A proposal is made to make the ocean surface as the field of human activity in the future.The surface is the only space left on the earth where vast areas as well as air, sunlight and water are easily and freely available. In this proposal, a part of the ocean surface is surrounded by a floating breakwater for forming a man-made bay on the surface. Within the bay, several artificial islands or facilities are designed to float, which include various kin ds of facilities necessary for the purpose of human activities. In the first stage of this proposed project, facilities of the primary industry type are to be built such as grain units, forest units and energy units. For example, the forest unit comprises a pool consisting of a huge rubber boat and stored rainwater, and an artificial ground made by piling up soils on a large-scale rubber mat. The forest unit made of a flexible rubbery sheet is immune to stress concentration. Therefore, the forest unit can be built as a huge construction. Furthermore, it hardly cost to obtain fresh water since rainwater is available. According to our estimation, the unit can be constructed at a cost of 3, 000 to 30, 000 yen/m². Following the units for the primary industry, units for residence as well as for secondar yand tertiary industries are to be built. Thus, the utilization of the ocean surface would extend the activity field of mankind, and control the degradation of the natural environment.

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The comparison of 4 questionnaires on city tap water revealed interesting facts concerning the effectiveness of filtering the Kasumigaura lake water. The filtration facilities consists of activated carbon and microorganism' s purification. A portion of people who claimed odor of chlorine and other agents in the tap water became about a half in these two decades. However, even now, about 21 percents of people who use the water taken from the lake complain of smells besides chlorine, and about 40 percents say that the water taste is not good. The people of Tsuchiura city by the lake want to avoid health interference by the poor water quality. The “preventive-expenditure” required, as estimated from revelations in the questionnaires is 43.4 billion yen per year for 390-thousand water users. Tsuchiura people's “ willingress-to-pay” to improve the lake water quality is approximately same as that by people by the Biwa Lake. They are Yen 5, 454 for the former and Yen 3, 964 per person per month for the later, respectively. If they invest the sum to improve the Kasumigaura water quality, the present value will reach Yen 482 billion with a 5-percent discount rate and a project life of 3 decades.

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[in Japanese]

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