issue 3, december 2005

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08 ...SAFETY NEWS

CONTROL OF MOSQUITO BREEDING IN LTA PROJECT SITES

Introduction

In May this year, Singapore saw a dramatic increase in the numberof dengue fever cases. It was to be the worst dengue epidemicever experienced in Singapore’s history that eventually claimednineteen lives and resulted in over twelve thousand cases by thetime it tapered off in late October.* The situation would have beenmuch worse if not for the government’s prompt actions to tacklethe problem.

There were public concerns expressed in newspaper forums thatconstruction sites might be serving as breeding grounds formosquitoes. LTA invited the representatives from the mass mediaand the National Environment Agency (NEA) to one of the sitesto see for themselves the efforts by LTA and its contractors inensuring that there were little opportunities for mosquitoesbreeding at their project sites.

The following are the four main methods of control adopted by LTA:

A. Management’s Commitment

Recognising the serious health problems associated withdengue fever, management took the initiatives by supportingthe nation-wide effort to tackle the problem.Committing manpower to step up vigilance and inspection onall LTA project sites.Committing time for control measures and improvedhousekeeping.

LTA has also developed and implemented a “zoning method” tobetter streamline and concentrate its efforts to effectively identifyand destroy potential breeding grounds in LTA project sites.

Seven-zone method

This method is used internally to supplement the external licensedpest control companies who should be combing through the entiresite on their visit. This method divides the site into a maximumof seven zones and concentrating efforts in just one zone eachday. As the life cycle of mosquito larva takes seven days to reachadulthood, breaking the cycle will prevent the emergence of adultmosquitoes. This method of concentrating focus on just one areaeach day is much more effective compared to combing throughthe whole site. This method of control has proven to be quiteeffective and it reduces the need for thermal fogging.

Use of larvicide in a ground instrumentation point

C. Physical and Chemical Control

Identifying sources of stagnating water and eliminating them.

Application of anti-mosquito oil and granular larvicides.

Filling in of ground depressions.

Drilling of holes in walers.

Capping or sealing water-filled barricades.

Increased frequency of thermal fogging.#

Regular trimming of grass to deprive mosquitoes of resting

areas.

Topping up tree holes with sand.

Increased house-keeping efforts to prevent mosquitoes from

breeding on site.

B. Education

The following forms part of the education programme:

Prominent display of posters on worksites.

Environmental engineers from Safety Division visit various

project offices and divisions to educate and create awareness

amongst project staff and contractors on the prevention of

mosquito breeding.

Daily tool box meetings to educate workers on prevention and

personal protection.

Use of posters to spread the safety message

Roads Facilities

LTA also demonstrated its concern for the public by identifyingpossible breeding grounds in other areas of its operation. The RoadsFacilities Division is currently in the process of sealing off guttersin seven hundred and twenty-five bus shelters. This will be carriedout in two phases: the first phase is scheduled to complete by endof this year while the second phase should be completed by March2006. Future bus shelters will no longer have gutters as they canact as potential breeding grounds for mosquitoes when fallenleaves choke up the gutters.

SAFETY NEWS... 09

D. Monitoring

Proper documentation to identify vulnerable areas on site.

Stepped up inspections by project team as well as environmental

engineers from Safety Division.

Use of ovitraps to monitor adult mosquito population.

Monitoring of project sites found by NEA breeding mosquitoes.

Ovitrap

Media Visit to LTA Construction Site

On 20th October 2005, LTA did a presentation to the press, TVmedia and the NEA on how LTA manage and control the mosquitobreeding issue on its construction sites and public facilities suchas bus shelters and covered linkways.

They visited one of project sites of the Kallang-Paya LebarExpressway where they were able to witness some of the controlmeasures such as application of anti-mosquito oil to walers andfilling in of ground depressions. They could also see that the siteoffices and containers have pitched roofs to drain off rainwateras well as the notice boards carrying posters warning on thedangers of dengue fever and the preventive measures.

Conclusion

As Singapore is in a region where outbreaks of dengue fever arehighly possible, LTA will continue to support other governmentagencies’ efforts in combating this epidemic. LTA will do its partby preventing the breeding of mosquitoes on its project sites. Itwill explore for more sustainable and environmental-friendly waysof controlling mosquito breeding including the use of bacillusthuringiensis israelensis (Bti) products.

by Chew Boon Bwan, MattEnvironmental Engineer

Safety Division

* Source: The New Paper – October 27, 2005# Frequency of fogging has since been reduced

Water-filled barricade with missing filler cap

Water-filled barricade with filler cap

Bus shelter without gutters

Media and NEA visit to C423 project site

In the meantime, LTA’s contractors are carrying out weekly cleaningof gutters on bus shelters and covered linkways as well as applicationof larvicides to prevent breeding.


Layout of Safety Barrier

Flare Rate

Deflection Zone

Edge-Line OffsetTerminal Anchorage

Terminal Anchorage

Traffic Direction

with proper leading

end treatment

The non-rigid safety barrier will deflect to

contain and redirect the errant vehicle

The impacting vehicle is directed

to glide along the surface of the

rigid safety barrier for it to be

contained and redirected back

onto the travelled carriageway.


AFR

Month

Jan

4.03.5

2.72.5 2.4

2.22.3

2.1 2.1 2.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0

Feb Mar Apr

LTA Achievement 3.0 - 2004 Industry Figure

May Jun Jul Aug Sep Oct Nov Dec

Cumulative Accident Frequency Rate (AFR)

SR

Month

30002606

1711

1263

1016

720 625 552

2500

2000

1500

1000

500

0

LTA Achievement 536 - 2004 Industry Figure

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cumulative Severity Rate (SR)

6 6

844

FSI

Month

3.0

2.5

2.0

1.5

1.0

0.5

0.0

LTA Achievement 1.3 - 2004 Industry Figure

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cumulative Frequency - Severity Index (FSI)

2 .7

2 .1

1 .71 .5

1 .21 .1 1 .1

1 .4

0 .5

issue 3, december 2005

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