Jim I hate so say it..
but my boss wants me to play shovel muffin on monday "looking for a leak"..I really should hold my guns until he buys me a vac. My thought is to put a master valve on the 2 mains and see how it plays.. When we installed these valves in the ground there was water, it is known this estate is a wetland, there is a natural pond on site.. Water just stays on the surface and my boss is in his mind dig dig dig.. I say master valve first and monitor the well...
Once before a HOA thought we had a leak on a 2 inch main system..we dug and dug for days.. no leak...Had a plumber come in and plumb up a master valve in each water closet...still the problem came...1 year later we decicded it wasn't a leak...it wasn't...I talked to some people who lived in the area and they said the entire housing site was built on a salt marsh... and at high tide the water came through the curb's, road, sidewalks...They gladly paid us over 5k for digging for a while and putting in pointless valves..