From the TSP website:

L 2010 Fund to close — The L 2010 Fund reached its time horizon on July 1, 2010 and now has a final asset allocation that is identical to the L Income Fund. On December 31, the L 2010 Fund will be closed. If you have investments in the L 2010 Fund, they will be moved to the L Income Fund on December 31. If you have allocated any portion of future contributions to the L 2010 Fund, that allocation will be automatically changed to the L Income Fund. You do not need to take any action, but if you want to change your contribution allocation or do an interfund transfer to change the investment mix of money already in your account, visit My Account.
Source: https://www.tsp.gov/whatsnew/plan/planNews.shtml|

Homepage = www.tsp.gov