As the website says: “With your help, Tucson's Christopher Franklin Carroll Centennial Park will transform a 30' by 130' vacant lot into an attractive pocket park.” The website also describes gifts from Tucson Water, including an historic plaque, and has a page explaining how you can buy a commemorative brick to help fund this peaceful little parklet downtown, across from the Tucson Museum of Art and Historic Block.
Once it opens, I'll update this entry. In the meantime, if you have news, please leave a comment below!
Update (October 2. 2017): The park has been completed and open for more than a year. There are photos in today's blog entry Christopher Franklin Carroll Centennial Park.