The Study on Risk Management for Sediment-Related Disaster on Final Report Guide II

Selected National Highways in the Republic of the Philippines Inventory Survey and Risk Assessment

CHAPTER 3

DETAILED INVENTORY SURVEY

3.1 General Information

The Detailed Inventory Survey (DIS) is used to inspect in detail the present condition of slopes
selected under the Preliminary Inventory Survey (PIS), and to plan the appropriate countermeasures.
The DIS is comprised of risk assessment, planning of countermeasures, and indicative feasibility
assessment, using the Inventory Format Sheets 3, 4 and 5. The outputs of the DIS are the detailed
record of the present condition of road slope disaster sites, the countermeasure plan for each disaster
site and indicative feasibility assessment of the proposed countermeasure.

3.1.1 Objectives and Procedures for the DIS

The objectives and procedures for the DIS are shown in Table 3.1. The DIS is carried out by
completing the inventory sheets designed specifically for this study as shown in Sheets 3 to 5.

Table 3.1 Objective and Procedure for the DIS

Inventory
Format Objective Procedure
Sheet
Sheet-3 1) Findings and classification of road 1) Draw the front view of the road slope
slope failure 2) Draw the cross section of the road slope
2) Measurement of disaster
magnitude
Sheet-4 3) Planning of countermeasures 3-1) Draw elevation view plan of the
(3 alternatives) countermeasure
3-2) Draw the standard section of the
countermeasure on the cross section sketches
4) Cost estimation of the 4) Estimate the cost of the countermeasure
countermeasures referring to the unit cost table
Sheet-5 5) Indicative feasibility assessment of 5) Calculate the feasibility indicators for the
the countermeasures countermeasures based on the form
Sheet-6 6) Correction of road slope disaster 6) Fill in the format sheet by DEO
records

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3.1.2 Work Flow of the DIS

The flowchart for the DIS is shown in Figure 3.1 and is composed of four main steps. The inspectors
have to follow the flowchart systematically for accuracy. Preparation work is required, especially in
the review of the PIS results. The inspectors are required to make accurate measurements for Sheet 3.
These measurements are used, together with the District Engineer’s comments, for planning
countermeasures as required in completing Sheet 4. At least two alternative countermeasures should be
planned based on the judgment of the engineer. The judgment of the inspectors based on the present
condition is required for Sheet 5. The last step of the DIS flowchart is checking and approval of the
data and other input by the Section Chief of Maintenance/Planning, and the approval by the District
Engineer or his assistant. The results of the DIS are then entered into the database.

Start
- Review of the PIS data
- Review of geological condition
Preparatory Works - Road Map of the DIS sections

Sheet 6
Collection of the disaster
records
Sketches
- Survey of cause(s) of disaster
Sheet 3 - Geometry Survey
Field Inspection - Prediction of magnitude of potential
disaster

District Engineer’s
- Basic design planning of countermeasure
comments
- Estimation of countermeasure work
quantities
Sheet 4 - Cost Estimation
Countermeasure Planning
- Input of disaster frequency and
magnitude
- Calculation of annual losses
Sheet 5 - Calculation of feasibility indicators of
Indicative Feasibility Assessment countermeasures

Checking and Approval by DEO

(Checked by [Section Chief of Maintenance/Planning])
(Approved by [District Engineer or assistant])
Detailed Inventory Survey

Database Utilization for Planning of Risk Management on RSD

Figure 3.1 Flowchart of Detailed Inventory Survey

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3.2 Method of Investigation (Sheet 3)

3.2.1 Tools for the Survey
In the DIS, tools are needed for field inspections, as well as for office works when planning the
countermeasures and encoding the data into Sheets 3 to 5. The staffs require safe equipment for field
inspections, and knowledge of how to accurately use the measuring tools. Computers and scanners are
needed to input Sheets 3 to Sheet 5.

The required tools for each survey team are shown in Table 3.2.

Table 3.2 Tools for Field Inspection for DIS

Items Specification Usage
Vehicle For travel to DIS section.
Camera Digital camera or Record the road slope condition of DIS
negative print camera section.
Arrange the photographs on Sheet 1.
Tape measure More than 10 m Measure distance or dimensions of objects.
One (1) roll
Measuring Pole Minimum 2 m Measure distance or dimensions of objects.
One (1) pole To use to determine the height of road
slopes.

Clinometer Or a magnetic compass Measure angle of road slope.

One (1) set
Stationery Pencil/Eraser/Ruler/ Record conditions and dimensions of the
Protractor/Pen road slope on Sheet 3.
Hammer For geological survey Inspect soil or rock on the road slope.

Safety Outfit Brush knife/Gloves/ For protection when on road slope, in

Hardhat/Ropes/Raincoat/ bush, etc.
Torch/Boots.

Stationery Pencil/Eraser/Ruler/ Draw the countermeasure on Sheet 4.

Protractor/Pen (Black Record the dimensions clearly with pen
ink) before scanning.
Scanner Compatible with Scan Sheet 3 sketch and Sheet 4
Windows OS. countermeasure plan for conversion into
Minimum A4 scan size digital files.
Computer Windows OS, Microsoft Used to make the digital files of Sheet 3
Excel for filling out of the and Sheet 4.
inventory sheet. Encoding countermeasure cost on Sheet 4
and each parameter on Sheet 5.

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3.2.2 Procedure of Drawing Sketches

To evaluate the magnitude and mechanism of the causes of the potential hazard for the DIS slope,
Sheet 3 (sketch) is prepared. The inspector carries out the field inspection through a survey of the
road slope and its vicinity using the suggested tools. The condition of the DIS slope is sketched in a
front view and cross section on Sheet 3.

The sketches on Sheet 3 are used as the basis for the countermeasure plan on Sheet 4, where an outline
of the present conditions of DIS slope. Sheet 3 sketches should be drawn clearly for scanning and
inserted as a digital image in Sheet 3 in Excel format. The key points, items required and methods of
sketches are as follows:

(1) Key Points of the Sketch

The inspector should complete the accurate observations before drawing the sketch of the DIS slope,
to enable him to draw the sketch easily and plan sufficient countermeasure alternatives. The
following items are key points of observation in the procedure for creating the sketch.

(a) The location of the disaster and the road, i.e. evaluate the influence of the disaster on the road;

(b) The original (before the current collapse/slide) surface line of the road slope and road structure;

(c) Water traces, geology of the road slopes, and any other factors that may trigger the disaster;

(d) Warnings of disaster such as cracks, springs, or a small collapse;

(e) The phenomena which may indicate the cause of the disaster;

(f) Major mechanisms of the disaster;

(g) It is necessary to sketch the range of countermeasures planned; and

(h) Existing structures to consider in the construction of countermeasure works (e.g. telephone
lines, etc.).

(2) Basic Information/Items to be Included in Sheet 3

The following items are to be incorporated into the sketch to record the present condition of DIS
slopes and countermeasure plans (see Table 3.3).

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Selected National Highways in the Republic of the Philippines Inventory Survey and Risk Assessment

Table 3.3 Basic Information/Items to be Included in Sheet 3

Basic road slope structure - Distance from road center to the toe of the road slope;
- Geometry of the road slope (gradient, height, width);
- Facilities on the road and road slope; and
- Existing countermeasure works on the road slope.
Topography - Road slope condition (flat area, roughness, knick line) and
- Gullies (natural drainage).
Road slope hazard condition - Collapsed road slope/scarp of landslides
- Deformation in the road and road slope
(depressions/upheaval)
- Distribution of exposed rock and their stability mass
- Distribution of pebbles and boulders and their stability
Existing Countermeasure - Layout of countermeasure
- Profile of countermeasure
- Damage situation of countermeasure and current state of
effectiveness
Geological data - Soil/rock type
- Condition of surface soil (moisture content)
- Structure of bedding
- Condition and structure of cracks and fracture zones
- Weathering grade
- Pattern of cracks
Photographs - Location of photography
Location of cross section - For front view sketches only

(3) Procedure for Drawing the Sheet 3 Sketch

The procedure for drawing the sketch in Sheet 3 is shown in Figures 3.2 and 3.3. At the survey
section, put marks on the road with paint or other similar material every 20 m from the start-point
of the DIS section before drawing the sketch in order to measure the objects accurately. Investigate
the DIS section before drawing the sketch. Draw the sketch using your judgment as the inspector
(refer to the stylized sketch in Figure 3.4 if needed).

A legend for the sketch for Sheet 3 has been prepared for the inventory survey. Some of the
symbols were selected from the Design Guidelines Criteria and Standards Volume-I (DPWH),
while some have been created in consideration of actual conditions of the national highway. The
legend consists of structures, topography and geology. Geological symbols are limited to clay (or
clayey soil), sand (or sandy soil), gravel (or gravelly soil), weathered rock, fractured rock and
fresh rock to simplify the sketch.

The sketch is to be drawn clearly and highlighted by clearly visible black lines since it will be
shown as a monochrome image in the RSMS. If the sketch is drawn using pencil, it should be
retraced on a new sheet or the drawing highlighted using a black pen without any dirt on the sheet,
so that it can be scanned clearly. Scan the original sketch of Sheet 3 and paste it on the digital file
for Sheet 3. An example of a sketch is shown in Figures 3.5 and 3.6.

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Start

Mark distance on the road every 20m

Investigate DIS section

Draw the Sketch

Highlight using black pen

Scan the original sketch

Paste the scanned sketch on the digital file for Sheet 3

Sheet 4

Figure 3.2 Flowchart of Procedure for Sheet 3 Sketch

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Start drawing the sketch:

- Draw the road survey section.
- Draw the existing structures,
geometry and actual road slope
conditions.

Continue the sketch:

- Draw the contour lines.
- Draw the detailed information of the
existing structure, geometry and
geological structure of the road slope.
- Draw vegetation.

180m
60m

Clayey soil
60°
Spring water
Fresh rock
Phot-1
Phot-3 Phot-2
Grouted Rip Rap
Finish the sketch:
- Record dimensions of the objects.
Clayey soil
Weathered rock 17m 25m - Record information regarding the
0.8m 6m existing structures, geometry, geology
Fresh rock and the road slope conditions.
1.2m
1m - Record the location on photographs.
Drain

Figure 3.3 Procedure for Drawing the Sheet 3 Sketch

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Selected National Highways in the Republic of the Philippines Inventory Survey and Risk Assessment

Structure

CL Traffic Lane
Center Line

A SP Asphalt Co. Concrete Drain

Em.
Catch box Embankment Shoto Crete
Shotcret Slope Works
TELEPHONE

Co. Facilities POWER LINE Lines 3cm. Crack

etc.

10m
Dimension Line Extension Line

original surface line

Cross section line assumed collapsed slide line
Topography

70
o Natural slope 45
o Cutting Slope

Collapsed slope o
Callaped
/ Scarp
slope 30 Knick
Knickline/ point
line Overhang
/ Score 70o over

-0.8m Depression +0.5m Upheaval

up heaval Infiltration

Shoreline Overflow 45
o
Gradient

B Bare Grass Plantation

Tree, Bush Talus cone Spring water

0.5 l

River Flow River flow

for section Mangrove

Geology

Clay W Weathered rock

R

Sand F Fractured rock

R

Gravel Freshrock
R

Structure Structure of
30
o Sructure of
of bedding Figure Structure
30
o 4 Legend of crack
Sructure offor Use in Sheet30o3 Sructure of
fracture zone crack fracture zone
fracture zone

Figure 3.4 Symbols Used in Sheet 3

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100m 80m
60m
40m
20m

0m

Figure 3.5 Example of Sheet 3 Sketch (1)

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Figure 3.6 Example of Sheet 3 Sketch (2)

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3.3 Countermeasure Planning (Sheet 4)

Countermeasure planning for the DIS section has been discussed in Step 1 of Sheet 3, and is
undertaken after the inspectors have drawn the sketch in the field. The inspectors ask the District
Engineer’s advice/comments on the countermeasures before drawing the countermeasure on Sheet 4. A
minimum of three alternatives of possible countermeasures should be chosen and drawn on Sheet 4.
The steps for planning, identification of the options, selection of the countermeasure and completion
of inventory Sheet 4 are described below.

3.3.1 Countermeasure Plan

The methodology for countermeasure planning is shown in Table 3.4.

Step 1: Discuss and plan the countermeasures in the field in accordance with the concepts shown
in Table 3.5.

Step 2: Plan the countermeasures with the participation of the District Engineer, draw its basic
plan, and prepare a rough cost estimate in Sheet 4. The planning engineers determine the effect of
the countermeasure and encode the reduction ratio of RCDp on Sheet 5.

Table 3.4 Method of Countermeasure Planning

Step Method Inventory Format Sheet
Field work
1 - Discuss the concept of the countermeasure. Sheet-3
- Plan a rough layout of the countermeasure.
Field and office work
- Basic design of the countermeasure (layout).
2 - Estimation of quantity of works. Sheet-4
- Estimation of unit price of works (construction and 20
years maintenance).

Table 3.5 Countermeasure Alternative Policy

Alternative Effectiveness Risk Reduction Ratio
High Effectiveness
0.7-1.0
Alternative-I Permanent countermeasures to prevent
(70%- 100%)
disasters
Moderate Effectiveness 0.3 – 0.7
Alternative-II
Mitigating the disasters to some extent (30% - 70%)
Low Effectiveness 0.0-0.3
Alternative-III
Some treatment (0-30%)
The Risk Reduction Ratio (Annual Loss) should be determined by the planning engineer and
input into Sheet 5 (refer 3.4.2 (3) 3-2).

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3.3.2 Countermeasure Options

The engineer-in-charge of the DIS can select any type of countermeasure that he chooses. When
planning for countermeasures, traditional/common methods used in the Philippines are to be applied as
far as practicable. However, if road slope conditions are determined to be too difficult to prevent
disasters by using traditional methods, new methods should be considered and selected from the
countermeasure options shown in the following sections (Refer to the detailed information on
countermeasures in Guide III Design of Countermeasures). Proposed countermeasures for each
disaster type are shown in Appendix 2 with the typical/standard structures.

Main considerations for selection of countermeasure options are given below:

(1) Water Treatment

(a) Surface Drainage and Sub-Surface Blind Drainage
The cross-section of the drainage facilities should be large enough to cope with the rainwater or
sub-surface water to be collected. Sub-surface drainage works shall be adopted if spring water
exists under normal conditions and/or during rainfall.

(b) Horizontal Drain Holes

Attention should be paid to the target location of the drainage, configuration, diameter, angle,
length, outlet protection, and connection to surface drainage (channel).

(c) Flow Structure

The location of the causeway, where debris flow or surface water will be allowed to pass, is
important. If water is to be allowed to pass over the road surface, the surface should have thick
pavement that is resistant to scouring from the flow. In case of a culvert (under drain), attention
should be paid to length, gradient, structure and cross-section size. Large under-drains (2 to 3 m
deep) with collecting walls are suitable for ground with low permeability.

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(2) Earth Works

(a) Cuts
Cuts should be applied at the source of the collapse and head of a landslide following the standards
for cutting described in the “Manual on Planning and Designing of Countermeasures.” In cases
where a large road slope is present above the target area, it is necessary to ascertain that no
potential disaster areas exist in the area. Proper measures should be taken to prevent potential
disasters. The cutting of the road slope must be planned with proper protection works.

The appropriate gradients for cuts are shown in Figure 3.7.

5 – 10m 1:1.5
Hard rock

5 – 10m 1:1.2
1:0.8 Weathered rock
Fractured rock
5 – 10m 1:1.0

Clayey/silty soil
1:1.5 Sandy soil
5 – 10m Gravelly soil
1:1.2

Gradient
Character of Soil or Bedrock Height(m)
(Vertical : Horizontal)
Hard rock 1:0.3 - 1:0.8
0 – 10m 1:0.6 - 1:0.8
Weathered rock 20 – 30m 1:1.0 - 1:1.2
Fractured rock
More than 30m 1:1.2 – 1:1.5
Less than 10m 1:0.8 - 1:1.0
Clayey/Silty soil Less than 5m 1:1.0 - 1:1.2
5 – 10m 1:1.2 - 1:1.5
Sandy soil
Less than 5m 1:1.0 - 1:1.2
Gravelly soil 5 - 10m 1:1.2 - 1:1.5
Note: Without slope stability works such as ground anchoring, the gradient is the same as shown in the
guideline on road earth works (Japan Road Association, supervised by the Ministry of Land Infrastructure
Transportation of Japan)
Figure 3.7 Appropriate Gradients for Cuts

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(3) Fills
Counterweight filling should be planned at the toe of the target disaster area. It is important to use
permeable materials for filling. In general, under drains and drainage mats should be provided so
that no free groundwater (unconfined ground water) level forms in the fill.

Reinforced filling is a new technology for the mitigation of road slope disasters, particularly on a
steep and deep valley side with limited space for construction. This has the same function as a
retaining wall.

Sandbag walls are newly developed geo-textile reinforced earth walls in Japan. Sandbag walls are
generally designed as a retaining wall to retain soil mass on steep slopes or in a restricted
right-of-way situation. Its typical application includes the restoration and stabilization of road slips,
highway retaining walls on steep slopes, embankment walls for temporary or permanent road
widening, and so on.

(4) Vegetation Works

Vegetation is a method of road slope protection with plant cover to (a) reduce surface erosion
caused by running water and rainfall; (b) prevent infiltration from rainfall; and (c) fasten
subsurface soil to a root system. Mangrove planting is a method of preventing coastal erosion to
reduce the force of waves crashing onto the coastline. These works should be used as widely as
possible because of their lower cost and low impact on the environment and landscape.

(5) Structures
(a) Slope Works
Slope works mainly include pitching work, shotcrete and crib works. These works are primarily
used to protect against surface weathering and erosion, and in some cases, to control small-scale
rock falls.

Pitching works are commonly used on slopes gentler than 1V:1.0H. When the slope gradient is
greater than 1V:1.0H, the methods used are concrete retaining walls, stone masonry retaining walls
and block masonry retaining walls. Pitching works are applied to prevent surface weathering,
scouring, stripping and erosion and, in some cases, to prevent small-scale soil slope collapse.

Crib works are commonly used on steep slopes of highly weathered or heavily jointed rocks
accompanied with abundant springs, especially where falls cannot be fixed with shotcrete works.
Crib works are chiefly applied (a) to prevent surface weathering, scouring and erosion and, in
some cases, (b) to control both rock fall and small-scale slope failure.

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(b) Walls and Resisting Structures

This work is composed mainly of retaining walls and catch works. Generally, retaining walls are
classified by the design criteria, applications, function, etc. into several types, namely; gabion
retaining walls, stone masonry retaining walls, and concrete retaining walls. Retaining walls are
used for (a) prevention of small-scale shallow soil slope collapse and toe collapse of large-scale
soil slope collapse or landslides, and (b) foundations for other slope protection works such as crib
work.

In principle, retaining wall design includes the analysis of (a) sliding, (b) overturning, typically at
the toe of walls, (c) bearing capacity of the foundation ground, and (d) overall stability (Stability
analysis must not consider only the stability of the wall itself, but also of the overall slope of which
the wall may be a part of).

Catch fences are designed to protect road traffic from rock fall damage, but differ from rock nets in
that they are installed near the road to be protected. Rock nets are used to cover slopes that have a
potential for rock fall in order to protect road traffic from rock fall damage.

(c) Anchoring and Piling

Where the other works cannot meet the degree of safety required, rock bolts with concrete cribs
can be used. The method is generally planned to cope with small, shallow surface collapse of about
3 to 5 m in thickness. Rock bolts in association with concrete cribs is applied to stabilize the
shallow surface collapse by exerting a force the increased resisting power against shear force by
the tension force of the rock bolts. Rock bolts with concrete cribs keep the overall slope together,
consequently preventing local collapse.

Compared with other countermeasures, ground anchors are costly but reliable. Recently, this
method has been applied increasingly to cut slopes at toe of landslides. Compared with rock bolts
and soil nailing, ground anchors have a relatively large resistance to sliding force and are therefore
used to stabilize relatively large-scale slope failures. Ground anchors are intended to prevent
landslides through the tensile strength of the high tensile strength steel wire or bars installed across
the slip surface.

Similar to ground anchors; steel pipe piles are costly but reliable. The work is recommended
especially when the ground is firm and has sufficient resistance against landslide mass. Moreover,
steel pipe piles are generally used when the slope of a landslide area or sliding surface is relatively
gentle or a potential landslide has a large scale. Steel pipe piles are intended to prevent landslides
through the doweling action between the landslide mass and stable ground by applying the shear

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strength of the steep piles to the sliding surface or by using the wedge effect of steel piles.

(d) Protection Works

These works includes Rock sheds, Check dams and Wave-absorbing (or wave-dissipating) works.

Rock sheds are reinforced concrete or steel structures covering a road. They are very costly and
should only be planned and designed in areas of extreme rock fall hazard. It is applied to reduce
road disasters due to rock fall or rock mass failure by absorbing the impact force of a falling rock
mass or shifting the movement direction of the rock mass failure and rock fall.

Check dams are implemented (a) to prevent erosion and toe failure of potentially unstable slopes;
(b) to prevent and eliminate damage from the debris flow itself; and (c) to improve the stability of
a slope through sedimentation behind the dam.

Wave-absorbing works are a common countermeasure for coastal erosion in Japan. These works
are very costly and should only be planned and designed in areas where other works cannot meet
the degree of safety required.

(6) Other Works

Other works include re-alignment, bridges and so on, that require different judgment criteria for
re-opening a practical/feasible route.

3.3.3 Countermeasure Selection

The general flow of countermeasure selection is shown in Figure 3.8. The flow describes the
procedure for deciding on the selection of countermeasures. The inspectors can select the
countermeasures based on their own judgment and experience. The inspectors should select three
alternatives for one DIS section. More than one countermeasure may be selected for one alternative
plan under the present condition of the DIS section.

The concept of selection is based on the following four criteria:

(1) Effectiveness of overcoming problems with water;

(2) Effectiveness of vegetation works or earth works;

(3) Effectiveness of structures; and

(4) Re-alignment only.

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Primary consideration in the procedure for the selection is the treatment of problems with water for the
DIS section. The major causative factors for a disaster are surface water and sub-surface water from
heavy rains. The next consideration is vegetation or earth works, which are generally simpler methods
than structures. The third consideration is choosing an appropriate structure that is compatible with the
permanent countermeasures for Alternative I. The final consideration is re-alignment, only this
requires different judgment criteria for re-opening or identifying of a detour/ practical route.

A flow chart for the selection of the different disaster types is shown in Appendix 3.

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Start
Countermeasure
- Surface Water Drainage
- Sub-surface Blind Drainage
Would treatment of - Horizontal Drilling
surface or ground water be
YES - Flow Structure
effective?
Soil Works
- Pre-Splitting
NO - Rock Fall Foot Protection
- Banking (Embankment)
- Reinforced Embankment
- EPS Embankment
- Sand Packed in Cracks
YES Planting Work
Would soil works or planting - Coconut Fiber Nets
works be effective? - Vegetation Spraying
- Mangrove Planting
NO
- Rip Rap
- Gabions
- Grouted Rip Rap
- Gabion Walls
- Crib Walls
- Shotcrete
- Cast-in-Place Cribs
Would structures be - Concrete Retaining Walls
YES - Stone Masonry Retaining Walls
effective? - Gabion Retaining Walls
- Bolting
- Steel Piling
- Ground Anchoring
NO - Rock Nets
- Catch Fences (Rock fall Protection)
- Rock Sheds
- Concrete Check Dams
- Gabion Check Dams
- Wooden Stockades
- Grouted Rip Rap (Coastal)
- Reinforced Concrete Retaining Walls
(Coastal)
- Rock Armor Protection (Coastal)

YES
Is re-alignment the only Re-alignment
feasible solution?
Bypass

End
Figure 3.8 General Flow of Countermeasure Selection

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3.3.4 Completion of Sheet 4

(1) Procedure for completion of Sheet 4
The procedure for completion of Sheet 4 is shown in Figure 3.9 and illustrated further in Figure
3.10. Remarks for filling out Sheet 4 are shown Figure 3.11. This consists of five steps as given
below:

Step 1

Trace the outline of the DIS section from Sheet 3 to Sheet 4. The outline will consist of the road
structure, dimensions of the disaster such as information related to the countermeasure plan.

Step 2 Draw the countermeasure plans on Sheet 4, that is a plan and a section for each
alternative countermeasure. The plans are to be drawn clearly and highlighted with highly visible
black lines since it will be shown as a monochrome image in the RSMS. If the sketch is drawn
using pencil, it should be highlighted using a black pen without any dirt on the sheet for scanning.

Step 3 Estimate the construction quantities of structure or potential collapse volume for the
unit cost estimation. Record the quantities on Sheet 4 with a pencil or a pen.

Step 4 Scan the original plans of the countermeasures (Sheet 4).

Step 5 Paste the scanned plans of the countermeasures on the digital file of Sheet 4 and
encode the countermeasure works, units, quantities and unit prices into the appropriate cells. The
costs of the countermeasures are calculated automatically.

(2) Rough Cost Estimates

The inspectors can assume unit costs for the countermeasures according to each DEO’s standards.
However, if unit costs are not set, refer to Tables 3.6 and 3.7. Pay attention to the unit price
differentials per region for their application. Re-opening cost is included in the cost estimation and
cost of cutting. Maintenance cost for 20 years for the planned countermeasures is estimated by the
inspector and included in the total cost of the countermeasures.

If a countermeasure selected is not among the standard types, rough cost estimates should be done
for the plan by the inspectors.

Example of Sheet 4 is shown in Figures 3.12 and 3.13.

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Start

Trace the outline conditions of the DIS Section from Sheet 3

Draw the countermeasures on Sheet 4; three alternatives as far as possible

Estimate the quantities of the objects

Estimate the cost of the countermeasures

Scan the original plans of the countermeasures (Sheet 4)

Paste the scanned plans and encode the costs on the digital file of Sheet 4

Sheet 5

Figure 3.9 Procedure for Completion of Sheet 4

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Sheet 3 Sheet 4
180m
60m

Clayey Trace outline of

60° Sheet 3 to Sheet 4
Spring water
Fresh rock
Phot-1
Phot-3 Phot-2
Grouted Rip

Clayey soil
Weathered 17m 25m
0.8m6m
Fresh rock
1.2m
1m
Drain

170m

Draw countermeasure plans on Sheet 4.

Estimate the total quantities of the

structure or potential collapse volume
using units of measurement for the cost
180m estimations.

Record the quantities on Sheet 4.

Unit calculation
m×m Record the countermeasure works, units,
0.2m quantities and unit prices for encoding to
25.5m Unit calculation Sheet 4 digital file
m×m
3.0m

1.0m

Figure 3.10 Procedure for Drawing Sheet 4 Countermeasure Plan

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They will be easy to visualize from sectional views

(1) Illustrate the construction plans.

(It is not necessary to illustrate the form of the countermeasures exactly)

(2) Pay attention at the origin and destination point side of the slope.

(1) Assess the future potential slope disasters.

(2) Select countermeasures for an assumed disaster.

(3) Plan three types of countermeasures.

(High, medium and low effectiveness for disaster reduction)

(4) Pay attention to both the valley and mountain side slopes.
(The possibility of construction should be evaluated.)

Calculate
automatically

Figure 3.11 Remarks for Filling out of Sheet 4

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Table 3.6 Unit Cost of Countermeasures (1) (2006 Price)

Type Item Work Item Unit Unit Data Remarks

No. Price source
(PHP)
SC1 Cutting m3 430 1 Soil/Soft Rock
SC2 Coconut Fiber Net m2 260 1 with sodding
SC3.1 Surface Drainage m 2,910 1 Reinforced concrete
Soil Slope Collapse

Water gutter
SC3.2 Drainage Catch Basin ea 6,210 1 80 x 80 x 80 cm
SC4.1 Cast-in-Place Crib m2 2,270 1 Excluding riprap
SC4.2 Crib Vegetation m2 330 1
Spraying
SC5 Concrete Retaining Wall m 17,440 1
SC6 Stone Masonry Retaining m 13,000 1
Wall
SC7 Gabion Retaining Wall m 1,366 2 3 meter high wall
RC1 Pre-Splitting m3 1,570 1 Scaling & trimming of
rock
RC2 Rock Fall Foot Protection ea 5,720 1
RC3 Shotcrete m2 1,970 1 100 mm thick
Rock Slope Collapse

RC4.1 Cash-in Crib m2 2,270 1 Similar to Item SC 4.1

RC4.2 Place Crib Shotcrete m2 1,970 1 100 mm thick
RC4.3 Vegetation m2 330 1 Similar to Item SC 4.2
Spraying
RC5 Concrete Retaining Wall m 17,440 1 Similar to Item SC 5
RC6 Stone Masonry Catch Wall m 13,000 1 Similar to Item SC. 6
RC7 Bolting ea 4,150 1 20 mm dia. long steel
bars
RC8 Rock Net m2 320 1 Japanese description
RC9 Catch Fence (Rock fall m 5,720 1
Protection)
LS1 Cutting m3 430 1 Similar to Item SC 1
LS2 Banking Ordinary Soil m3 490 2
Selected m3 742 2
Borrow
Landslide

LS3.1 Water Drainage m 2,910 1 Similar to Item SC 3.1

LS3.2 Drainage Catch Basin ea 6,210 1 Similar to Item SC 3.2
LS4.1 Sub-surface Crushed m 5,070 1
Blind Stone Placing
LS4.2 Drainage Catch Basin ea 6,210 1 Similar to Item SC 3.2
LS5 Gabion Wall m3 1,366 2 Similar to Item SC 7
LS6 Steel Piling m 21,380 1 500 mm dia. steel pipe
Note: Data Source 1: Refer Appendix-5, 2: Nation wide average of IPRSD of DPWH in 2006

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Table 3.7 Unit Cost of Countermeasures (2) (2006 Price)

Type Item Work Item Unit Unit Data Remarks

No. Price source
(PHP)
RS1 Cutting m3 430 1 Similar to Item SC 1
RS2 Coconut Fiber Net m2 260 1 Similar to Item SC 2
Road Slip

RS3 Reinforced Soil Embankment m3 1,520 1

RS4.1 Water Drainage m 2,910 1 Similar to Item SC 3.1
RS4.2 Drainage Catch Basin ea 6,210 1 Similar to Item SC 3.2
RS6 Banking m3 490 2 Similar to Item LS 2
DF1.1 Concrete Check Dam ea 467,360 1 Reinforced concrete
Check Dam 2 m base x 5 m height
structure
Debris Flow

DF1.2 Cutting m3 430 1 Similar to Item SC 1

DF1.3 Gabion m 9,490 1 2 layers about 4 m
long
DF2.1 Gabion Check Dam ea 179,030 1 4 layers gabion box
Check Dam 1 x 1 x 2m
DF2.2 Cutting m3 430 1 Similar to Item SC 1
RE1 Rip Rap m 2,590 1
Eros

m3
River

RE2 Gabion 1,366 2

i

RE3 Grouted Rip Rap m3 1,919 2

RE4 Wooden Stockades m 3,000 1
CE1 Grouted Rip Rap m3 1,919 2
Ero

CE3 Concert Retaining Wall m 17,440 1 Similar to Item RC 5

Costal

CE4 Mangrove Planting m2 7 2 5 trees per 4 sq. m on

cross-stitch
Note: Data Source 1: Refer Appendix-5, 2: Nation wide average of IPRSD of DPWH in 2006

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Step 1

Step 2 Step 3

Figure 3.12 Example of Sheet 4 Countermeasure Plan

(Lagawe-Banaue Road: 301km + 200: Alternative-I)

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Inventory Sheet-4 Planning of Countermeasures Alternative
Road Name 0
Station from km 0 m 0 Side of Left side of
4-1 Plan of Countermeasures (plan layout and descriptions)

20.0m

Cutting
26.0m
Road(co)

Drainage

10.0m

Cast-In-Place
Crib
７.0m

Step 4

4-2 Section of countermeasures

Cutting (1.63m2)

Road(co)
Drainage
Cast-In-Place Crib
Step 5
11.0m

70 °
Cutting(10.5m2)

4- 3 Cost estimates

No. Work Unit Quantity Unit price (pesos) Amount (pesos)

1 Cast-In-Place Crib m2 330.6 17,250 5,702,850

2 cutting m3 252.4 1,500 378,600

0
0

0
0
0
Total Cost 6,081,450

Note
Numerical value or terms should be inputted.
Numerical value is automatically inputted.

Figure
Figure 3.13
3.13 Example
Example of of Sheet
Sheet 4CountermeasurePlan
4 Countermeasure Plan
(Wright-Taft
(Wright-Taft Road: 858
Road: 858 + 250:
+ 250: Alternative-I)
Alternative-II)

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3.4 Indicative Feasibility Assessment (Sheet 5)

The indicative feasibility assessment, which is the preliminary estimate of the economic
viability of specific countermeasures identified to mitigate RCDs, is carried out in Inventory
Sheet 5 (Sheet 5).

3.4.1 General
In Sheet 5, the estimates of disaster frequency and magnitude, annual losses, risk reduction ratio
due to implementation of a specific countermeasure and cost/benefit analysis of the
countermeasures are undertaken.

The equations used for the indicative feasibility assessment differ per disaster type, which
requires a different sheet for each type and results in the preparation of seven different sheets
(Sheet 5-1 to Sheet 5-7).

3.4.2 Setting the Method for Inputting Required Values

(1) Disaster Frequency and Magnitude

1-1) Disaster Frequency or FRCDp

FRCDp has been previously calculated in Sheet 2. The calculated value of FRCDp is used
and has been linked to the appropriate cell in Sheet 5.

1-2) Accumulation Volume on the Road per RCD/Length of Road Closure Site
(Accumulation Volume on the Road per RCD for Sheet 5-1: Disaster type - Soil Slope
Collapse and Sheet 5-2: Disaster type - Rock Slope Collapse)

The “accumulation volume on the road per RCD” is computed by multiplying the “ratio of
accumulation” to collapsible materials and the estimated volume of collapsible materials
per RCD”, as shown in the following equation:

g = e*f (equation 3.1)

where:

g = accumulation volume on the road per RCD (m3 per RCD)

e = volume of collapsible materials per RCD (m3 per RCD)

f = ratio of accumulation to collapsible materials (ratio)

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(Length of Road Closure Site for Sheet 5-3: Disaster type - Landslide and Sheet 5-4: Disaster
type - Road Slip; Sheet 5-5: Disaster type - Debris Flow; Sheet 5-6: Disaster type - River
Erosion; and Sheet 5-7: Disaster type - Coastal Erosion)

The ‘length of the road closure site’ is estimated based on the current range of slope
deformation, referencing to past closure examples in nearby areas and similar slope
conditions.

1-2-1) Coefficients for Volume Estimation

The method for estimating the dimensions of the collapsible material/area is selected from
the following and as shown in Figure 3.14

Max : The maximum dimensions of the collapsible material area are predicted.

Average: The average dimensions of the collapsible material area are predicted.

No input: In case the dimensions cannot be predicted such as for rock fall phenomena.

If ‘Max’ is selected: “a”, the coefficient for the volume estimation is empirically set at
a = 0.7

If ‘Average’ is selected: “a”, the coefficient for volume estimation is set at a = 1.0

If ‘No input’ is selected: no coefficient for volume estimation is set.

Profile line for b: length and d: depth (max)

Profile line for b: length and
d: depth (average)
c: width of
collapsible (max)
d: depth of
collapsible
c: width of (average)
collapsible
(average)
d: depth of
collapsible
(max)
Road
Road

Plan Profile

Figure 3.14 Instructions for Estimating the Dimensions of Collapsible Volume

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1-2-2) – 1-2-6) Length, Width, Depth, and Volume of Collapsible Materials

The volume of collapsible materials is automatically calculated by inputting the required
dimensions, namely: length, width and depth of the collapsible materials using the
equation given below (refer to Figure 3.14):

e = a*b*c*d (equation 3.2)

where

e = volume of collapsible materials (m3 per RCD)

b = length of collapsible materials (m)

c = width of collapsible materials (m)

d = depth of collapsible materials (m)

a = coefficient for volume estimation

In case max values (for length, width, and depth) are used, a = 0.7

In case average values (for length, width, and depth) are used, a = 1.0

The length, width and depth dimensions are estimated based on the current range of slope
deformation and referring to past collapse examples in nearby areas and similar slope
conditions.

When these dimensions cannot be predicted, for example in the case of rock fall, the
‘volume of collapsible materials’ is estimated using Figure 3.15, which shows the
relationship between the collapsible volume and the slope gradient per slope height
category.

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25
H > = 90m
Volume of Collapsible Material per road length (m3/ m)

H = Height of slope
20

15

90 m > H > =60 m

10

5
60 m > H >=30 m

0 30m > H
G >= 60° 60° > 40° > 20° > G
G >= 40° G >= 20°
Category of Slope Gradient: G
This chart was formulated using the data from the PIS questionnaire results as of 2006 and
disaster observations in Benguet and Ifugao provinces in September 2006.

Figure 3.15 Chart for Estimating Collapsible Volume

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1-2-6) Ratio of Accumulated Materials to Collapsible Materials

The ratio of the accumulated volume of soil/rock on the road and the collapsible volume of
soil/rock is estimated by referring to past collapse experiences in nearby areas or similar
slope conditions.

When the ratio of the accumulated volume of materials to the collapsible materials cannot
be calculated, it is estimated by using Figure 3.16. This was formulated based on
experience and is the relationship between the ratio of accumulated materials and
collapsible materials and the slope gradient category for each ‘distance from the road to
the toe of the mountainside slope.

1.0
1m<D
D : Distance from toe of
0.8 mountainside slope
Ratio of accumulation materials to collapsible materials

0.6

0.4 3m>=D>1m

0.2
5 m > = D >3 m

D> 5 m
0.0
G >= 60° 60° > 40° > 20° > G
G >= 40° G >= 20°
Category of Slope Gradient: G
This chart was formulated based on the PIS questionnaire results in 2006 and
disaster observations in Benguet and Ifugao provinces in September 2006.
Figure 3.16 Chart for Estimating the ‘Ratio of Accumulated Volume to Collapsible
Volume’
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(2) Annual Losses

The total annual loss due to the occurrence of RCD in the target site is estimated as follows:

u= j + m + t (equation 3.3)

where:

u = total annual loss (pesos per year)

j = annual reopening cost (pesos per year)

m = annual value of human lives lost (pesos per year)

t = annual detour cost (pesos per year)

The calculation for “u” is automatic by inputting the following:

2-1) Annual Reopening Cost

The annual reopening cost is estimated by referencing local conditions.

The following equations have been formulated using data of reopening costs of a specific
Philippine national road and should be used for reference only.

(for Sheet 5-1: Disaster type - Soil Slope Collapse and Sheet 5-2: Disaster type - Rock Slope
Collapse)

The annual reopening cost is calculated using the equation below:

j = FRCDp * RC (equation 3.4)

RC= h * g+ i (equation 3.5)

where:

j = annual reopening cost (pesos per year)

FRCDp = potential frequency of road closure disaster (no. per year)

RC = reopening cost per RCD (pesos)

h = reopening cost per accumulation volume at closure site (excludes fixed

cost) (pesos per m3)

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g = accumulation volume on the road per RCD (m3 per RCD)

i = fixed cost for reopening per RCD (pesos per RCD)

The value of ‘h’ and ‘i’ in equation 3.5 should be set by referring to local experience and
actual results obtained, though this assumes that the engineer of the DEO would be
responsible for preparing the estimate.

Just as a reference, a chart showing the relationship between accumulation volume and
reopening cost (data from questionnaire survey for RCDs on national highway in the
Philippines from 1996 to 2005) is shown in Figure 3.17. From the correlation analysis of
this data, ”h” of equation 3.5=540 pesos and ”i” =10,000 pesos.

1,000,000
RC: Reopening Cost per RCD

RC = 540 g + 10,000
Correlation Coefficient = 0.65
800,000

600,000
(
400,000

200,000

0
0 500 1,000 1,500

h = reopening cost per accumulation volume at closure site (excludes fixed

cost) (pesos per m3) = 540

i = fixed cost for reopening per RCD (pesos per RCD) = 10,000

Figure 3.17 Chart showing the Relationship between Accumulation Volume

and Reopening Cost (Data from questionnaire survey for RCDs on national highway in the
Philippines from 1996 to 2005)

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(for Sheet 5-3: Disaster type –Landslide; Sheet 5-4: Disaster type - Road Slip; Sheet 5-5:
Disaster type - Debris Flow; Sheet 5-6: Disaster type - River Erosion and Sheet 5-7: Disaster
type - Coastal Erosion)

The annual reopening cost is calculated using the equation below:

j = FRCDp * RC (equation 3.6)

RC = h * LRC+ i (equation 3.7)

where:

j = annual reopening cost (pesos)

FRCDp = potential frequency of road closure disaster (nos. per year)

RC = reopening cost per RCD (pesos)

h = reopening cost per length of road closure site (excluding fixed cost) (pesos
per m)

LRC = length of road closure site (m)

i = fixed cost for reopening per RCD (pesos per RCD)

The value of ‘h’ and ‘i’ in equation 3.7 should be set by referring to local experience and
actual results obtained, though this assumes that the engineer of the DEO would be
responsible for preparing the estimate.

Just for reference, a chart showing the relationship between the Length of the Road Closure
Site (LRC) and the Reopening cost per RCD (RC) on national highways in the Philippines
(data of questionnaire survey for RCDs from 1996 to 2005) is shown in Figure 3.18. From
the correlation analysis of this data, ”h” and ”i” of equation 3.7 are obtained and shown in
Table 3.8.

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Table 3.8 Reference Value for Estimating Reopening Cost

Disaster Type h= reopening cost per i = fixed cost for reopening per Correlation
length of road closure site RCD coefficient
(excluding fixed cost) [pesos per RCD]
[pesos per m]
LS: Landslide 4,800 8,800 0.22

RS: Road Slip 4,600 170,000 0.36

DF: Debris Flow 1,200 12,000 0.39

RE: River 1,600 890,000 0.25
Erosion
and
CE: Costal
Erosion
(Data from questionnaire survey for RCDs on national highway in the Philippines from 1996 to
2005. The correlations are low in each disaster type)

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Landslide

2000000

1500000

1000000

500000
RC = 4,800 x LRC + 88,000
Correlation coefficient = 0.22
0
0 50 100 150 200 250

Road Slip

1,000,000

800,000

600,000

400,000

200,000
RC = 4600 x LRC + 170,000
0 Correlation coefficient = 0.36
0 10 20 30 40 50 60 70 80 90 100

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Debris Flow

150,000
RC = 1,200 x LRC + 12,000
Correlation coefficient = 0.36

100,000

50,000

0
0 10 20 30 40 50 60

River Erosion and Costal Erosion

5,000,000
RC = 1,600 x LRC + 890,000
4,000,000 Correlation coefficient = 0.25

3,000,000

2,000,000

1,000,000

0
0 200 400 600 800 1,000 1,200 1,400 1,600 1,800 2,000

Figure 3.18 Charts for Estimating Reopening Cost per Length of Road Closure
(Data from questionnaire survey for RCDs on national highway in the Philippines from 1996 to
2005)

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2-2) Annual Value of Human Lives Lost

The value of human lives lost is estimated using the following equation:

m= FRCDp * k * l (equation 3.12)

where:

m = Annual value of human lives lost (pesos per year)

FRCDp = Potential frequency of road closure disaster (no. per year)

k = Average number of human deaths per RCD

l = Value per human life lost (deaths)

2-2-1) Average Number of Deaths per RCD

The average number of deaths per RCD is the total number of deaths due to RCDs divided
by the total number of RCDs for the period under consideration.

The estimate of the average number of deaths per RCD is given below:

0.003 (persons per RCD) (equation 3.13)

This was estimated using the data shown in Table 3.9.

Table 3.9 Average Number of Deaths per RCD

Data Period = 2 years (2004 & 2005)
Total number of death for all Total number of RCDs Average number of
RCDs (A more accurate figure is being estimated) deaths per RCD
14 5,415 0.003

2-2-2) Unit Value of Human Lives Lost

One estimate of the unit value of human life lost due to road accidents is PHP 2,300,0001
based on a study conducted jointly by the Asian Development Bank (ADB) and the
Association of Southeast Asian Nations (ASEAN) in 2004 and is recommended for adoption
in this survey. The evaluation is shown in Appendix 6.

1
ADB-ASEAN Regional Road Safety Program Accident Costing Report: The Cost of Road Traffic
Accidents in the Philippines, Manila, 2004.

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2-3) Annual Detour Cost

The annual detour cost is estimated in terms of the additional vehicle operating cost incurred
in using a detour road when the survey site is closed due to RCD.

When an alternative route to the closed survey road exists, the equation to estimate the annual
detour cost is as follows:

t = FRCDp* p*q((o*s)-(n*r)) (equation 3.14)

where:

t = Annual detour cost

FRCDp = Potential FRCD (no./ year)

p = AADT: Annual Average Daily Traffic on the survey site

q = Nos. of estimated closure days for the survey road

n = Length of survey road (from entry to exit point of detour road to avoid the
road closure site on the survey road [see Figure 3.19]) (km)

o = Length of detour road (from entry to exit point of detour road to avoid road
closure site on survey road [see Figure 3.19])) (km)

r = Average Vehicle Operating Cost/unit of AADT/km on the survey road

s = Average Vehicle Operating Cost/unit of AADT/km on the detour road

RCD Site Detour Road Reference points for

measuring lengths of
Detour and Survey
Roads

Survey Road

Figure 3.19 Reference Points for Measuring Lengths of Survey and Detour Roads
2-3-1) Lengths of survey and detour roads are measured by the DEO
The reference points are the vehicle entry/exit points on the detour road to avoid the RCD
site.

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2-3-2) AADT: Average Annual Daily Traffic on the Survey Site

Latest AADT of the surveyed section is filled out. The data is processed as shown in the
Baguio-Bontoc Road (Halsema Highway) example to subsequently estimate the average
vehicle operating cost on the survey and detour roads per AADT unit. .

Table 3.10 Example of AADT and Percent Share of Each Vehicle Type
(Baguio-Bontoc Rd)

Vehicle Types Volume % of Total AADT

Motor driven Tricycle 19 0.64
Car 1027 34.44
Passenger Utility 242 8.12
Goods Utility 1546 51.84
Small Bus 19 0.64
Large Bus 1 0.03
2 Axle Truck 64 2.15
3 Axle Truck 57 1.91
4 Axle Truck/trailer 1 0.03
5 Axle Truck/trailer 6 0.20
4 Axle Trailer 0 0.00
5 Axle Trailer 0 0.00
AADT 2,982 100.00

2-3-3) Number of Predicted Closure Days of the Whole Width of the Road on the Survey
Site per RCD
The number of closure days of the whole width of the survey road due to a disaster is
predicted and the corresponding cell filled out. When traffic on one lane is open in the
prospective disaster site, the closure day is equal to 0.

Figures 3.20 to Figure 3.21 can be used as reference for the prediction of road closure days
due to disaster.

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80
SC
70 RC
LS
RS
60 DF
RE
Number of RCD (full lane)

50 CE

40

30

20

10

0
0 days ～0.5d ～1d ～3d ～7d ～15d ～30d 30d～

Road Closed Days

Figure 3.20 Frequency Distribution of Road Closure Days per RCD

（Based on available data of 229 RCDs on the national highway from 1996-2006）

LS
o : Nos. of closure days predicted of
the whole width of the road (days)

70
LS: Landslides
60
o = 0.0631*LRC
50

40

30
20

10
0
0 20 40 60 80 100 120 140 160
Length of road closure (LRC : m)

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RS

o : Nos. of closure days predicted of

the whole width of the road (days)
70
RS: Road Slip
60
50
40
30
20
o = 0.2509*LRC + 0.9863
10
0
0 5 10 15 20 25 30 35 40
Length of road closure (LRC : m)

DF
o : Nos. of closure days predicted of
the whole width of the road (days)

70
DF: Debris Flow
60
50

40

30
o = 0.0081*LRC + 2.3799
20
10
0
0 100 200 300 400 500 600
Length of road closure (LRC : m)

RE
o : Nos. of closure days predicted of
the whole width of the road (days)

70
RE: River Erosion
60
50

40
30
o = 0.1264*LRC
20
10
0
0 20 40 60 80 100 120
Length of road closure (LRC : m)

Figure 3.21 Charts for Estimating the Number of Road Closure Days by Length of
Road Closure Alignment for various RCDs
(Based on available data on RCDs on national highways from 1996-2006)

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2-3-4) Average Vehicle Operating Cost per AADT unit/km on the Survey and Detour
Roads
The Average Vehicle Operating Cost (AVOC) per AADT unit/km on the Survey and Detour
Roads should be input based on the typical condition of the survey and detour roads, i.e., the
closed road is paved and in fair condition, while the detour road is unpaved and in poor
condition. The methodology for calculating the AVOC uses the data given in Tables 3.4.6 and
3.4.7.

The DPWH regularly updates its estimate of vehicle operating costs used in the evaluation of
road projects. This is applicable in the analysis of detour cost and the most recent estimate (as
of October 2006) given in Table 3.11

Table 3.11 Estimated Vehicle Operating Cost (VOC) per Road Surface Type and
Condition per km (VOC/km) (pesos)
SURFACE Vehicle Running Fixed Running Time VOC
Type Cost Cost + Fixed Cost Running +
Type Condition Fixed + Time
PAVED V.BAD CAR/VAN 10.99 0.53 11.52 1.73 13.25
JEEPNEY 7.58 2.60 10.18 2.56 12.74
BUS 14.21 4.76 18.97 14.76 33.73
TRUCK 18.28 5.59 23.87 0.00 23.87
MCYCLE 1.38 0.32 1.70 2.28 3.98
OTHERS 1.68 5.64 7.32 1.29 8.60
BAD CAR/VAN 9.62 0.40 10.02 1.30 11.31
JEEPNEY 6.64 1.95 8.58 1.92 10.51
BUS 11.97 3.57 15.54 11.07 26.61
TRUCK 15.39 4.19 19.58 0.00 19.58
MCYCLE 1.20 0.24 1.44 1.71 3.15
OTHERS 1.47 2.82 4.29 0.64 4.93
FAIR CAR/VAN 8.24 0.27 8.51 0.87 9.37
JEEPNEY 5.69 1.30 6.99 1.28 8.27
BUS 9.72 2.34 12.07 7.27 19.33
TRUCK 12.51 2.75 15.26 0.00 15.26
MCYCLE 1.03 0.10 1.13 0.65 1.81
OTHERS 1.26 1.61 2.87 0.37 3.24

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SURFACE Vehicle Running Fixed Running Time VOC

Type Cost Cost + Fixed Cost Running +
Type Condition Fixed + Time
PAVED GOOD CAR/VAN 6.87 0.23 7.10 0.74 7.84
JEEPNEY 4.74 1.11 5.85 1.10 6.95
BUS 7.48 2.01 9.49 6.24 15.74
TRUCK 9.62 2.36 11.98 0.00 11.98
MCYCLE 0.86 0.08 0.94 0.57 1.51
OTHERS 1.05 1.41 2.46 0.32 2.78
UNPAVED V.BAD CAR/VAN 13.05 0.93 13.99 3.04 17.03
JEEPNEY 9.01 4.57 13.58 4.51 18.09
BUS 17.20 8.26 25.47 25.62 51.09
TRUCK 22.13 9.70 31.83 0.00 31.83
MCYCLE 1.63 0.32 1.95 2.28 4.23
OTHERS 2.00 5.64 7.63 1.29 8.92
BAD CAR/VAN 10.99 0.55 11.55 1.81 13.35
JEEPNEY 7.58 2.71 10.30 2.68 12.98
BUS 14.21 4.91 19.12 15.22 34.34
TRUCK 18.28 5.76 24.04 0.00 24.04
MCYCLE 1.38 0.24 1.62 1.71 3.33
OTHERS 1.68 2.82 4.50 0.64 5.14
FAIR CAR/VAN 8.93 0.39 9.33 1.29 10.61
JEEPNEY 6.16 1.93 8.09 1.90 10.00
BUS 11.22 3.72 14.94 11.54 26.48
TRUCK 14.43 4.37 18.80 0.00 18.80
MCYCLE 1.12 0.12 1.24 0.86 2.09
OTHERS 1.37 1.88 3.24 0.43 3.67
GOOD CAR/VAN 7.90 0.30 8.20 0.96 9.16
JEEPNEY 5.45 1.45 6.90 1.43 8.33
BUS 9.35 2.62 11.97 8.12 20.08
TRUCK 12.03 3.07 15.10 0.00 15.10
MCYCLE 0.99 0.10 1.09 0.68 1.77
OTHERS 1.21 1.41 2.62 0.32 2.94
Source: DPWH Planning Service

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(3) Indicative Feasibility Indicators for the Countermeasures

The objective of the DIS is to determine the indicative economic viability of each
countermeasure and to compare the viability indicators of all possible countermeasures to
select the most economically viable countermeasure. Potential frequency of road closure
disaster with countermeasure and three benefit/cost analysis measures are used to estimate
the economic worth of the specific countermeasure: Benefit/Cost Ratio (BCR), Economic
Net Present Value (ENPV) and the Economic Internal Rate of Return (EIRR) of the
countermeasure’s benefit and cost streams. These are estimated assuming a 20-year project
life:

(equation 3.15)

where:

BCR= Benefit/Cost Ratio at 15% discount rate

x= decrease in annual loss due to countermeasure

v= cost of countermeasure including 20 year maintenance cost

y= year from countermeasure installation (year of countermeasure installation is

y = 0)

(equation 3.16)

where:

ENPV= Economic Net Present Value

x= decrease in annual loss due to countermeasure

v= costs of countermeasure including 20 year maintenance cost

y= year from countermeasure installation (year of countermeasure installation is

y = 0)

0.15= assumed discount rate (opportunity cost of capital or OCC)

EIRR= Economic Internal Rate of Return

It is the “discount rate r” where the present value of the benefit stream is equal to the

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present value of the cost stream over the project life.

y=20
Σy=0[(xy-vy)/(1+r)y] = 0 (equation 3.17)

where:

y= year from countermeasure installation (year of countermeasure installation is

y = 0)

xy= benefit in year ‘y’ (pesos/year)

x0= 0, x1, x2 ……….. x20 = x (x: decrease in annual loss due to countermeasure)

vy= cost in year ‘y’ (pesos/year)

vy= cost of countermeasure inclusive of 20 years maintenance, v1, v2 ……v20 = 0

r= discount rate = Economic Internal Rate of Return

The proposed countermeasure is viable from the economic viewpoint if the estimated BCR >
1, ENPV > 0 at the 15% discount rate; and the computed EIRR > 15%.

Table 3.12 illustrates the estimation of the BCR, ENPV and EIRR.

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Table 3.12 Estimates of BCR, ENPV and EIRR using Microsoft Excel
Assumptions:
Discount rate: Opportunity cost of capital =15%
V0 =Cost of countermeasure with 20 yeas maintenance = PHP 10 million
x =Annual benefits (reduction in losses due to RCD) = PHP 1,250,000
Economic life of countermeasure = 20 years

y: year v0: cost of countermeasure xy: annual benefit Net Benefits

inclusive of 20 year (pesos/year)
maintenance
(pesos)
0 10,000,000 -10,000,000
1 1,250,000 1,250,000
2 1,250,000 1,250,000
3 1,250,000 1,250,000
4 1,250,000 1,250,000
5 1,250,000 1,250,000
6 1,250,000 1,250,000
7 1,250,000 1,250,000
8 1,250,000 1,250,000
9 1,250,000 1,250,000
10 1,250,000 1,250,000
11 1,250,000 1,250,000
12 1,250,000 1,250,000
13 1,250,000 1,250,000
14 1,250,000 1,250,000
15 1,250,000 1,250,000
16 1,250,000 1,250,000
17 1,250,000 1,250,000
18 1,250,000 1,250,000
19 1,250,000 1,250,000
20 1,250,000 1,250,000
Present Value at 15% 8,695,652 7,824,164
discount rate
BCR at 15% discount 0.90
ENPV at 15% discount -1,892,031
EIRR 10.93%

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3-1) Cost of Countermeasures with 20 Year Maintenance

The estimates of the costs of the countermeasures are given in Sheet 4 and are linked to the
appropriate cells in Sheet 5.

3-2) Risk Reduction Ratio in RCD Due to Specific Countermeasure

The specific countermeasure reduces the RCD/FRCDp. The risk reduction ratio
corresponding to the different countermeasures’ effectiveness should be input in the
appropriate cells. Example of the risk reduction ratios are shown in Table 3.13

Table 3.13 Examples of Risk Reduction Ratios

Countermeasure’s Effectiveness Example of Disaster Type of Countermeasure

Reduction Ratio
High Effectiveness: 0.7 – 1.0 ‰ Retaining walls for RS
RCD reduction is between ‰ Embankment of landslide toe
70%-100% ‰ Cutting of LS head
‰ Sabo dams for DF
Moderate Effectiveness: 0.3 – 0.7 ‰ Catch walls
RCD reduction is between ‰ Guard fences
30%-70% ‰ Retaining walls for SC
‰ Road drainage for RS
Low effectiveness: 0.0 – 0.3 ‰ Vegetation for SC
RCD reduction is between
0%-30%

3-3) Annual Benefits Due to a Specific Countermeasure

The benefits that are generated by a countermeasure are the decreases in annual losses due to
avoidance of reopening costs and detour cost and decrease in the occurrence of deaths. These
are estimated as follows:

xI = u*w (equation 3.19)

where:

x = Decrease in total annual losses due to the specific countermeasure

u = Total annual loss

w = Risk reduction in RCD due to the countermeasure

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