*Translated by Google translate

Introduction

Do you ever feel the weight of 400 years of time?

Built in the 17th century, the Tamagawa Aqueduct, which supplied the people of Edo with vital water, was converted into an underground culvert in the latter half of the 20th century, and a greenway was built above it. We residents have cherished and taken pride in this greenway, which alleviates the summer heat and provides a place of relaxation, as a gift from our ancestors.

▲Former greenway

Shibuya Ward is proceeding with the redevelopment of this greenway due to its aging infrastructure, and plans to "collaborate with world-renowned landscape architects and others" with the aim of making the greenway a "world-class landmark." As a result, the contract for commissioning the design is quite expensive, with 369.9 million yen for the initial construction section alone, and 2.64 million yen for each bench made of terrazzo material. What is particularly noteworthy is that terrazzo paving material accounts for nearly half of the construction cost.

Such excessive expenditures cannot be considered necessary and violate the fundamental principles of local finance. Furthermore, the town council has not approved this construction, and the majority of residents expressed opposition at the information sessions. In short, there is no consensus among the residents regarding this construction.

We, the plaintiffs, are dissatisfied with the aforementioned expenditures by Shibuya Ward, and have filed this lawsuit after filing a resident audit request.

Background

We, the "Shibuya Ward Tamagawa Aqueduct Old Waterway Greenway Association," were formed in 2023 in response to the Shibuya Ward's unjustified felling of street trees along the greenway.

At that time, Shibuya Ward was planning to cut down 189 street trees, citing reasons such as their death. However, when we commissioned a tree researcher to conduct a visual inspection, it was discovered that only a small number of the trees were dead. We also launched a petition against the felling and gained the support of many residents. As a result, Shibuya Ward conducted another tree inspection and reduced the number of trees to be felled. Through these efforts, we were able to preserve healthy street trees.

▲Redevelopment work is underway on the Tamagawa Aqueduct Old Waterway Greenway

However, after it was discovered that Shibuya Ward was planning to use terrazzo, a paving material that is environmentally harmful and extremely expensive, we decided to continue our activities.

Terrazzo is an extremely thick, heavy, and water-impermeable material that hinders soil respiration, damages trees, and accelerates the urban heat island effect. It places a significant burden on the environment and is undeniably a step backward.

* Heat island effect: A phenomenon in which the temperature of a city becomes higher than the surrounding area.
(Ministry of Land, Infrastructure, Transport and Tourism, Japan Meteorological Agency, "Knowledge and Explanation" of the Heat Island Phenomenon)

▲The extremely thick, heavy, and water-resistant terrazzo material that will be used in this construction project.

We have collected opinions from experts and more than 3,000 signatures of opposition from citizens, and have appealed to Shibuya Ward to reconsider. In January 2026, the Japan ICOMOS National Committee, a general incorporated association involved in the protection of cultural heritage, issued "Recommendations for the preservation and transmission of the history and culture of the Tamagawa Aqueduct, a cultural asset of Edo/Tokyo spanning 400 years," which emphasizes the need for the preservation and restoration of existing trees.

Another major problem is the extremely high cost of this paving material. Typically, materials used for paving greenways include permeable interlocking blocks, which are environmentally friendly and safe for pedestrians. Terrazzo material costs approximately 32 times more than interlocking blocks. What is Shibuya Ward's reason for using such an environmentally impactful and expensive material?

▲The photo shows terrazzo in the foreground and interlocking blocks in the background.

The high cost of the paving materials has been raised as a problem many times in the Shibuya Ward Assembly. Council members who share our views have requested an explanation in committees and regular sessions, but we have not received any explanation or consistent response regarding the selection process or reasons.

Furthermore, although the vote was evenly split between those for and against the plan, the redevelopment plan was passed by the assembly in March 2025 without sufficient discussion. Currently, construction is being carried out forcibly in some parts of the greenway.

Following these events, we filed a resident audit request with the Shibuya Ward Audit Committee to question the nature and progress of the Tamagawa Aqueduct Old Waterway Greenway redevelopment project. However, our audit request was rejected, and we then filed a resident lawsuit.

*Please note that this lawsuit only concerns the first phase of construction work related to the Sasazuka Greenway and Oyama Greenway, which have already been completed as part of the greenway redevelopment project.

Issues in the trial

The central issue in this case is whether the expenditures on the redevelopment project planned by Shibuya Ward violate the principle of "minimum cost, maximum effect" in local finance. Specifically, the issues at hand are: ① the outsourcing of design, ② the use of terrazzo paving material, and ③ the outsourcing of cost estimation subsidies and construction management.

In this lawsuit, the plaintiffs argue that the expenditures on the redevelopment project were excessive in relation to the original purpose of the greenway redevelopment, which was to "make use of the abundant resources currently available and to create a renewal that will make the area even more appealing to local residents."

1. Regarding the commissioning of design work

Shibuya Ward commissioned the design of the greenway for a hefty sum of 369.9 million yen. Furthermore, part of the commissioned design work was subcontracted by the original company to another company for 226 million yen.

Looking at the breakdown of the design contract between Shibuya Ward and its contractor, expenditures for items labeled "design" amount to approximately 23 million yen, representing less than 7% of the total. The items that stand out in terms of amount are "direct expenses" and "general and administrative expenses." These amounts together total approximately 290 million yen, accounting for nearly 90% of the total.

Furthermore, in a prior resident audit request, Shibuya Ward expressed the following view regarding the subcontracting agreement:

This view indicates that Shibuya Ward has not scrutinized at all whether the amount paid to the subcontractor responsible for the actual design is reasonable, and it must be said that this is unreasonable.

2. Regarding the use of terrazzo material

The aforementioned renovations, including the use of terrazzo material, have resulted in higher costs than typical renovation projects. Furthermore, considering the original purpose of the redevelopment—to "make use of the abundant resources currently available and create a renovation that will be even more familiar to local residents"—and the content of the redevelopment, there is no rational reason to use expensive terrazzo material.

3. Outsourcing of cost estimation assistance and construction management

Shibuya Ward outsources tasks that do not actually require outsourcing, such as cost estimation assistance (assistance in calculating estimates for maintenance projects) and construction management, which should be entrusted to the contractors performing the work. These expenditures cannot be considered to be the bare minimum necessary.

▲Redevelopment of Tamagawa Aqueduct Greenway: High material costs

social significance　

This lawsuit alleges that the expenditures for the redevelopment project of the Tamagawa Aqueduct in Shibuya Ward are excessive for the purpose of redeveloping a greenway, and seeks a review of these expenditures. However, the social significance of this lawsuit is not limited to a single construction project in a single area. This lawsuit has three social implications.

The primary significance lies in highlighting the current situation where urban development projects are being carried out without the consent of residents, and in questioning the proper procedures for urban redevelopment carried out by the government.

Shibuya Ward claims that discussions have been taking place since 2017, but the name of the residents' council was not well-established in the community, making participation difficult, and the progress of the discussions was not properly reported. Therefore, it cannot be said that open discussions took place. This lawsuit is significant because it clarifies the problematic nature of this approach.

The second significance lies in the question of how cultural assets should be maintained and passed down.

The Tamagawa Aqueduct is not solely a part of Shibuya Ward, and the former waterway greenway is not just an empty lot.

As stated in the ICOMOS Japan recommendations, the Tamagawa Aqueduct is a "cultural asset of Edo/Tokyo's 400-year history," and is a historically and environmentally important social cultural asset spanning 42 kilometers. The redevelopment of the former waterway greenway, which is part of the Tamagawa Aqueduct, should ideally be carried out after incorporating the expertise of specialists in various fields, providing sufficient information to residents, and obtaining their agreement. Only when the value of the greenway is widely shared can appropriate expenditures for redevelopment be calculated. This lawsuit questions how the government should approach cultural assets.

The third significance lies in the very act of raising objections to excessive tax expenditures through resident lawsuits.

In this case, as in other administrative projects, decisions regarding projects are sometimes made based on the wishes of the head of the administration or the majority in the assembly, without adequately reflecting the voices of the residents. In such cases, the assembly may not adequately explain the appropriateness of the expenditures, as was the case with the Shibuya Ward Assembly.

However, in a lawsuit, the administration is required to clarify and explain the basis for its expenditures, and the court will determine whether the expenditures are illegal based on the principle of "minimum cost, maximum effect." We believe that questioning the way the administration operates through the process of litigation will have an impact not only on Shibuya Ward but also on local governments across the country that are facing challenges.

As described above, this lawsuit aims to realize local administration that engages in sufficient dialogue with residents and avoids the wasteful use of taxpayers' money.

▲ The former greenway (left: photographed November 30, 2023) and the greenway under construction (right: photographed October 7, 2025)

Use of Donations　

① Expenses for filing a lawsuit (including attorney fees)
An audit request was filed in March 2025, and in June, 10 residents filed a lawsuit as plaintiffs.

② Costs for opinion papers, etc .: This includes opinion papers from experts regarding the impact of paving materials on forests, concerns about the administration's lack of consideration for residents, etc.

③Transportation expenses

④ Public relations expenses : We are considering public relations activities, such as distributing flyers in the community, to inform local residents about the progress of this lawsuit.

Message from the plaintiff　

Plaintiff: Noriko Takao

In April 2023, when the COVID-19 situation had finally calmed down, I learned about a redevelopment plan for the greenway I use to walk my dog. I asked people I met on my walks, neighbors, and even checked with the neighborhood association, but no one knew that construction would begin four months later or what the redevelopment entailed. Moreover, the redevelopment plan was intended to use the greenway as an event venue, which was far removed from how residents actually use it and the quiet residential area it is now. I will never forget the shock I felt when I learned about that plan.

If the area is to be redeveloped, I hope that it will be made into a Musashino walking path befitting the historic Tamagawa Aqueduct, by adhering to the Basic Act on Biodiversity enacted in 2008, using permeable pavement, and planting native species.

Plaintiff: Haruhiko Higashi

Plaintiff Chiyo Kuge

Messages from supporters

Seiichi Mizuno (President and CEO of IMA Co., Ltd., former president of Seibu Department Stores, former member of the House of Councillors)

The reason I moved to Oyama Town 40 years ago was because of the wonderful greenway. This greenway, which carefully preserved natural trees rather than being a man-made park, was the perfect walking path for the dogs I had at the time. Now, that greenway is being transformed into an artificial park. I hear that the sidewalks will be paved with terrazzo, a pink artificial marble. "Richness" is not about placing benches that cost millions of yen. It's about regaining a "rich heart" that can appreciate nature.

Eiko Kyo (lyricist)

Message from the assigned attorney

Shibuya Ward has the Tamagawa Aqueduct Old Waterway Greenway, which has long been a beloved spot for local residents. It is extremely important to develop this greenway to be safer, more user-friendly, and a vital place for the community.

However, the funds used for this maintenance are the taxes of the ward residents. In this redevelopment, expensive paving materials and other materials have been adopted, but it cannot be said that the reasons why this method was necessary and why other, less expensive methods would not suffice have been adequately explained to the residents.

This lawsuit is not against the development of greenways themselves. Rather, it questions the transparency of how tax money is used and how public works projects are carried out, in order to create greenways that are truly easy for local residents to use and that will be cherished for a long time.

In public works projects undertaken by local governments, even if the objective is to "create something good," it is necessary to carefully explain to residents how much money will be spent and why a particular method is being chosen. This is because the development of local parks, roads, and green spaces directly affects our daily lives.

Through this lawsuit, we hope to ensure that public works projects are carried out in a more transparent and open manner for residents, not only in Shibuya Ward but also in municipalities throughout Japan. We would greatly appreciate your interest and support.

Introduction of the legal team

Satoshi Oshiro, Tokyo Chiyoda Law Office
Miho Kumazawa, Tokyo Chiyoda Law Office

In conclusion

As previously stated, this lawsuit is a residents' lawsuit against excessive tax expenditure, seeking sufficient dialogue with residents and the realization of an administration that does not waste taxpayers' money. It questions the redevelopment project of the Tamagawa Aqueduct in Shibuya Ward and the way local administration should be conducted.

We have received a great deal of support in the past, including through signatures and other means.

Filing a lawsuit and conducting a thorough legal campaign will incur the aforementioned costs. We hope that many people will take an interest in this issue and support this lawsuit through donations, contributions, or by sharing it with those around them.

Thank you very much for your cooperation.

<Please also sign the online petition.>

We are collecting online signatures to call for a reconsideration of the redevelopment:

https://www.change.org/p/the-history-culture-natural-environment-to-the-future-handover-to-the-future-environment-of-the-jewel-water-river-path-to-the-future-environment-of-the-jewel-water