How add duplicate column name into datatable ?

I have write a store procedure and also passing some parameter. Now I am trying to making pivot table and binding to the gridview. But problem is that my datatable is not accepting duplicate column name. if my table column name is different. So how I can add same column name into datatable. First I am taking column from ROW_SOURCE of text name is ‘Sakhare Dam’ and second I am taking column from PURE_SOURCE of Textname is ‘Sakhare Dam’. So how do it take if taking different column name..
My coding getting error in second loop of for…
for (incVal = 0; incVal < source.Rows.Count; incVal++)
{
if (!report.Columns.Contains(source.Rows[incVal][(int)FieldsNRW.RAWSOURCE].ToString().ToUpper()))
{
report.Columns.Add(source.Rows[incVal][(int)FieldsNRW.RAWSOURCE].ToString().ToUpper(), typeof(decimal));
}
}

for (incVal = 0; incVal < source.Rows.Count; incVal++)
{
if (!report.Columns.Contains(source.Rows[incVal][(int)FieldsNRW.PURESOURCE].ToString().ToUpper()))
{
report.Columns.Add(source.Rows[incVal][(int)FieldsNRW.PURESOURCE].ToString().ToUpper(), typeof(decimal));
}
}

This is Table data…
ID DATE RAW_SOURCE RAW WATER PURE_SOURCE PURE WATER OUTGOING WATER MBR OUTGOING WATER ESR
47 1/8/2013 Sakhare Dam 5.94 Sakhare Dam 5.84 5.84 5.84
46 2/8/2013 Sakhare Dam 3.75 Sakhare Dam 3.65 3.65 3.65
45 3/8/2013 Sakhare Dam 5.3 Sakhare Dam 5.2 5.2 5.2
44 4/8/2013 Sakhare Dam 4.75 Sakhare Dam 4.65 4.65 4.65
43 5/8/2013 Sakhare Dam 4.84 Sakhare Dam 4.74 4.74 4.74
42 6/8/2013 Sakhare Dam 5.85 Sakhare Dam 5.75 5.75 5.75
41 7/8/2013 Sakhare Dam 6.21 Sakhare Dam 6.11 6.11 6.11
30 8/8/2013 Sakhare Dam 6.12 Sakhare Dam 6.02 6.02 6.02
31 9/8/2013 Sakhare Dam 4.48 Sakhare Dam 4.38 4.38 4.38
32 10/8/2013 Sakhare Dam 6.85 Sakhare Dam 6.75 6.75 6.75
33 11/8/2013 Sakhare Dam 6.67 Sakhare Dam 6.57 6.57 6.57
34 12/8/2013 Sakhare Dam 6.4 Sakhare Dam 6.3 6.3 6.3
35 13-08-2013 Sakhare Dam 6.03 Sakhare Dam 5.93 5.93 5.93
36 14-08-2013 Sakhare Dam 6.12 Sakhare Dam 6.02 6.02 6.02

I want output..

Date Sakhare Dam Sakhare Dam OUTGOING WATER MBR OUTGOING WATER ESR
1/8/2013 5.94 5.84 5.84 5.84