Roughly three months and $4.55 million later, Zone 7 Water Agency has completed a bank stabilization project in the 7800 block of Foothill Road where homes were threatened by significant erosion last winter.
Crews wrapped up the project in mid-December when the final plants were installed on the rebuilt slope, according to Carol Mahoney, Zone 7 manager of integrated water resources.
“It’s really nice to see that we were able to come together with the regulatory agencies and come up with a plan that did not involve really hardscape types of solutions,” Mahoney said in a recent interview. “We were able to see how we can create a more natural slope in the area and encourage the stream to react more like a natural stream in that area as opposed to using things like steel piles or concrete.”
The bank stabilization work began late last summer.
Crews cut away a portion of the slope at 3 Verona Way — a vacant parcel that Zone 7 used eminent domain to acquire, arguing it was necessary for the project — and pushed the slope back to divert water flow away from homes. Water was also diverted downstream through pipes while heavy equipment operated in the creek.
Soil and rock was put inside geotextile fabric that was then wrapped up and placed against the eroding slope, one layer stacked on top of the next.
Construction finished around Nov. 1. The slope was then planted and seeded so grass can grow on top.
Crews continue to visit the site for monitoring and maintenance.
Asked how the new design has done in stormy weather this winter, Mahoney said, “so far so good.”
“We’ve seen the site holding up well and directing the water exactly where we want it to,” she said.
Zone 7 opted for the geotextile fabric slope after initial design options proposed for a permanent repair, including ones that involved supports made from large rocks or metal beams, were rejected by regulators who give out construction permits.
The geotextile fabric design also proved to be more expensive. In August, the Zone 7 Board of Directors authorized spending an additional $2.85 million on the project — on top of $1.7 million approved in March — bringing the total cost to approximately $4.55 million including contingency.
Crews initiated an interim repair in March to guide the majority of the water toward the center of the channel and away from the eroded bank while Zone 7 staff worked on a design for a permanent repair.
The erosion was first brought to the agency’s attention by the Belshe and Raun families, next-door neighbors in the 7800 block of Foothill who lost much of their creekside backyards amid heavy rains last winter. A gradual change in the configuration of the Arroyo de la Laguna — which homeowners have asserted is a result of development upstream — created an s-turn that was propelling water toward their properties and caused ground to erode away.
Zone 7 holds an easement for the Belshe and Raun properties, along with seven other parcels on Foothill Road and the arroyo, which gives them the right to “construct, maintain, operate, inspect, and repair flood control facilities and appurtenances.” Up until March, the agency had never undertaken projects there. The creek within that area is owned by the residents themselves.
Homeowner Dave Raun said in an email Tuesday that he thought Zone 7 “did a nice job” with the bank stabilization work.
“I believe this should protect homes in this area,” Raun said.
He continued, “I do believe with the continued growth upstream, Zone 7 and the other agencies must come up with a solution for the entire arroyo that is next to homes. Individual homeowners are helpless with this and only an agency like Zone 7 can make this work. It is just a matter of time before we have a disaster impacting many people.”
