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. Appropriate management of infrastructure is critical as the population falls, budgets become reduced, and staff numbers dwindle. The Japan Society of Civil Engineers evaluates infrastructure soundness and publishes the results to promote understanding of the current situation and to emphasize the importance of maintenance. We devised indices for evaluating deterioration of drinking-water distribution pipelines and maintenance management systems for the pipelines. The indices are the percentage of old pipelines, the percentage of ineffective water, change in the number of technical staff per unit length of pipe, and the repair rate of water leaks. Using these indices, the evaluation result for Japan overall was a C (Caution) in terms of deterioration and Downward in terms of maintenance management. This is an Open Access article distributed under the terms of the Creative Commons Attribution Licence (CC BY 4.0), which permits copying, adaptation and redistribution, provided the original work is properly cited (http://creativecommons.org/licenses/by/4.0/). doi: 10.2166/aqua.2020.112 ://iwaponline.com/aqua/article-pdf/69/4/355/724743/jws0690355.pdf Hiroshi Sakai (corresponding author) Mei Satake Yasuhiro Arai Department of Civil and Environmental Engineering, School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1-1, Minami-osawa, Hachioji-city, Tokyo, 192-0397, Japan E-mail: h_sakai@tmu.ac.jp Satoshi Takizawa The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan


INTRODUCTION
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 popu- 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.

MATERIALS AND METHODS
Waterworks' infrastructure includes pipelines, treatment plants, and pumping stations. As treatment plants and pumping stations include electrical and mechanical equipment, they were not evaluated in this study. Of the various pipelines, we evaluated only distribution pipelines; raw water pipes, transmission pipes, and service pipes were not included. Bulk water-supply systems were also excluded because they generally lack distribution pipes. As for other sectors, we evaluated deterioration and maintenance management systems (Table 1). Deterioration was graded from A to E. Maintenance management systems were graded as Upward, Flat, or Downward. Upward, Flat, or Downward means the current state of deterioration will improve, will not change, or worsen, respectively, when current maintenance management system continues. We developed multiple indices of deterioration and maintenance management systems and weighted them equally when making overall evaluations. Deterioration was scored as A (!80), B (!60), C (!40), D (!20), or E (<20). After evaluating the deterioration of all water utilities, overall evaluations were performed for various supply categories, and for Japan overall. The average values of all indices in specific categories were used for the analysis. We established five categories of water-supply sizes based on population served: (i) !600,000 (Tokyo and ordinance-designated cities), (ii) 100,000-600,000, (iii) 30,000-100,000, (iv) 10,000-30,000, and (v) <10,000. Overall maintenance management system indices were calculated based on Equation (1)

RESULTS AND DISCUSSION
The indices 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.

Pipeline age
Possible indices of deterioration were sought among watersupply statistics. As drinking-water pipelines are buried, visible inspection of the outer surface is difficult and expensive, unlike with bridges or roads. Moreover, drinking-water pipelines are pressurized to distribute water of appropriate quality to all households. Therefore, pipelines are always filled with purified water, rendering it near-impossible to inspect the inner surfaces with low cost at whole nation level. Thus, as neither the inner nor outer surfaces of pipes can easily be evaluated, we took the length of pipe above the statutory useful life (40 years) as an index of deterioration, calculated for each utility as follows: Percentage of old pipeline (%) ¼ Length of pipe aged over 40 years (m) Total length of distribution pipe (m) 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    Works Association (). Although ineffective water is different from the concept of non-revenue water, we employed this indicator because it has been used in Japan for a long time. Another reason is that ineffective water will be closer to real losses than non-revenue water, if we assume unbilled metered consumption is negligible.
'Leaked water' accounts only for water wasted prior to repair, and not for undetected (and thus unknown) leakage;  leaked water may not reflect real leakage volume. In total, 229 of 1,381 water utilities reported leaked water as 0 (or blank) in FY 2015. Therefore, we used the ineffective water volume as an indicator rather than leaked water. The ineffective water percentage was calculated using Equation (3): Percentage of ineffective water (%) ¼ Amount of ineffective water (10 3 m 3 ) Amount of water supply (10 3 m 3 ) We scored each utility based on 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%.
Depending on the results of Equation (4.2), maintenance systems were graded as Upward (!5.0%), Flat (from À5.0% to 5.0%), or Downward (<À 5.0%), based on Table 5. The average unit number of technical staff (Equation (4.1)) tended to be higher for large water utilities. The average unit number for utilities serving populations !600,000 was 82.44 people/1,000 pipeline km, more than four-fold greater than the average of 20.18 for utilities serving populations <10,000, as in Table 6. Therefore, larger utilities can afford more technical maintenance staff.
In terms of the percentage change in the unit number of technical staff (Equation (4.2)), the average value for all water utilities was À6.15% (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.

Repair rate of water leaks
Another possible index for assessing maintenance management systems is the repair rate of water leaks; this is a goods and services measure. Earlier, we mentioned that leaked water in water-supply statistics refers only to known (repaired) leaks; ineffective water was assumed to be the real leakage volume. Thus, we established a 'repair  rate of water leakage' index (Equation (5)). As leakage volume may vary annually, we used the three-year average of Equation (5), as the index value. If all leaks are detected and repaired, the index should be 100%.

Overall evaluation
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. 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.

CONCLUSIONS
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.