leakage detection of buried water carrying services affecting slope speakers: miss carman lam ir dr....

Leakage Detection of Buried Water Carrying Services Affecting Slope

Speakers: Miss Carman LamIr Dr. King Wong

Date: 26 Feb, 2011

Ref: HKIUS-GEN-018 BWCS 1

Hong Kong is also full of

• Slopes ( 斜坡 )And • Many of Us Live

next to the slopes


Why detect leakage of BWCS?• Water loss( 流失 ) from leakage( 滲漏 ) takes

up nearly a quarter of total water consumption( 用量 ) in HK. (around 230,000,000m3 of water lost)

• Leak water erode ( 侵蝕 ) the soil and create void( 空隙 ) underground. This destroys( 破壞 ) the soil structure and the soundness( 完整性 ) of the ground.


Why detect leakage of BWCS?• Leakage of BWCS affecting slope can cause

landslide without notable( 明顯 ) signs( 徵兆 ).• Kwun Lung Lau Landslide ( 觀龍樓事件 ) in

1994 caused 5 fatalities and 3 injuries.

• There are about 5,7000sizeable man-made slopes in Hong Kong


(Source: SCMP 23 July 1994)

“Three die in landslip due to drain problem” July 1994

1994 年 7月觀龍樓事件


Kwun Lung Lau Event On 23.7.94Kwun Lung Lau Event On 23.7.94Professor Morgenstern Lead Investigation Professor Morgenstern Lead Investigation

Morgenstern’s Report Concluded That:Morgenstern’s Report Concluded That:調查結論調查結論

• Leakage of Nearby Buried Drains Was a Key Factor Contributing To The Tragedy鄰近被埋水渠洩漏是引致這水慘劇的主要原因

• A Program of Direct Monitoring and Repair of Buried Services Where Leakage Might Impact On Slope Stability Should Be Developed.

• 應建立機制直接監察帶水道因洩漏引致影響斜坡的穩定性


Why detect leakage of BWCS?• Causes( 原因 ) of Kwun Lung Lau Landslide

Intense Rainfall


Why detect leakage of BWCS?• After the incident, Professor Morgenstern

recommended in the report thatGovernment should develop a programme for

direct monitoring and repair of buried services affecting slope.

Buried services at hazardous locations should become mandatory in a 5-year interval.


Code of Practice• Code of Practice on

Inspection and Maintenance of Water Carrying Services Affecting Slopes

• published by the Works Branch in 1996 in correspondence of the Kwun Lung Lau Incident


Code of Practice• Code of Practice on

Monitoring and Maintenance of Water Carrying Service Affecting Slopes

• Second Edition published by the ETWB in Nov. 2006


Objective & Scope of COP

• Give guidance on the inspection and maintenance of buried water-carrying service affecting slopes

• To present procedures and practice to prevent leakage of buried services affecting slopes

*Code of Practice on Inspection & Maintenance of water Carrying ServicesAffecting Slopes


Key issues in the CoP• Planning for monitoring and maintenance• Methods of inspection and maintenance• Specification for CCTV Survey, Manhole

Internal Condition Survey and Leak Detection for Water Mains

• Record Keeping


Inspection & Investigation of Buried Water-Carrying Services

• Leakage investigation– Fresh Water Supply System– Salt Water Supply System

• Closed Circuit Television Survey for Sewers & Drains

• Man-entry Inspection for Sewers & Drains

*Code of Practice on Inspection & Maintenance of water Carrying ServicesAffecting Slopes


Purposes of Leakage Detection

• To identify potential leaks from water mains or drains( 給、排水查漏 )

• To prevent landslip due to leakage( 避免因漏水而引起的斜坡倒塌 ) • To save lives( 拯救生命 )• To save costs for damage repairs( 減少維修支出 ) • To improve living standards( 提高生活水平 )


History of Leakage Detection Industry in Hong Kong ( 香港查漏行業 - 歷史 )

• Before 80s, Mainly carried out by WSD( 水務署 ).• Early 80s, First CCTV Inspection contract awarded.( 首個合約 ) by

HKHA ( 房屋署 )• 80-90, Term contracts for CCTV Inspection from DSD( 渠務署 )

and HKHA.• 1994-Kwun Lung Lau Event.( 觀龍樓事件 ) • 1995-First Contract for Leakage Detection on buried water-

carrying services Affecting Slopes by HKHA.( 房屋署發出首個主要斜坡查漏合約 ) • 1996-Publication of the Code of Practice for Leakage Detection

Affecting Slopes by Works Branch.( 香港政府工務局頒發首個斜坡查漏工作實務守則 )


History of Leakage Detection Industry in Hong Kong(con’t) ( 香港查漏行業 - 歷史 )

• 1997-2000, first round of contracts were awarded from WSD, DSD & Highways Department and HKHA as Term contracts for Leakage detection affecting slopes

• 2002, second round of contracts were awarded from WSD, DSD & Highways Department and ASD as term contracts or work orders.

• 2002, Leakage detection contract from HKHA were awarded under slope maintenance contractors.


History of Leakage Detection Industry in Hong Kong(con’t)

• July, 2002, the formation of Hong Kong Institute of Utility Surveyors, HKIUS.

( 香港地下管線測量師學會成立 )• ·31 March, 2003, the final of the Constitution( 憲章 ) of

HKIUS.• ·1 April, 2003, the formation of the first executive

committee of HKIUS.( 第一屆行政委員會成立 )1 April, 2005, the formation of the second executive

committee of HKIUS.


Scope of inspectionAffecting slope means…• A strip of land adjacent ( 鄰接 ) to the crest ( 頂

點 ) of the slope with a width equal to the maximum vertical height of the slope

However, the scope should extent depends on…• Hydrogeological( 水文地質 ) conditions of the

ground• Nature( 性質 ) of slope• Type & age of pipe• Any structures( 建築物 ) on the slope


Methods for detection• Visual inspection ( 觀察 )• For drains - CCTV Survey & ME Survey - Manhole Internal Condition Survey• For Water Mains - Leak Noise Correlation - Acoustic leak detection (MLD/ELD) - Noise Loggers - Hydrogen Gas DetectionRef: HKIUS-GEN-018 BWCS 19

Planning for inspectionIdentify the alignment of the pipes/drains to be surveyed•Check past records•Utility Survey/ Mapping•Ground Penetrating Radar Survey (GPRS)


Check past records• For private assets/properties ( 私人資產 ) - The asset owners ( 資產擁有者 )should

provide the information• For public utilities ( 公共設施 ) - Information can be found from various

government departments


Check past records

Slopes Geotechnical Engineering Office ( 土力工程處 )of Civil Engineering and Development Bureau (CEDD) ( 土木工程署 ) (http://hkss.cedd.gov.hk) contains updated information on 57,000 registered man-made slopes

Drains Drainage Services Department

Water Mains Water Supplies Department

Public Utilities


http://hkss.cedd.gov.hk/

Work Procedures• Calibration and preparation• Checking past record.• 翻查紀錄。• For private services, collect all information available regarding

the assets from the client (asset owner).• 若是私用設施，向客戶 / 資產擁有者索取所有相關資料。• For public services, information can be obtained from various

relevant Government Departments.• 若是公用設施，可從相關政府部門獲取相關資料。


Work Procedures• Reconnaissance survey• 初步勘查• The full extent of assets (manholes, pipes, catchpits and other

ancillaries) located within the survey extents.• 搜尋檢測範圍的所有相關結構（沙井、管道、截留井及其

他有關結構）。• Any other manholes and additional features not shown on the

base mapping or layout plans, and/or revisions to match existing conditions on site.

• 有否其他圖則遺漏了的沙井及其他結構，及有甚麼需要按現況作修改


Work Procedures• Safety precautions include Permit-to-work

(PTW), Temporary Traffic Arrangement (TTA), Personal Protective Equipment (PPE), etc.

• 執行安全措施，包括工作許可証 (PTW) 、臨時交通安排、個人保護措施等。


Work Procedures• Operation• Locating buried water-carrying services• 探測地下帶水管道位置。• Observe surface installations.• 觀察與管綫相關的地面設施。• Carry out utility survey. • Electromagnetic method (PCL) for metallic pipes .• GPR for non-metallic pipes • 進行管綫測量。• 以電磁法 ( 管綫探測儀 ) 探測金屬電纜。• 以探地雷達探測非金屬電纜。


Work Procedures• Visual inspection to find out clues of leakage

like water spots and seepage.• 觀察地面有否水漬或滲水。


Work Procedures• Inspection of drains• 檢測水渠• High pressure water jetting if found suitable. • 如有需要，先進行高壓清洗。• CCTV survey / Man-entry survey if necessary.• 閉路電視檢測 / 人員進入管內檢測 ( 如有需要 ) 。• Manhole internal condition survey.• 沙井內部狀況評估。


Work Procedures• Inspection for water mains.• 水管檢測。• Leak Noise Correlation Survey. • 噪聲相關檢測。• Mechanical Leak Detection/ Electronic Leak

Detection.• 使用機械測漏儀 / 電子測漏儀。


Data processing• Due to the potential danger of landslip caused

by water leakage, the urgency of rehabiliatation work is higher.

• In the grading system of CCTV survey, defects of conduit on slopes should deserve a higher grade, that is a more serious condition.


Structural Performance Grade (SPG) in CCTV Survey

• Supplementary information about the surrounding is considered

• V is a variable adjusting the ICG by considering the addition information affecting the grade


Year of Installation:

Less than 30 years

Between 30 and 50 years

More than 50 years

On slope +1 +2 +2

Not on slope 0 +1 +2

SPG = ICG + V

Work Procedures• Reporting

• Reconnaissance ( 事前勘查 ) Survey Report1.Location plan showing survey extent and

assets in the region in A3 size.2.Location photographs showing the slopes to

be surveyed.


Reports of BWCS• Slope report


Reports of BWCS

*The report shall have the SLOPE REFERECE NUMBER clearly displayed in the COVER and EACH PAGE of the reportRef: HKIUS-GEN-018 BWCS 34

Record keeping• Results of inspection shall be documented and

well-kept for late retrieval and reference• All records shall be kept by the owner• Duplicate copies shall be made and kept by - Owner’s corporations - Maintenance agents - Property managers


Training and Accreditation of Personnel ( 操作員要求 )

Type of Personnel

Role Minimum Training Requirement

Minimum Years of Experience

Project Leader

Contractual arrangement, check and

certify reports

Training courses for relevant survey/detection

methods and data management

10 years in contract administration,

preferably in relevant disciplines

Team Leader

Works arrangement, check data quality and

consistency

Training courses for relevant survey/detection

methods and data management

5 years in works of relevant disciplines

Crew Leader

Supervision of field works and site safety

Training course and valid training certificate for

relevant discipline


Operator On site inspection and operation of

equipment

Training course and valid training certificate for

relevant discipline



Guide to Leakage Detection of Buried Water-carrying Services

• Planning and preparation• Surveying methods -Utility Survey - CCTV Survey - WLD Survey• Procedures• Personnel Requirement• Reporting• Sample photos and forms


BWCS pamphlet• A brief introduction to BWCS survey


Q&A


leakage detection of buried water carrying services affecting slope speakers: miss carman lam ir dr....

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