PROPOSAL OF ADAPTIVE MANAGEMENT METHODOLOGY INCLUDING QUALITY CONTROL OF MATERIALS USED FOR FILLING BORROW PITS IN ENCLOSED BAYS

As a result of active dredging activities during the postwar high growth era, many borrow pits are located in enclosed bays in Japan. Borrow pits have been identified as sources for anoxic water masses and hydrogen sulfides that adversely impact the nearby ocean and borrow pits in various locations are being filled. Obtaining material to fill borrow pits is important for environmental restoration of enclosed bays. As the amount of dredged spoil from harbor construction work is inadequate, it will be necessary to effectively use soil and sand from sources including river and road construction works. However, schemes for quality control of materials from various sources have not been established. Based on the results of borrow pit filling in Osaka Bay, this study proposes a quality control scheme for the beneficial use of materials from various sources as well as an overall methodology for the adaptive management.