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Preliminary Design Report Pulang Lupa Reservoir_rev+Comments

Jun 04, 2018

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    1.0 PROJECT DESCRIPTION

    1.1 Basic Project Background and Information

    Clark Water Corporation (CWC) is responsible for the provision of water and

    wastewater services under a concession agreement with Clark Freeport Zone

    (CFZ). To cope up with the projected demand due to the increasing number of

    locators/investors in the CFZ, the existing water transmission and distribution need

    to be expanded and additional storage facilities need to be constructed.

    1.2 Project Rationale

    CWC took responsibility for operating the existing water supply and wastewater

    infrastructure systems in 2000 under a 25-year concession agreement. The

    systems were constructed many years earlier to serve the US Clark Air Force base

    which was vacated by US Forces after the eruption of Mt. Pinatubo in 1991 and

    later turned into the CFZ.

    The upgrading program intends to address the following major issues

    .1.3 Options for Water Supply and Sewerage

    Options recommended for augmentation of the water supply system envisaged for

    Clark Water Corporation are summarized below.

    1.4 Data for Preliminary Design

    1.5 Scope of Preliminary Design Report

    1.6 Final Preliminary Design Report

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    2.0 BACKGROUND INFORMATION

    2.1 Project Location

    The Clark Freeport Zone (CFZ), in which CWC is responsible for the provision of

    water and wastewater services under a concession agreement, is located in the

    provinces of Pampanga and Tarlac in Central Luzon. The boundaries of the CFZ

    are comprised of two distinct areas, i.e.

    Sub-Zone:

    o Boundaries: ODonnell River (north), McArthur Highway (east),

    Abacan River (south), lower E slope of Zambales Mountain (west)o Drainage: ODonnell, Bongarit and Malago-Marimla Rivers and

    Sapang Cauayan Creek

    o Area: 23,600 ha

    Main Zone:

    o Boundaries: Sacobia and Bamban River (north), Abacan River (south)

    o Drainage: Sacobia, Bamban and Abacan Rivers

    o Area: 4,400 ha

    The western portions of the CFZ are generally undulating ravines formed by

    watercourses. The upper soil layer, at least 30 m thick, is composed of volcanic

    ash deposited during the eruption of Mt. Pinatubo in 1991. This eruption blanketed

    the Main Zone with ash fall deposits that resulted in the topography being

    modified. Ground surface elevations within the CFZ range from 107 m MSL on the

    floor of the eastern side of the valley, rising more than 275 m MSL on the western

    side.

    The main development features in the Main Zone comprise:

    Airport, serving military and civilian flights (runway 3.2 km long)

    Area IE-5: Area abutting Angeles, including shopping centers (including SM),

    industries

    Key industries include: (i) Luen, (ii) SMK, (iii) Nanox, (iv) Yokohama, (v) Texas

    Instruments, (vi) Bertaphil.

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    2.2 Climate

    The climate of Clark, Subic and Tarlac belongs to Type I of the modified Coronas

    Classification of Philippine Climate. This type is characterized by two pronounced

    seasons, dry from November to April and wet during the rest of the year.

    Particularly for Subic area, the months of May and October are considered the

    transition period.

    2.3 Topography and Drainage

    The regional topography is characterized by rugged steep terrain of high relief on

    the west and relatively flat alluvial plains on the east. Prominent peaks comprising

    the western mountain range the Zambales Range, include Mt. Pinatubo (1,445

    masl), Mt. Dorst (829 masl), Mt. Balakibok (843 masl), and Mt. Natib (1,243 masl).

    A lone volcanic edifice - Mount Arayat, mars the otherwise f lat terrain of the

    Central Plain of Luzon.

    Six rivers drain through the project area: Marimla, Sapang Cauayan, Sacobia-

    Bamban, Dolores, Quilanquil and Abacan Rivers. Headwaters of these rivers

    emanate from the slopes of Mount Pinatubo. The volcanos eruption in 1991

    blanketed the lowland region with centimeters of ashfall deposits, while proximal

    valleys to the volcano were inundated and buried by tens of meters thick of

    pyroclastic flow deposits. The attendant changes in topography and watershed

    hydrology, and abundance of sediment resulted in frequent sediment-laden flows-collectively called lahars, along these rivers during enhanced rainfall. Ten years

    after, rivers remain in a quasi-equilibrium state, thus a constant source of concern

    of river and road management engineers.

    The Dolores-Mabalacat-Sapang Balen River is one of the rivers and creeks

    draining the Clark Freeport Zone (CFZ). It traverses the northwestern boundary of

    the CFZ, and at its nearest approach is about 500 m from the proposed

    wastewater treatment plant, Locally, the river segment above 110 masl is referred

    to as Dolores Creek, and as Mabalacat River along the short segment transecting

    Mabalacat town from 110 masl to 90 masl. Below 90 masl the river is referred to as

    Sapang Balen River.

    The Dolores-Mabalacat-Sapang Balen River is perennial stream draining a

    catchment area of about 6 km2 above 100 masl. Stream gradient is less than one

    degree along the stream segment below 160 masl. Channel morphology is

    typically box-shaped, with channel depths of two to five meters, and widths of 15-

    20 m. Active flow occupies less than two meters of the channel bed under

    normal/low streamflow conditions. Channel bed is sandy with occasional gravel-

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    dominated patches and boulders. No historical stream flow data is available for the

    Dolores-Mabalacat-Sapang Balen River based on DPWH and NWRB data.

    However, in November 2000 a low flow discharge was estimated at less than one

    m3/sec along a section of the river at elevation 130 masl.

    2.4 Regional Geology

    The CFZ straddles the lower slopes of Bataan volcanic arc and the flat terrain of

    the Central Plain of Luzon. The subzone falls from the upper slopes of Mt.

    Pinatubo to the Sacobia-Bamban river valley. The Main Zone incorporates lower

    volcanic slopes in the west and flat alluvial Central Plains in the center and east.

    The site is underlain by a sequence of volcanics and volcanic-derived alluvium, as

    summarized below:

    Regional Geology

    Unit LithologyRecent alluvium andlahars

    Detrital deposits, mostly sand and gravel

    Bamban Formation(east/downslope: MainZone) (Quaternary)

    Upper partly continental tuff and tuffaceoussandstone sequence, lower section sandstone,shale and conglomerate

    Quaternary Volcanics(west/upslope:sub-zone)

    Andesite, basalt and dacite porphyries

    Tarlac Formation (Mio-Pliocene)

    Sandstone, siltstone, shale, limestone andconglomerate lenses, with andesite lavas and dykesin the upper sequences

    Zambales UltramaficComplex (Cretaceous-Eocene)

    Ophiolite sequence: dike complex and gabbro

    Source: EIA Upgrading of CWC Waterworks prepared by bmp Environment and Community Care,Inc. and Black and Veatch, 29 September 2003.

    2.5 Site Geology

    Philippine Mines and Geosciences Bureau mapping indicates the Main Zone is

    underlain by unconsolidated Recent alluvium in the Sacobia/Bamban River valley

    and semi-consolidated and consolidated sedimentary and pyroclastic deposits of

    the Bamban Formation beneath the alluvium in the river valley and at surface over

    much of the reminder of the Main Zone. The Recent alluvium comprises boulder to

    clay sized alluvial deposits laid down in a braided river environment, as well as

    lahar deposits. Much of the subzone is underlain by the Moriones and Malinta

    Formations. The younger (mid-Miocene) Malinta Formation comprises inter-

    layered tuffaceous, thickly bedded sandstone and siltstone with occasional

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    conglomerate. The older (early Miocene) Moriones Formation comprises locally

    inter-layered sandstone, siltstone and conglomerate with some lapilli tuff.

    2.6 Existing Land Use

    Clark Freeport Zone is divided into two major zones the 4,440 hectares of fully

    developed land in the Main Zone and approximate 29,000 hectares of developable

    area, known as the Sub-Zone, within the provinces of Pampanga and Tarlac.

    Industrial estates, tourism and recreational attractions and a huge civil aviation

    complex, are currently occupying the Main Zone. The Sub-Zone is principally

    intended for agricultural projects, corporate farming, agro-industries and food

    processing.

    The major land use of the Main Zone is the civil aviation complex that features two

    parallel runways, each being more than 3000 meters long. Adjoining the airport

    complex is an area appropriate for use by the Philippine Air Force.

    The Main Zone also features a number of golf courses, the most notable of which

    are Mimosa and Fontana. Residential areas are located at the center of the

    recreational areas. Areas for industries are located on east, north and south of the

    Main Zone.

    2.7 Rainfall

    The rainfall stations used in this project area are: (i) Iba, Zambales; (ii) Cubi Pt.,

    Subic Bay, Zambales, (iii) Clark International Airport, (iv) Cabanatuan City, Nueva

    Ecija, (v) Gabaldon, Nueva Ecija, (vi) Minalungao, Gen. Tinio, Nueva Ecija, (vii)

    Science Garden, Quezon City, (viii) Angat Dam, Norzagaray, Bulacan and (ix)

    Baler, Aurora.

    These stations run from West to East (coast to coast), across Central Luzon,

    Rainfall augmentation procedures was used to fill-up gaps in the rainfall records to

    complete the records from 1961 -2007.

    Subic and Iba, Zambales are located in the west coast of Luzon along the China

    Sea coast and west of the Zambales Mountain Range. Clark is East of ZambalesMountain Range. The valley to which Clark belongs is the Central Luzon Valley,

    which is east of the Sierra Madre Mountain Range.

    The central valley which includes Clark has less annual rainfall than both the West

    and East coast of Luzon. From January to April, the east coast to the center of the

    Central Luzon valley, there is a very minimal rainfall. While from May to

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    September, during the Southwest monsoon, rainfall is higher at the east coast.

    From October to December, rainfall is higher at the East coast of

    Luzon which is an effect of the Northeast monsoon.

    For annual trend analysis, the only viable station in Central Luzon with continuous

    record from 1961 to 2007 is the Angat Dam Station in Norzagaray, Bulacan.

    The cumulative average seems to show a downward trend on annual rainfall. This

    could be interpreted by some as an effect of global warming.

    The 5-year moving average seems to show that the 5 consecutive wettest years

    may have occurred from 1971 to 1975, while the driest 5 consecutive years are

    1981-1985. It also shows peaks and lows every 5 to 10 years.

    The 15-year moving average shows a downward trend from 1948 to 1991, and

    upward trend after. This does not support the idea that there is a general

    downward trend on annual rainfall. This seems to indicate that the rainfall series is

    a part of a cycle, and there is a need of a longer record to be able to see the

    complete cycle of changes in annual climate.

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    3.0 DESIGN CONCEPTS AND CRITERIA FOR THE PRELIMINARY DESIGNOF THE ELEVATED RESERVOIR

    In accordance with engineering standards, the Pulang Lupa reservoir shall be designed

    to provide stability and durability, as well as protect the quality of the stored water. The

    reservoir design criteria are intended not only to establish the structural integrity, but also

    to ensure water system adequacy, reliability, and compatibility with existing and future

    facilities.

    3.1 Type of ReservoirReservoirs may be classified according to their function, relative position withrespect to earths surface, manner of operation and as to type of material of

    construction.

    The Pulang Lupa storage scheme is an elevated reservoir which is envisaged to

    supplement the existing Lily Hill Reservoir or alternatively, could be the future

    source of water supply to PSPC and adjoining locators. Pulang Lupa is a hilly area

    within the proximity of PSPC at elevation 170 maslwhich could be developed to

    provide the projected demand by operating independently or floating-on-the line in

    tandem with Lily Hill Reservoir.

    3.2 Definition of Source as Used in Sizing the New Reservoir

    Any source classified as either permanent or seasonal may be considered a

    source for the purpose of designing the new reservoir facility provided that the

    source is continuously available to the system and at a minimum meets all

    primary drinking water standards To be continuously available to the system

    means that: (1) the source is equipped with functional pumping equipment (and

    treatment equipment if required); (2) the equipment is exercised regularly to assure

    its integrity; (3) water is available from the source year round; and (4) the source

    is activated automatically based on pre-set parameters (reservoir level, system

    pressure, etc.)

    For the purpose of designing the new reservoir facility, the following are

    considered sources:

    1. Each pump in the well field comprising of wells pumping into the zone served

    by that particular reservoir.

    2. Each pump installed in a large capacity, large diameter well which could be

    developed in the future to complement the existing pumps which can be

    taken out of service without the need to interrupt operation of any other

    pump.

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    3.3 Storage Volume

    The capacity of the reservoir shall be such that it will operate properly in

    conjunction with the water treatment plant and appurtenant facilities. In general,

    the reservoirs should be capable of supplying the incremental difference between

    maximum day and peak hour demands. The capacity of a reservoir shall include

    the storage needs of one or more of the following:

    1. Operational storage (OS);

    2. Emergency Storage (ES); and

    3 Fire suppression storage (FSS).

    The total capacity of all reservoirs within a service zone shall be equal to or in

    excess of the storage needs required for operational storage, emergency storage

    and fire-fighting storage.

    3.4 Operational Storage (OS)

    Operational storage is defined as the storage which can be drawn upon during

    peak hour demands and subsequently replaced during low demand periods which

    production facilities are being operated at nearly constant rates.

    The amount of operational storage required will be 25 percent of the Average Daily

    Demand (ADD) projected for PSPC and Australian Schools as follows:

    Projected Average Day Demand (ADD):

    PSPC = 6,000 m3/day

    Australian School = 1,700 m3/day

    Total: 7,700 m3.day

    Required Operational Storage = 25% x 7,700 = 1,925 cu. meter.

    Operational storage is the volume of the reservoir devoted to supplying the water

    system while, under normal operating conditions, the source(s) of supply are in

    off status. This volume will vary according to two main factors: (1) the sensitivity

    of the water level sensors controlling the source pumps, and (2) the configuration

    of the tank designed to provide the volume required to prevent excessive cycling

    (starting and stopping) of the pump motor(s). The definition specifies that

    operational storage is an additive quantity to the other components of storage.

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    3.5 Emergency Storage (ES)

    The amount of storage should be determined on the basis of an evaluation of the

    water system and the duration of a service outage which could be expected.

    However, facilities equipped with stand-by power generators will negate the need

    for emergency storage in the planning of ground reservoirs.

    3.6 Fire Storage

    The quantity of fire-fighting storage will depend on the population of the service

    area and shall be determined on the basis of the following schedule:

    Area Population Fire Storage

    Below 100,000 320 cu.m.

    100,000 to 500,000 640 cu.m.

    Above 500,00 950 cu.m.

    3.7 System Pressure Considerations

    The water level elevations of the reservoirs hydraulic shall be established through

    system pressure consideration of the service areas following the detailed hydraulic

    analysis which will be undertaken in consonance with the design criteria for new

    and existing water systems.

    3.8 Effective Storage

    Effective volume is equal to the total volume less any dead storagebuilt into the

    reservoir. The amount of effective storage may also be dependent upon the

    location of the storage relative to the place of its use (whether or not it is in a

    different pressure zone and what distance the water needs to be conveyed).

    3.9 Dead Storage (DS)

    Dead storage is the volume of stored water not available for distribution. The dead

    storage is the volume below the outlet pipe which shall be 0.6 m. from the floor

    level. The dead storage volume is excluded from the volumes provided to meet

    the Operational Storage (OS) requirement for the system.

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    3.10 System Pressure Considerations

    The hydraulic design of the system shall be such that the average day demand

    (ADD) shall be available to all service connections at 20 psi.

    3.11 Design Life

    Storage facilities are normally designed to serve the needs of the community for a

    planned number of years, or to accommodate full system build-out (if they serve a

    particular subdivision or planned development, or fulfill a condition of plat approval,

    etc.) The design life for properly maintained concrete and steel storage tanks is

    typically assumed to be about fifty years. Any other type of storage tank that doesnot have the historical longevity of these tanks needs to be evaluated on a life

    cycle cost basis before being considered for use.

    3.12 Ground Level and Underground Reservoirs

    The following criteria shall apply to ground level, partially buried and underground

    reservoirs:

    1. Ground level, partially buried and underground reservoirs should be placed

    outside the 100-year flood plain.

    2. The area surrounding a ground level or below grade reservoir should be

    graded in such a manner that will prevent surface water from standing within

    15 meters of the structure, at a minimum.

    3. When the reservoir bottom is below normal ground surface, it should be

    placed above the groundwater table, if possible. If this is not possible,

    special design considerations should include providing perimeter foundation

    drains to daylight and exterior tank sealants. These are necessary to keep

    ground water from entering the tank and to protect the reservoir from

    potential flotation forces when the tank is empty.

    4. Partially buried or underground reservoirs should be located at least 15

    meters from sanitary sewers, drains, standing water, and similar sources of

    possible contamination. Pipe typically used for water mains should also be

    used for gravity sewers if they are located within 15 meters of the reservoir.

    These pipelines should be pressure tested in place to 50 psi without leakage.

    5. The top of the reservoir should not be less than 0.6 m. above normal ground

    surface, unless special design considerations have been made to address

    maintenance issues and protection from surface contamination.

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    4.0 Design Standards and Considerations

    4.1 Tank Materials in Contact with Potable Water

    All additives, coatings, and compounds proposed for use in substantial contact

    with potable water, such as those listed below, musthave ANSI/NSF certification

    for contact with potable water. These materials also need to be carefully applied in

    accordance to the manufacturers recommendations for that particular material.

    4.2 Reservoir Appurtenant Design

    All reservoir appurtenances should be designed to be water tight and shall have

    means to prevent entry by birds, animals, insects, excessive dust, and other

    potential sources of external contamination.

    4.2.1 Reservoir Drains

    Reservoirs shall be designed with drain facilities that drain to daylight or have an

    approved alternative that is adequate to protect against cross-connection

    contamination. The facilities should be capable of draining the full contents of the

    tank without entry to the distribution system, or causing erosion at the drainage

    outlet.

    In locations where the topography is such that a drain to daylight is not feasible,the reservoir should be designed with a sump to allow for emptying the reservoir

    through use of a sump pump.

    If an outlet pipe is also used as a reservoir drain, it should include a removable silt

    stop in the reservoir.

    Drain lines may discharge directly to a dedicated dry well(s) provided precautions

    are designed and constructed to insure protection against backflow into the

    reservoir or distribution mains.

    4.2.2 Reservoir Overflow Valve

    Reservoirs shall be designed with float controlled valve that will prevent overflow

    discharge which will create pressure build-up to effect automatic control of pump

    operation through variable frequency drive (VFD) motor.

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    4.2.3 Reservoir Atmospheric Vents

    Reservoirs shall have a screened roof vent which should allow air into the reservoirat a rate greater than or equal to the rate that the water is withdrawn from thereservoir to prevent implosion or structural damage to the reservoir.

    Upward facing vents shall not be used in any application. Screens shall be

    provided on the vents to prevent entry by birds or animals. Ground level or

    underground reservoirs should terminate in an inverted U construction with the

    opening 0.6 to 0.9 m. above the roof or ground, and covered with No. 24 mesh

    non-corrodible screen. Screens on ground-level reservoir vents should be located

    within the pipe at a location minimally susceptible to vandalism.

    4.2.4 Roof Drainage

    The roof of the reservoir should be well drained. The slope of the reservoir roofshould be a minimum of 2 % (6 mm. vertical per 0.6 m. horizontal). To avoidpossible contamination, downspout pipes shall not enter or pass through thereservoir.

    4.2.5 Tank Level ControlThe reservoirs should be equipped with a level control system designed tomaintain reservoir water levels within a pre-set operating range (operating

    storage).

    A high level and low-level alarm system with direct annunciation of notification tooperation personnel should be installed. There should also be a local levelindication, through ultra-sonic level measurement and transmitter.

    4.3 Piping Material

    Piping material used for pipelines constructed directly below the reservoir, andextending to at least 3 meters from the perimeter, should be sturdier material suchas ductile iron pipe or AWWA C205 steel pipe with a corrosion resistant coatinginside and out.

    4.4 Operational Constraints and Considerations

    All new reservoir designs are expected to meet all applicable OSHA and WISHA

    requirements. In addition, reservoir design and construction should consider the

    following issues:

    1. Disposal of chlorinated water after construction and disinfection.

    2. Disposal of tank drain line outflow and tank overflow stream.

    Pls. verify what is the minimum slope.2% is not equal to 6mm vertical per 0.60m horizontal

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    3. Impacts to system operation if the new reservoir were to be taken off-line in

    the future for maintenance and/or cleaning.

    4.5 Piping and Valving

    Reservoir design shall include a provision for equalizing and isolating pipes and

    valves in order to be able to perform maintenance.

    Inlet pipe 150 mm. dia. shall enter each tank from the main pump discharge line

    and shall be installed 0.3 m. below the roof level.

    Each tank shall be provided with individual discharge pipe 200 mm. and shall be

    connected to the main discharge line 300 mm. dia.

    Each tank shall be provided with an isolation valve, which shall permit isolating the

    tank from the water system. An air release/vacuum relief valve should be installed

    on the distribution side of the isolation valve. A sample tap should be installed on

    the tank side of the isolation valve to allow for the required sample collection

    capability.

    4.6 Geotechnical Engineering Evaluation

    The geotechnical engineering evaluation provided assessment of the site

    condition, recommendations and conclusions based on the results of the

    Geotechnical Investigation conducted by Robei Drilling Services. The evaluation

    involved an independent review of the results of the investigation and providingalternative recommendations for geotechnical design parameters for consideration

    in the design of the design of the reservoir.

    The evaluation also included assessment of results of the seismic structural

    analysis related to the obtained soil bearing pressure.

    4.6.1 Allowable Soil Bearing Capacity

    The Allowable Soil Bearing Capacity recommended for use in the design

    considered the critical soil formation underneath the reservoir which may still be

    affected by the foundation loadings. While SPT values at foundation level are high

    indicating either stiff or dense formation, down below at depth about 8m to 9m

    below the existing grade are loose or soft formation critical for settlement. Thus, an

    allowable soil bearing capacity reduced to consider the presence of the critical soil

    layers of 200KPa as compared to previously considered allowable soil bearing

    capacity value was recommended. This allowable soil bearing capacity is

    recommended for use for normal static loadings. For transient loadings like

    earthquake and wind loads an increased of up to 33% is considered acceptable.

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    4.6.2 Foundation Pressure Overload based on results of StructuralAnalysis using Factored Load Condition

    The calculated 350 KPa foundation pressure obtained from results of the structural

    analysis using factored loads which included earthquake and wind loads, which

    effectively reduce the Factor of Safety for this portion of the loaded area to close to

    1.0, much less than the normal recommended FS of 3, may still be considered

    allowable, since the indicated width coverage of the 350 KPa foundation pressure

    is less than 2m and not expected to induce significant overstress over the critical

    layer at depth 4m below foundation level.

    4.6.3 Lateral Soil Pressure

    Considering the nature of the reservoir wall which is not designed to allow

    deflection to mobilize the active state of the soil, the coefficient of lateral earth

    pressure at rest of about 0.50 is considered the more appropriate for use in the

    lateral soil pressure calculations.

    4.6.4 Reservoir Foundation Level above the 4 meters proposed depthof Embedment

    The evaluation of the foundation assumed an embedment of 4m below natural

    grade. It also considered in the analysis, results of the drillings below this depth. It

    is, thus, recommended that during the construction of the foundation, excavationbe made to depth of 4m below grade. Then at overcuts, grade be restored to

    foundation level using properly compacted suitable granular materials.

    4.6.5 Effect of Sloping Grounds in the Vicinity to Soil Bearing Capacity

    Based on the cross-sections provided, analysis on the effect of the sloping ground

    adjacent the reservoir have also been undertaken. The recommended allowable

    soil bearing capacity of 200 KPa for normal operating loads, already took into

    consideration the slight reduction in soil bearing capacity due to the effect of the

    adjacent slopes.

    Under transient loading due to seismic and wind loads as represented by the

    factored loads, the overload on the sides of the reservoir near the adjacent slopeparticularly at Reservoir 2 may induce vertical deformation due to foundation

    overstress near the slope but this is expected to cover only the small area of the

    overstress and not to affect the overall stability of the reservoir. The magnitude of

    this deformation should be within the calculated maximum vertical deflection which

    has been allowed in the design. Defects, if any, caused by deformation created by

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    the overstress, may be repaired after the occurrence of the loading of the design

    earthquake.

    4.6.6 Effect of the Reservoir Loads to the Stability of the adjacentSlopes

    Analysis has also been conducted to check if the reservoir loading will affect the

    natural stability of the adjacent slopes. Although Reservoir 2 is located nearer the

    adjacent slope, the reservoirs are located relatively distant from the slopes to

    impose significant load on the slope. Under normal operating condition, the

    reservoir loads have very minimal effect on the natural stability of the adjacent

    slopes.

    During occurrence of earthquake, the overloaded small portion of the side of

    Reservoir 2 at about 350KPa, could, however, induce significant load on the

    nearby upper slope to have some effect on its stability. But this is likely to be only

    localized and not expected to have significant effect on the overall natural stability

    of the slope nor the stability of the reservoir.

    4.7 Reservoir Structural Design

    This structural analysis and design report outlines the general structure design

    criteria and parameters, as well as the structural design philosophy under the

    approved codes and standards.

    4.7.1 Codes and Standards

    The requirements contained in the following codes and standards shall form a part

    of these criteria, in the manner and to the extent specified herein.

    The following Codes of Practice will govern under Structural Analysis and

    Investigation:

    a. NSCP National Structural Code of the Philippines Vol. 1, 5th Edition, 2001

    b. ACI 318 Building Code Requirement for Structural Concrete, 1999 (as

    adopted in NSCP 2001)

    c. ACI 350 Code Requirements for Environmental Engineering ConcreteStructures, 01

    d. ACI 315 Manual of Standard Practices for Detailing R.C. Structures, 1999

    e. ASCE 7 Minimum Design Loads for Building and Other Structures, 1995

    f. AASHTO Standard Specifications for Highway Bridges, 16th Edition, 1996

    g. AWWA American Water Works Association

    Deleted: the latest edition of

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    h. AISC Manual of Steel Construction, Allowable Stress Design 9th edition

    Specification for Design, Fabrication and Erection of Structural Steel (as

    adopted in NSCP 2001).

    The following Standards of Practice will govern under Materials and Construction:

    a. PNS Philippine National Standards

    b. ASTM American Society for Testing of Materials

    4.7.2 Materials

    4.7.2.1 Reinforced Concrete

    Concrete Compression Strength: Concrete cylinder compression strength

    measured in accordance with ASTM C-39-86 will be:

    a. fc = 34.50 MPa (5,000 psi) for columns, beams/girders, suspended slabs,

    footings and tank walls

    b. fc = 20.70 MPa (3,000 psi) for others

    4.7.2.2 Reinforcing Steel for Concrete

    Reinforcing bars Yield Strength: Reinforcement bars minimum specified yield

    strength measured in accordance with ASTM A615 will be:

    a. Columns, beams/girders, suspended slabs, footings and walls:

    fy = 414MPa (60,000 psi) for deformed bars 16 and larger;

    fy = 276MPa (40,000 psi) for deformed bars 12 and smaller.

    b. Ties, Stirrups:

    fy = 276MPa (40,000 psi) for 12 deformed bars and smaller

    4.7.3 Design Loading

    The following loads considered in this report are those recommended in Chapter

    2, Loads and Actions of NSCP 2001 and American Concrete Institute ACI-350-01

    Code Requirements for Environmental Engineering Concrete Structures.

    4.7.3.1 Vertical Loads

    a. Dead Loads & Self Weight

    Deleted: PCA Portland CementAssociation

    Deleted: national

    Deleted: retaining walls

    Deleted: 3.80

    Deleted: 5.86

    Deleted: 5.86

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    Dead load includes the weight of the structure and all permanently attached

    equipment. If modeled, the self weight of the structure is usually generated by

    the computer by assigning the appropriate material density and member

    sizes.

    Reinforced Concrete Density = 24 KN/cu.m.

    Plain Concrete Density = 20 KN/cu.m.

    Structural Steel Density = 77 KN/cu.m.

    Unit weights other than the above shall conform to what is indicated in the

    National Structural Code of the Philippines (NSCP 2001).

    b. Live Loads

    Live load includes the loads due to the intended use and occupancy of area

    and moveable equipment.

    Roof Live Load = 1.92 KN/sq.m.

    Liquid Content = 9.81 KN/sq.m.

    4.7.3.2 Lateral Loads

    a. Wind Loads

    Wind Load, W shall be calculated in accordance with the static analytical

    method. The following data will serve as a guide in calculating the wind force

    on the structure as a closed structure.

    b. Earthquake Loads

    Seismic or Earthquake Load, E may be considered as lateral forces that shall

    act non-concurrently in the direction of each principal axis of the structure.

    These loads are actually dynamic forces that shall be used, among which, for

    structures 60m or more in height. However, an alternative static lateral force

    is recommended based on rational analysis of well established principles of

    mechanics.

    Seismic load shall be calculated in accordance with the formula as given in

    Section 208 of NSCP 2001 and using internationally accepted structural

    engineering software.

    4.7.3.3 Other Design Load and Forces

    The proposed ground reservoir structure is considered as a special

    environmental engineering concrete structure intended for conveying, storing,

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    or treating water. Considering the location of the structure in elevated land

    with high seismic risk area, the design analysis of the structure shall consider

    the non-sloshing (lower) and sloshing (upper) portions of its content which will

    induce hydrodynamic pressures on the structure; namely impulsive and

    convective pressures, respectively.

    4.8 Mechanical Design

    Water level sensors may vary from mercury-type float switches to ultrasonic

    sensors to pressure switches. Each type has a different sensitivity to water level

    changes from fractions of inches to more than a foot. The tank designer will have

    to account for the type of level sensor specified when determining the vertical

    dimension needed for proper operation of the device. Manufacturers

    specifications generally govern the determination of this dimension.

    Once the pump control device is selected, the tank designer will be able to factor in

    the vertical dimension when determining the other aspects of tank configuration,

    such as the width and height, as well as the shape. The volume of OS should be

    sufficient to avoid pump cycling in excess of the pump motor manufacturer's

    recommendation. Historically, a rule of thumb was to limit the motor to no more

    than six starts per hour. However, many manufacturers will warrant more frequent

    cycling for their pump motors, depending upon the size of the pump.

    4.9 Electrical System

    Systems relying on non-elevated reservoirs (i.e., reservoirs that can only supply a

    distribution system in whole or in part through a booster pump station) shall be

    equipped with onsite back-up power facilities or, at least, with the ability to readily

    connect to a portable generator.

    Back-up power facilities shall be designed to start, through an automatic transfer

    switch, upon interruption of the utility power supply.

    The primary intent for recommending back-up power is to assure that the system is

    pressurized at all times to minimize cross-connection contamination concerns.

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    5.0 Design Drawings