environmental assessment davao citw · 2016. 7. 17. · davao city and cotabato city, in finding...

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Republic of the PhilippinesLocal Water Utilities Administration

SEWERAGE AND SANITATION PROJECTWATER DISTRICT DEVELOPMENT PROJECT

WORLD BANk

ENVIRONMENTALASSESSMENT

lLoN REPORT

DAVAO CITW

Yp SA AS

_f 9 2_ ~DAVAOCITY

9wJINDAM ANXIOM ,9

March, 1997

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DAVAO ENVIRONMENTAL ASSESSMENT REPORT

ERRATA:

page 38, first paragraph: "Several potential sites... Planning Department (see Figure 3."

page 38, first paragraph of B. Toril:"Two sites have been identified (see Figure 3.2 by the City...."

page 58, first paragraph: "To evaluate the overall... district in Table 4.5 CDM (1994)....

page 59, first paragraph somewhere past midway: Table 4.5 shows that a conservative....

page 61, second paragraph, 2nd sentence: The coliform counts reported in Table 2.6...

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SCAIINNED

Republic of the PhilippinesLocal Water Utilities Administration

SEWERAGE AND SANITATION PROJECTWATER DISTRICT DEVELOPMENT PROJECT

WORLD BANK

ENVIRONMENTALASSESSMENT

UfON REPORT

b g DAVAO CITY

DAVAO

March, 1997

TABLE OF CONTENTS

P_ge

EXECUTIVE SUMMARY I

Chapter I INTRODUCTION 12

Chapter 2 BASELINE ENVIRONMENT - DAVAO CITY 16

Section I Existing Environment 16Section II Environmental Pollution 21

Chapter 3 PROJECT DESCRIPTMON AND ANALYSIS OF ALTERNATIVES 30

Section I Project Rationale and Objectives 30Section II Sanitation 30Section m Overall Sewerage Scheme 32Section IV Recommended Project Design for Davao City 49Section V No Project Scenario 53

Chapter 4 ENVRONMENTAL IMPACTS 54

Section I Beneficial Impacts of the Project 54Section II Project Iinplementation Impacts 63Section m Summary 66

Chapter 5 ENVIRONMENTAL MANAGEMENT PLAN 67

Section I Mitigation Plan 67Section II Monitoring Plan 69Section III Implementation Arrangements 69

Appendices

I. Bibliography2. Climatological Normals (1961-1995)3. Typical Noise Emissions of Construction Equipment4. Expected Noise Levels at Various Distances from Construction Equipment5. Environmental Quality Standards For Noise Maximum Allowable Noise Levels6. The Advanced Integrated Pond System (AIPS) of Wastewater Treatment

Environmental Assessment Report: Davao Citv

i

I

I?

I

EXECUTIVE SUMMARY

Introduction

In the Philippines, the typical urban area/built-up area is characterized by a heavy concentrationof activiies, both commecial and industrial. It is also the area where the density of populationis at its peak. These areas are also the sites where the production and consunption of raw andprocessed materials could be found. Consequetly the, pressure on the life support systems inthese areas are far higher than the suburban and nual areas. Advese environental conditonssuch as the generation and similarly the discharge of wastes into the environment is common inurban and built-up areas Unfortunately, the an, type and concenrion of wastegencrated exceed the capability of the local environent to absorb and assinilaethem. Thecariymg capacity ofthe life support systems are stretched to the limits. The urgn ofestabhlishing collection and tment methods which will preven adverse impacts to thc healthand well-being of the residents, and to the ecological systems which sustain them cannot beignored and overstated.

Most urban centers in the Philippines rely on individual septic tank systems for thetreatment and disposal of wastewater from domestic and commercial buildings. However,the designs for such systems is often inadequate. Facilities for land disposal of effluentsfrom the septic tanks are generally absent. Hence the partialy treated septic tank effluentsflow directly into storm drainage systems and other receiving bodies of water, therebyexacerbating an already grave poilution situation.

There are several possible options for addressing this problem, including improving thedesign of the septic tank system with the installation of soil absorption systems. But anenvironmentally sound alternative that is cost-effective and captures economies of scale isto connect individual properties directly to a sewerage system for the collection, treatmentand disposal of the urban wastes.

The provision of a cost-effective centralized wastewater collection, treatment, and disposal isthe pnmary objective of the proposed Water DisicU Dewiopmnent Poject. The proposedproject will assist the local governments of Dagupan, Calamba, Laguna, Cagayan de Oro,Davao City and Cotabato City, in finding solutions to the problern of sanitaLon.

Better sanitary conditions will thus be experienced in the areas served by the sewerage,drainage and sanitation systems. This will reduce water-borne pollution and water-loggingwithin the cities and in the surrounding water bodies, thereby bringing health benefits tolocal populations. In Davao, Cagayan de Oro and Calamba cities, pollution from humanwastes have affected recreational areas, such as beaches and lake front areas. Project

Environmental Assessment Report: Davao CitY I

investments in wastewater collection and treatment will also have positive benefits interms of improving prospects of saving the remaining beaches for the city residents. Theconstruction of the systems will protect shallow groundwater aquifers from contarnination,particularly in Toril area of Davao city, which forms the source of the city's water supplysystem.

Environmental Assessment Requirements

This Environment Impact Assesmen Report for Davao City has been prepared inaccordance with the P*eldental Decree No 1586 otherwise known as the EnvironmentlImpact Assessment Law and Department of Environment and Natural Resources RevisedAMsinimaiw Order Nos 36, the Rvised Water Usage and Clsszficataon/Water QualityCnteria and RevisedEffluent Regulmions of 1990 rqsevely, and WorldBank 'sOperationalDirectie 4.01 on EnviromnentalAuesment. The revised Administrative Order36 for Environmental Impact Statement System issued in 1996 is comprehensive and iscompatible with the World Bank's Operational Directive 4.01. It outlines the procedureto be followed by environmental critical proiects (ECP) and project to be located inenvironmental critical areas (ECA) in preparing enviromnental impacts statement (EIS) .ECP and ECA are defined in the AO It should also be noted that that local ordnances andregulations goveng projects of such nature have been taken into consideration in preparingtis report. Similar EIA reports are beng prepared for the other 4 cities.

This report has been prepared by a team of local conslants under the aegis ofthe Local WaterUtilities Adnwstration (LWUA) and the Davao City Governent Much of the work relaingto the envionmental impact analys was undertaken as part of the feasibility study done by C.Lotti and Associati. Consultation with the community is an on-going process. The sanitationcomponent of the project will be exeated in a participatory manmer, and detailed guidelineshave been speled out.

Selection of Priority Cities

The choice of the first batch of Philippine cities for sewerage investments was made afteran initial screening at the national level of urban areas facing the most serious problem ofpollution by untreated wastes. Of the five cities, Davao and Cagayan de Oro represent thelargest class of provincial cities with current population estimates in the range of a millionand half a million respectively. There are several major population concentrations in thecity; each being a source of sewage contamination for nearby surface and ground water.However, the largest volume of sewage is generated by the largest consumers of pipedwater supply; in the Central Business District or Poblacion area. Untreated wastewaterfrom this area has polluted low-lying coastal areas, and basically converted the principalrivers into open sewers.. The scale of the pollution problem can be appreciated by the factthat about 90 per cent of the daily water supply of 140,000 cubic meters in Davao city and

Tius is the term used by DENR and refers to the standard Environmcntal Assessment Reportrequired by the World bank as per OD 4.01

Environmental Assessment Report: Davao Citv 2

76,000 cubic meters in Cagayan de Oro is being discharged as untreated wastewater.Outside the Poblacion areas, there are pockets of population concentrations pollutingnearby streams, creeks and channels.

In the other three cities of medium size (Cotabato city, Calamba and Dagupan), currentpopulation estimates are close to 200,000. While the scale of urban pollution problems arenot comparable with Davao and Cagayan de Oro, these cities are located close toenvironmentally sensitive wetlands and water bodies. In Cotabato city, the urban area isactually below the mean sea level, exposing inhabitants to frequent waterlogging duringthe monsoon months. Calamba is located on the shores of Laguna Lake, which hasexperienced a rapid deterioration in water quality over the last two decades. Dagupan cityis close to a large estuarine zone with ecologically sensitive wetlands and fishponds. Ineach of these cities, Mayors and city officials have recognized for some time that unlesstheir complex environmental problems are tackled through a strategic plan of handlingwaste disposal, sustainabiity of urban growth could be seriously affected.

Overall Project Approach

The proposed project follows a demand-based approach, in the sense that facilities will beconstructed only if they conform with the preferences of local stakeholders, and servicesconform to their respective willingness to pay. The stakeholders represent the differenttiers of organizations from the City Council and Barangay (part of the formal LGUsystem), to the more informal purok, neighborhood and household levels. During projectpreparation, the idea of involving communities in the planning process was field-tested inthree barangays of Davao city, and found to be quite successfil. The basic decision-making process is as follows:

For the capital-intensive trunk system, consisting of the main transportationsewers, primary drains and wastewater treatment facilities, the projectdesign and implemnentation plan has to be approved by the City Council,because the latter is responsible to repay the loan [see Annex 3 on FmancialAspects, Staff Appraisal Report (SAR)].

For the feeder system, consisting uf collector sewers, secondary drains and on-sitesanitation facilities, barangays and local neighborhoods will be associatedwith the planning and implementation program. The design criteria havebeen simplified, so that the feeder system can respond to local preferencesand willingness to pay, rather than be bound by any conventional sewerdesign criteria used in industrialized countries. Detailed design will beconducted through a participatory process described in Annex 13, SAR_

Given the capital-intensive nature of the investments, the proposed project is only theinitial phase of a program to improve the sanitation infrastructure through a strategicplanning approach that involves a mix of on-site and off-site wastewater collection,treatment and disposal. Choice of initial service areas for sewerage has been confined tothe Central Business Districts or Poblacion areas because these are the major contributors


to municipal wastewater pollution. The only exception made is in the case of Davao City,where a second area of high growth prospects (TorI) has also been included on therequest of the LGU.

The project will construct a sewer network that will discharge sewage to a verticallyintegrated pond system designed to treat both sewage and septage. In each of the cities,with the exception of Davao, the treatment site was selected in areas free fromencumbrances.

For the sanitation and drainage components, the entire city has been included in theproject area, with final selections being made on the basis of demand. On-site treatmentsystems through the construction of VIP latrines, pit latrines, pour flush toilets and septictanks will also be constructed if there is demand from property owners. For thoseproperties with uncertain land tenure (as in squatter settlernents), the project will financethe construction of communal toilets, to be managed by NGOs and/or the private sector.The specific location of these facilities will be driven by the willingness to pay for theservices by beneficiaries at the barangay leveL provided of course that these are technicallyfeasible.

Analysis of Alternatives

The recommended solutions for wastewater treatment were arrived at after an intensiveprocess of evaluating alternatives during the project preparation in order to achieve costeffectiveness and acceptability. The alternatives considered were anaerobic/facultativePonds, modified lagoon systems and mechanical treatment. The evaluation of alternativesindicated that the modified lagoon systems, despite having a higher O&M costs comparedto anaerobic/facultative ponds (as it requires mechanical aerators and recirculation pumps)was appropriate. The selected option met the foliowing criteria the effectively:

irnimize overall pond area required

Minimize odor production

Meet DENR effluent quality criteria, including fecal coliform reduction

Minimize sludge production rate

Maximize potential to use surrounding land for recreational purposes

Environmerral Assessment Report: Davao Cirv 4

Summary Information on Project Cities

Davao Cagaan de Or o Cal D

Poqulation(1990) 849.947 339,598 127.065 173.453 12S.ooo

Housnng 163329 47.724 21.5S1 32109 21.219

Sizeof'CIaa 1000 l eOOOh 400hbecaa 120bc 95bets 50bedaeB _S~Diarc(CBD)

Morbiditv rae per 95 for 733 for diarrhta 3050 for diith 3l 2 for puastim 523 for pgi-10.000 f diseam diuXagturd (tird re*) (rtun ran) (second ra*) enteritis (thd

Ta-k ar" rank)diseases)

Wer bodies at risk DSaW nu ad Csapr nvrad About 50% of cty Laguna Lake About 50% of cItybecane of _cul a8 bead. claw adjondug beace a us- of am am wdilmds.poihg to city no it for on Mpajlsw Bay wdand fib ma l usd for fish

rea_ahal udit for pondse ad midity sidid farusug

P,_mpo bmmo(feesI_ _ ~~~~~~~~~~~~~~~~onnm tof n

The urban area/built-up area in the project cities is characterized by a heavy concentrationof commercial and industial activities. It is the area where population density is highest.These areas are also represent the bulk of economic activity in the informal sector - suchas, the production and consumption of raw and processed food, light manufacturingactivities and retail distribution. A large proportion of piped water supply from the localWater District is also consumed in the Central Business District. Consequently, thepressure from both solid and liquid wastes in these areas greatly exceed the capability ofthe land and water resources to absorb, assimiate and recycle them.

Davao City

Impact Dunng Construction Phase

The implementation of the project and-its components is projected to produce onlyminimal adverse environmental impacts. The socio-economic impacts will be beneficiaLand will result in a better standard of living for the municipalities and cities concerned. Inthe short-term the project will provide emnployment and livelihood opportunities to thepopulation of the surrounding communities through the jobs generated during theconstruction phase. In the long-term, better sanitary conditions will reduce sicknessescaused by water-related problems. Thus an improvement of the existing environmentalconditions is expected. The project will undertake mitigating measures to minimize, or ifat all possible, eliminate adverse impacts.

Air Quality. The implementation of the project will result in an increase in the ambientconcentration of suspended particulates in the vicinity of the project site. This would be

Environmental/Assessment Report: Davao Cirv 5

attributed to dust from land clearing and excavation activities, which expose soil to windand vehicular traffic over unpaved road.

Water Quality. Excavation activities in the project sites could also loosen soils andtransport of these materials to any surface waters, thereby increasing siltation andturbidity.

During the rainy season, surface runoff may increase total suspended solids, and causetemporary stress at the discharge points. However, the impact will be locaiized, and whenthe vegetative cover returns, impact on the receiving body of water caused by surface run-off will be eliminated.

Noise. The noise irnpact during the construction stage is expected to be generally minimaland will not require any special noise abatement measure. The treatment plant sites shallhave a setback away from residential clusters, which will definitely provide the necessary'buffer to reduce noise impact during construction of the modified lagoon systems.

During the pipe-laying, some noise will be generated due to the construction activities andthe temporary operation of heavy equipment. Noise from breaking concrete pavement andsidewalks may also pose a temporary problem. However, the noise level at the streets isexpected to be within the ambient noise quality standards.

Socio-economic. The only potentially adverse impact is likely to be in the Davao sewagetreatment site, where approximately 15 squatter structures are located in the vicinity of thetreatment plant site. The treatment plant, can, however, be constructed without affectingthese structures, and hence no resettlement action plan will be required. The CityGovernments will be requested at appraisal to indicate how they plan monitoringpotentially adverse impacts in the project cities.

Ecological Effects. As there are no rare, endernic species of flora and fauna in any of theproject area, project implementation has minimal impact on the terrestrial ecc!ogy.Vegetative cover shall be unavoidably cleared during civi works.

Impacts During Operation Phase

Air Quality. The operation of the wastewater treatment facility will have minimal impacton the air quality of the area. Aside from the occasional odor nuisance, it is not projectedto have adverse effect at all.

Water Quality. The implementation of the project will be beneficial to the general envi-ronment of participating cities and their environs. Discharging of untreated domesticwaste water from the high volume consumers in each city's Central Business Districts intonearby bodies of water would thus be minimized or eliminated. However, operations andmaintenance failures may result in occasional discharges.

Environmental .4ssessment Report: Davao City 5

Socio-economic. The provision of sanitation facilities in the project cities wouldundoubtedly benefit the general populace of these areas. The occurrence of epidemic-scale diseases caused by current unsanitary conditions will be reduced. This will result in amore healthy and productive population.

Sludge Disposal. The modified lagoon system or Advanced Improved Ponds System(AIPS) will require sludge disposal at very infrequent intervals. The sludge in theanaerobic pond/s remains for an extended period continuously undergoing organicdecomposition. This may take place over a 20-30 year period. One system in operation inthe U.S. has not been desludged in thirty years. Recent testing of this system has indicatedthat the sludge is well-digested and very stable. If desludging does become due,arrangemnents can easily be made with the city environment office for disposal at thesanitary landfill.

Mitigating measures to mininize, or if possible, eliminate adverse impact will beimplemented. Measures to enhance the existing environmental conditions in the projectsite shall be implemented to maintain the enviromnental sustainability of the area. Theimplementation of the project wilL inevitably produce impact, both adverse and beneficial.Table I shows the potential impact, risks and the proposed mitigating action.

Implementation and Monitoring of Management Plan

The PMO, with the assistance of LWUA-CPSO and consultants, would monitorcompliance with the ECC and carry out the requisite data collection. Monitoring reportswould be submitted to DENRIEMB and the World Bank periodically. Whileresponsibility for the various mitigation activities have been identified, the PMO willensure that the requirements are complied within addition, feedback from comnunities,city officials, NGOs, etc. wiU be pro-actively sought through the city public affairsprograms, regular monthly meetings of barangay captains and other methods. Funally,DENR, through its planned PPA system, would also periodically monitor and auditcompliance with the ECC, assisted by independent contractors.

Table 2 summarizs the responsibilities and timetable for the Mitigation Plan.

Environmental Assessment Report: Davao City 7

Table 1: Mitigation Actions

Construction Phase

Potential Impma & Risks Mitigation Action

* Poor qualty of consuon * Design and supevision contra will be separated from supplyand installation contract as a means of assuring quality ofconstrucion. Works engineers, with a relatively indepe tsource of information on construction progress, will be hired.

Air Polluion * Careful consructon planning and work phasiLg, specificationsand constrion methods to reduce the length of time that the

* Constuction equipment and soil is cxposed to the enviromentvehicles may cause higher * Provision of adequately and propely tainmtad storge forsuspended particult, odors and construction materials and equipmnfumes emissions - COt. CO, NO, * Expeditious and prompt removal of cvatd materials or

dedged spoils from construction sites.* Exposure of fine-grain particles to * Replar d andequate sprinkling of water on dust-generating

wind and vehicular traflic will mnds/piles resulting from eardhnoving activities and civillikely rsult in a decrease in air wrks.quality. * Good housekeepgi for all constructiwo affected as and

workpla.* Control of motor vehidcle and equipment ions* Use of protective gear by all workers.

Water Polution and Soil Erosion * Provide tempowy dainage and stoage failities for excavtionsoils, for fuel and oils needed for equipment

* Siltation * Carehfl and rational plnning of construction and post-construction phases of the prcect

* Maintesnce of adeae drnagp system.

* Noise from operation of construc- * Eect temporay sound barrie around the work sites; avoidtino equipnt woud be about 70- simultaneous use of heavy equipment; limit Jaytime work,80 dBA at 10 m; 50-70 dBA at 30 vebicle speed at 20 kph; egular maintenac of quipmetm. * Use of apppruiate mufflers and sound proofing of construction

machineies, quipment, and engies Use of apprpriate shock-absorbing mountings for mwainy.

. Establshment of buffer zones and noie zones

* Temporary Dlisruption of Traffic * To the extent possible, feeder and coUecon sewer lins will beFlow located along secondary sbeets

* Scheduling and increasing input resources so that period oftmffic disruption in primay roads are reduced.

* Coordinate with city tmtEc management office and the PNPTrafic Management Command

* Clear diretional signs and barriers in case traffic rerouting isneeded.

* Public Information campaign.

Environmental A.ssessment Report: Davao Citv 8

________________________ Operation PhasePotntial Impact & Risks MltigaZion Action

* Envuroncntal hazards due to * Carefully designed post-construction mantenance, contingencvaccidnts and man-made or natural and momtonng programs.disasters. * Well designed plan for detection of accident or natwal events

* Breakdown or malfunction of the including precautionary and remedial measures to besewer lift station will increase level taken/obsavednof pollution at the mouth of Davao * Adequate plans for environmental rehabilitation, clean-up,River as raw sewage will have to be restoraton, and disposition of temponary strcures and facilitiesdumped directv. nstIled dng the construition phase.

Water Pollution * Upgrade laboratory facilities of the Davao City Water Distnc tobe able to undrtake waster analysis.

* The effluent dischage point of the * Following the bubble concept, wastewater discharged into Davaotreaument plant is affected by tidal River shaL in the lng-tem, conform to the water qualityconditions (estuary). sadards established by the Department of Envionment and

Natual Resources as set foath in DAO No. 34 and 35, RevisedWate Usage nd Clasification/Water Quality Standards andRevised Effluent Regaltions of 1990, respectivly.

* A dispersion/dilution modelig study will be conducted to priorto cating the outall. Treted effluet discharge to Davao Rivershall be timed based on tidal conditions. The adopton of theAUPS pmcess for the treat plants should result intoatainment of effluent stands.

* Investiating the possibility of rchbaging the acquifer withurated wastewate fmn Toril teament plant

* Noise would be at about 65495 * Establshment of buffer zones and noise zones.dBA, pnncipally coming frotmsptage trucks unloading at theponds-

* Odors (organic and sulfit com- . Maintenance of greenbeit zones and vegetation.poumds mainly from the trucks * Pvison of ladscaped open sscs which wiU impWrove theunloading seWe) aesthtch of the ae by plantiung the gen stnps with approprate

plant or tre speci

Manasement and O&M of the System Institutional:* Management Conttact with DCWD which has proven utility

* Poor maintenance of pumps management and operations capacity.* User consltation at detailed engining d...agn stage to isure

* Low connections COODeCtiOn.* Sewerage stcharge should be sufficient to provide inctives for

DCWD to maintan system.* Requie M&E repoing to the DENR and LWUA.* Explore feasibility of BOO/BOT contrats for recretional

actvities in unused lands at treatmet sites.* Provide adequate training of DCWD and city staff.Retulatory:

* Require compulsory connection for all commecial, indusial andhigh domestic water users.

* Utilize Public Perfornance Auditing system being set up byDENR to monitor advere impacts.

Technical:* Provision of adequate maintenance eqwupment and spares with

DCWD.

Environmental Assessment Report: DavaooCity 9

Monitoring and Implementation Arrangements

Construction Phase

Ambient air quality measurements will be undertaken near construction sites. This will bemostly near locations where sewer network is being laid and treatment plant sites. Whenselecting sites due consideration will be given to sensitive receptors like schools, hospitals,houses etc. Total suspended particulates (TSP) will be measured once a fortnight, for 8 or24 hours, over the construction period.

Noise wiU measured at the same locations as TSP. Leq and L9o values will be measuredand recorded.

Overation Phase

Receiving water quality will be monitored by the Environmental Management andProtected Areas Service of DENR. The local Regional Technical Directorate agency iscurrently monitonng the status of Davao river and estuarne water quality on a monthlybasis. PMO will collect information on present conditions, observed changes in pollutionloads etc. It should be noted that all the pollution load will not be removed and theproposed sewerage infiastucture will greatly reduce the problemn. Once the plan becomesoperational, the operator would be required to set-up a laboratory and measure theefflluent quality.

Treatment Plant Operator will institute a monitoring program to measure the effluentdischarge. Daily representative values of PHK 5-day BOD, COD, Total Nitorgen andTotal Phosphorus will be measured during the start-up period. Once the plant operationsstabilize, weekly measurements (24-hourly basis) will be taken.

Quaterly reports showing the trends of effluent discharge and receiving water quality willbe reported to the PMO and DENR Regional Office.


Table 2Summary of Responsibilities and Timetable for the Mitigation Plan

Actiw* P-R_PM t Sbu Camp'

Sewoe ECC clec fSom DENR. CPSO-LW%'A De.itre 196 mUrdh 1997

CoUsei refe ce amb.a ai poamasi City PMU. wih DENR ional Mwdh 1997 May 1997dthe Propose nm pit aim at office

Pmj cti

Enae that the bid doamui imcue PMO Mwrb 1997 Mav 1997p-v for mnuution ndr the reap-d-lity ofthe comacor re,w coeuataoe workpait to amin co.qgiwAnc with -kvirunatal inupon- Pisa -_ _ _ _ _ _ _Tram opwann on O&M paciem & hw_h% PMO and CPSO-LWUA Deember 1997 April 1998

the Dano City Wer Dwit Dina_

Conduct mi. coemutwicsod udennatn Pn je City PMU. with ance May 197 DeaihercaNVIFg ofNGO. 1997

Monitor and repwt on co_pliance. PMO Bi-anl basis Bial bai

LWUAI,vrC:.tIWDDP%SOICM.W* 19. 19974:224 PM


1. INTRODUCTION

In the Plilippines, the typical urban aea/built-up arm is characteized by a heavy concentrationof actives, both conmiercal and industrial. It is also the area where the dnsity of populationis at it's peak- These areas are also the sites where the production and consumption of raw andprocessed materials could be found. Consequently the, pressr on the life support systems inthese areas are far hgh than the suburban and nual areas. Adverse eirmnmental conditionssuch as the generation and similarly the diLharge of wastes into the envirornent is common inurban and built-up areas. Unfortuatey, the amount, type and concention of wastegenemed exceed the capabiity ofthe local evronm to absorb and assimilate then. Thecariying capacity ofthe life support systems are streched to the limits. The urgency ofestabishing colection and treatment methods which will prevent adverse impacts to the healthand well-being ofthe residets, and to the ecological systens which sustain them cannot beignored and ovated.

The provision of a cost-efective calized watewater coDection, treament, and disposal isthe primary objective of the proposed WacrDi0is DewlopmaU Project. The proposedproject will assist the local goverets of Dagupan, Calamba, Laguna, C4gayan de Oro,Davao City and Cotabato City, in finding solutions to the problem of sanitation.

Most urban centers in the Philippines rely on individual septic tank systems for thetreatment and disposal of wastewater from domestic and commercial buildings. However,the designs for such systems is often inadequate. Facilities for land disposal of effluentsfrom the septic tanks are generally absent. Hence the partially treated septic tank effluentsflow directly into stormn drainage systems and other receiving bodies of water, therebyexacerbating an already grave pollution siuation.

There are several possible options for addressing this problem, including imnproving thedesign of the septic tank system with the installation of soil absorption systems. But anenvironmentally sound alternative that is cost-effective and captures econonies of scale isto connect individual properties directly to a sewerage system for the collection, treatmentand disposal of the urban wastes.

Better sanitary conditions will thus be experienced in the areas served by the sewerage,drainage and sanitation systems. This will reduce water-bome pollution and water-loggingwithin the cities and in the surrounding water bodies, thereby bringing health benefits tolocal populations. In Davao, Cagayan de Oro and Calamba cities, pollution from humanwastes have affected recreational areas, such as beaches and lake front areas. Projectinvestments in wastewater collection and treatment wi1l also have positive benefits intermns of improving prospects of saving the remaining beaches for the city residents. The


construction of the systems will protect shallow groundwater aquifers from contamination,particularly in Toril area of Davao city, which forms the source of the city's water supplysystem.

Overad Approach of the Proposed Project

The proposed project follows a demand-based approach, in the sense that facilities will beconstructed only if they conform with the preferences of local stakeholders, and servicesconform to their respective willingness to pay. The stakeholders represent the differenttiers of organizations from the City Council and Barangay (part of the formal LGUsystem), to the more informal purok, neighborhood and household levels. During projectpreparation, the idea of involving communities in the planning process was field-tested inthree barangays of Davao city, and found to be quite successfil. The basic decision-making process is as follows:

(a) For the capital-intensive trunk system, consisting of the maintransportation sewers, primary drains and wastewater treatment facilities,the project design and implementation plan has to be approved by the CityCouncil, because the latter is responsible to repay the loan (see Annex 3 onFinancial Aspects).

(b) For the feeder system, consisting of collector sewers, secondary drains andon-site sanitation facilities, barangays and local neighborhoods will beassociated with the planning and implementation program. The designcritena have been simplified, so that the feeder systenm can respond to localpreferences and willingness to pay, rather than be bound by anyconventional sewer design critena used in industrialized counties. Detaileddesign will be conducted through a participatory process.

Given the capital-intensive nature of the investments, the proposed project is only theinitial phase of a program to improve the sanitation infrastructure through a strategicplanning approach that involves a mix of on-site and off-site wastewater collection,treatment and disposal. Choice of initial service areas for sewerage has been confined tothe Central Business Districts or Poblacion areas because these are the major contributorsto municipal wastewater poliution. The only exception made is in the case of Davao City,where a second area of high growth prospects (Torii) has also been included on therequest of the LGU.

The project will construct a sewer network that will discharge sewage to a verticallyintegrated pond system designed to treat both sewage and septage. In each of the cities,with the exception of Davao, the treatment site was selected in areas free fromencumbrances.

For the sanitation and drainage components, the entire city has been included in theproject area, with final selections being made on the basis of demand. On-site treatment


systems through the construction of VIP latrines, pit latrines, pour flush toilets and septictanks will also be constructed if there is demand from property owners. For thoseproperties with uncertain land tenure (as in squatter settlements), the project will financethe construction of communal toilets, to be managed by NGOs and/or the private sector.The specific location of these facilites will be driven by the willingness to pay for theservices by beneficiaries at the barangay level, provided of course that these are technicallyfeasible.

The reconmnended solutions for wastewater treatment were arrived at after an intensiveprocess of evaluating alternatives during the project preparation in order to achieve costeffectiveness and acceptability. The altemnatives considered were anaerobic/facultativePonds, modified lagoon systems and mechanical treatment. In all the five cities evaluationof alternatives indicated that the modified lagoon systems, despite having a higher O&Mcosts compared to anaerobic/facultative ponds (as it requires mechanical aerators andrecirculation pumps) was appropriate. Details are available in project files. The selectedoption met the following criteria the effectively:

(a) Minimize overall pond area required

(b) Minimize odor production

(c) Meet DENR effluent quality criteria, including fecal coliform reduction

(d) Minimize sludge production rate

(e) Maxize potential to use surrounding land for recreational purposes

Environmental Impact Assessment

This Environmental Inpact Asmnent Report for Davao City has been prepared inaccordance with the PresidentialDecre No. 1586 othewise known as the Env SnenatImpact Assesment Law and Deprtent f bironment and Natol Resoucs RevisedAdmirnew Order Nos 36, the Revired Water Usage and Clamfication/Water QuabtyCriteria and Rev sed Effluent Regulations of 1990 respectivd, and World Bank'sOperatonal Directve 4.01 onEfvirnraentAsessmeni. The revised Administrative Order36 for Environmental Impact Statement System issued in 1996 is comprehensive and iscompatible with the World Bank's Operational Directive 4.01. It outlines the procedureto be followed by environmental critical proiects (ECP) and projects to be located inenvirornental critical areas (ECA). in preparing environmental impacts statement (EIS)'.ECP and ECA are defined in the AO It should also be noted that that local ordinances andregulations governing projects of such nature have been taken into consideration in preparingthis report. Similar EIA reports are being prepared for the other 4 cities.

This is the tenn used bv DENR and refers to the standard Environmental Assessment Reportrequired by the World bank as per OD 4.01


Ths report has been prepared by a team of local conltants under the aegis of the Local WaterUtilities Adminisration (LWUA) and the Davao City Govenunent. Much of the work relaingto the environmental impact analysis was undertaken as part of the feasibility study done by C.Lotti and Associati. Consultation with the community is an on-going process. The sanitationcomponent of the project will be executed in a participatory manner, and detailed guidelineshave been spelled outL

LWTUAJJaC. IWDDPiCK PJDOCAc 19, 197 4.26M

Environmental Assessment Report: Davao Cty i5

2. BASELINE ENVRIONMENT - DAVAO CITY

Introduction

This chapter is in two sections. Section I profiles the existing environmental situation inDavao and Section 2 analyses the water pollution impacts (historical) of uncontrolledsewage discharge.

Section I - Existing Environment

2.1 Land Reources and Use

Davao City, the major development center in Mindanao, is among the highly urbanizedcities in Mindanao. The city is situated in the west central portion of Region x) inSouthern Mindanao, bounded in the north by the Municipality of Kapalong, Davao Pro-vince; in the northeast by the municipality of Panabo, Davao Province; in the south by themunicipality of Sta Cruz, Davao del Sur; in the east by the Davao Gulf, in the west by Mt.Apo and North Cotabato; and in the northwest by the province of Bukidnon.

Davao City is approximately 950 kdloneters southeast of Manila It is the largest city inthe Philippines in terms of land area (244,000 has.). The city is divided into threecongressional districts which is further sub-divided into eleven (11) administrativedistricts: Poblacion, Talomo, Agdao, Buhangin, Bunawan, Paquibato, Toril Tugbok,Calinan, Baguio, and Marilog for efficient and expedient delivery of basic services. It hasa total of 180 barangays. (See Figure 2.1)

Table 2.1 shows the Land-Use in Davao City based on aerial photos taken in 1994 and asplotted by the City Planning and Development Office, Davao City. Table 2.2 presents theUrban Land-Use in the city.

2.2 PhvsioMraohv and GeoloRy

The topography of the area is relatively flat and rolling. The soil is very rich and fertile asevidenced by the agricultural activities in the area. The area has undergone physiographicchanges in recent times with the southern portion expanding due to deposition and thenorthem portion being eroded. These natural processes were direct results of the actionof the Davao River.


T Canowo C. * /X" ngan~~~~~jnmnI,-

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a vane ~~~~~~~~~~* AIO \:-N~~~~~~~~~~~~~~.~~~4~~~ , Miasma ~~~~~~~ ~ i/hre\¶ind-

gokp- rm~~~~~~~~~~~~~~ u Mandul "'.0 ribun~~~~~~

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Clastic sedimentary rocks are the most common outcrops in the City. Limited outcrops ofvolcanic rocks are found in the extreme western part of the City. The most imposinggeological characteristics within the city are Mt. Apo and Mt. Talomo. These inactivevolcanoes account for the steep slopes west of the city and also the radial drainagepatterns found along the slopes.

The geologic history of Davao City could be traced back to the pre-Tertiary period ascharacterized by the basement complex rock unit located in the northernmost section ofthe city. The basement complex was exposed during the pre-Tertiary period and remainedso until the sea covered the area during the mid-Tertiary period resulting to the depositionof the Kabigtican Sandstone. Further encroachment of the sea resulted to the depositionof the Upian Lirnestone and the Masuhi Sandstone. During a period of regression in thelate-Tertiary period the Mandog Sandstone was deposited.

The volcanic activity of Mt. Apo and Mt. Talomo, as well as of other peaks to the north,dominated the post-Tertiary environment resulting to broad expanses of volcanicdeposition west of the city (CDM, 1994).

2.3 Climate

Davao City is characterized by a mild tropical climate with no pronounced dry or wetseason, suitable for year round agricultural production. The lowland areas are faidywarm, however, the hinterlands, especially in the areas of high elevations, such as Calinan,Baguio, Paquibato and Marilog districts experience cooler temperatures throughout theyear.

The average annual rainfall is 1,749.8 mm and is evenly distributed throughout the year.The City being situated outside the typhoon belt, makes it an ideal place for the culture ofexotic fuiits such as durian, mangosteen, marang, pomelo and other agricultural produce.The City has an average of 168 days of rainfall. Appendix 2 shows the climatologicalnormals for the city of Davao.

2.4 Hvdrologv and Water Ouality

The receivin; body of water for the treatment plant is the Davao River. As per the De-partment of Environment and Natural Resources Classification, the upstream portion ofDavao River is classified as Class A while the downstream portion is classified as Class B.

The portion of the river where the discharge point of the proposed treatment plant shall belocated exhibits the characteristics of an estuary. The area is highly influenced by tidalfluctuations, i.e. the flow of the river reverses during high tide. Table 2.3 shows the waterquality of the Davao River as monitored by the Environmental Management Sector of theDepartment of Environment and Natural Resources Region 11. Sampling data extendfrom February 1990 to May 1996 at irregular intervals. Hence a time series could not beconstructed.


Table 2.1: General Land-Use

Land-Use Area (in Has)

Built-up 10,195

Agricultural 187,480

Forest Land 46,325

Total 244,000

Table 2.2 - Urban Land-Use

Land-Use Area (in Ha)

Residential 4,055.25

Conunercial 782.24

Industrial/Agro-Industrial 836.48

AgrialturalIdletVacant 21,648.78

Marine/Fishponds 179.20

Institutional 477.60

Open Spaces, RecreationaL etc. 196.80

Structures/Utilities 48.00

Dumpsites 1.28

Total 28,225.61

Sourc City Deveopmmt PIamg Offwr, Davao CitY


Table 2.3

Results of Physical and Chemical Analysis of Water

Davao River, Davao City

Date Sampled August 28 1996

Station ID 1: S0m. from the confluence w/ Tamugan River

2: Tamugan River, approx. S0m. upstream from the confluence w/ Davao

River

3: 800m. downsrem from the confluence w/ Davao River

4: Davao River, Mandug Area

S Davao River, Diversion Bndge, Ma-a

6: Davao River, Gov. Genmeso Bridge

7: Davao River, Bolton Bridge

8 Mouth of the River

CharcterisIics 1 2 3 4 5 6 7 18

Color Units 25 10 20 20 20 20 20 20

Tenatue, C° 29 29 29 29 29 29 29 29

pH 8.0 8.0 8.0 8.0 8.0 8.0 8.0 8.0

Dissolved Oxygen. n's/L 7.1 8.0 7.8 7.6 7.3 7.0 6.6 6.6

BODS. mg/L I

2.5 VeUctation and Wildlife

The proposed site for the wastewater treatment plant along the Davao River is situated ina built-up area. Portions of the site is planted to cash crops such as coconut trees, rice,fruit trees, etc.

The floral and faunal characteristics of the area has been highly controlled by human in-terference. Domesticated animals, such as dogs, cats, goats, chickens, are found in thearea. There are no significant, endangered nor rare species of flora and fauna existing inthe area.

2.6 Socio-economic Aspects

The population of Davao City is distinct because of its highly heterogenous composition.This was a direct result of the influx of nigrant settlers from Luzon, Visayas and the otherprovinces of Mindanao. Based on the 1990 census undertaken by the National StatisticsOffice, Davao City has a population of 849,947.

The 1990 census listed 159,976 households with an average of 5.4 persons per household.Davao City accounts for 19.0 % of the total regional population of 4,457,076. As of1990, the population density of the City is 347.82 persons/sq.km. The urban populationof Davao City accounts for 73.5% of the total population. This has brought on increasedpressure for the provision of basic services by the city.

Section II- Environmental Pollution

As in most other major cities, the urban area/built-up area in Davao City is characterizedby a heavy concentraton of conmnercial and industrial activities. It is also the area wherepopulation density is highest. These areas are also the sites where the production andconsumption of raw and processed materials could be found. Consequently, the pressureon the environment in these areas are far higher than the suburban and rural areas.Adverse environmental conditions such as the generation and discharge of wastes onto theenvironment are common in urban and built-up areas. Unfortunately, the amount, typeand concentration of waste generated exceed the capability of the local environment to ab-sorb and assimilate them. The carrying capacity of the life support systems are stretched.

2.7 Water Pollution in Davao City

The basic geography of Davao City is illustrated in Figure 2.2. There are several majorpopulation concentrations in the city, each a source of sewage contamination For nearbysurface and ground waters. Undoubtedly, the largest volume of sewage is generated in thearea of Poblacion and Agdao. There are three main drainage canals in the Poblacion area,all of which empty directly into the Gulf of Davao. Two smaller drains flow into theDavao River, which flows into the Gulf between Poblacion and Matina. Agdao Creek,which extends west to east in the area immediately behind the Agdao Public Market, also

Environmental Assessment Report: Davao Cutv 21

serves as a drainage area as well as a receptacle for sewage disposal before it flows intothe Gulf.

Squatter settlements in Poblacion are undoubtedly major sources of sewagecontamination. The highest concentration is in Piapi, fronting the Gulf, but there are othersettlements lining the Davao River as far north into Poblacion as the public market atBankerohan. Before it passes between Poblacion and Matina, the Davao River traversesseveral heavily-populated zones to the north. These factors make the river a likely conduitfor large volumes of sewage.

Other streams drain into the ocean northeast and southwest of the central city areas, andsome of them pass through significant population concentrations. Sewage volume in theTori area is already large, and promises to grow rapidly as population expands westwardfrom the central city area.

Figure 2.2: The Basic Geography of Davao

Coastal Population Clusters inDavao City

= Population Cluster]Davao R.

aon

. 1Gulf of Davao

Envwronmental Assessment Report Davao Citv 22

2.8 Environmental Impact of Uncontrolled Sewage Discharge

To analyze the impact of uncontrolled sewage discharge, four factors were considered:human health, fisheries, recreation, and land values. The available data is sparse and everyeffort has been made to capture the magnitude of the problem. The description follows.

2.9 Health Problems faced by Davao Residents

Sewage contaniination is a prime cause of diarrheal diseases, so it is not surprising thatthey have been ranked third among causes of morbidity in Davao City since 1991.However, official estimates of the actual incidence vary by two orders of magnitude. In1995, the Davao City Health Office (DCHO) reported a total of 73 medically-confirmedcases of diarrheal disease. For the same period, the Philippines Department of Health(PDOH) reported a total of 6012 cases - greater than the DCHO estimate by a ratio of82:1! Comparison with other cities was used for arrived at one set of estimates. PDOHnumbers have been chosen, because they yield incidence rates similar to those for Cagayande Oro.

The DCHO has reported diarrhea cases by district. Assuming the same rate ofunderreporting in each district, the district-level estimates are given in Table 2.4. Theyindicate a roughly constant rate of infection (6 per 1,000) across districts, with thepossible exceptions of Matina and Bunawan. This is confirmed visually by the scatter plotin Figure 2.3, which shows an approximately straight-line relationship between populationand PDOH-reported cases of diarrheal disease. Analysis demonstrates, the critical pointis simply that health-related priority for sewage projects is roughly proportional todistrict population.

Table 2.4: Population and Iltestidal Disease by District, Davao City

Population Diarrheal InfectionPopulation Density Disease Rate

District 1995 (/hectare) Cases (/100,000

Matina 60,886 34.1 574 940Bunawan 78,563 10.5 328 420Agdao 85,998 154.0 492 570Tonil 94,227 6.3 574 610Buhangin 135,346 12.8 820 610Talomo 148,534 16.6 820 550Poblacion 161,146 137.2 902 560

Environmental Assessment Report. Davao CUty 23

Figure 2.3: District Populatioo vs. Diarrheal Disease, 1995

1000

900 . - . -1-- . . ... ........800. . ... :...... .

o .: - -. - .... ~~~~~~~~~..... .. ---.,-,.- + ...:-: * °500 --- :

Q ~~~~~~~~~~.- :. :.- . :-.-. .-.-.::.----. ... .. :z O ,......................~~ ~~~................

O :- '.' ,,.'. ,,.,-'.,-- '.. ..... .. .. .. ;'

l : ~~~~~~~~~~.:. :-.::-. .:. ... :O -: - - ~~~~~~~~~~~~. --. --. :.:-:.;.; .-. ; :., -,,-,----. - - . . -.....-

300

200 ... .. . ....

100

00 20,000 40.000 60,000 80,000 100.000 120,000 140,000 160.000 180,000

2.10 Drinkins Water Contamination

Protection of drinking water from natural sources is another health-related issue which isof concem to the city. The aquifer basin located in Dumoy (Figure 2.2) is the main sourcefor the Davao City Water District (DCWD). Its water is notable for purity, and is ofcommercial interest because it has attracted bottling plants for several national bea andsoft drink companies. Although the city could combat contamination with chlorination,this would greatly reduce the appeal of the aquifer water for the bottling firms. Almost aOlof the expansion that the DCWD has planned over the next 10 years involves sinking morewells in the aquifer near Toril. When the assessment began, the city govermment wasconcerned about sewage contamination of the aquifer. The aquifer is located at a depth ofat least 800 feet, underneath a layer of hard rock. The technical consensus at the DCWDis that the aquifer is in no real danger from sewage contamination by an expanding Torilpopulation. It is well-protected by its depth.

The situation in Bunawan, however, may be more serious. Bunawan is in the northeasternarea of Davao City, somewhat removed from the other populous districts. It sits on top ofthe Mt. Apo catchmnent basin, which currently provides water for the district through wellsand springs. The DCWD's master plan doesn't anticipate extension of water service toBunawan until 2010, so the condition of the Mt. Apo basin water is a matter of concern.Recent chemical analysis performed by the DCWD has detected the presence of fecalmatter in this basin, including fecal coliform and enterococcus. Although the DCWDreports that contamination is not at unacceptably high levels, Bunawan has had outbreaksof cholera in both of the past two years. They may or may not connected to fecalcontamination in the basin water, but the correlation is at least suggestive.

Environmental .4ssessment Report: Davao c'tv 24

2.11 Damnaee to Fisheries

Data for the Gulf of Davao show a significant decrease in the productivity of localfisheries during the past 10 to 15 years. Originally, the impact of sewage contaminationon the Gulf fisheries was considered to be of concern. However, the reported decline isfor the entire Gui£ including waters well outside any possible influence from organiccontamination by sewage. It seems mostly attributable to overfishing, both legal and byillegal means which include dynamiting and fine-mesh netting. Therefore, fecalcontamination of coastal waters is probably not significantly affecting the catch. Theremay well have been some contamination of fish caught near the city shore, but the impactis difficult to assess.'

2.12 Loss of Recreational Amenities

The beaches of Davao City have traditionally served the city as major sources ofrecreation. They may have been particularly important for poor families who cannotafford travel to more distant sites in the Gulf For this reason, the contamination ofoffshore waters by sewage is an important political and social issue in Davao City.For the Times Beach area which abuts Poblacion and Matina, it is also not a new issue.In 1985, water samples drawn at three offshore points yielded the total coliform countsreported in Table 2.5.2

Table 2.5: Total Coliforn Counts (MPN/100), rimes Beach, 1985

Station I Station 2 Station 3Average 3,263 | 2,692 | 1,784 |Standard Deviation 5,943 5,977 2,293

In Table 3.2, the size of the standard deviations registers the effect of extremely highcoliform counts in some daily sample results. Variation of this type is typical, :-4 even inbeach areas with high average contamination, some days have safe readings because of thecombined effects of wind and tide. Unfortunately, there is no way of predicting such days,or informing the public in a timely fashion. Average coliform counts are therefore taken asgood indicators of risk, with numbers above 1,000 considered unsafe for swimming. Thenumbers in Table 2.5 make it clear that the beach area of central Davao City had becomeunsafe for swimming by 1985, when its population was considerably smaller than it is now.

lIn a recent survey (Whittington et. al., 1993), the residents of several districts were asked for their assement oftrends in the quality and size of fish caught during the preceding 20 years. Almost half the respondents saidboth quality and size were -much worse,' but there was no imputation of cause to pollution as opposed to over-fishing.

The t 98 5 samples were drawn at uitervals between lanuarv 8 and August 18. 1985.

Environmental .4ssessment Report: Davao Citv 25

In 1992, public concern mounted with publication of sampling results for eleven of Davao'smain beaches by the Philippines Enviromnental Management Bureau (EMB).3 The resultsare tabulated in Table 2.6 and displayed in Figure 2.4.

Table 2.6: Total Coliform Counts for Selected Davao Beaches, 1992

Beach Average Total StandardColiforms Deviation

Kalayaan 1757 1698Villa Victoria 654 1060Seagull 821 1044Times (between Saavedra & 1999 2452Bonguyan)Times (in front of Liberty Beach) 3568 8509Times (in front of Marina Azul) 1607 1158Coaco 1011 828

After the EMB results were published in the local press, recreational use of Times Beachdropped sharply. Less attention was apparently paid to the results for other beaches,although some also registered dangerous levels of contamination. Seagull and CoacoBeaches had average coliform counts at or near the critical threshold, and Kalayaan Beachwas substantially beyond it.

Figure 2.4: Population Clusters and Beach Coliform Conuts, 1992

Davao R.

X 0 *0b,4~~~011Coaco

35686 Times Beach

175 Vila Seaul (Liberty)

Kalayaan Victoria Gulf of Davao

3 The samples were drawn between July 7 and November 22. 1992. at intervals of roughly 4-5 days.


Since population clusters are the source of sewage contamination, it is logical to supposethat the condition of Davao's beaches is closely related to the size of the hinterlandpopulations whose waste drains into the Gulf Figure 2.5 plots beach contaminationagainst hinterland population and confirms that the relationship is a relatively close one. Itsuggests that installation of sewerage and treatment in any of the more populous coastalareas would significantly reduce the level of risk associated with swimming at the localbeach.

The study began with the assumption that upstream communities along the Davao Rivershould be counted as part of the Times Beach 'hinterland,' because the river transportstheir sewage to its mouth near the beach area. The policy implication of this assumption issignificant: If upstream contamination were a significant factor, installation of sewerage inPoblacion and Matina alone would leave rimes Beach highly contaminated. This wouldeliminate an important reason for an exclusive focus on sewering Poblacion and Matina inthe first phase of the project.

However, water quality infornation for the Davao River provided by EMB suggest.P thatthe original assumption was incorrect.' The data suggest that coliforn counts are likely tobe in the safe range, even at the mouth of the river after it has traversed all the unseweredpopulation clusters.5 By implication, contamination of Times Beach is due to drainage

from Poblacion and Matina, not to upstream contamination of the Davao River.

By accepted international standards, the pollution levels recorded offshore from severalDavao beaches are dangerous for swimmers. For days with particularly high coliformcounts, one can expect to see a heightened incidence of waterborne disease or skinirritation among people swimming at the affected beaches. However, examination of theavailable clinical health records from the beach areas shows no signs of such outbreaks.There are at least two possible interpretations of this finding: First. the people of Davaomay be accustomed to low-level intestinal disease because sewage contamination hasmade it endemic. If so, people would not regard post-swimming episodes of diarrhea asworth a clinic visit. Secondl] the traditional standards for safe swinniing may simply betoo conservative, so health damage is minimal. In any case, the people of Davao Cityhave already registered their own judgment on the matter. The use of beaches aroundDavao City, and particularly Ttmes Beach, has decreased considerably in recent yearsbecause people know that fecal contamination levels are high.

4 Sampling data provided by EMB extend from Fenuxary 1990 to May 1996 at irregu1ar intervais. There arereadings for almost everv month in 1990 but only for one month, February, in 1995.

5 While the EMB data do not include coliform counts, they do record measures of organic pollution and dissolvedoxygen. There is known to be a close relationship between these measures and coliform counts when the majorsource of water pollution is human waste. Even at the mouth of the Davao River, the results show levels ofdissolved oxygen and organic pollution which are well within the safe range. Thus, fecal coliform pollution atthe mouth of the nver is unlikelv to be at dangerously high levels.


Figure 2.5: Hinterland Population and Beach Contamination, 1992

Population vs.Average Total Coliforms

3.21.

3.2--.-.1e -/

l g 3.3 .. ............................. - -- ]~~~~~~~~~~~M........

2.9

2. . ......2 ....... .........--..

2 54 4.2 4.4 4.0 4.8 5 5.2 5.4

Log Populbtion

2.13 Reduced ftDortunities for Commercial Development

Accelerated high-rise construction and sharp increases in property values haveaccompanied the installation of sewerage in the Makati district of Manila and the centralbusiness district of Jakarta, Indonesia In somne Latin American cities, central-ctyproperty values are reported to have increased by as much as 20%/ after sewerage wasinstalled. It would not be surprising to see similar results in Davao City if sewerage wereinstalled in the Poblacion distfict. Davao is well-positioned to become a conmercial hubfor its region, and the city teadership cleary aspires to this role for the city. Rapidexpansion of high-rise commercial activity in Poblacion seems very unlikely unless the areais served by a sewer system.

2.14 Summary of Findings of the Existing Environment

Health-related problems related to sewage contamination are of uncertain magnitude, butare an important consideration for the city leadership. The available evidence suggeststhat the rate of infection is roughly constant across populous districts with the possibleexceptions of Matina and Bunawan.

The evidence suggests that the absorptive capacity of the Davao River is quite high, sinceits dissolved oxygen and organic pollution readings are well within the safe range even atthe river's mouth. The river does not seem to be adding significantly to the pollution ofTimes Beach.

Environmental .4ssessment Report: Davao City 28

Pollution of Davao Gulf near each beach is closely related to drainage from theneighboring population. Times and Kalayaan Beaches presently have the worstcontamination. Pollution reduction will depend on the proportion of the local populationwhose sewage is treated or safely removed from septic tanks.

There is no concrete evidence of health damage from beach pollution, even at levels whichare quite high by international standards. Nevertheless, there has been a sharp reductionin beach visits as Davao's residents have become aware of the contamination problem.

Dumoy Aquifer is in no danger of contamination, so Davao's main drinking water sourceand commercial beverage production are not likely to be threatened by sewage for theforeseeable future. The Mt. Apo catchment basin, which serves Bunawan, is alreadysomewhat contaminated; there have been two cholera outbreaks in the district during thepast two years.

Fishing productivity in the Gulf of Davao has declined, but sewage contamination has notbeen a significant factor.

Commercial development in the Poblacion is repressed by the absence of sewerage.Installation of a system would permit high-rise construction and a significant increase inproperty values.

LWTVAICrC:1WDDPHAPhR.ZDOCIaRdk 19. 97 4:25 PM


3. PROJECT DESCRIPTION AND ANALYSIS OFALTERNATIVES

Introduction

This chapters begins with an explanation of the rationale of the proposed project and thengoes onto describe the project. The main components - sanitation and scheme aredescribed separately. Descziption includes the analysis of alternatives considered inamving at the final choice. The chapter concludes with the recommended design and plan.

Section I - Project Rationale and Objectives

Chaper 2 describes the existing enviromnental sintation in Davao, and illsrates theworsening health impacts caused by the uncontrolled discharge of sewage. Less than 1%of urban Davao has piped sewerage. There are no treatnent and disposal facilities forseptage removed from septic tanks. Septic tank soakaways and overflows enter the drainsand the groundwater.

The proposed project is, therefire, aimed at addressing the problems of inadequatesanitation and sewerage in the City of Davao by providing sustainable sanitation andsewerage fcilities, thereby reducing public health risks and environmental poilution fromwastewater sources. The project is designed also to provide a learning experience forfuture expansion of sustainable sanitation services for tne city as well as for other cities.The selection of final project design is driven by: (i) demand-based approach, (C) level ofwastewater treatment to be achieved; and (iii) the need for protecting the enviromnent.

Section II - Sanitation

Proposed Facilities

The sanitation component will include the construction of 140 communal toilets in thePoblacion area. The sanitation works were based upon an identified deficit of sanitationfacilities of 37%. The location of the communal toilets is not defined yet and will dependon the consultation of potential beneficiaries. The areas to be served by the communaltoilets may include public areas such markets and low-income squatters or blighted areas.

Envwronmental Assessment Reporr: Davao City 30

The possibility to construct on-site facilities is site specific. As the majority of squattersare located on government owned property, that is, along river banks and shoreline it isunlikely that communal toilets, with on-site disposal will be technically feasible. In theselocations communal toilets will only be feasible if there can be a direct discharge to aproposed sewer.

The sizing of the facility is dependent upon the depth to groundwater, the permeability ofthe ground and the availability and cost of land.

The objective is to construct the communal toilets in areas where, through publicconsultation, there is an established demand and willingness to pay for the service.

The arrangements for construction and operation could take many forms such as:

(i) City constructs and operates;

(ii) City constructs and contracts out the operations either to a private company or tothe local conumunity the facility is serving through a leasing arrangement;

(iii) Construction and operation contracted through a concession arrangement.

It is recommended that arrangement (d) be given preference over the others, particularly ifthe local community is willing to operate the facility.

The different arrangements should be eamnined following consultation between the Cityand users, in order to implement the preferred option. Then following a monitoringpeniod, the more successful operation can be repeated. A balance has to be soughtbetween affordability to construct (the quality) and willingness to pay. The facility has tobe made "attractive" to the users and provide the service they require and, therefore, inselecting the option the following aspects should be considered:

D Site - central location to proposed users (designed to serve 250 users, orapproximately more than 40 properties);

- proximity to a proposed sewer line, if any, of the land area required(including for septic tank/soakaway)

- availability of water supply,

- availability of power supply;

- area not prone to flooding.

* Services - need for inclusion of showers/laundry facilities.

* Design - attractive to users;- clean, odor/insect free;

- well lit; good security;

- facilities designed for intense usage; need to be functional and durable.


Cost Estimates

A. Capital Cost

The capital cost for the sanitation component is as follows:

Facifity ~ costBefiarsFacility (P million) | l

Communal Toilets- Construction 44.57 35,000

-Land 8.30Total 52.87

The construction cost includes 5% physical contingencies. The cost of engineering hasnot been considered on the assumption that the design and construction supervision can behandled directly by the City's concerned department because of the simplicity of thestructures.

B. Operation and Maintenance Cost

Annual O&M costs for each communal toilet has been estimated at P192,780. This wouldrequire an user fee of about PL .20-1.40 per visit- on the the assumption of 250 personsusing the facility twice daily. It is intended that the cost of O&M plus the operator's feehave to be covered by the users.

ImDlementation Schedule

It is assumed that all 140 communal toilets will have to be constructed during the 5 yearsimnplementation period of the project. Therefore, an average of 28 communal toiletswould be constructed annually including the required time for consulation and design.

Section III - Overall Sewerage Scheme

C'issification

Sewerage refers to the collection and treatment, at a single location, of water-borne waste(sewage) discharged from individual properties. It includes the collection and treatment of"domestic" sewage only and not for any "industrial" waste discharge.


The sewage is collected and transported through a network of underground pipes, orsewers, to a WWTP, where the sewage is treated to produce an effluent that can bedischarged to a receiving water body (river, sea, etc.).

Sewage flows along the sewers by gravity, that is, the pipes are laid at a slope or gradientwhich is sufficient to ensure that the sewage will flow without causing blockage.

To minimize depth of excavation, sewers, generally, should follow the slope of theground, that is, they go downhill. If the depth of a sewer becomes too deep (greater than5 m) a pump station would be used to elevate the sewage, either to another sewer or tothe WWTP. The sewers are divided into two classifications:

* coHlector sewers - sewers connecting an individual property or group of severalproperties to a sewer located in the street or right-of-way,

* transportation sewers - those sewers receiving the sewage flow from the"collection" sewers and transporting the sewage to the WWTP.

The transportation sewers can be considered as the "main road", with the collector sewersacting as the "feeder roads".

Seiction of Service Areas

A. Poblacion

The Poblacion area is considered a priority area for the following factors:

* increasing population density and limitations for on-site sanitation;

e presence of large commercial establishments, and institutions such as schools,universities, college, government offices and hospitals;

* health hazard and ris' posed by Ehe increasing wastewater flow on the municipaldrainage system;

* high level of urban development with a population density capable of payingwastewater service charge;

* biological degradation of Davao City beaches. The DENR found that the majority ofbeaches in the city are polluted with human excreta and that tests performedindicated positive for fecal coliforms. This pollution is being caused by the lack ofon-site sanitation facilities in the peri-urban areas as well as discharge or disposal ofseptic tanks effluent to the main drainage interceptor along Dacudao Avenue, andM. Roxas Street, and raw sewage along the Davao River.


The identified Initial Service Area (ISA) comprises a total of 40 barargays with an area of1,109 ha and a total population of about 213,000 in 1995 projected to increase to about300,000 in 2015. The ISA is bounded on the west by the Davao River, on the north by theCircumferential Road, on the east by Cabangui St. and on the south by the Davao Gulf.

As shown in Figure 3.1, the ISA is subdivided into three stages of implementation.

Stage I Service Area has been outlined to include those areas which can provide thehighest impact in terms of improvements to the environment as well as to the social andeconomic conditions of the City. The areas included are:

* the city's center including the Central Business District where commnercial andinstitutional establishments, such as universities, hospitals, and offices are located;

* the barangays that are highly urbanized and densely populated, extending tobarangays in Agdao District;

The Poblacion Stage I Service Area has a land area of 486 ha with a population of about105,000 in 1995 projected to increase to about 121,400 in the year 2002 (starting ofoperations) and to 147,300 in 2015.

The population which will connect to the system has been estimated at 60% of the servicearea population. At the starting of operations, in the year 2002, the system will serveabout 72,800 users, with 13,480 connections, projected to increase to about 88,400 usersin 2015 with 16,370 connections.

The figure that 600/o of service area population will connect to the system is based on theassumption that 85% of the population (year 2015) would be connected to the DCWDsupply system, and of those, 70% would be connected to the sewer. Expansion of thesystem would be dependent upon the number of sewer connections and the sewage flowfrom each co.nection. The capacity of WWTPs and pump stations would have to beincreased once the 60% design flow is reached. This .aay or may not correlate to theactual connected population.

B. Toril

Toril district was declared an environmentally critical area by the City because its aquiferis the source of the water system operated by the DCWD. The majority of the populationin Davao City, including the Poblacion and Toril areas, rely on the water supphed by theDCWED for domestic use, which is drawn from the Toril wellfields. Its selection was,therefore, based on the priority need to protect the aquifer and on the long-term benefitsto the environment, and to the people that may be adversely affected by the impact ofwastewater polluting the aquifer taking also into account the rapid urbanization of Torildistrict.

Environmental Assessment Report: Davao Cutv 34

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The identified Tori ISA includes the three barangays of Toril District, namely, BarangaysToriL Daliao and Bayabas Crossing. It is bounded on the north and west by LipadasRiver, on the east by Barangays Lubogan and Talomo, and on the south by the DavaoGulf. It has a total land area of 707 ha and 1995 population of about 30,500. The area isa typical residential area with scattered commercial and institutional establishments.

As shown in Figure 3.2, the Toril ISA is subdivided into three priority stages ofimplementation.

The Toril Stage I Service Area has been outlined to include those barangays that: (a) arehighly urbanized and densely populated, where the commercial and institutionalestablishments are located; and (b) can provide the highest impact in terms ofimprovements to the environment as well as to the social and economic conditions of thedistrict.

The Tori Stage I Service Area has a land area of 215 ha with a population of about14,000 in 1995 projected to increase to about 15,900 in the year 2001 (starting ofoperations) and to 19,700 in 2015.

The population which will connect to the systetn has been estimated at 63% of the servicearea population at the starting of operations, in the year 200 1, or about 10,1 00 users with1,868 connections. In the year 2015 100% of the service area population will be servedwith 3,642 connections.

For Tori the connection factor applied is to gradually increase the connected populationto reach I00% in the year 2015. The aim of this scheme is the protection of theunderlying aquifer, therefore, the system has been designed for the connection of allproperties to the sewer system.

Potential Treatment Plant Sites

A. Poblacion

The strategy to identify potential treatment plant sites for Stage I was:

* take advantage on the availability of small parcel of lands with minimal number ofsettlers, if not totally vacant;

* divide the system, as recommended in the 1994 Feasibility Report, into smallercatchment areas considering the potential treatment plant sites, as well astopography and drainage characteristics.

Availability of land for a wastewater treatment plant to serve the Poblacion Area is amajor issue in planning the sewerage system. Potential lands are either occupied withnumerous squatters, as in the case of the original Bucana site, or, owned by private


individuals who either have no intention to sell or are demanding a high price. Other siteshave limited area which could not accommodate the treatment plant proposed in the 1994Feasibility Report.

Several potential sites, including a reclamation area along the Davao Gulf shore, have beenidentified and their suitability and availability reviewed with the City Planning Department(see Figure 3.1 (4.2). Most of the identified sites were of a small area and have high landvalue. On the overall, the site along the Davao River appears to be a good option sincethe area is sparsely populated and requires minimal resettlement which can be achievedwithin the samne area.

To evaluate alternative schemnes the following sites have been considered:

(i) Bucana which was proposed in the Feasibility Report and, as already mentioned,would require the relocation of a large number of families. The land value of thearea has been indicated by the City Planning Department at PIO,000/sq.m;

(ii) Davao River which, as discussed above, would require a minimal resetdement offamilies with a land value of A1,000/sq.m as indicated by the City PlanningDepartment;

(iii) Davao Gulf shore which is an area intended for reclamation by private investors.The land that can be made available for a WWTP would be limited at an estimatedcost of 10,000/sq.m.

B. Toril

Two sites have been identified (see Figure 3.3 (4.3)) by the City Planning Department, asfoilows:

• Daliao - Located southeast of Toril, the site is owned by the National Govermnent.There are several large warehouse structures located on the site. However, theWWTP can be located to mininize the need for demolition The City believes thatthe site can be acquired from the National Goverranent at reasonable cost. A strip ofland between the site and the coast nas residential development. A portion of landwill have to be acquired for the construction of the outfall from the treatment plantto the Davao Gulf

* Lizada - Located west of Toril. The City has proposed to purchase the area for useas a sanitary land fill where a WWTP could also be located. Effluent from theWVWTP could be discharged to the Lipadas River.

The land value of both sites as been indicated at l1,000/sq.m.


Treatment Process Oitions

For the treatment of sewage to be collected from the Stage I service area, utilizing eitherone or twvo treatment plants, three process options were assessed, as follows:

* anaerobic/facultative lagoons;

* modified lagoons;

* mechanical activated sludge.

1. Anaerobic/Facultative Lagoons

This sytem comprises of two or more ponds in series: the initial anaerobic pondfollowed by facultative pond(s). Each pond is defined as follows:

* Anaerobic Pond - used primarily as a pre-treatment process for high-strengthwastewater. They may be used for septage, night-soil" and high-strengthdomestic sewage. The advantages of using anaerobic ponds are that theyeffectively decrease the land requirements of subsequent facultative andaerobic ponds and the accumulation of large sludge banks in subsequenttreatment ponds is avoided.

- Facultative Pond - are the most common type used for wastewater treatment.Raw wastewater enters at one end of the pond and suspended solids settle tothe pond bottom. Over a period of time, a sludge layer develops that is voidof dissolved oxygen. The bottom sludge decomposes anaerobically. Abovethe sludge layer, the pond has a facultative layer that alternates from aerobic,during daylight hour, to anaerobic at night. The upper layer of the pond isaerobic at all times due to oxygen supplied primarily by photosynthesis andwind action. Facultative pond effluent would have to be further treated forthe removal of suspended solids before discharging to the receiving water tomeet the effluent discharge standards.

The Feasibility Report selected this process for the initial septage treatment facilityand for identifying the land area requirement for the deferred sewage treatmentplant.

Envur-nmental Assessment Report: Davao Citv 39

The design criteria for the process is as follows:

* Anaerobic Ponds

- Dual ponds; depth of 4.0 m, side slopes of 3:1; rectangular with length of 1.5to 2 x width.

- Organic loading of 0.3 kg of BOD/day per cu.m of pond volume.- Detention time at least 1.5 days.

- Pond volume to be determined by the higher value.

- Assumed BOD removal for subsequent treatment of 65%.

Facultative Ponds

Dual ponds in series; depth 1.5 m side slopes 3:1; rectangular shape, withlength 2 x width.

Organic loading rate of 400 kg of BOD/day per hectare of pond surface area(based on 40 g of BOD per capita and 10,000 persons per ha). Loading rate tobe applied to residual BOD in effluent from anaerobic ponds.

Detention time to be 6 days, total for all ponds in series.

- Pond volume to be determined by the higher value.

- Estimated BOD remnovals of 70%/o of influent BOD (overall BOD remnovalsestimated at 900/.).

While providing a treatment system that has a reduced land take (compared toa complete facultative lagoon system) and utilizes no mechanical equipment,there are concerns as to its ability to operate satisfactordy. Concerns raisedinclude:

* Anaerobic Pond

- Will produce odors - particularly if sulfates are present in the influent.

- Sometimes difficult to manage if pH varies on the acid side. Processeffectiveness decreases or fails completely. Short detention period uds toreduce buffer capacity. Once the system becomes acid, it must be treated withlime or some other chemical to neutralize the system.

- Removal of sludge required. Frequently depends on severity of the solids -BOD loading and nature of composition (sludge disposal was not addressed inthe Feasibility Report).

- Ability to treat low strength domestic sewage and variable rates of flow.


* Facultative Pond

- Shallow ponds at depths of 1.5 to 1.75 meters subject to turnover because oftemperature variations or wind and wave action. Temperature not as much ofa factor in areas of low fluctuations.

- Anaerobic and aerobic processes tend to be in state of flux and vacillatebetween stages reducing treatment effectiveness.

- Tends to increase land requirements because of the relatively shallow depth.

- Limited detention period will not ensure the removal of fecal coliforms to anacceptable level.

2. Modified Lagoens

The modified lagoon system is a non-structural design which utilizes earthenconstruction practices to simplify and reduce construction costs. The system isdesigned to optimize natural biological processes in order to improve treatmenteffectiveness and reduce power requirements and chemical additives while limitingland requirements. The design concept is to minimize sludge production, eliminatedaily sludge handling and restrict desludging to a long term 20- to 30-year cycle.

The modified lagoon system is an integrated, multi-stage biological reactor systemtreating municipal, agricultural and industrial wastewater. The reactors may berelatively deep and constructed of compacted earth as open surface pond areas.The biological reactor has discrete and isolated biological zones integrated into asingle unit; a deeper anaerobic cell(s) at the bottom of the reactor, sludge blanketsuspended over the deepened zone and an overlying aerobic zone comprised ofaerobic bacteria, algae and a saturated oxygen media provided by a combination ofalgae and surface aeration.

In many cases the initial reactor is followed by a similar second reactor operatingin series with the provision to recirculate to .ne first pond depending on conditionsand circumstances. Recirculation lends flexibility and buffer (shock loading)capacity and adsorption abilities with highly variable hydraulic or organic loadingsor where there is a potential for receiving toxic spikes.

The primary facultative pond with an aerobic surface and extremely anoxic internalcells for sedimentation and fermentation is the initial treatment element in the seriestreatment train. In this element raw or screened wastewater is introduced directlyinto the bottom of a relatively deep internal cell(s) where settable solids aredigested anaerobically. The overflow velocity in the cell is maintained at a lowrate such that the suspended solids and BOD5 removal efficiency approach 100and 65%. respectively. These rates are maintained at less than the settlingvelocities of helminth ova and parasite cysts. Consequently, the majority of these


organisms remain in the cells and are permanently removed from the effluent.Settled solids in the anoxic cells ferment to the extent that only ash remains due tothe large cell volume. Hence, sludge removal is seldom required.

The rising gases and upwelling of wastewater from the anaerobic cell pass througha thick anaerobic sludge blanket, that is formed as a result of the fermentationprocess, and remains suspended above the anaerobic cell. The hydraulic detentiontime in this anaerobic zone and corresponding rise velocity is variable by designand nature of the waste stream.

Treatment of soluble waste continues in the overlying aerobic zone, comprised ofaerobic bacteria and algae. These organisms are maintained in an oxygenated stateby photosynthesis, recirculation and surface aeration. The nature of the surfaceaeration creates a circular motion over the entire pond surface area which in turnensures an oxygen rich continuity.

Soluble wastewater componen

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