Main Category

Asset Management and Facility Renewal

Sub Category

Facility Development

Japan's first pressurized water supply system started its operation in Yokohama City in 1887,
with its major objective being to ensure public health by preventing waterborne diseases andto protect wooden houses from fires. Later, as the population increased and urbanization
progressed, the demand for water rapidly rose, facilitating the expansion of water supply
facilities nationwide. New water facilities were constructed and existing facilities reinforced, inparticular during the rapid economic growth period from 1954 to 1970 and into the latter halfof the 1980s.
Japan is now in the middle of a facility renewal period, however, especially for the renewalof distribution mains buried from the 1950s to 1980s. A look at the population change over thelast 140 years shows the country’s population has tripled from approximately 40 million in 1887
- when the modern water supply system first began in Yokohama - to 126.8 million at the endof the 20th century. During the facility expansion period, the facility renewal mostly consistedof enlarging existing mains diameter and increasing existing treatment plants’ capacity toaddress rising water demand. Later, water utilities also began seismic reinforcement of facilities
and development of emergency water supply facilities and/or equipment because of thecountry's high propensity to earthquakes. Japan's population had still been increasing at thebeginning of the 21st century but it began to decline in 2008, and the declining trend is expected
to continue into the future, which means the facility renewal from now on will have to include
the downsizing of facilities, such as reduction in mains diameter and treatment capacity, as wellas consolidation of existing water treatment and distribution plants, while still promoting
seismic reinforcement.
In terms of operational cost, municipalities (water utilities) have been supplying sufficientamount of clean affordable water in a financially self-reliant manner, meaning the water supply
has to be operated from the revenues of water rates alone, as stipulated by the Local PublicEnterprise Act. For this reason, utilities have made constant efforts to secure financial resources
and minimize facilities’ initial/running costs both during the facility expansion period and thecurrent renewal period. In such an effort, for instance, aiming at cost reduction as well as
environmental protection, utilities have implemented PFI schemes and installed solar and/or
small hydroelectric power generators at water treatment plants. Also, some utilities in urban
areas have managed to renew their facilities via specialized construction methods, such as
relocating facilities to a new location as they are without partial deconstruction, or expanding
a plant’s treatment capacity by relocating a chain of treatment processes and their equipmenton multiple floors of a building on the plant’s premises. These measures were taken because oflimited available sites around some water treatment plants situated in the middle of residential
districts.
As for the renewal of distribution mains (whose statutory depreciation period is 40 years),
utilities estimate their degradation using specialized software programs fed by various data
including pipe’s installation year, material, and soil conditions. In terms of pipe material, ductile
iron pipes and high-density polyethylene pipes with high seismic resistance have come to bewidely used in Japan, and their manufacturers advocate a long service life of 100 years for bothtypes of pipes. This means that in future it might be possible to extend those pipes’ renewal
cycle, depending on their physical inspection and software simulation results. In terms of mains
construction methods, there are various kinds available depending on the existing mains’
conditions and their surrounding environment as well as the long-term capital improvement
programs adopted by utilities. These construction methods include the open-cut method,
propulsion method, joint trench construction method, the shield method (primarily used fortrunk mains construction), and the pipe-in-pipe method for downsizing and renewal.

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