"It is profusely foul," said 39 year Castro Valley resident Theresa Menchini.
She says the offending sewage drops happen weekly, sometimes more. Their neighborhood borders Lake Chabot Regional Park near Lake Chabot and Arcadian roads.
"It's raw sewage. I don't know if it's been treated or not. It certainly doesn't smell like it's been treated," said Chris MacChesney, Castro Valley resident.
MacChesney snapped pictures of East Bay Regional Park District trucks supposedly dumping sewage into pipes at the park. There's a manhole cover with a smaller fitting on top for a hose to be inserted. The prevailing breeze pushes the smell directly east into the neighborhood. Worst still, it lingers.
"Once they were done the odor would linger for an hour in our homes and we would smell like a porta-potty basically," said MacChesney.
"Many of our parks are in rural areas and still need clean and functioning bathrooms so we do have sewer discharge services lined up to help make that happen for the greater community," said Dave Mason, spokesman with the East Bay Regional Park District.
Mason explained that some of the district's 74 parks do not have sewer connections. He didn't elaborate on the system or the dump location in question, but essentially sewage is pumped from bathrooms, trucked to another location, and then pumped into a sewer line. Mason says there's a longstanding contract with Castro Valley Sanitary District for the sewage disposal.
Up until this summer neighbors say the dump location was farther up the hill.
"The people up the hill were complaining about the smell," said MacChesney.
The new location stinks to those in the path of the stench.
"We've tried to ask them what they've done to make this change and nobody really answers the question," said Menchini.
"Personally, I think they should drive it to the sewage plant where sewage should be dropped," said MacChesney.
Mason said the district tests regularly for odor, "tests as recently as this week showed actually no odors in the area."
Residents are considering legal action to stop the sewage disposal near their homes.