Permanente Creek project protects homes, businesses, the environment

The Santa Clara Valley Water District has long championed the benefits and need for the Permanente Creek Flood Protection Project, and the Santa Clara County Civil Grand Jury released a report this month that agrees.

The project is an effort to protect 2,200 homes and businesses, including schools and a hospital, from what is known as a 100-year flood, or a flood that has a 1-in-100 chance of happening in any given year. It includes work in Rancho San Antonio County Park, McKelvey Park in Mountain View and along Permanente and Hale creeks.

The project is representative of the holistic approach the water district takes to flood protection, in which we evaluate the entire length of the stream instead of concentrating on separate segments without regard to their effect on upstream and downstream neighbors.

The community was also involved in the long process to determine the best project. Over 10 years, the water district collected public input and evaluated 26 alternative project ideas to find the one that best met the goals of the project and reflected community values.

That includes taking a natural flood protection approach, which means that whenever possible, we blend our work with the existing environment. Not only is the result visually appealing, but it improves habitat, and the Permanente Creek Flood Protection Project will increase and enhance habitat for the endangered California red-legged frog as well as provides potential to restore downstream river habitat.

Besides flood protection, the Permanente project will provide other elements in Rancho San Antonio that will benefit neighbors as well as park-goers. These include:

  • A gently sloped, 15-foot-deep vegetated detention basin in Rancho San Antonio park;
  • Replacement of the existing maintenance bridge;
  • New bathrooms;
  • A new, larger, paved parking area that increases the number of defined spaces from 25 to 59;
  • Dozens of new, native trees;
  • Removal of non-native trees that compete with the native landscape.

Detention basins are the most environmentally sensitive approach to flood protection and are supported by regulatory agencies such as the state Department of Fish and Wildlife and the U.S. Fish and Wildlife Service, among others.  The detention basins also help the water district avoid building costly floodwalls and levees downstream through dense residential and commercial areas.

In McKelvey Park, the detention basin is expected to be used only during an approximately 50-year flood or larger. Features include:

  • New 0.7-acre mini-park facility with playgrounds and other features;
  • Construction of an inlet and outlet to allow water flows to enter and exit the fields;
  • Architecturally treated retaining wall around the lowered fields;
  • Basin to collect peak storm flows from Hale and Permanente creeks; and
  • Replacement planting and landscaping

Farther downstream, the project will build 2- to 3-foot floodwalls on top of the existing Permanente Creek levees from Charleston Road to U.S. Highway 101, channel modifications from Mountain View to Valencia Avenue and a new culvert at Mountain View Avenue for Hale Creek.

Altogether, the two detention basins and floodwalls will provide flood protection for thousands of households and businesses in Mountain View and Los Altos.

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The Civil Grand Jury investigated the project, and in its report issued this month, stated that it “did not discover credible data to support the allegation of fraud or to invalidate Water District engineering decisions regarding this project.”

In fact, the Grand Jury issued two positive findings:

  1. The Santa Clara Valley Water District Permanente Creek Flood Protection Project has the potential to prevent flooding of some residential and commercial properties within the cities of Los Altos and Mountain View; and
  2. Completion of the Permanente Creek Flood Protection Project could result in redefinition of the flood plain by the Santa Clara Valley Water District and the Federal Emergency Management Agency with subsequent removal of the requirement for flood insurance for some properties in the cities of Los Altos and Mountain View.

While the water district has remained confident in the engineering and design of the project, the Grand Jury’s report joins an independent review of the project’s hydrology by an outside firm hired by Mountain View in helping put to rest any doubt anyone may have. The water district will move forward even more confident in this project that will save property owners more than $1 million in flood insurance every year, protect against flood damages, and put at ease the minds of those living and working in an area that has experienced significant historical flooding.

The next step for this project is for the water district Board of Directors to advertise for construction bids so work can begin. The bid advertisement is scheduled for June 28 at 6 p.m. as part of the board’s regular meeting.

Learn more about this project at



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