Environmental characteristics of post-closure landfill site with municipal solid waste and its land use

A post-closure landfill site with municipal solid waste differs significantly from other sites in that it involves problems such as gas eruption incidental to the decomposition in the landfill, ground subsidence, leachate production, and so on. Such problems present challenges in the subsequent land use of the site. To make a plan for a public park on such a landfill site that was closed ten years ago, a study was conducted which entailed the following tasks: 1) ascertain the environmental characteristics of the landfill site and its impacts on the surrounding area as a prerequisite to the development of the site, and 2) formulate a zoning plan corresponding to the land use form in the park based on the results of the study. This paper presents the findings of the study and offers a land use policy for a post-closure landfill site that was developed in the course of the preparation of a public park plan on such a post-closure landfill site. The subject area consists of two valleys. Each valley has a different composition of landfill materials: one (Valley A) was reclaimed with putrefactive domestic waste, and the other (Valley B) with non-degradable waste including the demolition and construction waste. There are substantial differences in the environmental characteristics of the two valleys as for the observed gas eruptions, land subsidence and the like. In addition, the apparent effect of the depth of the earth cover on the plant life and the volume of gas erupted suggests that the composition of the landfill materials and the depth of the earth cover are key factors in preparing a land use plan for such a post-closure landfill site. For the past four years, studies have made on the conditions of the subject area and the situation is rather clear. First, the decomposition in the garbage layer still continues, even ten years after closure, which suggests that gas eruption, ground subsidence, etc. will continue over the long-term, as reported in other papers. Second, there is a significant difference in the effects caused by the different kinds of landfill material in the two valleys. Third, the depth of the earth cover, etc. has a marked effect on the concentration of gas eruption, plant life, and other aspects of the site. Lastly, the georesistivity tests were demonstrated to be useful in determining the extent of the earth cover depth. The major impacts caused by landfill materials, such as gas eruption and ground subsidence, in addition to the earth cover depth were used as indices for zoning. In addition, the policy for the land use of a post-closure landfill site was established with a matrix which considered the structures to be constructed corresponding the land use form in a park, the normal behavior of the park users (seeing, smelling, etc.) and the land use form in a park (pitching a tent, building fires, etc.).