Randy,
I have a situation at my place much the same as you described in your post. After a good rain, I will see a spot about 5 feet from the pond bank that discharges a liquid with an oily film. There is no smell to it and my leach field is a little over 100 feet from the pond. I have not noticed the blue-gray coloration you described though. My pond has all the typical algae problems you see a number of posters talk about but there has been no detrimental effects on the fish in my pond.
I do not have an answer to your question but if you look down the posts on this topic, you will see another heading about septic systems. If you read this, you'll see a post by FOZZYBEAR, who may be able to address your question. His profile lists an e-mail address so perhaps you could shoot him a note and ask him to give his opinion.
Russ
