Multikriterieanalys av dagvattenreningstekniker : Med fokus på Västra vägen i Gävle

Sammanfattning: Gävle municipality strives to treat all stormwater that may prevent river and lakes from achieving a good water status under the EU water framework directive. There are three stormwater outflows at Västra vägen in Gävle that discharge untreated stormwater to Gavleån. Gävle municipality has an ambition to clean stormwater as close to the source as possible. The purpose of this study is to conduct a multi-criteria analysis to identify stormwater treatment solutions that are suitable from a technical, ecological, economic and sociocultural perspective. According to EU water framework directive Gavleån does not achieve a good chemical and ecological status because of the presence of contaminates in the river. The alternatives that will be evaluated in the multi-criteria analysis consists of a screen pool, percolation storage and four different types of filters. Except these six solutions a null alternative will be included to evaluate if the situation does not change and the stormwater is not treated as it is today. These seven alternatives will be evaluated by a panel that consists of people who work with stormwater or with matters related to the categories in the multi-criteria analysis. The panel's main priority of categories and criteria is produced by the average value of all participants’ weightings and ratings. The most important category was considered to be the sociocultural perspective and the least important was the technical perspective. The criteria that were considered important for the respective categories were operating and maintenance cost (economic perspective), reduction of pollution (technical perspective), environmental impact, land use (ecological perspective, shared position), and outdoor recreation (sociocultural perspective). The option that received the highest score in the analysis was null alternative followed by the screen pool. That is because the null alternative is considered to have the most positive impact on the socio-cultural perspective, ecological perspective and financial perspective while screen pool scored highest in the technical perspective. The results of the MCA should also be interpreted by different stakeholders' priorities and can be seen in Section 6 in which the scoring of all treatment alternatives are reported.