Report cards for aging and maintenance assessment of water-supply infrastructure

During past periods of rapid economic growth, infrastructure development in Japan was intense. This infrastructure now requires both renovation and replacement. Obviously, infrastructure quality greatly affects daily life; when infrastructure ages, the risk of accidents increases, which has an enormous impact on daily life and many long-term economic activities. Appropriate infrastructure management is critical as the population falls, budgets are reduced, and the number of technical staff dwindles. Thus, the Japan Society of Civil Engineers evaluated infrastructure soundness and published the results in 2018. Similar efforts have been made in the United States (National Council on Public Works Improvement (US) 1988; American Society of Civil Engineers 2017), the United Kingdom (Institute of Civil Engineers 2014), Australia (Engineers Australia 2010), and South Africa (South African Institution of Civil Engineering 2017); these evaluations, published as infrastructure report cards, inform policy on infrastructure development. In the United States, evaluations have been performed periodically since 1988 (National Council on Public Works Improvement (US) 1988), covering 16 categories (Aviation, Bridges, Dams, Drinking water, Energy, Hazardous waste, Inland waterways, Levees, Ports, Public parks, Rail, Roads, Schools, Solid waste, Transit systems, and Wastewater). The evaluation items include Capacity, Condition, Funding, Future needs, Operation and maintenance, Public safety, Resilience, and Innovation.

Japanese report cards have focused on infrastructure soundness, based on statistics and published reports. Using these data, the Japan Society of Civil Engineers (2018) devised indices evaluating deterioration and maintenance management systems. The reports were published by sector (such as roads, rivers, and wastewater); a draft report on the drinking-water sector had been planned for 2019. In the financial year (FY) 2020, a general report will be published, evaluating various types of infrastructure. The current status of the drinking-water sector has attracted much attention recently. A new water-supply vision was formulated in 2013 by the Ministry of Health, Labour and Welfare (2013), and water-supply laws were amended in 2018 (Umeda 2018). Certain tools for evaluating the drinking-water sector are already available; these include performance indicators (guidelines) for water utilities (Japan Water Works Association 2016), the Replacement Criteria for Waterworks Facilities (Japan Water Works Association 2005), a business-focused analysis of municipal utilities conducted by the Ministry of Internal Affairs and Communications (2017), and a cost-effectiveness analysis performed by the Ministry of Health, Labour and Welfare (2011). Although several evaluations using these tools have appeared (Koizumi et al. 2006; Ishii et al. 2008; Inakazu et al. 2012, 2017; Nishimura et al. 2017), no report has comprehensively examined the deterioration of, and maintenance management systems for, drinking-water pipelines in the context of infrastructure aging.

Therefore, we attempted to devise appropriate indices when preparing the 2019 draft Infrastructure Report Card on drinking water. Multiple indices were formulated that can be calculated using water-supply statistics; these were then used to evaluate water utilities.

Indices of deterioration and maintenance management systems were selected from candidate lists. Generally, pipe deterioration results in leakage, poorer water quality, and periods of no supply. An index of the proportion of water wasted was devised to cover these parameters; the data were readily available, reliable, and easy to interpret. The fundamental cause of pipe deterioration is aging. Therefore, pipeline age was used as another index of deterioration.

For maintenance management systems, we considered various resources including people, goods and services, and money. Of these, the number of technical staff and the leakage repair rate were included as indices due to the data availability and reliability, and ease of interpretation.

We have employed this index due to data availability. Actual useful life will be different for pipe material and diameter; however, the Japanese accounting system employs the same statutory useful life for all pipe materials and diameters. Furthermore, statistical data are available only for the total length of aged pipes, and breakdown data for materials and diameters are not available.

We scored each utility based on Table 2. The histograms in Figure 1 show the results for each population category. In FY 2015, the average value for all utilities was 10.85; values tended to be higher for large utilities and lower for small utilities, as in Table 3. The average value for utilities supplying populations <10,000 was 9.09% versus 17.41% for utilities supplying populations ≥600,000. For utilities supplying populations <30,000, the dominant class was 0–1.5%; for utilities supplying populations ≥30,000, it was 10.0–30.0%.

In addition, a relationship was evident between the population supplied and the commencement of water supply. Many large utilities are old, while many small utilities are relatively new. Pipeline age reflects the date of water-supply commencement.

We scored each utility based on Table 2. Histograms are shown in Figure 2. For the FY 2015 data, the average percentage for all water utilities was 12.22%. For some utilities, the percentage exceeded 40%; most were assumed to supply resorts or vacation homes (Nishimura et al. 2017). For utilities supplying populations ≥600,000, the average percentage was relatively small (4.94%). For utilities supplying populations <10,000, the percentage was 16.64%, i.e., approximately three-fold greater than the 4.94% mentioned above. The ineffective water percentage was lower for large utilities, and higher for small utilities, presumably reflecting the maintenance management systems; large-scale utilities can afford to take measures to reduce the ineffective water percentage.

During calculation of Equation (4.2), the following rules were applied to handle instances of 0 and 100%:

• i.

  If both the denominator and numerator are zero, the index value is 0%.

• ii.

  If the denominator is zero and the numerator is not, the index value is 100%.

• iii.

  If the calculated value exceeds 100%, the value is replaced by 100%.

In terms of the percentage change in the unit number of technical staff (Equation (4.2)), the average value for all water utilities was −6.15% (Figure 3). We then evaluated the situation for each population category (Equation (1)); all outcomes were Downward. Therefore, human resources for maintenance management systems are shrinking overall. As far as the authors are aware, automation has not been employed for pipe replacement for the last 10 years in Japan, to improve efficiency. Therefore, human resources would reflect the maintenance management system.

The number of utilities classified as Downward was almost twice the number classified as Upward. Excluding systems supplying populations ≥600,000, the rate of decline (Equation (4.2)) was greater for small water utilities, inevitably reducing the number of technical staff of such utilities.

The possible grades were Downward (<20%), Flat (20–80%), and Upward (≥80%) (Table 5); histograms are shown in Figure 4. Of all utilities, 46.55% were graded Upward and 37.61% Downward. An obvious divide was apparent; for utilities serving populations <100,000, the histograms showed two peaks, indicating major differences in efforts to repair water leakage. However, most utilities supplying populations ≥100,000 were graded Upward.

The repair rate was 85.63% for water utilities supplying populations ≥600,000; such utilities detected and repaired the most leaks. On the other hand, the figure was 49.89% for utilities supplying populations <10,000; only about half of the leaks were repaired. The overall average repair rate was 54.47%; nationwide, most leaks were not repaired. The grade was Upward for water utilities serving populations ≥100,000 and Flat for the others. Large utilities repaired leaks more effectively.

Based on our four indices, we evaluated deterioration and maintenance management systems; the results are summarized in Tables 3 and 6, respectively. Overall, deterioration was classified as a C (Caution) and maintenance management systems were graded as Downward. This report card will be open to the public through Japan Society of Civil Engineers, to inform Japanese citizens of the current status of water supply infrastructure. For that purpose, we have employed a rather simple scoring method, which can be calculated from published statistical data. Criteria for a report card in the US include capacity, condition, funding, future needs, public safety, and resilience and innovation. Among those criteria, the Japanese report card focuses on condition and maintenance, because infrastructure aging is of great concern to Japanese citizens.

In terms of deterioration, for large water utilities, pipelines were generally old, and ineffective water was small. Therefore, the two indices cancelled each other out, yielding overall ratings of C or D. As shown in Figure 5, the proportion of water utilities with total scores of 80–100 (A) increased as the population served decreased, being 12.0% for water utilities serving populations <10,000, 1.9% for those serving populations of 100,000–600,000, and 0% for those serving populations ≥600,000. The proportion of utilities rated E (0–20 points) was 0 for those serving populations ≥100,000. Therefore, for small water utilities, the evaluation results were heavily dependent on the individual utility.

In terms of maintenance and management systems, the grades were higher for large utilities both in terms of ‘the rate of change in the number of technical staff per length of distribution pipe’ and ‘the three-year average repair rate of water leaks’. The rate of change in the number of technical staff was graded Downward, indicating that numbers are shrinking. The repair rate of water leaks was graded Upward at utilities serving populations ≥100,000 and Flat for the others. The overall grade was Flat; thus, the overall maintenance management grade was Downward.

It is one of the characteristics in this study to show each indicator by each population category. As Table 3 shows, larger utilities are scoring higher for percentage of ineffective water, even though the score for percentage of old pipeline is lower. Considering the evaluation of maintenance management systems in Table 6, it may be suggested that the score of ineffective water is higher in larger utilities because the repair rate of water leaks is higher, which may be due to the larger number of technical staff per length of distribution pipe.

We devised indices assessing the deterioration of, and maintenance management systems for, drinking-water distribution pipelines. We have employed a rather simpler scoring method than other countries, intending to use this report to be available to the public. The indices were the percentage of old pipelines, the percentage of ineffective water, the change in the number of technical staff per unit length of pipe, and the repair rate of water leaks. Using these indices, we evaluated the extent of deterioration of water pipelines and the effectiveness of maintenance management systems. Overall, Japan scored a C for deterioration and received a grade of Downward in terms of maintenance management. Comparison of indicators by population category suggests larger utilities could reduce ineffective water possibly by a larger number of technical staff.