Only a project administrator can request that his / her own project be removed. In order to verify the project administrators account he / she will need to log into Sourceforge.net:
https://sourceforge.net/auth/
After the project administrator has logged in he / she will need to create a ticket requesting that the project they administer be removed:
https://sourceforge.net/p/forge/site-support/new/
After a ticket is created a SourceForge.net Staff member will process your request.