| Company name | Group | Parent | Subsidiary | Customer | Supplier | Alliance | Bank | Shareholder |
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| OLY推進部 | ||||||||
| 井口建設株式会社 | ||||||||
| 株式会社山栄テクノ | ||||||||
| Port Civil Co., Ltd. | ||||||||
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| 東京都水道局・東京都下水道局 | ||||||||
| 茨城県小美玉市 |
In order to undertake civil construction contracting work.
Relocated headquarters to 9-12 Akabane Minami 1-chōme, Kita-ku, Tokyo.
Relocated headquarters to 3-3 Akabane 3-chōme, Kita-ku, Tokyo.
Received Construction Industry Permit Registration No. 51-7293 from the Governor of Tokyo.
Relocated headquarters to 10-8 Minami Mizumoto 1-chōme, Katsushika-ku, Tokyo.
Achieved A‑rank in the Tokyo Metropolitan Waterworks Bureau grading for sewer and general civil engineering works.
Received Construction Ministry Ministerial Permit Registration No. 61-11694.
Awarded by the Tokyo Metropolitan Waterworks Bureau as a 3‑year excellent contractor.
Received approval for on‑floor registration from the Japan Securities Dealers Association.
Ibaraki plant obtained the Ministry of Land, Infrastructure, Transport and Tourism certified “R‑Grade” for steel welding.
Awarded by the Tokyo Metropolitan Waterworks Bureau as a 3‑year excellent contractor.
Achieved 1.8 million hours of accident‑free record (Category 5).
Obtained a patent for the company‑developed pipe‑in‑pipe transport system: “Pikars Method”.
Awarded by the Tokyo Metropolitan Waterworks Bureau as a 4‑year excellent contractor.
Awarded by the Tokyo Metropolitan Waterworks Bureau as a 5‑year excellent contractor.
Awarded by the Tokyo Metropolitan Waterworks Bureau as a 3‑year excellent contractor.
Awarded by the Tokyo Metropolitan Waterworks Bureau as a 3‑year excellent contractor.
Awarded by the Tokyo Metropolitan Waterworks Bureau for being an excellent contractor for 4 years.
Taisei Kogyo Co., Ltd. received an award from the Director General of the Tokyo Metropolitan Government Bureau of Sewerage as an outstanding contractor, in recognition of its consistently excellent work performance over the five fiscal years from 2021 through 2025. The company says it will continue contributing to social infrastructure development by applying its construction expertise.
Daisei Industrial Co., Ltd. has received an order for reconstruction work near Ichigaya Yakōji-cho, Shinjuku Ward, from the Tokyo Metropolitan Sewerage Bureau.
Daisei Kogyo Co., Ltd. has secured a reconstruction contract from the Tokyo Metropolitan Waterworks Bureau for the area near Chomiichome 1-chome in Koto Ward.
The OLY method implementation by Omori Kogyo Co., Ltd. has exceeded 5,000 sites nationwide, and its adoption in design has increased.
Daisei Industrial Co., Ltd. has received an order from the Tokyo Metropolitan Sewerage Bureau for Reconstruction Near Higashi-Jujo 2-3 Chome, Kita Ward, Construction 3.
Daisei Industrial Co., Ltd. has received an order from the Tokyo Metropolitan Sewerage Bureau for reconstruction work near Saga 2-chome, Koto Ward.
Daisei Industrial Co., Ltd. has received a reconstruction project near Fuyuki, Koto Ward, from the Tokyo Metropolitan Sewerage Bureau.
Oomori Industries Co., Ltd. has been recognized by the Tokyo Metropolitan Sewerage Bureau Director for four years from Reiwa 3 to Reiwa 6 for performing sewerage construction with excellent results.
They have started mud slurry type thrust boring work and are thoroughly implementing measures against combustible gases to ensure safe construction.
Received an order for the replacement of water main installation work in Chiyoda Ward from the Tokyo Metropolitan Waterworks Bureau.