What info/indications are there that the bacterial levels have anything to do with septic systems? There is plenty of surface 'material' to consider.
FWIW, it is normal for well to septic system separations to be set at 100' as common practice all over the country. So septic leaching distance are not all that far. So that begs the question of what any significance there may be in any interaction groundwater levels and septic fields.
It is common practice at least at the NJ beaches to test for bacteria levels after a lot of rain. Why? Because crap flows into the water. Some areas get more than others, its not uncommon for certain beaches to be closed for 2-3 days until the levels drop
Understood; no news there. But what is the connection between septic fields and that issue?
And I'm honestly not picking on you at all....But the exact mechanisms are not being identified here. Is it surface 'stuff' or fertilizers and other nutrients being washed into the waters and promoting bacterial growth? Is it because of septic tanks overflowing like the above observation? Or what exactly? 'crap flows into the water' is just not a useful statement of the issues, and no one should make some presumed connection.
Manny/most folks don't even know how a septic system works. If they did, they would know that no solids should exist in the leach field, only 'digested' liquids. So if real solids are showing up, then the issue is in the tank area. Or there is an old existing connection from an old waste system into the storm drains....which has nothing to do with septic systems.
OBTW, that discharge pipe that you were near is probably one that has been discussed here somewhere in past threads....Unfortunately, I can't recall the explanation.