Bedömning av föroreningsspridning kring en nedlagd bensinstation i Karlaby, sydöstra Skåne

Sammanfattning: In Karlaby, southeastern Skåne, the groundwater beneath a former petrol station has been showed to contain hydrocarbons. The objective of this project is to identify possible flowpaths that soluble contaminants may take, to delimit an area in which the contaminants may have spread and to calculate times needed for the contaminants to reach adjacent creeks. A geologic/hydrogeologic model over the investigated area has been constructed on basis of geologic mapping, drilling and meassurements of groundwater levels. It can be concluded that contaminant transport is possible through sorted inter-till sediments in a westward path for c. 80 meters from the former petrol station. Further westwards the sediments are predominantly sorted. Due to the fact that continuation of the inter-till sediments is not exactly known, two different scenarios have been put up when calculating the shortest transport routes - and thus duration of time - to ajacent creeks. Just north of the petrol station is a creek flowing in a westerly direction. Calculated transport time to this creek is in the order of 55 - 400 days, depending on used max/min values of hydraulic conductivity. After about 360 meters westwards the creek makes a turn and then flow soutwestwards. Calculated transport time from the petrol station to that point is 2,5 - 3,5 years depending on used max/min values of hydraulic conductivity. The creeks are supposed to act as hydraulic boundaries and thus delimit the area in which contaminants can spread in a northerly and westerly direction. Towards the south there is no hydraulic boundary whitin the investigation area. However, as the creeks seem to have a strong pull on the groundwater flow, creating hydraulic gradients towards them, it is suggested that contaminant spreading is inhibited in a southerly direction. Computer models indicate that the distribution of the inter-till sediments have a large influence on the direction of contaminant transport in the area.