The National Environmental Health Association (NEHA) created a certification and testing program for installers (CIOWTS).  If an installer has this certification, he should have the required experience to sit for any installer test.  I recommend that the proposed regulations include a reference to this certification and state that this certification meets the required experience for the sewage system installer license.  You can find the link here about the certification: http://www.neha.org/onsite/index.htm

If an installer meets the NEHA certification standard, I would also recommend that any test be waived to encourage installers to get the NEHA certification.