The relevant SAFO is 15009, but linked here.
http://www.faa.gov/other_visit/aviat.../SAFO15009.pdf
The FAA AC for pre landing runway assessment is here.
http://www.faa.gov/documentLibrary/m...5-32_Final.pdf
Aero, #4, re 15%, it depends which 15% is being considered.
If based on certificated Landing data; 1.15 dry distances for wet, then ‘this 15%’ may be insufficient in many situations. The FAA SAFO appears to relate to this, but caution because their ‘manufacturers actual’ distances (Boeing term) is not the same as AFM certificated distances.
Post TALPA and using Operational Landing Distances (OLD) which provide a more realistic view of achievable landing distance (actual); then manufactures and regulators (FAA AC) recommend a further 15% minimum addition, often published a Factored OLD (FOLD). This 15% should relates more closely to what happens in day to day operations on wet runways. However ‘how wet is wet’, there are some, many combinations of water depth, runway surface, tyre/brake condition, etc which warrant use of more than 15% minimum addition.
Some of the technical aspects are here
https://skybrary.aero/bookshelf/cont...hp?bookId=3841