What are the best practices for communicating SEA's (significant environmental aspects), objectives/targets, and monitoring/measuring to ensure employees will retain the information and can intelligently communicate them to an external auditor?
I cannot call these as best practices. They are some of the practices I follow.
Employees are not expected to know all significant environmental aspects), or objectives/targets, or monitoring/measuring requirements. What is expected is that they know which are relevant for their job, which ones they can contribute to or influence.
Normally, what I recommend doing is designing a homogeneous audience based on location, and customize a game where people are invited to determine significant environmental aspects from their job and learn about the best practices to handle each one.
Develop the environmental policy day. A day where the environmental policy is presented, with special attention to its commitments, and a link to the environmental objectives and targets.
Again, with a homogeneous audience based on location you can develop a kind of brainstorming about “How can I contribute, in my work, to meet the objectives and targets?”
For each relevant location periodically post the results of monitoring / measurement that people can influence during the performance of their work