Engineered Wood Fiber (EWF) is one of the types of surfacing that meets ADA. It is not highly recommended for truly usable accessible playgrounds because often a wheelchair tire can get stuck in the fiber. Also, parents who have children with autism have reported that their children mouth the wood chips.
However, for many the low cost of EWF is the deciding factor in using this type of surfacing in a new playground. If the playground uses EWF how it is installed and maintained in crucial. International Playground Equipment Manufacturer Association (IPEMA) has come out with a position statement about EWF. Reading this information is incredibly important so that customers who are purchasing EWF can ensure that whomever they hire to install it is doing it to the best standards. http://www.ipema.com/Documents/EWF%20maint-install%20position%20statement.pdf