Case

Restructuring of water supply facilities to address aging infrastructureand declining water demand

Water utility

Saitama City Waterworks Bureau

General information of the utility (as of 2021)
Operation

Public (retail watertypesupply)

Population
servedService area (km2)

217.43

1,333,897

Distribution (m3/d)

373,320

99.9

Pipe length (km)

3,669

4.7

Number of staff

370

Servicecoverage(%)
NRW (%)
Number ofwater

Surface water (13), Groundwater (16), Others

sourcesWater
rates (JPY)979+385(in case of 10m3 of water per month forresidential customers with 13mm diameter)At the end of FY 2020, Saitama City formulated the "Saitama City
Water Supply Facility Restructuring Plan", which outlines basic policies
and initiatives for the restructuring of waterworks facilities over thenext 30 years, including the consolidation and downsizing of facilities in
anticipation of a future decline in water demand, in order to pass on
facilities in good condition to the next generation.
Under the "Saitama City Comprehensive Development Plan," which isSummary

a high-level plan, the "Saitama City Waterworks Long-Term Concept"and "Saitama City Waterworks Mid-Term Management Plan" wereestablished. The restructuring plan is based on the long-term vision,basic principles, and basic measures of the long-term vision, andpresents basic policies for individual projects necessary to realize thevision and basic principles. In addition, major projects and investment
plans that should be focused on are reflected in the medium-term
management plan, and are to be addressed in conjunction with theplan, including progress management.
1. Current Status
The City has 7 water treatment plants that use only groundwater as

Current

their water source (one of which ceased operation on November 30,

Status &2021), and 13 water distribution plants that use groundwater andChallenges

water purchased from Saitama prefectural government as their water
source, with a total facility capacity of 538,000 m3/day.
In recent years, the water treatment/distribution plants have been

operating at a maximum operating rate of about 75% (the ratio of themaximum daily water supply to the facility capacity) and a facility
utilization rate of about 68% (the average daily water supply to thefacility capacity), which is sufficient to meet the water demand. In
addition to the facility capacity, the water treatment and distribution
plants have reserve capacity to ensure a stable water supply even in
the event of an emergency, such as the shutdown of facilities due to adisaster, or the shutdown of water distribution trunk lines.
2. Issues(1) Optimization of Facility Capacity
Based on recent trends, future water demand inis expected toremain at the same level as at present until around FY2030, until which
the population is expected to continue to increase, but in the future,
the population is expected to decline gradually.
Therefore, if the current facility capacity and reserve capacity aremaintained, the costs for operation, renewal, and maintenance of thefacilities will eventually be excessive, which will have a significant
impact on financial management. This anticipation makes it necessary
to optimize facility capacity and reserve capacity in line with futurewater demand, taking into account emergency capabilities (Figure 1).
Reservecapacity

Facility capacity
Now

Planned average daily
distribution

Extra capacity

Planned max. daily distribution volume
Emergency distribution volume

If current capacity is maintained…

2050
Extra capacity

Decreased due todemand reduction

Excessive

Figure 1 Relationship between facility capacity
and water supply volume(2) Aging of water treatment and distribution plants
Many water treatment plants were constructed in the 1950s, andmany water distribution plants were constructed in the 1960s and1970s. Civil engineering facilities such as water distribution reservoirs
and buildings such as administrative buildings are aging, in particular.
Currently, appropriate maintenance and management are being carriedout to prevent accidents and extend the service life of these facilities,
2 / 6but they will all be due for renewal in the near future (Figure 2).
Capacity of water
treatment plant(m3/d)

Capacity of water
distribution plant(m3/d)

Facility capacity

Approximately 70% of all water
distribution plants were constructedfrom 1960s to 1970s.
⇒ They will all be due for renewal
in future.

Year of construction

Figure 2 Facility capacity of water treatment and distribution
plants by year of construction
Aging water supply facilities lead to increased risk of accidents, suchas shutdown of facilities, and thus systematic renewal is becoming
necessary to meet the increasing demand for renewal.
Measures &Solutions

1. Consolidation of water treatment/distribution plants and review offacility capacity
To optimize facilities, Saitama City examined the possible consolidationand elimination of water treatment and distribution plants. The City has
formed a block system that divides the water supply area into four
blocks, and a facility block system that further divides each block. Since
the facility block has been developed as a distribution pipe network
around a single water distribution plant, the water distribution plantsthat form the facility block will continue to exist in the future.
Next, based on past drought experience and other factors, theamount of groundwater source required under normal and emergency
conditions was determined, and it was decided to abolish the water
treatment and distribution plants on the condition that the required
amount of groundwater source is secured for each supervisory block.
The selection of water treatment/distribution plants to be discontinued
was based on comparison and consideration of the current operational
status, water distribution pressure under normal conditions, and theimpact of backup operations during emergencies, and it was decided to
discontinue one water treatment/distribution plant for each supervisory
block (Figure 3).

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Iwatsuki
supervisory block

Hokubusupervisory blockTobu
supervisory block
Distribution plantSeibu
supervisory block

Treatment plant

Supervisory block
Facility block

Figure 3 Water treatment/distribution plants to be demolishedIn addition, the facility capacity of the water treatment anddistribution plants will be downsized in stages by upgrading thedistribution pumps to appropriate capacities while securing the reserve
capacity needed in case of emergencies such as distribution plant
shutdowns or water main breaks (Table 1).
Table 1 Policy for securing facility capacity

2. Systematic renewal in consideration of operational workloadbalancing
Although the statutory service life of water supply facilities is defined
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by the Enforcement Regulations of the Local Public Enterprise Act,
actual facilities can be used for a longer period than the statutory
service life by ensuring safety through appropriate maintenance andmanagement. Therefore, in anticipation of future increases in renewal
demand and associated maintenance costs, the City has decided tolevel out renewal project by setting its own standard renewal period
and lengthening the renewal implementation period.
The standard years for renewal of facilities and equipment wereestablished based on a survey of actual renewal results in the city andexamples in other entities (Table 2). The concept of the renewal period
based on the standard renewal period is that, in principle, facilities andequipment should be used for a longer period than their legal useful life
through appropriate maintenance and management, and their renewal
should be based on the standard renewal period (Figure 4).

Table 2 Standard renewal year of facilities and equipment
Category

Statutory useful life (years)

Standard renewal year

Distribution reservoir(PC, SUS)

60

100

Distribution reservoir (RC)60

6050 (60)

Seismic-resistant: 80
Non seismic-resistant: 60

Intake pump

1520

Distribution pump1530

Filtering machine

2060

Electricity receiver anddistributor

2030

Monitoring and control
equipment

Conventional type: 15LCD: 10

20

Self power generator

1530

Control centers, etc.

[Example] In case of renewing a distribution reservoir (PC) built in 2000

Year of construction
2000

Statutory useful life (60 years)

Standard renewal year (100 years)
2100

2060

Distribution
reservoir(PC)Renewal period

Time for renewal

Figure 4 Concept of renewal period
As described above, Saitama City have prepared a maintenanceschedule plan based on the facility maintenance policy indicated in theFuture Plans"Saitama City Water Supply Facility Restructuring Plan". In
implementing the projects in this plan, the City will strive forappropriate progress management through the PDCA cycle, along with
5 / 6the evaluation of target indicators in the mid-term management plan.
Since water demand forecasts are subject to significant fluctuations
depending on future social conditions, it is necessary to make estimates
as appropriate and revise them accordingly after considering the impactof the results on the currently planned discontinuation of water
treatment and distribution plants.
Saitama City,References

Saitama City Waterworks Long-term Concept 2021-2030
Saitama City Water Supply Facility Reconstruction Plan
https://www.city.saitama.jp/001/006/002/048/001/index.html

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