IV. RESULT AND DISCUSSION
Applying the data and methods described above, a mud volcano vulnerable o has been established. The result of
ing multi-criteria evaluation and vulnerability using analysis covering the study areas in Sidoarj
perform Fuzzy AHP are put
together and discussed here.
ud volcano vulnerability were obtained from studies
2
S, CH
4
Methane and Carbon Dioxide
2 .
4.1 Evaluation Criteria
The evaluation set considered for m of some previous research about mud hazard in Sidoarjo, interview
and discussion with some experts from BPLS, Environmental Geology and Risk Management expert. The criteria consist of subsidence, bubble gasses, flooded
area and water quality. 1.
Subsidence occurred on land surface. This criterion is characterized based on levels of impact to building structures.
2. Bubble of gas that emerged on certain area. This criterion is characterized
based on the gas effect included in almost bubbles. The gases were used consist of Hydrogen Sulphide H
CO 3.
Mud flooded area. This criterion is characterized based on history of frequency of area surrounding mud pond inundated by the mud overflow.
4. Water quality based on STORET status. STORET short for STOrage and
RETrieval is an EPA Environmental Protection Agency developed database for water quality, chemical, and physical data that is used by state
environmental agencies, EPA and other federal agencies, universities, and
private citizens adopted by State Minister of Environment Environment Ministerial Decree No.1152003. For this research, water quality status is
only based on physical and chemical values. Physical characteristics are such as colour, turbidity TDS solid substance dissolved and chemical
e des fo
discussed as follow:
1 u
Land f
ction of tim
subsurface ex
heavy n
n y an accumulation of mud in a surface and mass reduction in the ground. The
ct of land subsidence usually could not be significantly observed immed
measurement using GPS Global Positioning System, the deformation of subside
following Watukosek fault pattern Abdurrohim, 2008. characteristics are such as Cl, NO
3,
SO
4
, PH, etc. Th
cription and classification standard used r each criterion is
. Land S bsidence
Subsidence is defined as lowering of ground sur any factors such as heavy flow of mud and gasses from
ace in a fun es caused by m
to surface, groundwater extractions, oil s settlement, etc ITB, 2007. Land subsidence i
ploitations, constructio
Sidoarjo is caused b
result of the impa iately, but in some cases it does. In Sidoarjo, some physical facts such as
some cracks on the wall, floor, and tiles indeed already occurred as the impact of land subsidence ITB, 2007.
Based on interpretation of PALSAR Phased Array type L-band Synthetic Aperture Radar image, subsidence occured with ellips form and the direction is
from west to east towards the centre point of gush. According to the interpretation of field
nce shows a non-linier ellipsoid pattern with radius of 1 – 1.5 km from the centre point which have relative direction from South-West to North-East
49
The classification of subsidence for this research uses The Australian Standard Classification with modification where the subsidence is classified based
o building structures Mine Subsidence Engineering, 2007. The
Im Category
on levels of impact t classification of subsidence is displayed in Table 4.1.
Table 4.1 Subsidence classification of impact with reference to building
pact Description of typical impact to walls and
required repair Approximate crack
width limit mm
Low Hairline and Fine cracks which do not need repair.
1 Mo
windows stick slightly. derate
Cracks noticeable but easily filled. Doors and 1 - 5
High and possibly a small amount
5 – 15 or a Cracks can be repaired
of wall will need to be replaced. Doors and windows stick.
number of cracks 3 to 5 in one group
Ve replacing sections of walls, especially over doors
ry High Extensive repair work involving breaking-out and
and windows. Window or door frames distort. Walls lean or bulge noticeably.
15 but also depends on number
of cracks
2.
wat e flammable or
com stan
Ins and
EP
inc
Bubble Gas
The gushing of bubble that emerged in some areas not only consists of er and mud, but also contains hazardous gas which ar
bustible, explosive, toxic, an irritant or radioactive. Several international dards are used to classify the hazard in this research consisting of the National
titute for Occupational Safety and Health NIOSH, the Occupational Safety Health Administration OSHA, and Environmental Protection Agency
A. There are several gases contained in bubble gush, but the hazardous gasses
lude Methane CH
4
, Hydrogen Sulfide H
2
S and Carbon Dioxide CO
2
50
which are found in many l ssification of each gas
is discussed as
• Metha
Methane C as Na
orless and lig
It tends to rise accum
gher, stagnant parts of enclosed buildings. The main hazard is its flammable, explosive
nature. Methane can explode at concentrations of 50,000 ppm or more a level of 5. Methane can displace oxygen in confined areas, resulting in an
oxygen-deficient atmosphere. The lowest concentration air-fuel mixture at which a gas or vapor can ignite
is called its Lower Explosive Limit LEL or Lower Flammable Limit LFL. Concentrations below this limit are too lean to burn. The highest concentration
that can be ignited is its Upper Explosive Limit UEL or Upper Flammable Limit UFL. Above this concentration, the mixture is too rich to burn. The
flammable limit for methane is between 5 LEL and 14 UEL. For large spills the personnel should be evacuated beyond 750 meters.
The Occupational Safety and Health Administration OSHA has no permissible exposure limit for methane, but the National Institute for
NIOSH recommended maximum safe methane concentration for workers during an 8-hour period is 1,000 ppm
0.1. Methane is considered as asphyxiate at extremely high concentrations
500,000 ppm and can displace oxygen in the blood. The Zone system makes
tensive use of the Lower Explosive Limit LEL concept. The classification of Methane hazard is described in Table 4.2.
ocations. The description and cla follow:
ne CH
4
H4 is most commonly known tural Gas. Methane is od
hter than air. and
ulate near the hi
Occupational Safety and Healths
ex
51
Table 4.2 Methane hazard class
Volume Hazard Class
Concentration Resulting Condition
No Hazard Condition 0.1
Safe concentration Low Hazard
0.1 - 5 Too lean to burn
Medium Hazard 5 - 14
The flammable limit High Hazard
14 Too rich to burn
• Hydrogen Sulfide H
2
S
r gas H
2
S is a flammable, colorless gas that is toxic
ording to areas of potential Hydrogen Sulfide or sou
at extremely low concentrations. It is heavier than air, and may accumulate in low-lying areas. It smells like rotten eggs at low concentrations and causes
us to quickly lose our sense of smell. Many areas where the gas is found have been identified, but pockets of the gas can occur anywhere. Flaring operations
associated with H
2
S production will generate Sulfur Dioxide S0
2
, another toxic gas.
All well-drilling sites should be classified acc andor actual exposure to H
2
S. Poster signs 500 feet from the location on each road leading to the location, warning of the hydrogen sulfide hazard. The
NIOSH classification of H
2
S hazard area is described as follow: o
No Hazard Condition Any well that will not penetrate a known Hydrogen Sulfide formation
would be categorized as a No Hazard Area. Locations where atmospheric concentrations of H
2
S are less than 0.13 ppm. o
API Condition I - Low Hazard Locations where atmospheric concentrations of H
2
S are less than andor equal to 10 ppm.
52
o API Condition II - Medium Hazard
Locations where atmospheric concentrations of H
2
S are greater than 10 ppm and less th
o A
II - H atmosp
oncen e higher than 30
• Carbon Dioxide CO
2
Carbon Dioxide gas is colorle low c
ss. At higher concentrations it has a sharp, acidic odor. It will act as an asphyxiant
de is a powerful cerebral dilator. Contact with the cold gas can cause freezing
exposure. NIOSH recommends a maxi
re and respiratory rate. Above 8 nausea and vomiting appear. Above 10,
an andor equal to30 ppm. PI Condition I
igh Hazard Locations where
heric c trations of H
2
S ar ppm.
ss. At oncentrations, the gas is odorle
and an irritant. Carbon Dioxi of exposed tissue. Moisture in the air can lead to
formation of carbonic acid that can irritate the eyes. All forms of Carbon Dioxide are noncombustible. Carbon Dioxide is heavier than air and should
not be allowed to accumulate in low lying areas. The U.S. EPA recommends a maximum concentration of Carbon dioxide CO2
of 1000 ppm 0.1 for continuous mum concentration of carbon dioxide of 10,000 ppm or 1 for the
workplace, for a 10-hr work shift with a ceiling of 3.0 or 30,000 ppm for any 10-minute period. OSHA recommends a lowest oxygen concentration of
19.5 in the work place for a full work-shift exposure. Post signs 200 m from the location on each of the location, warning of the carbon dioxide hazard
At concentrations between 2 and 10, Carbon Dioxide can cause nausea, dizziness, headache, mental confusion, increased blood pressu
53
suff
Volume Humans
ocation and death can occur within minutes. The classification of Carbon Dioxide hazard area is described in Table 4.3.
Table 4.3 Carbon Dioxide hazard class
Hazard Class Concentration
Resulting ConditionEffect on
No Hazard Condition 0.1
Safe concentration Low Hazard
0.1 - 2 Likely to feel drowsy
Medium Hazard 2 - 10
Can cause nausea, dizziness, headache, mental confusion, increased blood
pressure and respiratory rate High Hazard
10 Can cause suffocation and death
3. Mud Flooded A
g of mu some areas have been
inundated by the overflow story data show that certain areas
sometimes flooded more than once cause ud pond. The
determination of hazard classification of a proposed dam or reevaluating of the
haz ation of an
g dam is required including increm l flood
nalysis Harrington, 2003. ication of flooded area based on dam failure has been
perform
rea
Since the gushin d volcano in 1996,
of mud. The hi d by the failure of m
ard classific existin
enta a
The classif ed by some agencies and departments FEMA, 2004; Washington State
Department of Ecology, 1994.. The classification system categorizes dams based on the probable loss of human life and the impacts on economic, environmental,
and lifeline interests. The frequency or probability of an event can be used to identify project and ecosystem components that are at high risk to impacts from
natural hazards that would warrant further quantification DMFC, 2004.
54
The interpretation of area ever flooded by mud shows that the flow of mud never caused loss of life and the majority of flooded area are founded in highly
d
habited structures
Quickbird image interpretation, transportation, property and com
e th
ret com
ith classification from a
ve m ed references, the classification based on
eco d env
ent has th
me class . significa
hazard cla
ch then classifies mud flood. The clas
on od haz
is listed i able 4. 4.
. 4 ud flood hazard classification
Hazard Classification Estimating Frequency
Frequency
eveloped, densely populated suburban or urban areas with more than
100 in
munity life line featur s. Due to is interp ation and
pared w bo
ention nomical an
ss. This resear ironm
al impact e sa
i.e nt
the hazard based on the occurring frequency of sificati
of mud flo ard
n T Table 4
M
No Hazard Condition Not likely to occur
Low Hazard May occur during the planning period
Significant Hazard Occur at least once during the planning
period = 2
High Hazard Occur several times during the planning
2 period
4. Water Quality
Th on of water quality criterion is based on the stored status.
The determ status by stored m
water quality value and water quality sta ording to the suitable usage.
he classification of water quality status as a result as presented in Table 4. 5 hows the total score higher than water quality standardBaku Mutu Air, BMA
and water quality status and also pollution level. The number of score from the e classificati
ination of water quality ethods is by comparing
ndard acc T
s
55
evaluation for each water quality parameter and its frequency or number of datanu
in Environment Ministerial Decree No. 1152003
Score of Parameter not fulfils BMA
mber of sample which is higher than BMA on certain monitoring site. Table 4. 5 Scoring Procedure of Water Quality Parameters Source: Canter, 1977
Number o Biology
f data samples Description
Physics Chemistry 1 Single
-3 -1
-2 Maximum -1
-2 -3
Minimum -1 -2
-3 10
Average -3 6
- -9
Maximum -2 -4
-6 Minimum
-2 -4
-6 Not Fulfils
the Requirements
= 10 rage
Ave -6
-12 -18 Fulfils the Requirements
Evaluating the water quality with STORET can be applied through one ies dat
lity o
obtaine rom the
total score, w
Total Score Quality Status
Water Quality
time data or time ser a. Qua
status and p llution level d f
hich reflects the number of unfulfilled parameter score, the more numbers mean more pollution in water. The relation between score and water
quality status is presented in Table 4.6. Table 4.6 Relation between Score and Water Quality Status Source: Environment
Ministerial Decree No. 1152003
A Fulfil Standard Water Quality
-1 to -10 B
Lightly polluted -11 to -30
C Polluted
Less than -31 D
Heavily polluted
56
4.2 Hierarchical Structure of The Criteria