If any reason you decided to delete the PWA site, you can do it from either “SharePoint Central Administration” site or “SharePoint 2010 Power Shell Commands”. When you delete the PWA site, it also deletes the site collection from SharePoint Central Administration site.
(FYI: You can view site collection by navigating to “SharePoint 2010 Central Administration -> Application Management -> View all Site Collections”)
1. Delete PWA site using SharePoint 2010 Central Administration
Launch SharePoint Central Administration site -> Application Management -> Manage service applications, On the Manage Service Applications page; click the Project Server Service Application -> On the Manage Project Web App Sites page -> Click the dropdown arrow against PWA site to be deleted -> Click “Delete” option -> Click “Delete” button to proceed
2. Delete PWA site using SharePoint 2010 Power Shell Command
On the Start menu, click All Programs, Click on Microsoft SharePoint 2010 Products -> Right click on SharePoint 2010 Management Shell -> Run as Administrator -> Use the following syntax to delete PWA site; Use the appropriate PWA URL within " " in below syntax
Remove-SPProjectWebInstance –Url “PWA URL”
Example: Delete PWA site; URL of the PWA site is http://chakserver/pwa