Tate Modern is this month submitting plans to Southwark council for a new extension designed by Swiss architects Herzog & de Meuron. The Ziggurat-style glass boxes will rise above the roof, on the south side of the gallery away from the river Thames. A decision on the planning application is expected next spring. The hope is that the new ten-storey building might be completed in time for the London Olympics in 2012. Costs are estimated at £165m ($297m). A grant application will be made to the National Lottery, but this will cover only a small proportion of costs. The only other funds already available for the new extension is £7m from the London Development Agency, which will be used to help EDF Energy develop a new substation on the site (this will require only half the area of the present substation, freeing land for Tate’s extension). The new building will add 7,000 sq. m of display space to the existing 9,000 sq. m, an increase of 44%. It will also include a large temporary exhibition gallery. Beneath the extension, two of the massive underground oil-storage tanks are to be used as performance spaces.