ASTM also has a standard for settlement plates (D 6598-07 is current). My favorite non-ASTM documents are from CalTrans (California Test CT 112, text and diagrams), Kentucky DOT (Drawing RGX-015-02), and Iowa DOT (Drawing RL-06).
Between these four (and the already-referenced FL DOT specifications), you should be able to come up with a workable design standard.
Jeff