Hi Sradha
See i dont hav any judgements to quote for but by reading the section i can prove that we can claim depreciation and additional depreciation on earthwork/civil work to support the wind mill
As per Section 43(1) of the Income tax Act which talks abt the Cost for the purpose of claiming depreciation. This section says that Cost includes Installation and Erection Charges Loading and Unloading Chargres Freight and Interest on Loan taken upto the date of usage of asset. Since eartwork/civil work are an integral part to support the windmill it shoul be added to cost of windmill. Thereby u shall be entitled to claim depreciation on that. And since if the same windmill is used for manufacture purpose u can claim additional depreciation too. If u hav any further doubts pls let me knw.