SELECT INTO #temp table Then add field

I'm creating a temp table in a stored procedure by selecting 4 fields from an existing table. Then I add a new field to the table into which I want to store the current date and time.  I'm getting an error on the update statement. The error is "invalid column DateAdded".

The code is:
SELECT WorkSites_ContactsImport.ExtOrgID, WorkSites_ContactsImport.ContactNum,
      WorkSites_ContactsImport.Location, WorkSites_ContactsImport.ContactName
      INTO #CNTCS_temp FROM WorkSites_ContactsImport LEFT JOIN WorkSiteContacts
      ON (WorkSites_ContactsImport.ContactNum = WorkSiteContacts.ContactNum)
      AND (WorkSites_ContactsImport.ExtOrgID = WorkSiteContacts.ExtOrgID)
      WHERE (((WorkSiteContacts.ExtOrgID) Is Null));
--SELECT * FROM #CNTCS_temp

ALTER TABLE #CNTCS_temp ADD DateAdded datetime
SELECT * FROM #CNTCS_temp
UPDATE #CNTCS_temp SET DateAdded = convert(datetime, convert(char(10), getdate(), 110))

The SELECT statement before the update gives this result, so I know the field is added.

What can I do to put the DateAdded into the temp table which will then be put into the production table using this statement.
INSERT INTO WorkSiteContacts (ExtOrgID, ContactNum, LocNum, ContactName, DateAdded) SELECT * FROM #CNTCS_temp

Thanks, Susan