過去開口契約之研究，發現在最後建議中提到不同規模、性質之維護工作考量，其開口契約適用情形不一，仍有待進一步探討和歸納，並將特點和目的具體地融入開口契約範本，也建議機關可針對不同性質工作，訂定不同開口契約的基本架構，過去關於此之研究，甚少探討到污水工程開口契約，本研究適可補足過去之不足。因此，本研究以我國、美國、日本及新加坡四個國家之污水下水道(含污水費結構)、開口契約、監造業務為文獻回顧，並切入開口契約之問題:(1)以開口契約之制度面、執行面和結構性問卷訪談，以三個面向來探討開口契約與一般契約差異，訪談對象以主辦機關、監造廠商、施工廠商並設立專家組對與照組共17 人員做對照研究，就開口契約主要特性探討並減少開口契約履約可能發生之爭議。(2)並以污水工程開口契約交辦案中340 個執行案例，基於資料蒐集與取得之「完整性」和「發 生機率」探討遭遇私地補償、中央天井、危建、管線障礙、既有人孔掩沒、地面高低差過大、老舊建物等七個障礙時可能衍生之問題、處理方式、主要問題態樣及最終目的為解決與對策。;ABSTRACT The past research of indefinite delivery contracts have discovered that different project sizes and characteristics affect the application of indefinite delivery contracts to the projects. They also suggested thatgovernment organizations can establish different indefinite delivery contract structures for the projects of different characteristics. However, past researches seldom discuss and analyze such topic on indefinite delivery contracts for sewerage construction. Therefore, this research focuses on the system, administration and implementation of indefinite delivery contracts for sewerage construction from the supervision perspective. This research starts with literature reviews of the current practices of sewer systems (including sewerage fee structure) in Taiwan, United States, Japan and Singapore as well as reviews of indefinite delivery contracts.The differences between indefinite delivery contracts and traditional contracts are then analyzed and discussed to understand the major characteristics of indefinite delivery contracts for sewerage. In addition, this research collects five real cases, which consist of seven different obstacles commonly encountered in the sewerage construction. These obstacles are compensation for private land, central skylight of buildings, dangerous buildings, underground pipeline barriers, submerged existing manholes, huge ground elevation difference, and old buildings. This research introduces these obstacles, and discusses and proposes meansand solutions to deal with these obstacles. All the discussions and analyses are validated through interviews with domain experts and questionnaire surveys. This research aims to organize the practical experiences in the domain and to provide a guide for future household sewerage pipes connections using indefinite delivery contracts in order to reduce possible disputes and guarantee smoother project implementation.