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ANNEX I: HAZARD IDENTIFICATION AND RISK ASSESSMENT
A. Source: Surface Water
Hazardous Event Hazard Likelihood Severity Score Risk Rating
1. Typhoon/Heavy Rains 2. Land slide, mud, debris
Physical (High Turbidity) Chemical
Microbial
2.5 5 12.5 High
3. Illegal Logging (denudation of watershed)
Physical (High Turbidity) 3 3 9 Medium
4. Human Access (Dumagat & Illegal Settlers)
Microbial (Fecal/e-coli) 2 5 10 Medium
5. Breakdown of NPC Auxiliary Turbines and Bypass leading to the use of Low Level Outlet (LLO) or spillway
Physical (High Turbidity) & Chemical (Manganese)
2 3 6 Medium
6. Malfunction of turbidimeter
7. (Wrong turbidity measurement leading to erroneous information can be relayed to water production for treatment)
Physical 2 3 6 Medium
8. La Nina (turbidity) Physical (High Turbidity) 1 4 4 Low
9. Malfunction of silt ejector Physical (High Turbidity) 1 3 3 Low
10. El Nino leading to the use of Low Level Outlet (LLO)
Physical (High Turbidity) & Chemical (Manganese)
1 3 3 Low
11. Disturbance of Manganese deposit within the watershed & sediments (Earthquake, landslide, human activity, terrorist act, project construction etc.)
Chemical 1 4 4 Low
12. Forest Fire Physical (High Turbidity) 2 2 4 Low
13. Terrorist Act Chemical toxic substance & Physical (High Turbidity)
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14. Oil spill Physical & Chemical 1 1 1 Low
15. Earthquake Physical (High turbidity) 1 3 3 Low
16. Theft/Vandalism of facilities (BNAQ’s) Physical (High turbidity) & Microbial (fecal/e-coli)
1 5 5 Low
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B. Water Treatment: La Mesa Water Treatment Plant 1&2
Process Step Hazardous Event Hazard Likelihood Severity Score Risk Rating
Caustic Soda Application Overdosing and under dosing of chemicals Chemical 2 2 4 Low
Potassium Permanganate application
Overdosing/ under dosing of chemical Physical Chemical
2 3 6 Medium
Screening
(Primary and Secondary)
1. Intrusion of garbage and floatables during normal & stormy weather due to
ineffectiveness of screen
Physical Chemical
3 3 9 Medium
Microbial 3 5 15 High
2. Uncontrolled raw water quality due to natural calamities like El Nino, La Nina & flash flooding in far off provinces like Quezon
Physical 2.5 3 7.5 Medium
Chemical 1 3 3 Low
Microbial
1 5 5 Low
Pre-chlorination 1. Formation of disinfection by-products
due to high raw water turbidity
Chemical
(LMTP 1) 1 4 4 Low
Chemical
(LMTP 2) 2 5 10 High
2. Under dosing / no pre-chlorination Microbial 2 5 10 High
3. Less effective disinfection due to high
turbidity - LMTP 2 Microbial 2 5 10 High
4. Insufficient Chlorine Supply Microbial 2 5 10 High
5. Chlorine Supply Quality (Non- Compliance)
Chemical 2 4 8 Medium
Microbial 2 5 10 High
Coagulation (LMTP 1 & 2) 1. Incorrect dispersal of coagulant due to
rapid mixer trouble
Physical 3 3 9 Medium
Chemical 3 3 9 Medium
2. Overdosing / under dosing Physical 3 2 6 Medium
Chemical 3 3 9 Medium
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Process Step Hazardous Event Hazard Likelihood Severity Score Risk Rating
of feed lines b) dosing pump / transfer
pump trouble Chemical 4 2 8 Medium
4. Insufficient Coagulant Supply Physical 2 2 4 Low
Chemical 2 3 6 Medium
5. Coagulant Supply Quality (Non- Compliance)
Physical 2 2 4 Low
Chemical 2 2 4 Low
Flocculation (LMTP 1) 1. Incorrect setting of variators /
flocculators Physical 3 1 3 Low
Chemical 3 2 6 Medium
2. Overdosing/Underdosing of coagulant aid Physical 3 2 6 Medium
Chemical 3 3 9 Medium
Sedimentation (LMTP 1) 1. Sludge blanket formation exceeds 10
meters length from entry into sedimentation basis
Physical 3 2 6 Medium
Chemical 3 2 6 Medium
Microbial 3 5 15 High
2. Sludge bulking Physical 1 3 3 Low
Chemical 1 3 3 Low
Microbial 1 3 3 Low
3. Floating leaves and other floatables Physical 5 1 5 Low
Chemical 5 1 5 Low
Microbial 5 1 5 Low
4. Formation of algae in Sedimentation
Basin (Launders) Microbial 2 3 6 Medium
Pulsation (LMTP 2) 1. Sludge blanket blowdown Physical 2.5 3 7.5 Medium
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Process Step Hazardous Event Hazard Likelihood Severity Score Risk Rating
Microbial 1 5 5 Low
2. Overdosing/Under dosing of primary
coagulant and coagulant aid Physical 2.5 3 7.5 Medium
Chemical 2.5 3 7.5 Medium
Microbial 1 5 5 Low
3. Vacuum pumps and compressor failure Physical 2.5 3 7.5 Medium
Chemical 2.5 3 7.5 Medium
Microbial 1 5 5 Low
Intermediate Chlorination
(LMTP 1) 1. Under dosing Microbial 3 4 12 High
2. Leak in Chlorine Pipes Microbial 2 5 10 High
3. Less effective disinfection due to high
turbidity Microbial 1 4 4 Low
4. Insufficient Chlorine Supply Microbial 2 5 10 High
5. Chlorine Supply Quality (Non-
Compliance) Chemical 2 4 8 Medium
Microbial 2 5 10 High
Filtration (LMTP 1 and LMTP 2)
1. Poor performance of filters as surface wash (LMTP 1), scour air blower (LMTP 2) are not operating well
2. Depleted filter media
3. Electro-mechanical and electro- pneumatic system failure
4. Excessive algal formation due to irregular and inefficient backwashing
Physical 1 3 3 Low
Chemical 1 4 4 Low
Microbial 1 5 5 Low
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Process Step Hazardous Event Hazard Likelihood Severity Score Risk Rating
Microbial 2 5 10 High
Recovery Highly Turbid Recovered Water Physical 5 3 15 Very High
Chemical 5 2 10 High
Microbial 1 5 5 Low
Post chlorination 1. Residual Chlorine greater than 1.50 ppm Chemical 1 4 4 Low
2. Under dosing Microbial 2 5 10 High
3. Leak in Chlorine Pipes Microbial 2 5 10 High
4. Insufficient Chlorine Supply Microbial 1 5 5 Low
5. Chlorine Supply Quality (Non- Compliance)
Chemical 2 4 8 Medium
Microbial 2 5 10 High
All process steps Power outage / unbalanced power supply
which stop the entire treatment process
Physical 2 3 6 Medium
Chemical 2 4 8 Medium
Microbial 2 5 10 High
Gen set breakdown Physical 1 3 3 Low
Chemical 1 4 4 Low
Microbial 2 5 5 High
Internal/external sabotage & illegal tampering of plant facilities like opening of alum tank drain, unauthorized resetting of dosing pumps or dumping of large volume of sand upstream
Physical 1 3 3 Low
Chemical 1 4 4 Low
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C. Putatan Water Treatment Plant
Process Step Hazardous Event Hazard Likelihood Severity Score Risk rating
INTAKE Elevated levels of manganese, chlorides, ammonia, turbidity, total dissolved solids and algal count during El Nino
Physical Chemical Microbial
1 5 5 Low
Human Access Physical
Chemical Microbial
2 5 10 High
Algal Bloom Physical
Chemical Microbial
2 5 10 high
Proliferation of Fish pens Physical Chemical Microbial
3 5 15 High
Heavy rains and typhoon lake water disturbance
Physical Chemical
3 4 12 high
Intrusion of garbage and others Physical Chemical Microbial
3 5 15 High
Discharges of domestic and industrial wastes nearby the intake
Physical Chemical Microbial
5 5 25 Very high
FOREBAY Siltation at the twin box culvert Physical Chemical Microbial
1 5 5 Low
Intrusion of drainage and sewage from the cracks along twin box culvert
Physical Chemical Microbial
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Algal Bloom Physical
Chemical Microbial
2 5 10 High
Solid Waste Intrusion (e.i.garbage and twigs)
Physical Chemical Microbial
4 5 10 high
Intrusion of MF backwash water from the water recovery system
Physical Chemical Microbial
5 5 25 Very high
Siltation at the bottom of forebay Physical Chemical Microbial
2 5 10 High
Siltation at the bottom of forebay Physical Chemical Microbial
2 5 10 High
DISSOLVED AIR FLOTATION COAGULATION/FLOCCULATI
ON/FLOTATION
Improper dosing of coagulant and potassium permanganate
Physical Chemical Microbial
2 5 10 high
Flash mixer not working (ACH addition) Physical Chemical Microbial
2 5 10 high
Rapid and slow mixers not working Physical Chemical Microbial
2 5 10 high
Non-compliance of chemicals Physical Chemical Microbial
2 5 10 high
Malfunction of surface and bottom scrapers
Physical Chemical
Maynilad Water Safety Plan Revision No.1/November 2012