City of Pleasanton staff and several members of a disgruntled neighborhood will form a panel to look into the cause of soil shrinkage that is causing substantial damage to some Pleasanton homes.
City staff met with dozens of members of the Gates neighborhood Thursday night to go over their analysis of a prior Zone 7 Water Agency study that evaluated the likelihood of soil subsistence in the Livermore Valley.
Residents of the Gates neighborhood, located just south of West Las Positas off Sutter Gate Park, were concerned with the cracks in their foundations, walls and driveways that have been appearing in the past few years, asking for answers to the shifting soil that has caused the damage.
Neighbors had previously questioned whether Zone 7's nearby well, which pumps groundwater from the deep underground aquifer, was the cause of the problem.
"I can say to a huge degree of certainly, like 99%, that the settling is not due to overpumping of wells," city of Pleasanton assistant director of operations services Leonard Olive stated.
Staff stated they believed Zone 7's analysis that the clay and silt that forms the structure for most of that neighborhood dried out faster than other components of the soil during the four-year drought, causing the areas with clay to shrink faster than the areas with dirt or gravel. The result is an uneven ground, cracking roads and home damage, he said.
A contractor hired by Zone 7 in the summer stated if soil collapse due to groundwater pumping -- called subsistence -- were occurring, the ground would be sinking evenly over a wide area and the Zone 7 well heads would be drastically higher than the soil level.
Neither situation is occurring in Pleasanton, the contractor stated at a community meeting in August. City engineers agreed with that assessment at Thursday's meeting.
However, some members of the neighborhood want a more through look at what is happening deep underground since Zone 7's study only looked at topsoil disruption.
Gates resident Michael Grossman said he and some of his neighbors weren't convinced, given the scope of the prior study, that Zone 7 pumping isn't at least partially responsible.
"Some Gates home foundations have dropped eight inches or more. Some repaired more than once. Some have cost $100,000 to repair the foundation, out of pocket," Grossman said.
Since members of the neighborhood feel uneasy about the determination -- and don't have viable solutions to prevent additional damage to their homes as long as a drought persists -- the community panel will do additional research to answer any lingering questions, Olive said.
The panel will be made up of city staff and four or five members of the Gates community. Once representatives are chosen, the City Council will be presented with a proposal for what the panel wants to investigate, how long it would take and what budget the panel would like to request, said Councilwoman Kathy Narum.
The council would have to vote to approve any proposal before the panel could start working, she said.
Narum said since a large group of residents are concerned about this issue, it makes sense to listen to their voices and study the issue further.
"I think the staff wants to take some time and try to get some answers to some of the questions," she said.