AWWA INF54004

The fifteen-mile long Hultman Aqueduct is the final stretch of the main water supply pipelineconnecting the Quabbin Reservoir in central Massachusetts, to the metropolitan Bostondistribution system. Installed in 1940, the Aqueduct has operated continuously for sixty years,carrying 250 million gal/day at pressures ranging from about 40 to 100 psi, without significantproblems or extended shutdown. However, because of concern about lack of redundancy in thesystem and the age of the pipe, the Massachusetts Water Resources Authority (MWRA)commissioned a study to evaluate the risk of failure and to design repairs to mitigate risks toensure continuous operation of the Aqueduct until the new Metro-West Water Supply Tunnel iscompleted in about 2005. The study employed innovative leak detection methods, non-destructive testing, deep test pit excavation, and sampling and laboratory analysis of wallspecimens. Soil-structure modeling and finite element analysis were conducted to evaluate thestructural safety of the pipe and to identify areas of potential overstress due to post-constructionchanges in surface cover and load. The investigation revealed that the overall condition of thepipe is excellent. However, it was found that a few areas of excessive cover and several activeleaks posed risk of structural damage, leakage, and progressive loss of pipe support. Also,corrosion damage of buried and exposed steel connections was identified as a significant threatto long-term service. The risk mitigation program included repair of corroded parts andexcavation, examination, risk assessment, and repair of active joint leaks. This papersummarizes the findings of the initial risk analysis of the Aqueduct and discusses the riskmitigation approach and the design and construction methods employed to reduce cover loadsand safely repair leaks without interrupting service. Innovations developed on this project aredirectly applicable to the assessment, analysis, and rehabilitation of other large diameter watersupply pipelines. Includes 3 references, figures.

Product Details

Edition:

Vol. - No.

Published:

06/01/2001

Number of Pages:

18

File Size:

1 file , 1.5 MB