AndyC and Paul Newman summed it up, "what we have here is a failure to communicate." That's quite predictable, all things considered. I can understand the County and Inyo not taking the time and effort to investigate and craft a better explanation - with the spring shut down, their a$$es are fully covered. But Doug could benefit by posting some info on his Portal website. Not sure how much this is affecting his business, but the campground is losing money:

Attention: Whitney Portal Campground is open at a reduced rate as there will be no water available until the end of the 2017 season. Recreation.gov will notify reservation-holders impacted by this reduced rate and provide a partial refund. You must bring all the water you will need for your stay including water for drinking, cooking, cleaning, etc. We apologize for the inconvenience.

Are wag bags or shallow catholes contaminating the groundwater? Maybe, but unlikely to be the root cause of this problem. More likely that a person or animal did their business near the spring and it ran off into the springbox. Does this deserve more testing and investigation? Absolutely.