Group 4

Jeremy Chen Jianrong (U086706A)

Ong Huiping Kelsey (U086676E)

Kuah Huizi (U086696X)

Zhu Wei Qiang Kenny (U086661B)

Adrian Soh Wee Kiat (U086723M)

Wu Te (U086717M)

Wong Kai Ting (U086705U)

Koh Chin Han (U086660N)

Content

1. Introduction

1.1Background

1.2Purpose

2. Current Excavation Process

3. Problems with Current Excavation Methods

3.1Risks of Damaging and Rupturing Existing Underground Utilities

3.2Inaccuracies of Detection

3.3Noise and Vibration

3.4Speed of Excavation

4 Case Study

4.1Woodlands Avenue 9

4.2Thrift Drive

5 Air-Max Trencher

5.1Specifications

5.2Process

6 Advantages of an Air-Max Trencher

6.1Eliminating Possibility of Utility Damage

6.2Safer and Neater Option

6.3Reduce Public Disturbance

6.4Cost Effective

7 Limitations

8 Overcoming Limitations

9 References

10 Appedices

1. Introduction

This report will analyse and evaluate on the current trenching procedures adopted in

Singapore’s construction industry. It will then further explore the possibility of adopting a

trenching machine which utilizes compressed air and vacuum suction technology to improve

the current trenching procedures in Singapore.

1.1. Background

Trenching is special way of excavation. It is a common process required in almost every

construction project that comes into contact with underground utilities. In addition, it

plays an important role in the installation and maintenance of pipes, cables and other

infrastructure which are buried underground.

Figure 1. Laying of Pipes and Cables Underground

Currently in Singapore, underground utilities network spans for hundreds of kilometers.

To ensure workability of our existing utilities, regular maintenance is necessary.

Trenching has to be done in order to expose the underground utilities for maintenance

work to be carried out.

To date, the mini excavator is the only type of construction equipment used for digging

trenches in Singapore. It can dig trenches of various lengths, widths and depths. Manual

excavation by workers is used to supplement the mini excavator in digging trenches as

the underground utilities get close to being uncovered.

Figure 2. Trenching using Mini Excavators

During the process of trenching, there is a risk of damaging these underground utilities.

Though developers, contractors and workers follow closely to and adopt safe practices

when carrying out such earth works, damages have still occurred during both manual

and mechanical excavations.

With the underground environment of Singapore becoming more complicated and

congested as more infrastructure move underground, the constant need to perform

trenching for the laying of new utilities or the maintenance of existing service lines thus

demands us to explore better options for excavation.

1.2. Purpose

The purpose of the report is as follows:

1. To evaluate the current trenching process involving underground utilities in

Singapore, and

2. To propose an improved trenching process with the Air-Max Trencher; a more 

efficient,   safer and   accurate equipment for stakeholders involved (i.e. personnel

involved in the excavation process and the general public affected when excavation

occurs.)

2. Current Excavation Process

The following illustrates the current excavation process from site investigation to the

completion of work.

1. A preliminary site investigation about the history of the site will first be conducted. A

record search with the site plans, and other legal documents will be done to identify

the location of underground utilities in the area to be excavated. For example, any

pipeline within 30 meters radius of the proposed disturbance must be identified.

2. Determine the regulations involved in the proposed ground disturbance Examples

include the Land Transport Authority (LTA), Public Utilities Board (PUB), and

telecommunication companies such as SingTel.

3. Notification and permission to excavate will be sent to the owners of buried

facilities. Notification times vary for different organizations. Usually, this is done

from two to ten days prior to the proposed disturbance. The owner(s) will

acknowledge the notification and excavations may only proceed after permission is

given.

4. A visual inspection of the area to be disturbed will be conducted with a hand-held

detector, the Ground Penetrating Radar (GPR). Trial holes are then dug to facilitate

the use of a detection equipment to locate the utilities underground before

commencement of any earth works.

5. Look out for signs of buried facilities and previous ground disturbances. This is

important as it will affect the level of precaution required in the process. An example

would be that more caution needs to be exercised where the top layer consists of

backfilled materials, which indicates previous excavations.

6. The owner of the buried facilities, or a third party company, will usually undertake

the tasks of locating, mapping and marking of buried facilities. Facilities must be

marked according to a standardized colour-coding system, e.g. blue for water pipes.

7. Pipelines and other underground facilities are to be exposed by mechanical

excavation. Where an estimated depth is reached, manual labour replaces the

mechanical excavation. Specific procedures will vary, depending on the type of

buried facilities present and which regulations or agreements are in force.

8. All specified clearance distances between mechanical excavation equipment and

buried facilities are to be respected.

9. In some cases, the owners of buried facilities must be notified and/or must inspect

exposed facilities before they are backfilled.

10. A competent supervisor will be appointed to oversee all ground disturbance

activities. Also, personnel directly involved in ground disturbance activities should

be adequately trained on ground disturbance procedures and site-specific

conditions.

11. All records required by applicable regulations and legal agreements are to be

maintained. This is to be used for future development on the same plot of land/soil.

3. Problems with current excavation methods

3.1. Risks of damaging and rupturing existing underground utilities

As seen in Figure 1, the most prevalent cause of cable damage is through Mechanical

Excavation (59%), followed by Manual Excavation (15%). Both procedures are adopted

for trenching in Singapore.

Current excavators used might not be safe and good enough for carrying out excavation

at areas with underground utilities. Similarly, manual excavation is not a fail-safe way to

ensure no underground utilities is damaged. Furthermore, manual excavation in fact

depends on an individual’s excavation proficiency. The damage to underground utilities

can be greatly reduced if a better and safer excavation machine is adopted.

Figure 3. Causes of cable damage (taken from SP PowerGrid)

Damage to cables and pipes by mini excavator’s steel tooth

Although the mini excavator is relatively small and light in weight, it may damage

surfaces it is driven on, including grass and hot asphalt pavements. Hence, it is not

surprising to note that the mini excavator also holds the risk of damaging the

underground utilities during the process of trenching.

Figure 4. Steel Tooth of Mini Excavator Damaging Concrete Slab

As seen in Figure 4, the bucket tooth of the mini excavator is capable of breaking the

concrete. If the bucket of the mini excavator accidentally comes into contact with

the cables and pipelines, it is capable of damaging them, especially older utilities that

are not encased in concrete. This evidence supports the previous statement made

that the current excavators are not safe enough to be adopted for excavation at sites

with underground utilities.

Danger posed to workers and general public

The lines buried underground can sometimes be explosive, charged and often

deadly. When damaged during excavation, these lines may explode and kill or injure

multiple workers performing the excavation. In addition to this detrimental effect,

innocent bystanders can also be killed or injured regardless of the activities

conducted near the excavation site.

In Singapore, an explosion in a manhole resulted in the injury of six Thai nationals,

who were working on an abandoned pumping main in the sewers when the

explosion occurred. (Channelnewsasia, 2009)

Cost incurred and Punishments

If a cable or gas pipe is damaged, the costs incurred are usually borne by one or a

combination of the following parties: - the Contractor, the locating company, utility

providers or insurance companies. Contractors will incur the cost of fines charged by

authorities. The utility providers will incur the cost of repairing the damage. On the

other hand, the public and business owners who are affected will also have to incur

the cost of operational downtime. The total amount of cost incurred can be

significantly huge. One can also be prosecuted for offences under the Public Utilities

Act.

Under the Public Utilities Act, Part V (Offences), Damage to property of Board, it

states that “Any person who wilfully  removes,  destroys  or  damages  any property 

belonging to or under the management or control of the Board or hinders or prevents 

the property from being used or operated in the manner in which it is intended to be 

used or operated shall be guilty of an offence and shall be liable on conviction to a 

fine not exceeding $10,000 or to imprisonment for a term not exceeding 3 years or to 

both.” (Public Utilities Act, Part V )

Inconveniences caused by disruption of utility services

In Singapore, a complex network of pipes and cables lie beneath the ground, island

wide. These pipes and cables are important and essential to maintain our current

way of life. Singapore also has one of the best electricity networks in the world.

What contributes to the good reliability and quality of our electricity network is the

existing fully underground cable system that we have in place. It protects the

network from negative environmental effects. However, once exposed to

earthworks, the electrical cables are vulnerable and susceptible to damages.

Cable damage can affect consumers, particularly those in high-technology industries

that use voltage-sensitive equipments. For them, a momentarily voltage dip can

cause voltage-sensitive equipments to malfunction, resulting in down-time for

affected production and process lines. (Prevent Damage to Underground Cables &

Gas Pipes Seminar, 2007)

Utilities damaged by earthworks can potentially cause major interruptions to nearby

businesses/facilities. A telecommunications company source said that construction-

related telecommunications disruptions occur 'quite a few times every year, usually

around road works and construction sites'. (Hou, 2009)

Figure 5. Congested Underground Environment

Lack of visibility of operator

The operator of an excavator is often unable to view the excavated area. This

lack of visibility applies to operators of excavators of any sizes. Another worker is

thus required to supervise and communicate with the operator during the

excavation process.

Figure 6. Operator Standing on Moving Excavator and Peering on Area to be Excavated

(Taken at Alexandra Road)

As seen in Figure 6, the operator is unable to look into the excavation site as the

machine is situated above the site. Another worker needs to stand opposite to the

excavator in order to communicate and direct the operator. This process is time

consuming and any misunderstanding in communication can result in accidents

which are not in control of the operator or the signaling worker.

3.2. Inaccuracies of Detection

Currently, the Ground-penetrating Radars (GPR) are commonly used by detection

workers to spot utilities. Locating utilities using the GPR is useful because maps and

plans often lack the pinpoint precision. In the case whereby maps are not provided or

plans are not updated, underground utilities can be missed entirely.

Detection of utilities takes a significant amount of time for contractors to reconfirm a

utility’s final location. This is especially so when all devices are never fail-proof. Thus, the

GPR only act as a guide and estimation for contractors.

Using the GPR requires considerable expertise and reading the data off from the

radargrams is not an intuitive process unless a trained specialist is present. Moreover,

the use of GPR may sometimes prove to be inaccurate as its performance may be limited

by signal scattering in heterogeneous conditions (rocky soils).

Other than the use of detectors, contractors will search for signs on the ground

indicating the presence of underground utilities. This include surface markers (Figure 6),

cable slabs buried underground, cable bridges and over-ground boxes.

Figure 7. Surface Markers on Roads

The following is a quotation from the SP PowerGrid’s website where an interview was

done by them in regards with the use of detectors on site where underground utilities

can be found.

"I had checked the area visually  and did not see any signs of underground electricity 

cables or gas pipes. I had even used a cable locator to check for cables and found none." 

(SP Powergrid FAQ)

The contractor was actually unable to locate the presence of underground utilities

despite employing the use of cable detectors. Thus, using detectors may not be reliable

in determining the exact location of underground utilities. This brings about a serious

problem of damaging pipes and cables that may be detrimental to all users and

authorities. Excavator operators would then need to be more vigilant and careful during

excavation.

3.3. Noise and Vibration

Road works are necessary and inevitable, especially when they are not anticipated.

Maintenance and installation of cables, burst pipes and gas leaks are some

circumstances where trenching comes into place. More often than not, trenching

creates high levels of noise and vibration.

Disturbance can come in the form of excessive noise and vibration from the operation of

the excavator and its engine. Vibration and noise in excavation can result from strikes

with the bucket or when boulders are pried loose.

These vibrations may be repeated over for a period of hours or days, depending on the

duration of the project. In different locations, the costs of planning and control work,

including vibration measurement may vary. Moving the excavator also results in causing

vibration. The noise level of an idling engine of an excavator is around 91dB, which is

considerably loud. (Ground X)

The place and time that trenching can be carried out is dependent on its surroundings

and the extent of excavation required. In view of this, the government has put in place

regulations to bring the level of noise pollution to a minimum.

One of these regulations is the allocation of specific timings (09:30am – 04:30pm) for

road works to be carried out near residential areas where disturbance is not welcomed.

Works on roads with high vehicular flow or near commercial buildings have to be carried

out at night so as not to affect the operation of businesses or the flow of traffic.

Constant monitoring of noise generated from the activities with a portable noise meter

is also mandatory.

3.4. Speed of excavation

The time taken for trench digging depends on many different factors including the types

of equipment used, ground and soil condition of trenching site, and the scale of

excavation of the project. Prior to this, pre-trenching activities are required to be carried

out. These activities include the application of clearance for work from the relevant

authorities such as the Land Transport Authority (LTA), SP PowerGrid, Public Utilities

Board (PUB), and the determination of underground by a Licensed Cable Detection

Worker (LCDW). For example, the Notice for Commencement of Earthworks (NCE) needs

to be submitted to SP PowerAssets and/or Power Gas 7days before actual earthworks.

Using Excavators

In a typical excavation of a trench, hydraulic mini-excavators are used to excavate

the trench up to a required depth. Subsequently, the remaining soil is dug out

manually by workers with a shovel to expose the buried utilities.

It is observed that the hydraulic excavator operates by shovelling a certain volume of

soil from the excavation site with the bucket attached to the hydraulic boom. After

which, it rotates on its base to deposit the soil onto another location nearby or into a

dump truck. The canopy and boom then turn back and continue the excavation

process. Hence, it can be seen that up 50% of the operation time of the hydraulic

excavator is not carrying load or is merely transferring the soil aggregate excavated.

In an interview session with Mr Joseph Lim, General Manager of PNH Resources, he

mentioned that the current excavation process uses mainly backhoe excavators that

can be divided into different categories in terms of sizes. A normal excavator ranges

from a weight of 6 tons to 9 tons, while mini excavators usually weigh less than 4

tons. Depending on the size of excavators used, bucket sizes vary from 0.036 m³ for

mini excavators to 4.5 m³ for large excavators. Hence the speed of excavation is

largely dependent upon choosing the right excavator for the right magnitude of

project tendered. An operator’s amount of experience and exposure to training also

has an impact on the speed of mechanical excavation as well. Contractors also look

into factors such as the maintainability and availability of parts in the market for

replacement when choosing excavators.

As drawn out during the planning stage, before the excavators reached the acquired

depth of approximately 1 metre away from the underground utilities, manual labour will

have to be employed to ensure that no damage is done to any utilities. This combined

process of mechanical excavation and manual digging is tedious and time-consuming.

Manual Digging

The time required for manual digging is dependent on the efficiency of each

individual worker. Factors affecting the efficiency of workers include fatigue, soil

conditions and weather conditions. (Canadian Health Centre for Health and Safety,

1999) When fatigue sets in, rest breaks have to be given to the workers. Manual

digging can cause injuries to the muscles, discs and ligaments to the back, whether in

the short term or long term. (The Centre for Construction Research and Training,

2009) The workers can also be afflicted with Hand Vibration Syndrome if exposed to

prolonged usage of vibration tools to loosen the soil.

Thus, the time required for manual digging can be long if the trench is big. Safety can

also be compromised if the space in the trench is small, restricting free movement

for the workers to carry out their assigned task. The workers are also susceptible to

injuries when they are doing long periods of manual digging. Hence, the speed of

excavation is largely reliant on the efficiency of the excavators and their operators

and as well as the workers involved in manual digging.

4. Case Studies

4.1. Woodlands Avenue 9

The following excavation was done at Woodlands Avenue 9 just before Woodlands

Crescent. The purpose of the works was to lay NEWater pipes to facilitate the areas

nearby. Hence, an excavation of a 5m by 5m by 2m deep hole was required to be dug on

the road. The project commenced on 22nd October and was completed by the 25th

October, a period of four days.

Traffic Disruption

As seen from Figures 8, 9a and 9b, the excavation work required 2 lanes to be partially

cordoned off. Although the Code of Practice for Works on Public Streets regulates the

one lane replacement method which states that only one lane is to be closed at any

point in time due to road works, larger excavation works, such as the following case,

makes the need to close more than one lane inevitable. The fact that the particular road

is 3-laned would mean that it is a busy road with many cars. In such cases, traffic

disruption would become be even more severe in addition to the time needed for such

an excavation size.

In addition, the heap of soil/sand left on the road (Figures 9a and 9b) meant that certain

measures meant to minimise impact on traffic flow were not being carried out. An

example would be the prohibiting of road works during peak hours. In such a situation,

road works will still continue since the sand/soil is already deposited on the road, and

work will not be stopped as doing so will cause a prolonged traffic disruption.

Figure 8. Digging of 5X5X2m deep hole. Figure 9a. Excavation process taking up 2 road lanes

Noise and Vibration

Given that this case study was at a rather open space, noise and vibration was generally

not a considerable factor. However, precautions were still taken to protect the road and

any possible soil movements. As can be seen from Figure 10, temporary earth retaining

systems are put in place to ensure that the excavation does not affect surrounding soil

conditions, or results in differential settlement in which would cause severe road

defects.

Figure 9b. Excavation process taking up 2 road lanes

Figure 10. Earth Retaining System around Trench

Use of Manual Labour

Through an interview with one of the contractors present at the site, it was mentioned

that the mechanical excavation commences only after the breaking of concrete/premix

with the use of hydraulic jack hammers. An approximate estimate of the location of

existing pipes can be determined using the cable detectors, and areas without any

hidden underground utilities are excavated first. After which, workers would be sent into

the excavated pit to continue with manual digging till the pipes are revealed. In this

manner, there is decreased probability of damage of pipes with the backhoe, which

could cause more harm. The workers would also be able to complete the whole

excavation process by digging areas where the backhoe is unable to reach, such as small

corners.

4.2. Thrift Drive

The second case study conducted was on the excavation at Thrift Drive, by Fuco

Contractors Pte Ltd. The purpose of the excavation works was also to lay water pipes.

The difference for this case study with the previous is that the excavation is done on the

pavement, while still overlapping a small portion of the road.

Figure 11. Excavation on Pavement

Lack of Safety Barriers

Figure 12. Lack of Safety Barriers

As seen from Figure 12, a passer-by, unknown to both the operator of excavator and his

colleague, was walking precariously near the excavator with no barriers or any warning

signs to inform the passer-by of any possible danger that could result from the swinging

of the boom.

In addition, the extra personnel on-site were too busy helping out in the excavation to

be looking out for any passer-bys. According to the code of practise for works on public

streets, it is stated that there should be a personnel assigned on-site to look out for the

safety of pedestrians and incoming traffic, however, this is usually not adhered to as all

personnel on-site has to be fully utilised to have the most economic use of the

labourers.

Workers’ Safety

Figure 13. Worker standing on site with close proximity to boom of excavator

It is impossible to eliminate human error when manual operation of the excavator is

adopted. Hence, there is always a danger factor posed to general public and workers on

site that are near to the excavator. In the photo shown above, it displays how near the

worker actually is to the boom of the excavator. Any negligence on the operator’s part

may very well result in causing injuries to him.

Danger to Oncoming Traffic

Figure 14. Oncoming Traffic Vulnerable to Excavator’s Movement

The site for this excavation is located at a slip road leading to a major expressway;

hence, the excavator is exposed to a lot of ongoing traffic. Given that it was considered a

small scale excavation, an advance warning zone was not required. In practice,

contractors will usually only place one or two warning signs along the pavement to warn

pedestrians and drivers of the ongoing excavation. The lack of advance warning systems

for such small scale excavations may cause the excavation to become a road hazard for

oncoming traffic.

Noise and Vibrations

As this project was done within close proximity to a residential area, noise and vibrations

generated by the excavation works are of particular concerns. Such noise pollution and

vibrations may cause distress and disturbance to the residents living in the area. While

such an occurrence is inevitable in the current process of trenching, this area is definitely

one of concern for general construction practices.

5. Air-Max Trencher

The Air-Max trencher adopts the compressed air technology in the area of trenching

works. It replaces the conventional method of trenching using buckets or grabs with an

efficient suction technology.

Figure 15. 3D Simulation of Air-Max Trencher (Side View)

5.1. Specifications

Standing at 2.7 metres tall, 2.5 metres wide and 7 metres long, Air-Max has a

hydraulically operated boom incorporating 3 sections of telescopic steel that is 7 inch in

diameter. This allows 3-dimensional movements of the suction hose. The boom is able

to extend up to 6 metres and has a dig depth of 3 metres. With such specifications, the

trencher is able to dig a trench as wide as 3 metres for normal road works such as laying

and fixing of underground pipes and utilities.

Figure 16. 3D Simulation of Air-Max Trencher featuring 3 sections of telescopic steel (Front View)

The suction intake attachment has 5 supersonic air jet nozzles that takes after the AIR-

SPADE supersonic nozzles that turn compressed air into a high speed, laser-like jet

moving at a speed of Mach 2 and has a soil removal rate of 1m³ per min. The suction

intake attachment has the ability to suck in rocks not greater than 7 inches in size, while

rocks larger than that size can be lifted out of the trench through its suction technology.

This ensures that the trenching process would not be disrupted even if larger rocks are

encountered and in the way of the excavation process. Therefore, allowing the

elimination of the need for extra equipment for removal of the rocks.

Figure 17. 3D Simulation of Air-Max Trencher featuring Suction Intake Attachment

A cable detection device, similar to that of the GPR but with higher accuracy, is fitted

onto the suction intake attachment to detect the presence of existing underground

pipes and utilities. This eliminates the conventional practice of locating existing

underground cables via maps given by the Land Transport Authority which may not be

very accurate. Furthermore, with this equipment fitted onto Air Max, allowing the

detection of underground cables and utilities while excavating. Workers no longer need

to enter into the trench and perform manual digging to excavate sensitive areas where

excavators cannot reach, hence, reducing risks of workers getting injured.

Feature Specification(s)

Boom

Hydraulically operated boom of 3

sections telescopic steel with 7 inch in

diameter

Extension 6m

Dig depth 3m

Trench size Maximum 3m wide

Size 2.7m tall by 2.5m wide by 7m long

Additional Feature Cable Detection Equipment

Soil removal rate 1m³ per min

Speed of compressed air nozzles Mach 2

Table 1. Air-Max Trencher Specifications

5.2. Process

The introduction of an Air-Max Trencher into a current excavation process helps to

streamline the entire process, highlights being that it is able to eliminate the need for

manual digging and offers a faster rate of soil removal.

Similar to the current excavation process, the procedures of preliminary site

investigation of the excavation site, determination of regulations to be applied and

sending of notification and permission to the owners of buried facilities are to be done

prior to any earthworks.

1. With a Ground Penetrating Radar attached at the end of the boom, the operator

is able to use the Air-Max trencher to detect the locations of the underground

utilities. Once located, the operator can immediately initiate digging of the trial

holes.

2. Although it is crucial to be mindful of signs of buried facilities and previous

ground disturbance as they may indicate previous excavation, the non-contact

supersonic air nozzles ensures that uncovered facilities will not be damaged.

3. After the owner of buried facilities or a third party company has located, mapped

and marked the buried facilities, the pipe lines and underground facilities can be

exposed. With the non damaging nature of the supersonic air nozzles, the Air-

Max Trencher is able to uncover the buried facilities single-handedly without the

need of manual labour.

4. Soil materials that is taken up by the vacuum suction passes through the Air-Max

Trencher and can be directed via a chute to deposit the backfill materials

anywhere next to the trencher or directly into a dump truck.

5. The Air-Max Trencher can also move along the area required for trenching if the

need to expose a specified length of underground utilities is longer than the

vehicle itself.

6. After the works to the underground utilities has been done and the owners have

been notified, backfilling can commence using the soil material deposited next to

the trench.

7. All records pertaining to the excavation required by the applicable regulations

and legal agreements are to be maintained for future development on the same

site.

As compared to the current excavation process adopted in the industry, the introduction

of Air-Max Trencher is able to reduce the process from a total of 11 steps to only 7

steps. In addition, the fact that the excavation speed itself is faster than conventional

mini-excavators used currently, this newly introduced process will definitely be a much

faster one.

6. Advantages of an Air-Max Trencher

In view of the importance of avoiding damage to the underground utilities and cable in

Singapore, our group has decided to raise the awareness of the use of compressed air

technology to perform trench excavation for laying or fixing of underground utilities and

pipes.

6.1. Eliminating Possibility of Utility Damage

Underground pipes and utilities are sensitive objects that one should avoid when

performing trench excavation. If workers are not careful during trenching, the existing

pipes and utilities underground will be damaged and in the process, incur a large sum of

penalty.

No Direct Contact with Underground Utlities

The Air-Max Trencher, unlike the conventional trenching method uses supersonic air jets

instead of hard cutting edge of shovels, buckets, blades or digging bar to dislodge the

soil. The compressed air is able to work in most soils, including compacted soil and hard

clays. (Guardair Corporation, 2009) When performing trench excavation in locations

where there are underground pipes and utilities, the supersonic air nozzles shoots out

jets of air to breaks up the porous soil effectively and is harmless to non-porous

materials like metal and PVC and even tree roots. (Nathenson, 1995) The compressed air

is also non-conductive in nature, ensuring that no static electricity is produced.

(Airforced Daylighting Ltd, 2009) This allows the Air-Max Trencher to work near

underground pipes and cables and as well as in sensitive environment like oil refineries.

Supersonic air jets that release the compressed air are strong enough to break and

loosen the soil into smaller aggregates. However, the compressed air will not damage

the underground utilities like cables and utilities as they are made of non-porous

materials. With the use of compressed air, manual labour is not required to reach the

depth of the buried utilities. Workers do not have to go down into the trench physically

to complete the digging. Chances of workers hitting the cables will also be eliminated.

The Air-Max Trencher can excavate soil starting from the top soil all the way to the

required depth to reach the underground utilities. With no direct contact with

underground cables, any chance of hitting underground utilities is greatly reduced,

thereby avoiding being fined for damage, and the extra cost incurred for repairs.

Added Precaution with Inbuilt Cable Detection Device

Also, with an inbuilt cable detection device, detection of utilities can be done using just

the Air Max Trencher. As the GPR system is inbuilt near the boom, it provides constant

feedback to the Trencher when utilities nearby are close. This constant feedback

provides the necessary additional precaution to safeguarding the possible damage of

underground utilities during the entire trenching process without having any person to

perform manual digging when near the utility or to oversee the process by the trench

while the Air Max Trencher is at work.

6.2. Safer and Neater Option

Remote Control

With the adoption of Air-Max Trencher, manual digging can be eliminated. Hence, the

chance of workers striking and damaging the cables during manual digging with shovels

or changko will be virtually non-existent. Death and injuries resulting from striking live

electric cables can then be avoided.

In addition, the Air-Max Trencher’s contactless excavation will not create sparks during

excavation. Hence, the Air-Max Trencher is suitable working in areas like oil refineries

where sparks are a concern due to inflammability. When working on gas pipes where

leakage might be of concern, using Air-Max Trencher will help to prevent explosion

triggered by sparks.

The conventional practice currently requires a supervisor to be in or around the trench

to guide the operator of the excavator to dig the soil. However, the operator of the Air-

Max Trencher will be using a tethered remote-control kit to control the vehicle and the

boom. (Battelle Memorial Institute, 1995) The operator will therefore have access and

full visibility of the trenching site. He is able to have full view of the trench and to direct

the boom of the trencher as he deem fit. This not only eliminates the need for an extra

man for guidance and also ensures the safety of the operator by preventing the

excavator from undercutting the soil beneath it.

Linear movement of boom

The boom of the Air-Max Trencher is capable of transversing up to 50 degree vertically

in or out and 25 degrees left or right. (Concept Engineering Group, Inc, 2005) During

excavation, the Air- Max Trencher only has to move its boom according to the width and

the depth of the trencher. Unlike current excavators which need to turn in order to

deposit excavated, the flow through design of soil removal enables the Air-Max Trencher

to discharge without having to move its boom. Hence, it eliminates the risk of a swinging

boom that will hit nearby workers or members of the public.

Instantaneous Removal of Soil Aggregates from Site

While current trenching methods are deemed to be rather efficient, the 1.0m3/min of

soil removal speed allows faster and neater trenching to occur. Unlike that of

conventional excavators used, Air Max Trencher is able to perform concurrent

excavation along with deposit of soil material. This process is much faster when

compared to current excavators, which after shovelling the soil, needs to turn to deposit

the soil.

6.3. Reduce Public Disturbance

Reduce Noise and Vibration

The compressed air and the vacuum suction force require a substantial and powerful

compressor. The amount of noise generated is an understandable concern. The

generator of the machine produces noise level of around 80 dB. In the Air-Max Trencher,

a high efficiency absorption chamber silencer effectively reduces the noise level by 10 to

15 dB. (Advanced Noise Solutions, 2008) It enables the Air-Max Trencher to perform

trench excavation at a noise level below the level of 75 dB as stipulated by regulations.

With mechanical excavation and moving parts, vibration cannot be avoided. However,

with the employment of compressed air and vacuum suction for trench excavation, the

Air-Max Trencher can be keep vibration to a minimal level. (Underground Moling

Services, 2008) This is particularly crucial when working near sensitive structures like

historical buildings.

Minimise Traffic Disruption

With a faster speed of removal, and the elimination of a relatively time consuming

procedure from the current trenching method used in Singapore when the Air Max

Trencher is adopted will certainly reduce the amount of time required for trenching. This

is especially helpful in terms of traffic control, as it reduces the possibility of traffic

congestion if the trenching needs to be done on the roads.

6.4. Cost Effective

These features of the Air Max Trencher, coupled with its ability to be remotely

controlled, greatly reduce the time and manpower needed for trenching. Much of the

entire process is automated and manual labour is only required to remotely operate the

machine and to serve as an additional precaution throughout the entire process. Unlike

present times, where a team of 6 to 7 persons are required on site, the adoption of the

use of Air Max Trencher also allows the reduction of manpower to that of 3 to 4 persons

per trenching project. In addition, the time to conduct trenching is also shortened.

These added features of the Air Max Trencher yield benefits that allow the contractors

to engage in more projects when available. The reduction of human labour in the entire

process also provides long term cost effectiveness to the contractors involved in

trenching processes.

7. Limitations

As no machine can be considered to be flawless or perfect, there are still certain limitations

to our Air-Max Trencher. Firstly, we are still unable to solve the noise issue caused by the

breaking of road surfaces/ pavements. However, with the Air-Max Trencher, we are able to

reduce the noise caused in the excavation of earth as compared to the traditional method.

Secondly, the high initial cost involved in implementing Air-Max Trencher would be

significant enough to deter many contractors from adapting this new innovation. However,

with the proposed benefits mentioned earlier, we are confident that the Air-Max Trencher

will be marketable when the cost of the technology is subsidized or reduced.

8. Overcoming Limitations

More research in this area will need to be done to better the current features proposed to

be incorporated in the Air-Max Trencher. The promotion of a safer alternative in adopting

the compressed air and suction technology of the Air-Max Trencher by relevant authorities

involved in the process of laying or uncovering underground utilities can also encourage

contractors in the industry to consider the use of specialised equipments in performing

these projects as the demand for such projects are significant enough for it to be utilized

fully in the context of Singapore’s underground environment.

9. References

(n.d.). Retrieved from Public Utilities Act, Part V :

http://statutes.agc.gov.sg/non_version/cgi-bin/cgi_getdata.pl?actno=2002-REVED-

261&doctitle=PUBLIC%20UTILITIES%20ACT

%0A&date=latest&method=part&segid=986262528-000845

(n.d.). Retrieved from SP Powergrid FAQ: http://www.sppowergrid.com.sg/protection-

faq2.htm

(1 Februry, 2007). Retrieved from Prevent Damage to Underground Cables & Gas Pipes

Seminar: http://www.ies.org.sg/e-newsletter/ContractorsAssociation.pdf

(21 October, 2009). Retrieved from Channelnewsasia:

http://www.channelnewsasia.com/stories/singaporelocalnews/view/1012819/1/.html

Advanced Noise Solutions. (2008). Noise Reduction Solutions that can Save £ thousands.

Retrieved 23 October, 2009, from Advanced Noise Solution: http://www.advanced-noise-

solutions.co.uk/industrial-noise-reduction.html

Airforced Daylighting Ltd. (2009). The Advantages of Air-Vacuum Excavation. Retrieved 30

October, 2009, from Airforced Daylighting Ltd: http://www.air-spade.com/Library/Airforced

%20Daylighting%20Ltd.pdf

Battelle Memorial Institute. (1995). Battelle: The Business of Innovation. Retrieved 25

September, 2009, from "SOFT TRENCHER" DESIGNED TO PROVIDE:

http://www.battelle.org/news/95/p7trench.stm

Canadian Health Centre for Health and Safety. (9 July, 1999). Shovelling. Retrieved 1

November, 2009, from Canadian Health Centre for Health and Safety:

http://www.ccohs.ca/oshanswers/ergonomics/shovel.html

Concept Engineering Group, Inc. (13 July, 2005). Soft Trencher. Retrieved 30 August, 2009,

from Concept Engineering Group, Inc.:

http://www.conceptengineeringgroup.com/special_projects_trencher.html

Ground X. (n.d.). Ground X. Retrieved 31 October, 2009, from Plant & Groundcare

Equipment Hire: http://www.groundx.co.uk/excavators.htm

Guardair Corporation. (2009). Air Spade, Technology. Retrieved 12 September, 2009, from

Air Spade: http://www.air-spade.com/technology.html

Han Kwong, L. (16 October, 2009). (Jeremy, Interviewer)

Hou, C. H. (4 July, 2009). Retrieved from The Straits Times:

http://www.straitstimes.com/Breaking%2BNews/Singapore/Story/STIStory_398940.html

Nathenson, R. D. (January/February, 1995). Technological Advancement Offers Safer, Faster

Excavations. Underground Focus Magazine , pp. 6-7.

The Centre for Construction Research and Training. (2009). Construction Solutions. Retrieved

31 October, 2009, from Pipes & Vessels:

http://www.cpwrconstructionsolutions.org/pipes_vessels/hazard/443/dig-grade-level-and-

cover-trenches-lifting-and-carrying-manual-materials-handling.html

Underground Moling Services. (2008). Suction Excavation. Retrieved 23 October, 2009, from

Underground Moling Services:

http://www.undergroundmoling.com/content/suction_excavation.php

10. Appendices

Appendix A

The Straits Times (Singapore)

July 4, 2009 Saturday

Company fined $500K for cable damage; Contractor caused Net and

phone disruptions

BYLINE: Chua Hian Hou

LENGTH: 534 words

THE Infocomm Development Authority of Singapore (IDA) has come down hard on a contractor whose workers

accidentally cut off phone, Internet and cellular access to thousands of users in Bedok last year.

Ah Boon Civil Engineering & Building Contractor was fined $500,000 last month by the Subordinate Court for

its error that left more than 3,000 residents and 70 companies on the blink. Last January, while putting in

shoring works to prevent the trenches they were digging from collapsing, Ah Boon's workers damaged

Singapore Telecommunication's (SingTel) fixed lines, fibre-optic Internet cables and mobile phone base

stations.

The damage cost SingTel $235,000 and took more than a day to fix, during which it received more than 800

complaints from irate users. Because of the 'serious and widespread disruption to business and personal

communications' caused, the telecommunications sector regulator decided to take action against Ah Boon.

Given the importance of the telecommunications network, due care must be taken by contractors doing work

in the vicinity of telecommunication cables to prevent cable cuts to the telecommunications network...IDA

takes a serious view of contraventions of the Telecommunications Act and will not hesitate to take strong

enforcement action against offenders,' said an IDA spokesman.

The authority has also started legal proceedings against a few other companies for similar transgressions,

added the spokesman. A telecommunications company source, who declined to be named, said that

construction-related telecommunications disruptions occur 'quite a few times every year, usually around

roadworks and construction sites'.

Under the Telecommunications Act, contractors must notify telecommunications companies one week ahead

of any earthworks and obtain plans for these cables, something the IDA said Ah Boon did not do. Contractors

must also ensure their works do not damage any telecommunications infrastructure.

Ah Boon said in mitigation last month that the problem was a 'one-off careless incident', not because it was

'wilful, malicious or reckless'.

The 26-year-old firm, which had been hired by the Public Utilities Board to build an underground drain, said it

had done the necessary checks to find out where SingTel and StarHub's cables lay. However, its workers forgot

to double-check the location of the cables after their lunch break, and so damaged them when they resumed

work. Ah Boon general manager Ken Koh said the firm will not be appealing.

Stay-at-home mother Jen Lim is supportive of the IDA's hard line, although she was not affected by Ah Boon'sa

ctions last year. The 32-year-old, who runs an online business on her blog, said: 'I need Internet access and my

handphone to update my blog and contact my customers, as well as to call for help in case of emergencies. My

son also needs the Internet to do research for his schoolwork, so not having these available is a big deal to my

family.'

IT manager Brian Lee was more understanding: 'Everybody has made mistakes due to complacency and

carelessness...But I guess the authorities felt it had to take action here in order to warn others to be more

careful, especially if it happens frequently.'

chuahh@sph.com.sg

LOAD-DATE: July 3, 2009

LANGUAGE: ENGLISH

PUBLICATION-TYPE: Newspaper

Copyright 2009 Singapore Press Holdings Limited

Appendix B

Damage to cables: $ 1m fine, jail, now

August 20, 1999

Ahmad Osman And Siti Andrianie

New maximum fine for damaging high voltage cables is five times the previous one. Parliament told of millions

lost because of such damage.

PEOPLE who damage high voltage power cables now face a maximum fine of $ 1 million and a jail term of up to

five years. The new maximum fine, which is five times the previous maximum of $ 200,000, was approved by

Parliament on Wednesday, when it passed the Public Utilities (Amendments) Bill.

This will deter contractors who may be tempted to risk hitting a cable during earthworks in order to avoid

delaying a project and having to pay liquidated damages to a developer. The changes to the PUB Act also

require Power Grid, the owner of such cables, and contractors to work together to prevent damage.

There are rules regulating earthworks and cable detection work in the vicinity of such cables belonging to, or

under the management or control of, a public electricity licensee. Those who fail to follow the prescribed

procedures risk a fine of up to $ 100,000 and up to five years' jail. The maximum jail term for the less serious

offence of damaging a low voltage cable has been reduced from three years to 12 months.

During the second reading of the Bill on Wednesday, Trade and Industry Minister George Yeo spoke of the

impact of high-voltage cable damage on high-tech industries. Between 25 and 30 times a year, he said, there

were voltage dips or momentary reductions of voltage levels, that had a severe effect on high-tech processes,

such as wafer fabrication. Between August 1997 and last November they had resulted in $ 3 million worth of

losses for five high-tech firms. This excluded production downtime, labour and delayed product delivery, he

said. He added that production downtime could be as much as 10 per cent of the monthly output of a wafer

fabrication factory.

$ 3m worth of losses VOLTAGE dips or momentary reductions of voltage levels had a severe effect on high-tech

processes, such as wafer fabrication. Between August 1997 and last November, they had resulted in $ 3-million

worth of losses for five high-tech firms.

CHANGES TO BILL <sol¬box> BILL: Under the Public Utilities (Amendments) Bill, those who damage

high-voltage power cables will be penalised. <sol¬box> PENALTY: A maximum fine of $ 1 million and a jail term

of up to five years. The previous maximum fine was $ 200,000.

OTHER CHANGES <sol¬box> The PUB Act also requires Power Grid, the owner of such cables, and contractors

to work together to prevent damage. <sol¬box> PENALTY: Those who fail to follow the prescribed procedures

risk a fine of up to $ 100,000 and up to five years' jail.

The maximum jail term for the less serious offence of damaging a low-voltage cable has been reduced from

three years to 12 months.

SECTION: Parliament; Pg. 46

LENGTH: 467 words

LOAD-DATE: August 20, 1999

LANGUAGE: ENGLISH

Copyright 1999 The Straits Times Press Limited

Appendix CThe Straits Times (Singapore)

Worker died during building of family court;

Bangladeshi died after explosion. As construction firm has folded,

alleged supervisor is now a potential defendant

May 30, 2002 Thursday

A DEADLY accident took place during the construction of the Family and Juvenile Court building more than a

year ago. However, the construction company managing the worksite cannot be prosecuted for negligent

supervision because it had closed shop, a coroner's inquiry heard yesterday.

Instead, the alleged supervisor of the digging works, Mr Robin Teo Cher Peng, 45, was the potential defendant.

Mr Teo was the mechanical and electrical engineer of Guan Choon Construction, which ceased operations in

March last year. It had hired three construction workers to lay underground pipes for phone cables at the site

of the court building, which opened officially in January this year.

They worked unsupervised. While digging, a high-voltage underground electric cable was hit.

In the explosion on Dec 1, 2000, one of them suffered burns on 39 per cent of his body. Bangladeshi Anowar

Hossain Kafil Uddin, 26, died 11 days later. The court heard that Mr Anowar and two others, one from

Bangladesh and the other from India, were going to lay pipes for telecommunication cables to be threaded

through from the Manpower Ministry, also in Havelock Road, to the court building.

While using a concrete-breaking machine, they hit a concrete slab which shielded a 6.6-kV electric cable.

As he was not supervised, Mr Anowar continued digging. Site project manager Chua Teck Hin, 47, testified that

he had informed Mr Teo to supervise the digging works. In response, Mr Teo said he had understood that Mr

Chua had asked a plumbing sub-contractor to supervise the work.

Mr Teo also alleged that the project site was 'poorly managed' as work was behind schedule and not all the

workers were supervised. He said that there was no proper handover of the work when he joined the company

in August 2000. Said his lawyer Suresh Divyanathan: 'The construction took place in a slipshod manner and a

catastrophic accident was inevitable at some stage.'

The inquiry continues today.

Explosion on Dec 1, 2000

MR ANOWAR Hossain Kafil Uddin, 26, was one of three workers who were laying underground pipes for

telecommunications cables. They hit a high-voltage electric cable at the site of the Family and Juvenile Court

building in Havelock Road on Dec 1, 2000. This caused an explosion. Mr Anowar, who suffered burns on 39 per

cent of his body, died 11 days later.

SECTION: SINGAPORE

LENGTH: 394 words

LOAD-DATE: May 30, 2002

LANGUAGE: ENGLISH

Copyright 2002 Singapore Press Holdings Limited

Appendix DThe Straits Times (Singapore)

Firm fined for damaging SingTel cables

October 4, 2001, Thursday

Elena Chong

Its subcontractor struck underground cables two years ago, disrupting telecom services to Suntec area for 18

Hours. A CIVIL engineering firm doing a sewerage project at Marina Centre two years ago damaged SingTel's

underground cables behind Suntec City.

The damage disrupted SingTel's telecommunication services to its customers at Suntec City Towers 1 and 2,

Millenia Tower and Centennial Tower for about 18 hours. Pipe-Jack Engineering & Construction, a Singapore

SME 500 company, paid SingTel $47,139 -- the cost of the physical damage it caused -- two years ago.

In court yesterday, Pipe-Jack admitted it was at fault and was fined $100,000 for damaging SingTel's five

copper cables, a fibre cable and a 24-way pipeline in Rochor Road on Aug 16, 1999.

This is a test case brought against the company by the Infocomm Development Authority of Singapore (IDA).

Offenders could be fined up to $1 million and jailed for up to three years for damaging any telecommunication

cable system belonging to, or managed by, a public telecommunication licensee. In mitigation, Pipe-Jack's

lawyer described the company as a respectable homegrown operation with $1 million paid-up capital.

Fewer than 10 companies here provided this kind of highly-specialised engineering services, he said.

The company went ahead to do sheet-piling work at a proposed sewer manhole without first locating SingTel's

plants or cables around the manhole. IDA's counsel, Mr Wendell Wong, told District Judge Tan Puay Boon that

the Environment Ministry had engaged the firm to lay sewer lines and build manholes in Rochor Road for the

Marina Centre sewerage project.

That day, its subcontractor, while doing sheet-piling work, struck SingTel's cables 2.2 m below the surface.

The subcontractor, Jiabin Services, a licensed cable detector, had assumed that the cables ran in straight lines

between SingTel's manholes and the proposed sewer manholes in the plans.

Pipe-Jack had a copy of SingTel's service plans on the layout of the cables but did not ask SingTel to help it

locate its cables.

Lawyer Sant Singh said the damage happened in a very narrow corridor, which was difficult to work in because

of the many cables, drains, pipes and other underground installations. He said his client relied on its

subcontractor's sketch plan, which did not show that the SingTel cable curved left abruptly.

SECTION: Home, Pg. H5

LENGTH: 403 words

LOAD-DATE: October 9, 2001

LANGUAGE: ENGLISH

Copyright 2001 Singapore Press Holdings Limited

Appendix E

INTERVIEW WITH CHRIS- SIA & YEO HEAVY EQUIPME NT

Qn: What types of excavators are used for the various types of excavations?

Ans: The size of excavators is actually correlated to the weight of the machine and thus to its

power. Excavators below 10tonnes are all considered mini excavators.

In Singapore, the roads are small, so usually the most widely used excavators are them

smaller ones. Excavators weighing less than 6 tonnes are called small excavators. A small

excavator should just take up only 1 lane of the road. Newer versions of excavators since

1998 have been created, but suppliers only started using in approximately 2006. The

common types used are 4 tonnes small excavators that can allow a dig depth of 3.5m.

Qn: What is the price range of typical excavators?

Ans: A new excavator would cost about 50-60k, and older ones would cost approximately

30k, depending on the year of the manufacture.

To save on the transportation costs; if buyers wish to off load the excavators on their own,

they would usually choose to purchase a 3-tonne excavator where they would need to

register then excavator for a Y plate and not a G plate.

Qn: What are the factors considered when a client purchases an excavator?

Ans: Clients usually like to buy older models of the excavators as they are inevitably cheaper

and already have several built-in features, so there will be no need for additional cost for

non-standard parts.

In addition, older models means there will be greater ease of replacement of maintenance

cost. Wear and tear parts that are usually spoilt are cheap to replace.

Pumps have higher chance of spoiling compared to engines. If any of the 2 parts are down,

then the whole excavator is rendered useless.

In typical cases, a new excavator can last for 3 years, depending on the amount of usage. An

excavator exposed to intensive work and human errors would last at most 6 months.

Qn: How does the current excavator work?

Ans: It operates on a hydraulic pump and runs on diesel categorised under Tier 2/3/4.

Excavators from 2007 onwards use Tier 2 diesel. One full tank of diesel contains

approximately 64litres and can run for 1 day (approximately 8 hours).

It is very fast and easy to use and training is not really required because it is easy to operate.

It merely takes practice to perfect trenching works. However, due to regulations, training

courses are still implemented. A 2-3 day full course costs about $300 per worker.

Qn: How fast can the current excavator operate?

Ans: The speed of excavation depends on the operator’s speed, accuracy and more

importantly, his experience and ease in operating the excavator. Also, the current trenching

process is labour intensive so it might actually take quite some time to completion.

Qn: What are the builders’ general considerations when they purchase excavators?

Ans: The most important factors are cost and time. Builders, if able to see cost efficiency

and shorter time spent to complete works, would be interested in that particular product.

Certain brands like Caterpillar and Kobelco are preferred due to their strong marketing

strategy, providing a full range of construction equipments. In addition, they have higher

market share, enjoy more popularity and the spare parts are easy to get. In fact, every

brand’s excavators are actually similar except they focus their selling point on one of the

better aspects of their excavator. For example, Yanmar would promote its engine strength.

Appendix F

Interview with Mr Lim from Tiong Seng Contractors Pte Ltd

1. What is the current situation relate to underground utilities in Singapore?

There are many underground utilities in Singapore. We have to ‘hide’ them due to

small land area and aesthetics purpose. Also, there is lower chance of power or

telecom being cut off during storms. The depth of cables is usually less than 1.8m.

The older ones may not be concreted in slabs or protected around. Hence, they are

vulnerable during trenching. Trial pits are needed to test for gas or water pipes from

PUB. They are usually 2m in depth; sewage lines usually 7m underground. The cost is

very high if there are any damages.

2. Currently what do we use to detect the underground cables?

We have licensed cable detectors to detect the cables. It applies for various agencies

for underground plans i.e. Telecom, PUB, Telemax, PowerGrid, PowerGas etc.

3. What is the current excavation process on road?

Apply for permit from the authorities to excavate first. Then cut the roads up, use

mini excavator to remove asphalt till a certain depth, then manual digging to prevent

the damage of any cables or pipes.

4. What do the current excavators run on? How is the speed and is it hard to

maintain?

Current excavators run on diesel. It needs approximately 5-6 workers (1 to operate,

1 to provide directions, the rest to either set up road barrier, divert traffic etc.). The

current excavators are not very difficult to maintain, most of these works are carried

out at night to minimize disruption to traffic. Therefore noise reduction is a big issue.

The speed will be approximately 10 cubic meters in 20min. Current excavator

operators all need to be trained and certified by BCA

5. How to prevent that the cables and pipes are not damaged by either mechanical or

manual machines?

We use fail-proof method. Provision of control mechanism is used to prevent

damage of utilities when near them. Some workers need to go down to check so that

to ensure actual depth of the utilities and there is no damage. In addition, in the

event where location of utilities are not confirmed, and/or for precaution purposes,

trail holes are bored to the ground for testing and to see if there is a need for

diversion trial trenches may be excavated instead.

6. How much is the rental cost of the current excavators?

The rental cost of current excavators is $3k-5k per month.

7. What is the general soil condition in Singapore?

Generally in Singapore, the first 1-2m is backfill materials and so they are softer. Soil

properties may differ on site with as close as 10m radius' proximity.

8. What are the areas to look into when you are choosing an excavator?

Ease of operation, maintenance (availability of parts and engine replacement) The

benefits for specialised materials must first be cost effective to potential buyers to

even consider.