% 29.0% 28.0%
Service Sector 182,193 243,802 328,073 441,472 594,068 799,410 6.1%
Total of NCR 293,862 388,140 519,901 696,416 932,894 1,249,716 6.0%
% share to the nation 31.4% 32.4% 33.2% 33.8% 34.2%
Region IV (Southern Tagalog)
Agriculture, Fishery and Forestry 34,404 37,346 38,279 39,236 40,217 41,222 0.7%
Industrial Sector 63,960 86,312 118,812 163,548 225,129 309,896 6.5%
Service Sector 50,014 67,732 92,055 125,115 170,046 231,114 6.3%
Total of Region IV 148,378 191,389 249,146 327,898 435,391 582,232 5.6%
% share to the nation 15.5% 15.5% 15.6% 15.8% 15.9%
T3-3
Table 3.3 Alternative Population Projection of Antipolo
Census Population (in thousand) Population density (persons/sq. km) Population growth rate (% per annum)
Area 1975 1980 1990 1995 2000 1975- 1980- 1990- 1995- 1975-
(sq. km) (May 1) (May 1) (May 1) (Sep. 1) (May 1) 1975 1980 1990 1995 2000 1980 1990 1995 2000 2000
MetroManila
Cities
Las Pinas 41.5 82 137 297 413 473 1,976 3,301 7,157 9,952 11,398 10.8% 8.0% 6.8% 2.8% 7.3%
Marikina 38.9 168 212 310 357 391 4,319 5,450 7,969 9,177 10,051 4.8% 3.9% 2.9% 1.8% 3.4%
Pasig 13.0 210 269 398 471 505 16,154 20,692 30,615 36,231 38,846 5.1% 4.0% 3.4% 1.4% 3.6%
Municipalities
Taguig 33.7 74 134 267 381 467 2,196 3,976 7,923 11,306 13,858 12.6% 7.1% 7.4% 4.2% 7.6%
Rizal
Municipalities
Angono 26.0 18 27 46 59 75 692 1,038 1,769 2,269 2,885 8.4% 5.5% 5.1% 4.9% 5.9%
Cainta 10.2 37 59 127 202 243 3,627 5,784 12,451 19,804 23,824 9.8% 8.0% 9.7% 3.8% 7.8%
San Mateo 64.9 39 52 82 99 136 601 801 1,263 1,525 2,096 5.9% 4.7% 3.8% 6.6% 5.1%
Taytay 38.8 58 75 112 145 198 1,495 1,933 2,887 3,737 5,103 5.3% 4.1% 5.3% 6.4% 5.0%
Total of eight cities/ municipalities 267 686 965 1,639 2,127 2,488 2,569 3,614 6,139 7,966 9,318 7.1% 5.4% 5.4% 3.2% 5.3%
cf: Antipolo 306.1 41 69 208 346 471 134 225 680 1,130 1,539 11.0% 11.7% 10.7% 6.4% 10.3%
Antipolo population in 2025 = 471 x (1+5.3%) ^ 25 1,713 thousand
Source: Each Population Census of NSO.
T3-4
Table 3.4 Assumed Wastewater Volume
Water Supply Sewerage
Treated
Groundwater
Wastewater Volume Sewer
Water Volume (MLD) 1) Infiltration Total Wastewater (MLD)
Year (MLD) 2) 3) (MLD) by coverage 4)
(MLD)
STP
Ave. daily Billed 27% of JICA MP
Area Billed water This Study %
demand Water x 0.7 Wastewater 1995
2000 Total 1,433 3,663 1,003 271 1,274 125 10%
East 683 1,519 478 129 607 18 3%
West 749 2,145 524 142 666 107 16%
2005 Total 1,740 3,783 1,218 329 1,547 284 18%
East 722 1,569 505 136 641 103 16%
West 1,019 2,215 713 193 906 181 20%
2010 Total 2,210 4,250 1,547 418 1,965 648 33%
East 883 1,698 618 167 785 400 51%
West 1,328 2,553 929 251 1,180 248 21%
2015 Total 2,919 5,033 2,043 552 2,595 2,473 1,037 40%
East 1,243 2,144 870 235 1,105 575 52%
West 1,675 2,889 1,173 317 1,489 462 31%
2020 Total 3,754 5,866 2,628 710 3,337 2,034 61%
East 1,723 2,693 1,206 326 1,532 843 55%
West 2,031 3,174 1,422 384 1,806 1,192 66%
2025 Total 4,886 6,980 3,420 923 4,344 2,631 61%
East 2,413 3,447 1,689 456 2,145 1,180 55%
West 2,473 3,533 1,731 467 2,198 1,451 66%
Note: 1) Water Volume is assumed under this Study.
2) Wastewater Volume and 3) Groundwater infiltration are assumed in the same manner as adopted in JICA Study 1995.
4) Sewer Coverage by concessionare is referred to targets under Concession Agreement.
Expressed as a percentage of the total population in the designated city/municipality
connected to the Concessionaire's water system at the time of the target.
Target coverage in 2025 was assumed as the same figure in 2020
Table 3.5 Sewer Coverage Targets under Concession Agreement
Service Target
City/Municipality
2001 2006 2011 2016 2021
(West Zone)
NCR Pasay 0% 0% 0% 16% 95%
Callocan 3% 2% 2% 32% 79%
Las Pinas 0% 0% 0% 0% 50%
Malabon 2% 2% 2% 38% 94%
Valenzuela 0% 0% 0% 24% 59%
Muntinlupa 0% 44% 57% 54% 61%
Navotas 3% 3% 3% 36% 90%
Paranaque 0% 0% 0% 0% 52%
Cavite Cavite City 0% 0% 0% 0% 0%
Bacoor 0% 0% 0% 0% 0%
Imus 0% 0% 0% 0% 0%
Kawit 0% 0% 0% 0% 0%
Noveleta 0% 0% 0% 0% 0%
Rosario 0% 0% 0% 0% 0%
(East Zone)
NCR Mandaluyong 0% 0% 100% 100% 100%
Marikina 0% 0% 0% 0% 0%
Pasig 0% 41% 68% 68% 68%
Pateros 0% 60% 100% 100% 99%
San Juan 0% 0% 100% 100% 100%
Taguig 0% 52% 75% 84% 100%
RIZAL Antipolo 0% 0% 0% 0% 0%
Cainta 0% 0% 0% 0% 14%
Angono 0% 0% 0% 0% 0%
Baras 0% 0% 0% 0% 0%
Binangonan 0% 0% 0% 0% 0%
Cardona 0% 0% 0% 0% 0%
Jala-Jala 0% 0% 0% 0% 0%
Morong 0% 0% 0% 0% 0%
Pililla 0% 0% 0% 0% 0%
Rodoriguez 0% 0% 0% 0% 0%
San Mateo 0% 0% 0% 0% 0%
Tanay 0% 0% 0% 0% 0%
Taytay 0% 0% 0% 0% 15%
Teresa 0% 0% 0% 0% 0%
(Common Concession Area)

NCR Quezon City
East 0% 0% 83% 87% 98%
West 0% 0% 0% 0% 54%
Manila
East
West 55% 71% 77% 83% 91%
Makati
East 22% 52% 100% 100% 100%
West
East 3% 16% 51% 52% 55%

West 16% 20% 21% 31% 66%
Sewerage service: The Concessionaure shall offer to supply sewerage services to all customers
in the Service Area who have sewerage connections for domestic sewerage and industrial
effluents compatible with available treatment processes.
CHAPTER IV SITE CONDITIONS OF PROJECT AREA
4.1 General
The Project Area covers the whole Agos River Basin and the area through which
the Kaliwa-Taytay Waterway passes.
This Chapter IV describes the site conditions of the Project Area including the
coastal conditions of Infanta Peninsula, which have been clarified through the 2nd
Field Investigation conducted in 2002.
4.2 Topographic Condition

The proposed Project contemplates to convey the water resources of the Agos River
Basin having a total catchment area of 940 km2 to Metro Manila. From the scale
of the catchment area, it appears that the Agos River Basin can be included in the
Major River Basins in the Philippines, since a catchment area of the Amnay-Patric
River Basin, the smallest catchment of the 20 Major River Basins, is 993 km2 that
is almost same as that of the Agos River Basin.
The Agos River is the downstream river course from the confluence of its two
major tributaries, namely the Kanan and Kaliwa Rivers. The Agos River has a river
course length of about 17 km to the river mouth. In the nearby confluence, it
dissects the Siera Madre Mountain Range with peak elevations of more than 1,000,
and it finally drains into the Pacific Ocean. The alluvial plain spreads along the
lowermost reach where there exist the two Municipalities, General Nakar and
Infanta. The Agos damsite is selected about 1km downstream of the confluence,
where the river bed elevation is about 40 m. One of the focuses of the 2nd Field
Investigation is the coastal change that might be cause by the construction of Agos
dam as discussed in the succeeding Section 4.7.
The Kaliwa Low Dam site is located on the Kaliwa River, about 10 km upstream of
the confluence. The river bed elevation is at El. 95 m. The Kaliwa Low Dam
site is topographically characterized by the steep slopes on both abutments thereof.
The Kaliwa Low Dam and Kaliwa-Taytay 1st Waterway are planned to be
developed in the Stage 1 Development of the Project.
The intake structure of the Kaliwa-Taytay Waterway is situated on the right bank of
the Kaliwa Low Dam site. The waterway tunnel (Tunnel No.1) initially takes a
southern route to run through the mountainous area on the right bank of the Kaliwa
River Basin and then the western direction to pass through the mountainous area of
400 m to 600 m in elevation which is northernmost parts of catchment of the
Laguna Lake. After going down along the moderate slope, the waterway reaches
the proposed Valve House No.1 site at Barangay Lagundi of Morong, Rizal
Province, whose ground elevation is in a range of 110 to 130 m.
4-1
The water treatment plan site is selected at the hilly area of 85 m to 105 m in
Morong, Rizal Province. After passing through the water treatment plant site in
Morong (Morong WTP), the waterway goes down to the low-lying area of 45 m to
50 m in elevation, which is mainly used for residential areas and paddy fields
where a pipeline is planned to be installed. The waterway again goes through the
mountainous area of 110 m to 230 m in elevation for a section of about 5.3 km till it
finally reaches the proposed service reservoir at Taytay (Taytay Service Reservoir)
in Rizal Province.
4.3 Hydrology
4.3.1 Rainfall
The rainfall data at 19 stations in and around the Agos River Basin were collected
in the Master Plan Study and Feasibility Study stages. The annual basin average
monthly rainfall of four (4) catchment areas in the Kaliwa River Basin were
estimated by means of the Thiessen Polygons method as summarized in the
following table:
Basin Average Monthly Rainfall
(Unit: mm)
Limutan Lenatin Kaliwa Low Kaliwa
Month
River Basin River Basin Damsite Confluence
Jan 194.4 143.1 168.7 199.3
Feb 119.8 89.9 105.8 127.2
Mar 100.3 76.5 88.6 103.7
Apr 105.9 84.8 93.1 106.4
May 223.0 190.1 188.5 191.7
Jun 405.3 359.2 337.6 320.2
Jul 509.2 460.8 423.1 396.7
Aug 510.6 456.8 423.6 390.3
Sep 461.0 410.5 387.8 373.2
Oct 496.6 397.6 425.2 458.5
Nov 369.9 278.0 317.2 363.1
Dec 270.8 204.7 244.3 296.8
Total 3,767 3,152 3,204 3,327
As shown in the above table, the annual rainfall in the Kaliwa River Basin range
from 3,200 mm to 3,800 mm, while the mean annual rainfall at Infanta situated
close to the Agos River mouth is about 4,000 mm for the period from 1930 to 2000
as tabulated in Part-C of Volume III. The isohyetal map prepared in the 1981
JICA study, which is illustrated in Table 2.2, indicates that the high annual rainfall
of more than 6,000 mm takes place in the Kanan River Basin
4.3.2 Low Flow
The streamflow data at 8 streamflow gauging stations were collected in the Master
Plan Study and Feasibility Study stages. The purpose of low flow analysis is to
estimate the long-term discharges at the planned dam and weir sites to be utilized
for the water balance and reservoir operation studies at the proposed weir and dam
sites in the Agos River Basin.
4-2
The Tank model method was used to generate the Kaliwa River low flow series.
The runoff analysis was carried out during the Master Plan Study stage as described
in detail in Part-C of Volume III and its results are summarized below.
(1) Runoff Analysis
The method of the runoff analysis adopted in the Study is as follows:
a) The tank model parameter of the Kaliwa River Basin was decided for the
Limutan and Lenatin streamflow gauging stations where discharge
measurement records are available.
b) The long-term discharge at Laiban damsite was estimated by summing up
the long-term discharge records at Limutan and Lenatin streamflow gauging
stations.
c) The tank model analysis for the Kaliwa Low Damsite and Kaliwa
confluence (before joining the Kanan River) used the parameters estimated
for the Limutan streamflow gauging station.
d) The runoff at the Agos confluence (just downstream of the Kaliwa-Kanan
confluence) and Agos Dam site was derived from the correlation with the
long term records at the Banugao streamflow gauging station situated in the
lower Agos basin (correlation by catchment area).
e) The runoff of the Kanan River Basin was estimated as the balance between
the runoff estimated at Agos confluence and Kaliwa confluence.
As discussed in the succeeding Chapter VI, the two (2) water resource facilities in
the Agos River Basin, namely Kaliwa Low Dam on the Kaliwa River and Agos
Dam on the Agos mainstream, are planned to be developed under the Project. The
estimated annual mean monthly discharges at the Kaliwa Low Dam site and Agos
Dam site are shown in the following table:
Mean Monthly Discharges Estimated at Selected Sites

(Unit: m3/sec)
Location Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Mean
Kaliwa Low
25.2 18.9 13.5 10.0 10.6 20.3 33.1 38.0 43.2 46.0 41.7 34.3 27.9
Dam site
Agos
155.4 104.9 75.5 47.6 42.1 51.3 74.5 88.5 92.2 161.6 221.8 244.4 113.3
Dam site
(2) Flow Duration Curve

The flow duration curves at the Kaliwa Low Dam site and Agos Dam site are
shown in Figure 4.1 and summarized in the following table:
4-3
Flow Duration Curve
(Unit : m3/sec)
Kaliwa Low Agos
Duration
Damsite Damsite
10% 56.63 236.87
20% 44.67 183.56
30% 36.62 140.30
40% 27.39 107.86
50% 22.52 85.27
60% 17.60 70.73
70% 14.23 57.14
80% 10.18 43.45
90% 6.40 30.24
95% 5.22 23.64
100% 3.27 7.58
The minimum flow to be released from each dam site to the downstream is planned
herein at 10 % of the 80 % discharge, which is a guideline figure used in several
previous studies and is adopted in this Study as a uniform criterion at the phase of
the Master Plan Study. Based on this criterion, the minimum flow rate to be
assumed at each site is calculated as follows:
- Kaliwa Low Dam site : 10.18 m3/sec x 10% = 1.02 m3/sec
- Agos damsite : 43.45 m3/sec x 10% = 4.35 m3/sec
4.3.3 Flood
The purpose of flood flow analysis was to estimate probable flood discharges and
hydrographs to be utilized in the studies relevant to spillway design and flood
control work in the lower Agos. The Study also included the estimate of probable
maximum flood (PMF).
(1) Statistical Analysis of Flood Records at Banugao Gauging Station
The maximum discharge records on the Agos River Basin are available at Banugao
gauging station for 26 years. For estimating the probable floods, two theoretical
probability distributions, Log Pearson Type III and Gumbel methods, were applied
to the annual maximum discharges. The results of the frequency analysis are
shown in the following table:
Probable Floods at Banugao Streamflow Gauging Station
Probable Discharge (m3/sec)
Return Period
Log Pearson Type III Gumbel
2-year 1,535 1,690
5-year 2,651 2,979
10-year 3,530 3,832
20-year 4,474 4,650
50-year 5,845 5,709
100-year 6,988 6,503
200-year 8,230 7,294
1,000-year 11,542 9,126
10,000-year 17,472 11,744
4-4
As shown in the above table, the Log Pearson Type III method gives higher values
than those results by the Gumbel method for a recurrence period of 100-year and
larger recurrence periods. Therefore, the Log Pearson Type III method was
applied to estimate the probable floods.
(2) Probable Flood at Proposed Damsites
The probable floods at proposed damsite were estimated from the corresponding
floods at Banugao gauging station and adjusted by the drainage area ratio using the
following Creager’s equation:
q = 0.503 x C x A x 0.386b
b = -0.93578 x A-0.048
where, q : Specific flood discharge (m3/sec/km2)
A : Drainage area (km2)
C : Coefficient obtained from the Banugao flood
The estimated probable floods at the respective damsites are shown in Table 4.1.
(3) Probable Maximum Flood (PMF)
The previous study adopted the maximum daily rainfall of 1,168 mm recorded
between July 14 and July 17, 1911 at Baguio as the probable maximum
precipitation (PMP). The PMP was then transposed to the Agos catchment.
Consequently, the PMF at the proposed Agos damsite was estimated at 17,300
m3/sec applying the PMP to the Nakayasu’s synthetic unitgraph.
In this Study, the probable maximum flood (PMF) at the proposed Agos damsite
was estimated applying the same methodologies and procedures as those in the
previous 1981 JICA study on the Agos hydropower project. As a result, the PMF
at the Agos damsite is revised to be about 17,100 m3/sec because of a small
difference of catchment area at the Agos damsite. On the other hand, the
10,000-year probable flood has been so often used as the maximum limit instead of
the PMF in designing large dams in the Philippines. As shown in Table 4.1, the
10,000-year probable flood at the Agos Dam site is derived to be about 17,000
m3/sec that almost coincides with the PMF of 17,100 m3/sec. In this Study,
accordingly, it is determined to adopt the PMF of 17,100 for the design of the Agos
Dam and its spillway taking the safer side design thereof. The hydrograph of PMF
is given in Figure 4.2.
4.3.4 Sediment Yield
(1) Review of Previous Sediment Study
The sediment analysis for the Agos River Basin is available in the feasibility study
on Agos River Hydropower Project (JICA 1981), which was carried out between
November 1978 and May 1980. Most of the subsequent studies assessed the
sedimentation of the Agos River Basin with reference to the analysis results of the
previous JICA study.
In the previous JICA study, 36, 11 and 19 sediment samples were collected at
Mahabang Lalim gauging station on the Agos River, Binugawan gauging station on
the Kanan River and Nio gauging station on the Kaliwa River, respectively.
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Based on those data, the previous study estimated the annual sediment yield,
consisting of suspended load and bed load, to be 557 m3/km2/year.
As the site reconnaissance conducted by helicopter in July 2000, on the other hand,
it was observed that the Kaliwa flow contained much sediment, while the Kanan
River water seemed comparatively transparent probably because of the smaller
rainfall in that month. Further, the sediment yield of 557 m3/km2/year might be
slightly small as compared with annual sediment yield rates estimated for the
existing and proposed reservoir dam projects in Luzon Island (see Table 4.2). A
feasibility study on the Agos Hydropower Project (ELC, 1991) recommended to
adopt a sediment yield rate of 1,000 m3/km2/year, although it is based on a
rule-of-thumb estimate.
(2) Estimate of Sediment Yield
Based on the sediment sampling data collected during the field investigation period
(May-August 2001 and January-April 2002), sediment sampling was conducted at
the 4 new stream gauging stations shown in Figure 2.2. Then, the sediment yield
was estimated at Agos Dam site, Kanan confluence and Kaliwa confluence as
summarized below:
Estimated Sediment Yield Rates
Annual Sediment
Catchment Annual Sediment Yield
Mean Yield/Area/
Location Area per Year
Discharge Discharge
(km2) (m3/sec) (103m3) (m3/km2) (m3/km2/m3/sec)
Agos Dam site 860 113.3 899.5 1,046 9.23
Kanan Confluence 393 74.5 434.7 1,106 14.85
Kaliwa Confluence 465 37.4 434.4 934 24.98
As far as the results of analysis of discharge and sediment rate relationship indicate,
the sediment yield rate per catchment area is almost similar in the Kanan and
Kaliwa River Basins, to be around 1,000 m3/km2/year or 0.9-1.1 mm/year in
denudation rate. Sediment yield at the Agos Dam site was adopted as 1,046
m3/km2/year.
Owing to the limited number of sediment sampling data, the above estimate still
contains uncertainties. Nevertheless, a certain extent of errors in the estimate can
be absorbed by a large volume of dead storage afforded in the Agos Reservoir.
Under the condition of the above estimated yield rate (1,046 m3/km2 /year), the
horizontal sediment level after 100 years is El.86.72 m (90 million m3). Even if
the rate is double, the sediment level is El.102.69 m (180 million m3), which is still
lower than the MOL (El.133.0 m) of the Agos Reservoir.
The catchment area at the Agos River mouth is 940 km2, including the residual
basin of 80 km2 downstream from the Agos Dam. The sediment yield at the river
mouth is estimated at 980,000 m3/year, applying the same yield rate as estimated
for the Agos Damsite, of which the yield from the residual basin is 83,000 m3.
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(3) Trap Efficiency of Reservoir
The sediment deposit volume of the reservoir is determined by sediment yield from
upstream basins and trap efficiency of the reservoir. The trap efficiency was
estimated by using the Brune’s method.
The trap efficiency and sediment trap volume for 100 years, estimated for the Agos
reservoir, are as follows:
Trap Efficiency and Trap Volume in Agos Reservoir
Item Unit Value
Reservoir Volume/Inflow 0.26
Catchment Area km2 860
Trap Efficiency % 93.0
Sediment Yield 103m3/100-year 90,000.0
Trap Volume 103m3/100-year 83,700.0
Sediment to Agos Downstream 103m3/100-year 6,300.0
After construction of the Agos Dam, sediment release from the Agos Reservoir is
some 6,300 m3/year. Adding the yield from the residual basin of 84,000 m3/year,
the total sediment yield at river mouth is derived to be 90,000 m3/year.
4.3.5 Examination of Water Loss in Limestone Areas in Kaliwa River Basin
The spot discharge measurement was carried out at several points on the Kaliwa
River as discussed in Subsection 2.4.3. Preliminary findings interpreted from the
measured data are described below.
Flow Distribution on the Lenatin River (Upstream from Laiban Dam)
a) Loss of flow at the limestone mass between Sta.1 and Sta.2 (Place A in
Figure 2.3) seems obvious (See Line 1- 2 of Table 4.3). It is noted that
flow at Sta.3 (downstream end of the Lenatin River) is also less than that at
Sta.1 (See Line 1-3 of Table 4.3), though the drainage area of Sta.3 is much
larger (131 km2 at Sta.3 and 75 km2 at Sta.1). This indicates that some
extent of leakage loss not returning to Sta.3 seems to be taking place. Sta.3
is just upstream of the Laiban Damsite.
Notes: 1) Specific discharge of the Lenatin River is far less than that of the Limutan
River (See Lines 3 and 4 of Table 4.3). This may be partly due to loss of flow
in the stretch between Sta.1 and Sta.3.
2) During the field reconnaissance, it was observed there is a possibility of water
infiltration at the Batangas Creek (upstream of confluence with San Andres
Creek, Laiban Creek, and Unnamed Creek situated between the former two
creeks). It could not be confirmed whether water returns back to the Lenatin
River.
b) There are two possibilities: (i) water lost in the limestone mass returns back
to the Kaliwa River channel in the reach downstream from the Laiban
Damsite, and (ii) water is lost southward into the Masungit limestone mass
and further to the Laguna de Bay Basin. Discharge measurement
conducted this time could not define which is the possible path of the
leakage loss.
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c) In both the cases of (b) above, leakage water does not return the points
upstream of the Laiban damsite. This infers a doubt for water leakage
from the Laiban reservoir.
d) However, this issue does not deny the feasibility of the Laiban Dam. It
was assessed in the earlier studies that limestone masses distribute at
scattered locations and occur at relatively higher elevations. This suggests
that provision of grout curtain walls at selected areas may be effective for
ensuring the reservoir water-tightness. Further hydrological and
geological investigations are required to look into this issue in more detail.
Flow Distribution on the Kaliwa River
a) No limestone mass occurs in the area downstream from Sta.8 (Kaliwa Low
Dam No.1 Site, see Figure 2.3). Hence, this point can be regarded as the
‘benchmark point’ in evaluating the distribution of the Kaliwa River flow.
b) First, discharges between Sta.(3+4) (Lenatin-Limutan Confluence, simple
addition of Sta.3 and Sta.4) and Sta.5 (2 km downstream of
Lenatin-Limutan Confluence) were compared. It was found that discharge
at Sta.5 was larger in most cases*1 (See Line 5-(3+4) of Table 4.3). Hence,
the flow at Sta.5 was regarded as the base flow for comparison with the
flow at downstream points. Theoretically, the flow at the downstream
points should be larger than the flow at Sta.5, if there is no leakage loss in
the stretch between the two places.
Note: *1 An exception is the case of 18-May, which may be due to error in discharge
measurement
c) Loss of flow was evaluated by dividing the river stretches into the following
three sections:
- Stretch 5-6: Sta.5-Sta.6 (Just upstream of Sabalanasasin Creek
Confluence)
- Stretch 6-7: Sta.6-Sta.7 (Daraitan Gauging Station)
- Stretch 7-8: Sta.7-Sta.8 (Kaliwa Low Dam No.1 Site)
d) The data show that loss of flow in the Stretch 5-6 is apparent (See Line 6-5
of Table 4.3). It is supposed that water infiltrates into the Daraitan
limestone mass occurring on the east bank (See Figure 2.3).
e) The data show that loss in the Stretch 6-7 itself is not so obvious (See Line
7-6 of Table 4.3). However, this is partly due to inflow from the
Sabalanasasin Creek, which is a major tributary flowing in just downstream
of Sta.6. It would be more conservative to assume some extent of leakage
taking place also in the Stretch 6-7.
f) In the Stretch 7-8, there is a notable increase of flow, 30.6% in average (See
Line 8-7 of Table 4.3). Since drainage areas of Sta.7 and Sta.8 are almost
similar, it is inferred that the increase of flow is due to extra inflow of
seepage water originated from the upstream reaches (Stretches 5-7). Also,
flow at Sta.8 is more than that at Sta.5 (See Line 8-5 of Table 4.3). These
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indicate that there seems less possibility of water leakage lost outside the
Daraitan limestone mass (leakage to the Laguna de Bay Basin).
Note: Table 4.3 also shows the comparison of specific discharges for reference. In
general, the implications readable from the data are almost similar to those
described above. A matter to be noted is that, although specific discharge is almost
comparable between Sta.5 and Sta.8 on the average, the specific discharge at Sta.8
is less than that at Sta.5 on two days (25-May and 3-June) (See Line 8-5 of Table
4.3). This does not directly imply that lower specific discharge at Sta.8 is due to
leakage loss outside the basin. Nevertheless, this should be confirmed by
collecting more number of discharge measurement data henceforward.
It is supposed that most of water lost in the Stretches 5-7 in the upstream part of
Daraitan limestone mass returns back to the Daraitan limestone gorge upstream of
Sta.8. As far as the present data indicate, there is no serious concern for the water
loss from the Daraitan limestone mass to the outside basin (water loss directing
southward). The observation from geological viewpoints also suggests less
possibility of water loss through this limestone mass (See Section 4.4 hereinafter).
4.4 Geology
The proposed sites of the Project facilities can be largely divided into three (3) sites,
namely (i) Agos Dam on the Agos mainstream, (ii) Kaliwa Low Dam on the Kaliwa
River, and (iii) Kaliwa~Taytay Waterway consisting of the Tunnel No.1 between
the Kaliwa Intake structure site situated on the left bank of the Kaliwa Low Dam
and Valve House No. 1 at Lagundi, and various waterway structures such as
Morong WTP, Pipeline No.1 and No.2, Valve House No.2, Antipolo Pump Station,
Antipolo Service Reservor and Taytay Service Reservoir in the Morong-Teresa-
Antipolo-Taytay area.
This Section describes the geological conditions of the Project facilities stated
above that were clarified in the geological investigation performed under the Study.
4.4.1 Regional Geology
The Philippine Islands are situated on the circumpacific seismic belt, which is one
of the areas in the world that is most conspicuously subject to earthquake.
Geologically, the Project Area is located in the Central Basin, which is
characterized by Paleogene and older clastic and volcanic deposits. The Central
Basin is bounded by the Philippine Fault system (Philippine Fault Zone: PFZ) on
the east and northeast (a branch of which was identified near Infanta) and by the
Valley Fault system on the west and southwest. Morphology indicates that the
fault near Infanta has been active in the comparatively recent geological times.
Further, there are other two faults, starting from the Marikina damsite (previously
proposed by MWSP III) in the SSW direction, forming the Marikina graben. Thus,
the Project Area can be divided into the following four morphologically and
geologically differing zones:
• The rugged mountains of the Sierra Madre between the Philippine Fault
(Infanta Fault) and the Faults running from Marikina in the SSW direction
• A triangular hilly zone between the SSW Faults and the Marikina graben
• The Marikina graben
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• Gentle hills located west of the Marikina graben, descending to the alluvial
plain of Manila Bay
Land of the Project Area, from the lithological viewpoint, consists mainly of eight
(8) geological units, namely Quaternary Alluvium, Laguna Guadalupe, Tignoan,
Madlum, Angat, Maybangain, Kinabuan, and Barenas-Baito Formations.
4.4.2 Active Fault and Seismic Risk
The previous studies pointed out that the Project Area is situated within a zone of
active tectonics represented by the Philippine Fault (Philippine Fault Zone: PFZ)
and the Valley Fault system as shown in Figure 4.3. Especially along the
Philippine Fault, many large-scale earthquakes were recorded in the past, and the
relative movement of 6 cm was observed in the period of 1991 to1993. Therefore,
it can be said that the Philippine Fault has a potential to cause the very high seismic
activity. According to the PHILVOLCS data, several “active faults” or “assumed
active faults” are shown in the Project Area, and some of them pass near the
proposed Agos damsite and No.1 Tunnel route.
(a) Agos Damsite
In the case an active fault passes through the nearby location of the proposed Agos
damsite, the following two technical problems need to be solved:
i) Seismicity caused by earthquake along active fault, and
ii) Deformation in dam-foundation caused by the movement of active fault
Analysis for i) above can be made through seismic study as described in Clause (c)
of this Subsection 4.4.2 hereinafter. With regard to ii) above, no firm analysis
method had been suggested in the previous studies. In this Study, therefore, analysis
of aerial photographs was carried out to confirm the distribution and certainty of
active fault. The photographic analysis was carried out by carefully observing and
interpreting the photographs to assess the lineament and topographical features of
the Quaternary formations in the area of 10 km in radius around the Agos damsite
as shown in Figure 4.4. The certainty of active fault is classified into three
categories of Class I, II, III. Class I means the high certainty and Class III
indicates the low certainty for active fault in the Japanese standard.
An assumed active fault is drawn 500 m upstream from Agos Dam axis almost
along the Kanan River according to the data gathered from PHILVOLCS as
A ” in Figure 4.3.
indicated as “○
As a result, however, the fault indicated as “○A ” is classified to be the Class III,
since no specific factors classifiable as active fault were found in the photo
interpretation. Accordingly, it is judged to be an lineament formed by old faults
based on the field reconnaissance. Therefore, it can be said that the active fault
which will have to be carefully treated does not exist near the Agos Dam site.
Meanwhile, the Agos damsite is located only 7-8 km distant from the active
Philippine Fault Zone (Infanta Fault), and large earthquakes attributed to the active
fault have been recorded in 17th to 19th century. The photographic analysis
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classifies the Infanta Fault into Class I, while other two (2) faults near the Infanta
Fault into Class II. Therefore, the high seismic risk should be taken into account in
the feasibility-grade design as described in the Clause (c) of this Subsection 4.4.2.
(b) Tunnel No.1 Route
The Tunnel No.1 is laid out between Kaliwa Intake Structure at the Kaliwa Low
Dam site and Valve House No.1 at Lagundi. The total length is about 27.5 km.
The tunnel will encounter a fault designated by PHILVOLCS (2000) as the
“assumed active fault” at around 25 km point from the Kaliwa Intake Structure as
indicated as “○B ” in Figure 4.3. The fault can be identified clearly through the
satellite imagery interpretation. The location of the assumed active fault is
indicated in the geological profile along the Tunnel No.1 as shown in Figure 4.9.
(c) Estimate of Earthquake Coefficients
As described above, the Project Area is situated within a zone having a high risk of
seismicity. Acceleration value of previous proposed damsites around the Project
Area is shown in Table 4.4. According to the previous studies, most of the
proposed five damsites: i.e. Laiban, Agos, Kanan B1, Kanan No.1 and Kanan No.2,
would be subject to high peak acceleration and exposed to generally high degree of
seismicity. The 1981 JICA and 1991 ELC studies suggested to adopt 0.58 g for
peak acceleration and 0.15~0.20 g as the design earthquake coefficient for the Agos
Dam. In this Study, the seismic conditions were re-analyzed on the basis of the
earthquake records for the period of 1907 to 2000. As a result, it can be said that
the values derived in the previous studies are appropriate in terms of static seismic
design. In the next detailed design stage, however, a dynamic analysis is required
to design the Agos Dam to confirm the stability of the dam body in case of
occurrence of large-scale earthquake.
4.4.3 Geology of Project Sites
(1) Agos Dam Site
(a) General
The Agos damsite is located just downstream of the confluence of the
Kanan and Kaliwa Rivers, about 15 km distant from the river mouth. The
comparatively steep geographical features continue from the damsite for a 8
km downstream stretch. The foundation rocks around the damsite consist
of the Maybangain Formation and Tignoan Formation of early to middle
stage in the Palaeogene Period.
In the Master Plan Study stage, the following four (4) geological issues
were pointed out for the Agos damsite selected in the previous studies:
i) Thick river deposit in the riverbed
ii) Thick residual soil or decomposed rock zone on the right abutment
iii) Fault in the riverbed and on the right bank
iv) Assumed active fault along the Kanan River by PHILVOLCS
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Taking the above issues into consideration, the alternative damsite was
selected in this Study, which is located 700 m downstream from the
aforesaid damsite. The geotechnical investigation including core drilling,
seismic prospecting, laboratory test and analysis of aerial photographs was
carried out for the two (2) alternative damsites, the upstream and
downstream damsites, during the 2nd Field Investigation in 2002.
(b) Foundation Rock
The base rock of the both damsites mainly consists of firm and impermeable
sandstone and conglomerate. Most parts of the rock are massive, showing
little bedding plane except for those observed in intercalation of thin layers
of fine sandstone and shale. The fresh part of the foundation rock at the
both damsites seems to have the sufficient shear strength to support the
proposed fill type dam according to the results of laboratory tests. With
regard to the foundation along the plinth of concrete face dam (CFRD)
proposed in this Study as discussed in the succeeding Chapter VI, the
decomposed rock and/or residual soil zone and cracky weathered rock zone
will have to be removed, because they have the medium to high
permeability and low shear strength. Moreover, the dam foundation
treatment will be performed by curtain grouting from the upper surface of
the plinth into the fresh rock zone that indicates more than 5 Lugeon value.
(c) Thick Sand and Gravel Layer of Riverbed
In this Study, additional core drilling and seismic refraction prospecting
investigations were carried out to confirm the thickness of riverbed deposit.
As a result, river deposit of sand and gravel has a thickness of 30 to 40 m
along the both dam axes as shown in Figure 4.6.
From the geographical point of view, the depth of river deposit seems too
thick as compared with the river width of some 120 m. The large
thickness of the river deposit, however, can be explained by the marine
transgression, according to the results of the geomorphological analysis
carried out in this Study. About 20,000 years ago, the sea level was
assumed to be more than 100 m below the present sea level, and the present
V-shaped valley was formed along the Ago River. The thick sand and
gravel might be deposited in the valley with the transgression after the
glacial period.
(d) Potential Landslide on the Abutments
On the right abutment of the upstream damsite, zone of residual soil and
decomposed rock is 20 to 30 m thick in the area below EL.120 m. On the
other hand, the zone is observed on the left abutment with 10 to 20 m
thickness. These weathered zones including talus and terrace deposits
developed at the foot of the slopes should be excavated during construction
of the Agos Dam.
It appears that such a thick weathered layer is caused by the landslide.
According to the analysis of aerial photographs, several potential landslide
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blocks are observed around the Agos damsites as shown in Figure 4.5.
Especially, the potential landslide blocks distribute on the both banks of
upstream Agos damsite. On the other hand, there seems to be no factor to
show the slope instability except only one unclear landslide block along the
downstream dam axis.
As for the upstream damsite, most of potential landslide areas will be
excavated during the construction of the Agos Dam and spillway. The
remaining volume of landslides which needs to be treated is estimated at
980,000 m3 on the minimum. Thus, the excavation works at the Agos
Dam site needs to be performed paying enough attention to the stability of
the potential landslide areas.
(e) Distribution of Fault
Six (6) low velocity zones are indicated in the base rock by seismic
exploration survey along the upstream dam axis. Out of them, the five (5)
zones may be faults extended in the E-W direction as shown in Figures 4.5
and 4.6. The faults extending in the E-W direction do not have any serious
problems for the stability of proposed Agos Dam, since they cross with dam
axis at a right angle. The replacement and grouting works, however, will
be required to prevent the water leakage from passing from upstream to
downstream of the dam body.
Only the one fault located in the middle part of the right abutment could be
investigated in detail by core drilling conducted under the Study.
Therefore, other four (4) faults will have to be investigated in more detail in
the next detailed design stage.
(f) Comparison of Upstream and Downstream Damsites
The upstream site is recommended in consideration of the following
geological conditions:
i) Both damsites are considered to have almost same conditions with
respect to the thickness of riverbed deposit, shear strength of base
rock and existence of faults.
ii) In case of the downstream damsite, most of potential landslide
blocks distributing around the Agos damsite will be submerged by
the reservoir water. The treatment cost of the potential landslides for
the downstream damsite is estimated to be much higher than that for
the upstream dam site.
iii) The left bank of the downstream damsite is formed by a narrow
ridge which may cause a large hydraulic gradient.
iv) There is not sufficient space to economically lay out the spillway,
diversion tunnel and powerhouse in case of the downstream damsite.
Figure 4.5 presents a distribution map of potential landslides and faults
around the Agos damsite. In addition, the profile of upstream damsite is
shown in Figure 4.6. The results of the detailed comparison of the two (2)
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alternative damsites for the Agos Dam are described in the succeeding
Chapter VI.
(2) Agos Reservoir Area
(a) General
The Agos damsite is located just downstream of the confluence of the
Kanan River and Kaliwa Rivers, about 15 km distant from the river mouth.
In case of FSL EL.159 m, the reservoir extends to 12 km upstream along the
Kanan River by air distance and 15 km upstream along the Kaliwa reaching
around the Barangay Daraitan. Situated in deep narrow gorge, the reservoir
area is surrounded by high ridges. Several landslide blocks are observed on
the abutments of the reservoir area by aerial photographs. Geologically,
most of the reservoir area is composed of the sandstone, conglomerate,
shale, pyroclastic rock which belong to the Maybangain and Tignoan
Formations in the Cretaceous to Miocene age. The fresh part of the rocks
is generally firm and impervious.
(b) Geological Assessment on Possibility of Water Leakage from
Daraitan Limestone Area
The most important geological concern of the reservoir area is the Daraitan
limestone mass situated at the Kaliwa upstream part in the reservoir area
with a width of 1.5-2.0 km, which generally distributes in the N-S direction.
As for the Agos Reservoir area and Kaliwa Low Dam site, the previous
studies focused on the possibility of water leakage toward south through the
soluable cavities in the limestone area. Many cavities, holes, and
water-spring points exist in the Daraitan limestone area. This indicates the
possibility of existence of many natural water routes inside the deeper part
of limestone mass.
In this Study, two (2) core drillings of 350 m and electric prospecting of 5
km in total length were carried out to confirm the continuity of the Daraitan
limestone mass toward south. The two-dimensional resistivity profiling
method was adopted to conduct the electric exploration.
It is considered that the water leakage problem from the limestone mass is
negligible from the results of the geological investigation as well as the
discharge measurement results along the Kaliwa River that are described in
the foregoing Subsection 4.3.5, as explained below:
i) The loss of water through the fault zone or limestone in the northerly
direction is physically impossible.
ii) The permeable limestone mass wedges out towards the south before
reaching the Makmira village at the 3 km southern point from
Kaliwa River as shown in Figures 4.7 and 4.8. The other
impervious beds distribute between the Makmira village and Laguna
Bay, which would stop water flow in the direction.
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iii) No loss of the river water flow in the sections of limestone area was
observed according to the result of discharge measurement (see
Subsection 4.3.5 ).
iv) Groundwater level seems to be shallow around Makmira to Santiago
village area because of existence of many surface water streams.
This fact indicates the distribution of the impervious bed rocks.
The distribution of limestone mass and water condition around the Daraitan
limestone area are presented in Figure 4.7. Figure 4.8 shows a profile of
the Daraitan limestone area.
(3) Kaliwa Low Dam Site
The site is located on the Kaliwa River with the river bed elevation of
around EL.95 m, approximately 5 km downstream of the Barangay Daraitan
located between the Ligundinan and Queboroso creeks, both being the right
bank tributaries of the Kaliwa River. The distribution of stiff rock forms
comparatively narrow valley around the site.
The Kaliwa Low Dam site consists mainly of firm conglomerate, sandstone,
shale that belong to the Maibangain Formation of the early Palaeogene
Period. As for the upper layer of conglomerate, the matrix part has a less
strength as compared with the hard gravel part. The foundation rock is
mostly massive and seems to have enough shear strength and low
permeability. Most of foundation rock around the dam axis indicates low
Lugeon value of less than 5.
The weathered bedrock is deeper on the right bank and the slope is gentler
than that on the left bank. The weathered rock zone of approximately 5 m
thickness in the minimum should be excavated in the construction. The
thickness of riverbed deposit (sand and gravel) is 1 to 2 meters.
The Kaliwa Intake Structure is proposed to be provided on the right bank of
the Kaliwa Low Dam site. The base rock consists mainly of old sandstone
and conglomerate that have enough bearing capacity to support the
proposed intake structure. The surface weathered zone at the site seems
to be comparatively thin at 5 to10 m or less in thickness and needs to be
removed in the construction.
(4) Kaliwa-Taytay Waterway
(a) Tunnel No.1
The 27.5 km long Tunnel No.1 is laid out between the Kaliwa Intake
Structure and Valve House No.1 at Lagundi. The proposed Tunnel No.1
route is geologically assessed as follows:
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i) Owing to alignment along the mountain ridges, there will be no
particular problem in view of ground cover and unbalanced ground
water pressure.
ii) The Tunnel No.1 will pass through the relatively homogeneous and
hard geological layers of the Cretaceous to Old Tertiary Period, not
encountering the Quarternary layers. According to the result of
laboratory test in this Study, the unconfined compressive strength of
foundation rock is estimated at 410-570 kgf/cm2. It is considered
that tunneling by TBM would be effective although the values are
derived from the limited number of core pieces sampled on the
tunnel route. On the other hand, the previous studies indicated that
some parts of foundation rock of the tunnel route have higher
unconfined compressive strength values of 500 to 700 kgf/cm2.
iii) In the fault-fracture zones and limestone sections, there may be
difficulties in the tunnel construction due to excessive water seepage
and unstable ground.
In the 17.5-22.0 km section from the Kaliwa Intake Structure, the
large Masunguit limestone body is chopped up on the surface. The
elevation of the bottom of this limestone mass seems to be higher
than EL. 200m, which is approximately 100m higher than the
elevations of the tunnel route.
In the next detailed design stage, it is required to clarify in more
detail the distribution of the limestone area.
iv) The tunnel will encounter a fault defined by PHILVOLCS (2000) as
“assumed active fault” at 25 km point from the Kaliwa Intake
Structure. Therefore, the tunnel route was aligned to cross the fault
at a right angle so as to decrease the tunnel distance which might be
affected by the suspected fault. NATM is recommended for the
construction of the upstream tunnel section of the fault.
v) In the 0-3.0 km section from the Kaliwa Intake Structure, an
attention needs to be paid to the unexpected fault with inflow of
confined hot water, since a confined hot spring was observed at a
point of about 600 m upstream from the Kaliwa Low Dam site
during the field reconnaissance conducted under the Study. The
spring seems to have the relation with the lineaments in the 0 to 3.0
km section of the Tunnel No.1 route from the Kaliwa Intake
structure.
Figure 4.9 shows the geological profile along the No.1 Tunnel.
(b) Valve House No.1
In the 2nd Home Office Work, the Valve House No.1 is newly proposed to
be constructed in the depressed area in Lagundi instead of the Lagundi
powerhouse as discussed in succeeding Chapter VI. It is required to carry
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out the geotechnical investigation at the Valve House No.1 site in the next
detailed design stage. From the geomorphological point of view, the
surface layer or several meters in thickness seems to consist of overburden
material such as plastic clay. Bed rock line will emerge in around 5-10 m
depth below the surface, although thick weathered rock distributes above
the bed rock line. The said bed rock and weathered zone seem to have
enough bearing capacity to support the proposed structure. The ripper
or/and blasting will be required for excavation of the bed rock.
(c) Morong Water Treatment Plant
A total of 1500 m x 650 m space in net plant compound area will be
acquired to construct the Morong WTP. The site is located in hilly area
mostly formed by the Quarternary deposits. These deposits belong to the
Guadalupe Formation composed mainly of tuffaceous sediments, tuffaceous
sandstone and tuff breccia except for weathered part near the surface zone.
The fresh part of said sediments have the sufficient bearing capacity to
support the proposed structure. The excavation by blasting will be
necessary at the hill side in the southern part because of existence of hard
basalt mass, while most of other areas will be able to be excavated by
blading and ripping by bulldozer. While, the ground will provide the good
basement for embankment except for the soft alluvial deposit poorly
distributed in the northern part of the proposed area.
(d) Valve House No.2
The Valve House No.2 is proposed at the low flat area formed by alluvial
deposits such as soft clay, silt or sand materials. The surface zone above
alluvial deposit seems to be 5-10 m or less in thickness and piling works are
recommended to support the proposed structure.
(e) Antipolo Pump Station
The structure is estimated to need a 150 m x 120 m space in the gentle-hilly
area. The ground mainly consists of compacted gravelly sand which is
mostly of weathered part of volcanic sediment. The upper zone of 4 m in
thickness consists of soft plastic clay as overburden. The ground below
the 4 m depth from the surface has enough bearing capacity in which the
N-value is around 40 to 50. On the other hand, small portion of
construction area seems to be located on the low flat area located near a
creek. The piling works will be required in case the main structure is
founded on the alluvial area.
(f) Antipolo Service Reservoir
The Antipolo Service Reservoir site is situated on the top of hill to have a
space of 600 m x 110 m. The basement is composed of extremely
weathered pyroclastic sediments. According to the results of core drilling,
soft overburden material exists in the depth of 0.80 m from the ground
surface. The weathered tuff breccia emerges in the depth of 5 to 20 m
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from the ground surface, which has the N value of 50. For excavation of
the planned reservoir, bulldozer and/or ripping are deemed to be suitable.
(g) Tunnel No.2
The Tunnel No.2 is laid out to pass through under the Antipolo plateau to
reach the Taytay Service Reservoir. The total length is about 5.3 km.
The proposed Tunnel No.2 route is geologically evaluated as follows:
i) In most of tunnel formation, the foundation seems to be composed
of hard and impervious rocks which belong to the Kinabuan
Formation of the Cretaceous to Old Tertiary Period. While, the
limestone mass distributes in the 0 to 0.7 km section from the
upstream tunnel portal.
ii) In the 1.3 to 3.3 km section from the upstream tunnel portal, there is
a potentiality that the Guadalupe Formation exists instead of the
Kinabuan Formation. The Guadalupe Formation is composed of
complex mixture of varied materials including soil, soft rock and
hard rock. The lowest layer of the Guadalupe Formation is
confined aquifer which supplies water to the wells in the residential
area of Antipolo plateau. The groundwater may have a head of
around 150 to 170 m according to the previous report (Groundwater
Development in Metro Manila, JICA, 1992). The subsurface
geological investigation is required to be performed in the next
detailed design to clarify the groundwater condition.
iii) Faults distribute at 0.3 km, 0.7 km and 3.6 km points from the upper
tunnel portal. In the fault zones, the tunnel excavation may
encounter the difficulties due to the excessive water seepage and
unstable ground.
(h) Taytay Service Reservoir
The excavation and embankment works will be required to provide the
Taytay Service Reservoir with a s total pace of about 780 m x 290 m. The
site is located around the boundary between gentle hilly area and a little
steep hilly area located near the housing land. The basement of the
excavation portion consists mostly of weathered rock belonging to the
Kinabuan Formation of the Cretaceous to early Paleocene. Bed rock line
emerges in around 10-15 m depth on the average below the ground surface,
although thick weathered rock indicating N-value of 50 distributes above
the bed rock line. The excavation will be conducted by ripper in the
shallow ground zone, while blasting will be necessary in case excavation
area reaches the fresh rock zone.
(i) Pipeline (WTP - Antipolo SR)
A total of 9.3 km long Pipeline No.1 is aligned to connect the Morong WTP
and Valve House No.2 sites, and Valve House No.2 and Antipolo Service
Reservoir sites. While 63% of the pipeline route passes through the
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gentle-hilly area, the remaining 37% is aligned on the low-flat area. The
low-flat area seems to be composed of soft clay, silt or sand. During the
construction, the excavation with sheetpiling is recommended for latter part
covering 37 % of the total pipeline route.
4.4.4 Construction Materials
(1) Agos Dam
Table 4.5 shows the necessary volume of construction materials and recommended
sources for the Agos Dam. The Agos quarry site is selected just upstream of the
confluence of the Kaliwa and Kanan Rivers. Besides, rock material can be
obtained from the excavation of dam foundation, spillway and diversion tunnel.
The fresh rock at these sites consists mainly of sound sandstone and conglomerate
with unconfined compressive strength of 500-600 kgf/cm2, which is hard and stable
enough for rockfill material to be used for embankment of the Agos Dam.
According to the previous 1981 JICA study report, however, the unconfined
compressive strength is derived to be 1160 to 1430 kgf/cm2 from the laboratory
tests on the 3 core pieces sampled from the nearby place of the Agos quarry site.
On the other hand, many calcite veins are observed in the base rock around the
southern part of the Agos quarry site. This may become the factor which will
cause weathering of rock material. In the detailed design stage, the additional
geological investigations including laboratory test will have to be carried out to
confirm the distribution of the calcite vein area in the quarry site and its durability
against weathering.
Filter and coarse aggregate materials will be acquired from riverbed deposit
which can be excavated at the damsite along the Agos River, as well as crashed
rock obtained from the Agos quarry site.
As for the impervious material, the highly to completely weathered rock
distributing around the Agos dam abutments will be used. The above extremely
weathered rock (residual soil) should be blended with gravel collected from river
deposit and/or crashed rock fragments.
(2) Kaliwa Low Dam
The construction materials required for the Kaliwa Low Dam include those to be
used for random fill, impervious fill, riprap of the dam body as well as concrete
aggregates for the Kaliwa Intake Structure.
The random fill and rock materials can be acquired from the excavation of the
Kaliwa Intake Structure and Tunnel No.1. The residual soil of extremely
weathered zone at the bank slopes will be used as the impervious material. The
riverbed deposit material around the damsite is suitable for concrete aggregates.
Rocks from the excavation of tunnel and intake are suitable for concrete aggregate
after crushing. To obtain the concrete aggregates to be used for construction of
the Kaliwa Intake Structure and lining of Tunnel No.1, the rock quarry site was also
selected 500 m downstream from the Kaliwa Low Dam site in this Study. The
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quarry site is composed of firm and stable sedimentary rock such as sandstone,
conglomerate and hard shale.
4.5 Water Rights in Agos River Basin

4.5.1 Granted Water Rights
The National Water Resources Board (NWRB) granted six (6) water rights for
irrigation, power and water supply purposes in the Kanan, Kaliwa and Agos Rivers.
The approved water rights are listed in the table below. No water right has been
granted on the use of groundwater in General Nakar and Infanta, Quezon.
List of Approved Water Rights

Amount of
Structure/
Permittee Source Location Purpose Water Granted
Facility
( m3/sec)
National Irrigation Agos R. Infanta Irrigation Intake 2.250
Administration
Farm Systems Agos R. Brgys. Irrigation Pump 0.270
Development Corp. Anoling &
Bangklos in
General
Nakar
National Power Kanan R. Bo. Matatio Power Dam 93.000
Corporation in General (proposed)
Nakar
MWSS Kanan R. General Water Supply Dam 38.000
Nakar (proposed)
Municipality of Kanan R. General Power Dam 38.000
General Nakar & Nakar (proposed)
Province of Quezon
MWSS Kaliwa R. Laiban, Water Supply Dam 23.000
Tanay (proposed)
Data Source: NWRB
Among the above permittees, only the National Irrigation Administration (NIA) is
using the water beneficially for irrigation. No development has been made yet by
the other permittees.
With the water right, NIA irrigates the entire service area of Agos River Irrigation
System covering 1,400 hectares of farmlands of Infanta and Real, Quezon.
The Farm Systems Development Corporation (FSDC) was already abolished.
Their water rights are usually transferred to NIA or Irrigators Associations. In this
case, however, there was no transfer of water right according to the records of
NWRB.
On the water right of MWSS in the Kanan River, there was a Memorandum of
Agreement (MOA) between MWSS and the Municipality of General Nakar in
August 1997. MWSS agreed to permit the local government unit (LGU) to use its
water right on Kanan River up to the year 2025 for the purpose of power generation
and water supply. The MOA however stated that the water shall be made available
to MWSS once they decide to develop and tap the Kanan River before 2025.
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In view of the above, the Municipality of General Nakar applied for a water right,
which was approved and granted 38 m3/sec for power generation purposes only.
In June 1999, the request for amendment of the water permit issued to the
Municipality of General Nakar on the Kanan River for power generation purpose to
include the Province of Quezon as Co-Permittee was approved by NWRB.
While the National Power Corporation (NPC) has withdrawn the Kanan Project
from the list of the projects for their immediate implementation.
4.5.2 Pending Applications of Water Rights
In 1998, there was a request for amendment of water permit issued to the
Municipality of General Nakar and Province of Quezon on the Kanan River in the
amount of 38 m3/sec to 93 m3/sec for power generation purpose. According to the
records of NWRB, the request is still pending.
Several water permit applications have been filed and these applications were
endorsed to the deputized agencies of NWRB for clearance. The pending water
permit applications are listed below:
Pending Water Permit Applications

Water Permit Name of Applicant Location
Application No.
10700 MWSS General Nakar
2482 Infanta-General Nakar Infanta
Water District
6547 Municipality of Infanta Infanta
83771 Aluyon-Burdias Farmers Infanta
Irrigation Association
83772 Sikap at Tiyaga ng mga General Nakar
Magsasaka
3640 Bisig at Pag-asa Farmers General Nakar
Association, Inc.
8007 Jaime V. Portales General Nakar
Data Source: NWRB
4.6 Water Quality in Agos River Basin

In the previous study of the Manila Water Supply Project III, water quality of the
Kaliwa River (samples collected in 1981 to 1983) is summarized as follows:
(a) Color readings ranging from 5 to 1000 color units
(b) Iron content from 0.05 to 3.5 mg/l
(c) Alkalinity ranging from 100 to 200 mg/l as CaCO3
(d) Hardness appears to be moderate with a low of around 70 and a high of
about 100 mg/l as CaCO3
(e) pH from 7.8 to 8.4
(f) Turbidity from a low of 0.2 to a maximum in excess of 420 turbidity units,
with a mean of 3 NTU
(g) No pesticides and herbicides are at detectable level
(h) Total organic carbon (TOC) varying from 0.6 to 5.9 mg/l
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The said report describes that additional sampling during 1985 and 1986 gave
similar results for the turbidity, i.e. 3 NTU as the mean turbidity, with the 80th
percentile of samples at 10 NTU. The condition of the catchment area can be still
described as good and unpolluted.
During the course of this Study, the water quality analysis was carried out for river
water of one sample collected from each of the Kaliwa, Kanan and Agos Rivers to
examine appropriate water treatment process. The results of water quality
analysis conducted in July 2001 and August 2002 are shown in Table 4.6.
Although the number of samples was very limited, water quality of the said rivers
shows that concentration of health-related inorganic constituents such as arsenic,
cadmium, chromium, cyanide, fluoride, lead, mercury and nitrate are very low and
below the detectable limits. BOD5, COD, KMnO4 consumption and ammonium,
which are indicators of contamination, also show low levels.
From the viewpoint of water treatment, color, turbidity, pH, alkalinity, iron,
manganese, etc. are the items to be evaluated. Table 4.7 shows raw water and
treated water quality of La Mesa No.1 Water Treatment Plant in August 2000 and
March 2001. In comparing the water quality of the Agos River Basin with water
quality at La Mesa Dam, there is no significant difference. Thus, the conventional
water treatment process adopted at La Mesa No1/Balara No.2 WTP can be
employed for the treatment of Agos water sources. Even iron with high
concentration observed in the samples can be easily removed by employing the
conventional unit process (coagulation/flocculation, sedimentation and rapid sand
filtration) with pre-chlorination. Intermediate chlorination aiming at manganese
removal may not be necessary considering the actual operation status of the
existing water treatment plants. In case of adopting intermediate chlorination,
further study will be needed regarding the type of manganese (soluble Mn2+) and its
concentration.
In addition, the direct filtration may be applicable for low turbidity of water source
during the dry season. For safety, feeding apparatus of activated carbon may be
equipped to deal with unexpected water contamination in the future.
To verify the adequacy of the selected water treatment process, further monitoring
of river water quality through the year is required.
4.7 Coastal Survey for Agos River Mouth

4.7.1 General
The Agos Dam, once built, will reduce sediment release to the downstream reaches.
This may cause some changes in the environment of coastlines of the Infanta
Peninsula (Infanta-General Nakar Alluvial Plain). In this context, this Section looks
into the probable features of future coastal condition.
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4.7.2 Available Coastal Data and Field Survey Conducted
For studying this issue, collection of the relevant data was attempted in both the
Philippines and Japan. To supplement the scarcity of the availability data,
preliminary field survey was also conducted.
(1) Data for Analysis of Present Condition
For analyzing the historical background and present conditions of the coast,
collected were satellite imageries, air-photographs, reports/papers and other
published data. Interview to the local people was conducted to collect the on-site
information.
As a result of visit to the concerned agencies, the Study found that no informative
data relevant to the existing condition of the Infanta coast were obtainable from the
existing literatures. Hence, the Study had to rely mainly on the limited information.
(2) Data for Coastal Sediment Analysis
To predict the coastal impact in terms of the topographical change of coastal area,
the features of sediment transport along the coast needs to be examined. For this
purpose, the existing reports/papers and other published data relevant to climate,
hydrology and hydraulics were collected. Supplemental field survey was also
conducted to obtain necessary field information, such as visual confirmation of
in-situ conditions and sampling of coastal sand for grain size analysis.
The sediment transport consists of sediment yielded from the Agos River Basin and
littoral drift along the beach.
To examine sediment yield from the basin, it was necessary to collect the data on
the river discharges, grain sizes of the riverbed sediments and the representative
river cross sections.
Analysis of the sediment transport along the coastline requires the data on wave
conditions specific to the area. However, visit to the agencies concerned revealed
the unavailability of the data. Hence, the Study was obliged to derive the wave
conditions based on wind speed/direction data.
Wind data (speed and direction) were made available from PAGASA records which
have been observed for the period of decades at Infanta meteorological observatory.
The wind data so collected cover both the daily and monthly data for the period
from 1961 to 2000. The method of calculation to derive wave condition from wind
speed/direction data is called the “wave forecasting” method.
4.7.3 Historical Change of Infanta Peninsula in Last 50 Years
Figures 4.10 shows the latest condition in 2000 as an example of the study output,
where the base map used in the Figure (1/50,000 map) shows the condition in 1951.
The results of the analysis are summarized below:
Changes of Sand Bar and Tideland
a) The changes of sand bar at the river mouth indicate active sediment yields
from the Agos River. The yielded sediments have filled the portions of
4-23
coastline including inner low-lying area and moreover developed sand
dunes. It also contributed to the formation of sand bar in conjunction with
the accumulation of sands transported by near-shore current.
b) Notwithstanding active sediment yields from the Agos River, the protrusion
of the river mouth sediments to the seaward direction has been of a limited
extent during these 50 years. This is because the sediment deposited at the
river mouth is constantly transported southward due to near-shore current.
Yet, the sedimentation at the river mouth seems to be active.
c) The sediment transported southward accumulates along the southern coast
extending up to the Dinahican area and partly diffracts into the Lamon Bay
forming small sandbars along the south coast of the bay. The rest of
sediment is transported to southern sea bottom.
d) In the southern part of the Peninsula plain, small streams originated from
the mangrove swamps flow into the Lamon Bay. These streams are virtually
the flow of small gradient in the low wet land and do not yield excessive
sediments. Nevertheless, the gradual development of low-lying tideland is
observed around the river mouth, expanding year by year. This may be the
result of sediment yield due to artificial development in the mangrove
forests, such as land reclamation, fishpond construction, etc.
4.7.4 Present Condition of Coastal Area
To confirm the present condition of coastal area, field reconnaissance and interview
to the local residents along the coast were conducted in February 2002.
(1) Sampling of Coast Sand and Analysis of Grain Size
Sampling of coast sand was Longitudinal Distribution of d50
10
conducted at nine (9) points
along the coastline of Infanta 8
and General Nakar to obtain the

d50(mm)
6
information of grain size
4
distribution of the sand. The
distribution of d50 along the 2
coast is shown in the right-side 0
figure. -6 -4 -2 0 2 4 6 8 10 12
Distance from River Mouth (km)
As shown in the figure, the
grain size of sand represented by d50 is coarser northward and finer southward. This
suggests that the sediment transport by littoral drift is evidently southward.
Accordingly, it is deemed that sediment discharged from the Agos River mouth is
transported to the south direction.
(2) Field Reconnaissance and Interview to Local Residents
The results of interview and field reconnaissance are as follows:
The findings from the field reconnaissance generally coincide with the result of the
aerial photograph analysis.
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The Agos River has yielded a large amount of sediment from old age and the
sediment is transported southward by nearshore current with wave force caused by
wind from the north. In the case of attack of typhoon of which north wind is
usually dominant, strong wave might have changed the coast especially at the
southern coast near the Agos River mouth.
The flow courses of the Agos River have changed heavily in the past due to
accumulation of sandbars in the river mouth area. The river course tends to move
northward, while sand bars in the southern area seems to be developing. The
southern sand bar functions as if it were a jetty creating a sheltered area for waves
at southern area of the river mouth. Local scouring at south of the river mouth is
caused by the unbalance of sediment transport, which resulted from the existence of
sand bar.
In a general term, the whole coast of Infanta Peninsula is under the stable condition,
although the occasional local scouring is seen in the area just south from the Agos
River mouth.
4.7.5 Prediction of Coastal Change after Completion of Agos Dam
(1) General
For the assessment of future coastal change, various data specific to the objective
site, such as sediment yield from the basin, energetic major wave condition
throughout the year, sediment size and topography of seabed, are necessary. Due
to the lack of these data, however, the coastal study at this stage had to adopt a
simplified method.
(2) Sediment Yield
The annual mean bed load yield of the Agos River is estimated at 322.7x103
m3/year. The ratio of sediment yield of bed load to suspended load is about 0.33
according to Annex C of Volume V.
Major sediment yield is distinguished in the period of NE monsoon from October
to February and less in summer season from April to June.
(3) Coastal Sediment Transport
The wave condition in deep see is estimated from the wind data measured at
Infanta.
The details are described in the Annex E of Volume V.
Wind Wave in Deep Sea
Wave condition in deep sea is calculated from the wind data, such as wind speed,
direction, length measured as wind blowing distance (fetch) and duration of wind
blowing time. This method is so called SMB method, which is widely used for
estimation of the significant wave in deep sea.
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Wave in Shallow Water
Coast from the Gabriel Point to the Dinahican Point was largely divided into seven
sections according to its face angle to the sea as shown in the figure below. Wave
condition in shallow water was calculated for each of these coastal sections.
As the water depth changes, wave height and wave length also change. The shallow
water wave conditions are calculated.
Sediment Transportation
Sediment transportation was
calculated by the CERC (Coastal
Engineering Research Center,
Bagnold/Inman/Komar, 1977)
equation, which is most widely used Gabriel Point
for calculation of the sediment Dinahican Point
transportation.
From the above results, the annual
sediment transport rate is estimated at
about 8.3x103 m3/year to 14.4x103
m3/year.
Coastal Change
On the basis of the estimated
sediment transport rate, the present
tendency of coastal change can be
assessed. A simplified method was Dinahican Point
applied to calculate the sediment
transport at every coastal point and
the coastal change. The method is so called ‘One line Model’, which is useful for
predicting the macroscopic change of coastline.
The tendency of coastal change under the present condition is estimated as follows:
Coastal Point 1 to 2: stable (+1.0m/year)
Coastal Point 2 to 3: shoreline retreat (-3.6m/year)
Coastal Point 3 to 5: weak shoreline retreat (-1.2m/year)
Coastal Point 5 to 7: stable (+0.2m/year)
The shoreline retreat presumed in the section of Points 2 to 5 is the result of the
present formation of sand bar deposited at the river mouth. The tendency of
coastal change estimated above is consistent with the information obtained through
interviews to the local residents.
(4) Future Coastal Change
Generally, the coast of Infanta Peninsula appears to be in the stable state at present.
But if the sediment supply to this area is reduced, the coast may be subject to
erosion due to nearshore current starting at northern part.
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It is presumed that, after the construction of the Agos Dam, about 90 % of sediment
yield from the Agos River Basin will be reduced. It is estimated that the bed load
yield of 322.7x103 m3/year at present will decrease to 32.3x103 m3/year after
completion of the Agos Dam. This will give a certain impact on the coastal area.
Hence, it is necessary to monitor the coastal change and carry out adequate
countermeasure if any adverse effect arises. The measure should be planned taking
into account the total balance of sediment transported to the Infanta Peninsula .
4.7.6 Installation of Monitoring System and Measures for Future Coastal Change
(1) Monitoring System for Coastal Line
Methodology
A possible approach is to estimate the shoreline position and its change by
comparing aerial photographs taken in different years.
The ground survey provides the highest quality data in terms of accuracy. The
shoreline position at the mean sea level can be obtained by positioning and direct
leveling on the beach at the timing coincident with the mean sea level given by the
tide table.
An importance is the determination of the exact shoreline position on the site.
The shoreline position should be delineated in relation to the mean sea level. For
this purpose, tidal stage, wave conditions and beach profile should be known at the
time of survey.
Establishment of Base Points
To make the survey easier and to maintain the required survey accuracy, the range
lines should be set along the shore at intervals of 0.5 km at the maximum.
The base point should be made with a deep-buried concrete post so as not to be
easily removed. Co-relation in elevation between the base point and mean sea level
should also be clarified.
Base points should be set before the construction of Agos Dam, and the existing
shoreline position should be surveyed to use it as the base line information versus
the future change.
Frequency
The measurement of shoreline change should be carried out at least twice a year
routinely to clarify the yearly change as well as seasonal change.
Additional measurement should be put into practice in the case a large coastal
change has occurred, for example, after a very big storm takes place.
Organization for Monitoring Work
The monitoring of coastal impacts should be conducted by an organization
concerned with this kind of monitoring with entrustment from MWSS.
The Department of Environmental Natural Resources (DENR) would be a suitable
organization because it has already been managing coastal resources. The
4-27
discussion among the concerned agencies is necessary to determine a suitable
organization that will be responsible for the continuous monitoring.
(2) Measures for Future Coastal Change
a) River Mouth Treatment
To cope with these concerns, construction of a training jetty is proposed as
shown in Figure 4.11. The purpose of the training jetty is as follows:
• To make the river mouth more stable and to protect the riverbank
• To discharge the sediment to the coast more smoothly
• To protect the northern and southern coast of the Agos River mouth
• To prevent the sea waves from intruding to the inside of river mouth
At this study stage, it is not possible to delineate the exact location of river
mouth in the future. The present natural condition of river mouth is so
complicated to predict the future shape of the river courses.
In the future, however, the river course at the river mouth will be more
stable. After such a tendency is observed, the riverbank would be protected
to fix the river course. The jetty should be constructed as the extension of
the riverbank protection.
b) Beach Protection
The beach protection should be done very carefully in utmost consideration
of the sediment transport balance. If the sediment along the coastline is
unbalanced at one place, the erosion that occurred at the place spreads to the
adjacent area (downstream side of littoral drift). Hence, it is important to
adopt the most adequate countermeasures that will have the lightest
secondary impact to the coast.
One of the methods commonly adopted for preventing the coastal erosion is
to construct the jetties. The jetty is expected to cause a relatively less
coastal impact, if the appropriate dimension is adopted. Its construction
involves less difficulty as compared with other countermeasures such as the
detached breakwater, submerged breakwater and headland. The coastal
revetment is also one of the selections, but it will deteriorate coastal use for
recreational and aesthetic purposes.
As for the sediment transportation, the most active part is breaker zone. If
the jetty is constructed in the whole length of breaker zone to stop the
sediment transport along the beach, the coast of downstream side of littoral
drift will result in heavy erosion. Hence, the length of the jetty protruding
to the breaker zone should be as short as possible in order not to stop the
whole sediment transport.
Generally, the coastal impact is not easy to predict, so that the construction
of coastal structure should be carefully done step-wise by monitoring the
result of the previous work. A preliminary plan of typical jetty structure is
shown in Figure 4.12.
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Interval of jetty installations along the coast should be determined on a trial
basis with observation of local erosion and sedimentation appearing actually
on the coast. It is supposed to take the period of decades until a stable
coastline condition is created.
c) Materials
The materials for construction of jetties on the coast and training jetty at the
river mouth are available either from the riverbed of the Agos River
(boulders and cobbles) or rock quarries easily found in mountainous area in
the west.
(3) Further Studies in Subsequent Stages
A preliminary plan of the proposed countermeasures was discussed in the preceding
sections. The plan should be further refined and detailed in the subsequent studies,
preferably during the next detailed design stage. The items of further studies are a)
directional wave measurement in deep sea, b) bathymetric and geographic survey
around the river mouth, c) sand sampling at coast and river for grain analysis, d)
cross sectional survey on the beach, e) daily discharge measurement at the
downstream point of the Agos River, f) tidal current measurement, g) periodical
aerial photography and mapping, and h) detailed numerical model of local coastal
area
4.7.7 Cost for Monitoring and Countermeasures
Monitoring Work
The costs for monitoring work consist of costs for the initial establishment of base
points and the recurrent measurement of beach cross sections/shoreline points.
The establishment of base points should be carried out before the completion of the
Agos Dam and the measurement of beach cross sections/shoreline points should be
carried out at least twice a year, with additional measurements as required in case
the big change of coast occurs. The base point should be installed at every 0.5-km
interval along the coast of Infanta Peninsula. The mean sea level of the area
should be calculated from the tide table. The cost is estimated as follows:
Cost of Monitoring Work
Unit Price Amount
Item Unit Quantity
(US$) US$ equiv. Peso equiv.
1 Establishment of Base Place 20 400 8,000 400,000
Points (Initial Work)
2 Survey of Beach Cross Section 20 40 800 40,000
Sections and Shoreline (Per
Positions (twice a year) survey)
Note: These costs are included as an item of O&M cost for Agos Dam.
Coastal Protection Work

a) Training Jetty
As described in Subsection 4.7.6 above, the construction of a training jetty
is envisaged on the left bank of river mouth. It is supposed that the timing of
4-29
implementation will be at the period of decades after the construction of
the Agos Dam, when the river mouth appears to become in the stable
condition.
b) Jetties along the Southern Coast
In case the tendency of retreat of coastal shoreline is observed in the long
time span, the coastal protection work will be necessary. One of suitable
countermeasures is considered to be the provision of a series of jetties. The
timing of implementation is difficult to predict at this study stage, but it
would be at the period of decades after the completion of the Agos Dam.
The cost for the protection works is estimated below:
Cost of River Mouth and Coastline Protection Works
Item Unit Quantity Unit Price Amount
(US$) US$ equiv. Peso equiv.
1. General Installation Lump 1 - 1,953,000 97,650,000
((2+3)x30%) Sum
2. Jetty Place 200 30,000 6,000,000 300,000,000
3. Training Jetty M 300 1,700 510,000 25,500,000
4. Miscellaneous Lump 1 - 1,692,600 84,630,000
((1+2+3)x20%) Sum
Total 10,155,600 507,780,000
Note: Necessity of these costs is unknown, depending on actual need of the protection works. For a
conservative assessment of the Project, however, the costs are included as a part of O&M
cost of Agos Dam, incurred over a period of 40 years after the completion.
4-30
Table 4.1 Probable Flood at Proposed Damsites
Unit : m 3/sec
Banugao Agos River Basin Kanan River Basin Kaliwa River Basin
Return
Gauging Creager's C Agos Afterbay Kanan No.2 Kanan Low Laiban Kaliwa Low
Period
Station Dam Weir Dam Dam Dam Dam
Drainage
Area 908 860 889 289 356 276 366
2
(km )
2 1,535 23 1,495 1,519 848 951 827 965
5 2,651 39 2,582 2,624 1,465 1,642 1,429 1,667
10 3,530 52 3,438 3,494 1,951 2,186 1,902 2,219
20 4,474 66 4,357 4,428 2,473 2,771 2,411 2,812
50 5,845 86 5,693 5,785 3,231 3,620 3,150 3,674
100 6,988 103 6,806 6,916 3,863 4,328 3,766 4,393
200 8,230 121 8,015 8,146 4,549 5,097 4,435 5,174
500 10,039 148 9,777 9,937 5,549 6,218 5,410 6,311
1,000 11,542 170 11,241 11,424 6,380 7,148 6,220 7,256
2,000 13,169 194 12,825 13,034 7,279 8,156 7,096 8,278
5,000 15,525 229 15,120 15,366 8,582 9,615 8,366 9,759
10,000 17,472 257 17,016 17,294 9,658 10,821 9,415 10,983
㪫㪋㪄㪈
Table 4.2 Annual Sediment Yield Estimated in Dam Projects in Luzon Island
Drainage Annual
Name of Dam Stream River System Area Sediment Yield Data Source
2 3 2
(km ) (m /km /year)
Existing Dam
Ambuklao Agno Agno 617 5,337 *1
Binga Agno Agno 860 4,900 *2
Pantabangan Pampanga Pampanga 916 1,500 *3
Angat Pampanga Pampanga 568 4,500 *3
Magat Cagayan Cagayan 4,143 1,600 *3
Caliraya Caliraya Caliraya 92 800 *3
Proposed Dam
Tina Labugaon Laoag 99 10 *3
Gosgos Solsana Laoag 71 10 *3
Cura Cura Laoag 63 10 *3
Paleiguan Beleiguan Ilocos 153 1,500 *3
Binongan Binongan Abra 377 2,000 *3
Chico IV Chico Cagayan 1,410 2,000 *3
Matuno Matuno Cagayan 593 600 *3
Casccnan Casccnan Cagayan 1,150 1,800 *3
Diduyon Diduyon Cagayan 477 1,107 *4
San Roque Agno Agno 1,250 6,500 *3
Balog-Balog Bulao Bulao 283 2,600 *3
Agos Agos Agos 867 557 *5
Note : Data Source
*1 : Ambuklao Rehabilitation, JICA 1988
*2 : Binga Dam Rehabilitation, JICA 1988
*3 : Study on Hydropower Project in Luzon Island, JICA 1987
*4 : Diduyon Hydroelectric Project, JICA 1980
*5 : Agos River Hydropower Project, JICA 1981
㪫㪋㪄㪉
Table 4.3 Increase/Loss of Flow in Limestone Area on the Kaliwa River
(Discharge Measurement by Current Meter)
Unit : m3/sec/100km2
Drainage
Station Location Area 13-May 18-May 25-May 3-Jun 10-Jun
2
(km )
Lenatin River
1 Upstream of Limestone Area 75 - 0.352 0.724 0.883 0.663
2 Downstream of Limestone Area 75 - 0.348 0.505 0.660 0.611
3 Downstream end of Lenatin River (before confluence) 131 0.098 0.202 0.383 0.438 0.342
Limutan River
4 Downstream end of Limutan River (before confluence) 145 0.312 0.670 0.896 0.925 0.465
Kaliwa River
(3+4) Lenatin-Limutan Confluence (Sta.3+Sta.4) 276 0.211 0.447 0.653 0.694 0.407
5 About 2 km Downstream of Limutan/Lenatin Confluence 278 0.349 0.381 0.735 0.833 0.413
Before Junction of Sabalanasasin River, about 1 km

6 292 0.266 0.448 0.636 0.672 0.500
Upstream of Daraitan S.G.S.
7 Daraitan S.G.S. 326 0.278 0.378 0.514 0.713 0.504
8 Kaliwa Low Dam No.1 335 0.498 0.561 0.648 0.742 0.587
㪫㪋㪄㪊
Table 4.4 Acceleration Value of Previous Proposed Damsites around the Project Area
Acceleration of Each Dam Site

Reports Type Kanan
Laiban Agos
-1 -2 B-1
0.15g (50years)
Manila Water Supply III Project
Peak Acceleration 0.20g (100years) - - - -
(1979, Electrowatt)
0.40g (1000years)
Feasibility Report Peak Acceleration - 0.58g -

on Agos River Hydropower Project
(1981, JICA) Design Accelerration - 0.15~0.20g -
Manila Water Supply III Project,

0.50g (MDE)
Engineering Report Peak Acceleration - - - -
0.40g (OBE)
(1984, Electrowatt & Renardet)
Peak Acceleration - 0.58g - - -

Feasibility Study - Agos Project
(1991, ELC Electroconsult)
Design Accelerration - 0.15~0.20g - - -
Peak Acceleration - - - - 0.46g

Small Hydropower Projects
: Kanan B1 Scheme, Design Accelerration - - - - 0.26g
(1992, Nippon Koei-Lahmeyer)
Design Accelerration - - - - 0.23g
Manila Water Supply III,

0.50g (MDE)
Project Review Peak Acceleration - - - -
0.30g (OBE)
(1997, Electrowatt & Renardet)
NOTE:
According to the guidelines of the ICOLD (International Committee on Large Dams);
For the MDE (Maximum Design Earthquake) a total failure of the structure has to be avoided, however major damage is
accepted. For the OBE (Operating Basis Earthquake)
㪫㪋㪄㪋
Table 4.5 Necessary Materials for Agos Dam Construction
Necessary Materials
Proposed Source
Structure Material Volume (m3)
Agos quarry site

(4,000,000 m3)
Rock material 12,000,000 Excavation of dam foundation,
spillway and diversion tunnel
(8,000,000 m3)
Main Dam
Excavation of riverbed deposit

Filter material 500,000 at the damsite
Riverbed deposit along Agos river
Residual soil on the abutments
Impermeable material 200,000
blended with rock fragments
Excavation of dam foundation,
Random material 760,000
spillwayb and diversion tunnel
Coffer Dams
Rock material 280,000

Excavation of dam foundation,
spillway, diversion tunnel
and Agos quarry site
Random material 640,000
Riverbed deposit along Agos river
Concrete for face slab of main dam,

spillway, diversion tunnel and 290,000
hydropower facilities
Crashed rock from Agos quarry site
㪫㪋㪄㪌
Table 4.6 Result of River Water Quality Analysis
Standard July 2001 August 2000
Value/
Category Laboratory Test Item Unit
Maximum Agos River Kanan River Kaliwa River Agos River Kanan River Kaliwa River
Level
Arsenic mg/L 0.01 mg/L 0.00130 0.00150 0.00053 0.00210 0.00060 0.00150
Cadmium mg/L 0.003 mg/L < 0.001 < 0.001 < 0.001 < 0.002 < 0.002 < 0.002
Chromium mg/L 0.05 mg/L < 0.05 < 0.05 < 0.05 < 0.05 < 0.05 < 0.05
Inorganic Cyanide mg/L 0.07 mg/L 0.002 0.002 0.002 <0.001 <0.001 <0.001
Constituents Flouride mg/L 1 mg/L < 0.02 < 0.02 < 0.02 < 0.02 0.062 < 0.28
Lead mg/L 0.01 mg/L < 0.002 < 0.002 < 0.002 <0.005 < 0.005 < 0.005
Mercury mg/L 0.001 mg/L < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.0002 < 0.0002
Nitrate as NO3- mg/L 50 mg/L 0.851 1.060 0.287 0.51 0.45 0.49
Color PCU 5 PCU 40 15 35 10 5 5
Turbidity mg/L 5 NTU 43.0 0.6 25.0 11.3 0.3 9.2
Chloride mg/L 250 mg/L 2.1 2.1 2.6 7.5 3.7 0.9
Copper mg/L 1.0 mg/L < 0.02 < 0.02 < 0.02 < 0.02 < 0.02 < 0.02
Hardness mg/L 300 mg/L 142 116 86 89 46 150
Physical
and Iron mg/L 1.0 mg/L 9.40 6.60 0.12 0.78 <0.06 0.58
Chemical Manganese mg/L 0.5 mg/L 0.18 0.12 < 0.02 0.28 0.22 0.03
Quality
pH * - 6.5-8.5 7.6 8.0 7.8 6.8 7.1 6.8
Sodium mg/L 200 mg/L 6.1 6.3 5.7 6.0 5.7 6.5
Sulfate mg/L 250 mg/L 3.9 4.9 2.1 13.2 11.6 2.7
Zinc mg/L 5 mg/L 0.038 0.120 0.046 < 0.02 0.020 < 0.02
Calcium mg/L N.S. 47 38 28 31 17 42
o
Temperature * C N.S. 28.8 28.2 29.0 22.0 21.0 22.0
Alkalinity mg/L N.S. 92.5 60.9 110.0 87.2 55.7 150.8

Electric Conductivity P㱅 /cm N.S. 215 150 252 200 100 200
Biocarbonate mg/L N.S. 123 149 82 106 68 184
Others Phosphate mg/L N.S. 0.23 < 0.01 0.28 8.07 < 9.81 6.95
BOD5 mg/L N.S. 2.4 1.0 2.5 3.0 5.0 4.0
COD mg/L N.S. < 5.0 < 5.0 5.0 19.0 30.0 17.0
KMnO4 Consumption mg/L N.S. 1.9 1.1 0.7 0.6 0.6 0.9
Anminia (NH3) mg/L N.S. 0.75 < 0.01 0.57 0.06 < 0.01 0.05
Note : N.S. ; No Standard Provided by the Department of Health (DOH)
* ; Measured on-site
㪫㪋㪄㪍
Table 4.7 Water Quality of Raw/Treated Water at La Mesa No.1 Water Treatment Plant
August 2000 March 2001
Item
Average Max. Min. Average Max. Min.
Tempareture Raw water 23.5 25 21.7 24.1 25.9 23.1
(0C) Treated water 24.5 26.7 22.4 25 26.4 23.4
Turbidity Raw water 29.3 101 8.01 8.95 73.7 1.68
䋨NTU㧕 Treated water 1.72 2.26 1.21 0.96 2.19 0.59
Raw water 7.62 7.78 7.47 7.53 7.87 7.37
䌰H
Treated water 7.07 7.34 6.9 7.22 7.49 7.02
Raw water 29.2 99.1 10.8 9.97 41.2 5
Color
Treated water 5 5 5 5 5 5
Physical Raw water 0.36 1.41 0.06 0.14 1.14 0.02
(mg/l) Treated water 0.02 0.1 0 0.02 0.04 0.01
Residual Clorine Raw water - - - - - -
㩿㫄㪾㪆㫃㪀 Treated water 1.28 1.35 1.17 1.19 1.36 0.98
㩷㪘㫃㫂㪸㫃㫀㫅㫀㫋㫐 Raw water 46.7 54 40 43.1 56 24
(mg/l) Treated water 36.3 48 28 36.5 46 22
Bicarbonate Raw water 57 65.8 48.8 52.6 68.3 29.2
Acidity Raw water 6 8 2 7.23 12 4
Free Carbonic Acid Raw water 5.28 7.04 1.76 6.36 10.5 3.52
-
Chloride (Cl ) Raw water 4.39 6 3 4.23 8 2
Total Hardness Raw water 59.8 74 44 66.4 78 54
㩿㫄㪾㪆㫃㪀 Treated water 60 70 44 63.9 76 46
Calcium Hardness Raw water 39.4 46 26 43 54 28
㩿㫄㪾㪆㫃㪀 Treated water 38.1 48 25 40.9 52 30
Total Manganese Raw water 0.26 0.93 0.04 0.1 0.63 0.02
㩿㫄㪾㪆㫃㪀 Treated water 0.02 0.04 0 0.01 0.05 0
Dissolved Manganese Raw water 0.02 0.05 0 0.01 0.04 0
㩿㫄㪾㪆㫃㪀 Treated water - - - - - -
2+
Calcium (Ca ) Raw water 15.7 18.4 10.4 17.2 21.6 11.2
㩿㫄㪾㪆㫃㪀 Treated water 15.2 19.2 10.4 16.3 20.8 12
2+
Magnecium (Mg ) Raw water 4.97 8.26 1.94 5.69 7.78 2.92
Electric Conductivity Raw water 126 138 100 129 139 102

P㱅 /cm) Treated water 132 143 110 133 140 102
Total Dissolved Solid Raw water 59.9 66 48 61.1 65 47
㩿㫄㪾㪆㫃㪀 Treated water 62.5 69 52 62.7 67 49
(Source) La Mesa No.1 Water Treatment Plant, MWSI
㪫㪋㪄㪎
120
Duration (%) Discharge (m3/sec)

Kaliwa Low Dam Site 10 56.63
100 20 44.67
30 36.62
40 27.39
80 50 22.52
60 17.60
70 14.23
80 10.18
60
90 6.40
95 5.22
100 3.27
40
20
0
0 10 20 30 40 50 60 70 80 90 100
Duration (%)
450
Duration (%) Discharge (m3/sec)

400 Agos Damsite 10 236.87
20 183.56
350 30 140.30
40 107.86
300 50 85.27
60 70.73
70 57.14
250
80 43.45
90 30.24
200 95 23.64
100 7.58
150
100
50
0
0 10 20 30 40 50 60 70 80 90 100
Duration (%)
Figure 4.1 Flow Duration Curve at Proposed Damsite

18,000
Peak Discharge ; 17,121 m3/sec
16,000
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
0 24 48 72 96
Time (hour)
PFegm
Easnbales
N
s
Za
Z: en
Tarlac
Ga t
t
ba
ldo
n
Fau
lt
Iba F
ault
Philippine FPau
San Fernando
FZ
Malolos
lt:IZnofanenta(Pse
Infanta
A
Marikina
FZg):
Balanga Manila
ystemm B
mIn
Fault S yste
enfat nta se
Manila
Agos Damsite
Valleyey Fault S
Antipolo
Project Area
gmen
Imus
Vall
t
Sta.Cruz
Nasugbu
Lucena
Batangas
Legend:
Active Fault:Solid line-trace certain
Approximate offshore projection

Ce
Min CentoraFault
ntr F
Aguver A
Boac
Min
Ri
Cenro Faul
Dashed line-trace approximate

al aul
Calapan
do
M t
bang t g
dor
tral t
Roads/highways
ari
FaguulbanFault
Rive
nd
City/Town
l
ug
r
0 15 30km
By PHILVOLCS (2000) Figure 4.3 Distribution of Active Faults in Southern Luzon
F4-3
n ce
D is t a S ite
km s D am
10 A go
fro
m F4
F5
F1 F3
F2
F8 F6
Agos Dam Site
Philippine Fau
(Infanta Fau
lt Zone
lt)
F7
LEGEND
Certainly of active fault
Class I : Active fault
It's certainly active fault.
Class II : Assumed active fault
It's almost certainly active fault.
Class III : Any clear factor is not observed
that indicated by active fault.
Factor of active fault
Fault bulge
Triangular slope
1,000m 0 1,000 2,000 3,000 4,000 5,000
Misalignment of river
Figure 4.4 Distribution of the Active Fault around the Agos Dam Site
Based on the analysis of aerial photographs
F4-4

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Table 3.

1 Population Projection by City/Municipality Up to 2025 (1/2)

(Common Concession Area)

East 3% 16% 51% 52% 55%

4.2 Topographic Condition

Mean Monthly Discharges Estimated at Selected Sites

(2) Flow Duration Curve

4.5 Water Rights in Agos River Basin

List of Approved Water Rights

Pending Water Permit Applications

4.6 Water Quality in Agos River Basin

4.7 Coastal Survey for Agos River Mouth

and General Nakar to obtain the

Coastal Protection Work

5 2,651 39 2,582 2,624 1,465 1,642 1,429 1,667

10 3,530 52 3,438 3,494 1,951 2,186 1,902 2,219

20 4,474 66 4,357 4,428 2,473 2,771 2,411 2,812

50 5,845 86 5,693 5,785 3,231 3,620 3,150 3,674

100 6,988 103 6,806 6,916 3,863 4,328 3,766 4,393

200 8,230 121 8,015 8,146 4,549 5,097 4,435 5,174

500 10,039 148 9,777 9,937 5,549 6,218 5,410 6,311

1,000 11,542 170 11,241 11,424 6,380 7,148 6,220 7,256

2,000 13,169 194 12,825 13,034 7,279 8,156 7,096 8,278

5,000 15,525 229 15,120 15,366 8,582 9,615 8,366 9,759

10,000 17,472 257 17,016 17,294 9,658 10,821 9,415 10,983

1 Upstream of Limestone Area 75 - 0.352 0.724 0.883 0.663

2 Downstream of Limestone Area 75 - 0.348 0.505 0.660 0.611

Before Junction of Sabalanasasin River, about 1 km

7 Daraitan S.G.S. 326 0.278 0.378 0.514 0.713 0.504

Acceleration of Each Dam Site

Feasibility Report Peak Acceleration - 0.58g -

Manila Water Supply III Project,

Peak Acceleration - 0.58g - - -

Peak Acceleration - - - - 0.46g

Manila Water Supply III,

Agos quarry site

Excavation of riverbed deposit

Rock material 280,000

Riverbed deposit along Agos river

Concrete for face slab of main dam,

Crashed rock from Agos quarry site

Duration (%) Discharge (m3/sec)

Duration (%) Discharge (m3/sec)

Figure 4.1 Flow Duration Curve at Proposed Damsite

Active Fault:Solid line-trace certain

Approximate offshore projection

Dashed line-trace approximate

By PHILVOLCS (2000) Figure 4.3 Distribution of Active Faults in Southern Luzon

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