Evaluation of the accumulation of sediment and heavy metals in a storm-water detention pond.

Accumulation of sediments and water quality were investigated in a wet storm-water detention pond in central Sweden. The drainage area surrounding the pond was covered by a section of highway and secondary roads. Sediment samples were collected from the pond and heavy-metal concentrations analysed subsequently in the laboratory. The depth of accumulated sediments was measured at several points around the pond. The investigation showed that during the 18 months that had passed since the pond was constructed, a 5-8 cm layer of sediments had accumulated near the inlet, and a 1.5 cm layer near the outlet of the pond. Storm water passing through the detention pond showed an average reduction rate of 26-84% for total metal content, 67% for total N, 78% for total P and 92% for COD.