Pipeline project will prompt trail closures at Palo Alto nature preserve

Visitors to the Arastradero Nature Preserve in Palo Alto may soon find their hikes disrupted by trail closures and heavy machinery as city crews embark on a two-year effort to stabilize a creek and relocate utility lines.

The city has been planning this project since March 2023, when a hiker noticed the exposed gas line near Arastradero Creek and notified the city. Later that year, city crews deposited cobblestones and other fill into the channel as a temporary measure to protect the exposed pipeline and prevent further erosion of the creek.

Now, the city is gearing up for more permanent improvements. The project that the city is preparing for entails lowering the gas line to protect it from future exposure in case of creek erosion. In addition to the gas line, the area includes an 18-inch potable water pipeline and an 8-inch sewer pipeline — infrastructure that serves the Palo Alto Hills neighborhood in the foothills. Both lines would be relocated away from the creek area.

“By burying the gas pipeline to a sufficient depth and relocating the water and sewer lines to an upland area outside the creek banks, the Project would remove these utilities from the active channel which is a beneficial outcome for the long-term restoration of Arastradero Creek,” a report from the Utilities Department reads.

The Palo Alto Parks and Recreation Commission held two public hearings on the project and voted 6-0 on Tuesday, with Vadim Axelrod absent, to approve a staff recommendation to proceed with improvements.

The construction would unfold in two phases in 2027 and 2028, respectively. The first phase, which is scheduled to take place between June 2027 and October 2027, will focus on construction in the channel. It would involve construction of log structures and weirs in and around the creek to direct water into a shallow pool below the weir. Utility crews would also relocate the gas pipeline in the channel.

The plan presented by utilities department staff calls for building about 10 step pools — constructions that resemble stairs made of stones of different sizes — and 25 “post-assisted log structures,” structures that are made up of logs, cobbles and other natural debris and held together by posts that span the channel, according to a city report.

Aaron Perkins, senior engineer with the utilities department, told the commission that the project “minimizes the impact to the existing habitat by constructing various small structures, mainly built with hand tools in strategic location throughout the creek.”

“This allows the creek to naturally fill itself over time and return the creek to an equilibrium point, which addresses the headcut that caused the pipeline to be exposed,” Perkins told the commission on July 28.

The second phase, which would stretch between June and October 2028, involves relocating the water and wastewater lines away from the creek area, according to utilities staff.

The plan is still awaiting final approval from various regulatory agencies, including the San Francisco Bay Regional Water Quality Control Board. The water board ordered the city to replace the temporary fill with permanent improvements or potentially face a penalty of $5,000 per day.

The board has already issued a preliminary approval for the gas relocation and creek stabilization plan. Perkins said the city expects to get the final approval by end of August. The city is also expecting the U.S. Army Corps of Engineers to issue its permit at the end of September. The City Council is scheduled to consider the project in December.

The parks commission broadly supported the project, which is relying on $386,754.75 in Federal Emergency Management Agency funding and $96,688.69 in state funding, according to staff. Even so, several members urged the council to be transparent about the impacts that the project would have on Arastradero trails.

“Please don’t assume that you can just stage whatever you want there for as long as you want,” former Commissioner Jeff Greenfield said during a public hearing on the project last year. “It impacts the community.”