Crystal Springs Dam Bridge Reopened to Motorists, Bicyclists

Article Source: County of San Mateo CA

Below is a news release on the exciting opening of Crystal Springs Dam Bridge.

Above Photo: Courtesy of SFPUC.

Jan. 11, 2019

Crystal Springs Dam Bridge Reopened to Motorists, Bicyclists & Pedestrians

County of San Mateo and SFPUC celebrate significant improvements and new trails

Redwood City — When the Crystal Springs Dam opened in 1888, Benjamin Harrison was the nation’s 23rd president, National Geographic magazine published for the first time and gasoline-powered automobiles were in their infancy.

After 130 years, much has changed in the world but the concrete gravity arch dam in unincorporated San Mateo County that served as a model for the Hoover Dam is significantly improved and with a new bridge that re-opened Skyline Boulevard to bicyclists, pedestrians and vehicles of all engine types.

The County of San Mateo Public Works and Parks departments, the San Francisco Public Utilities Commission (SFPUC) and other critical partners gathered Friday, Jan. 11, 2019, to celebrate the highly anticipated completion of the multi-faceted project which includes critical safety and water capacity improvements to the dam and provides new travel opportunities on the bridge and adjacent recreational trails.

County Supervisor Dave Pine told the assembled crowd that the multi-faceted project would not have been possible without close collaboration by several entities including the SFPUC which owns the dam, the County’s Department of Public Works (DPW) which replaced the entire bridge on top of the dam, County Parks which constructed the new trail segment and PG&E which relocated high-voltage transmission lines to the bridge’s underside.

“This watershed is among the most beautiful views in San Mateo County and I’m proud of the partnerships that made strengthening the dam and reopening the bridge possible,” Pine said. “It’s exciting after so long to see the first visitors travel across.”

The Lower Crystal Springs Dam crosses San Mateo Creek, forming the Upper and Lower Crystal Springs Reservoirs and is part of the SFPUC’s Hetch Hetchy Regional Water System. The structure is a concrete gravity arch dam, engineered in a way that revolutionized the dam and concrete industries and served as a model for Hoover Dam. Skyline Boulevard, also known as Highway 35, runs over the dam and has been closed to auto traffic between Crystal Springs Road and Bunker Hill Drive due to the interconnected projects needed to improve the dam and road.

State Sen. Jerry Hill, D-San Mateo, who served as a San Mateo County supervisor when the project plans were still on the drawing board, was excited to mark its completion.

“This is not just a celebration of the completion of an important project. It’s a new beginning for one of our county’s most extraordinary recreational and environmental resources,” Hill said.

From 2010 to 2011, before the SFPUC could begin its $35 million in renovations, DPW removed the original 1920’s era bridge from the top of the dam. That same year, the SFPUC began its improvements which include doubling the width of the spillway to 200 feet and raising the parapet wall on top of the dam by 9 feet. Construction of the dam finished in December 2012.

“More than one million people on the Northern Peninsula depend upon the drinking water stored in the reservoirs in this watershed,” said Steven Ritchie, the SFPUC’s assistant general manager for water. “By working together with our San Mateo County partners, we have been able to upgrade and maintain these crucial facilities for future generations.”

Meanwhile, the Board of Supervisors approved $13.1 million for the new bridge which is reimbursed with Federal Highway Bridge Replacement and Rehabilitation Program funds. Construction began in February 2016 and the new bridge includes a separate section for Crystal Springs Regional Trail users to connected to a new “South of Dam” trail section completed in 2015. Major construction finished in October 2018 with finishing touches made in the months leading up to Friday’s celebration.

The complexity of the interconnected projects was further challenged by its location in an environmentally sensitive area that houses the dusky-footed wood rat, California red-legged frog and San Francisco garter snake. But despite the hurdles, everyone involved lauded the outcome.

“There’s no question everyone involved had a lot to contend with on the road to success but I’m proud to say we did it and thankful for the patience of the community which has been so eager to see it complete,” County Public Works Director Jim Porter said.

FACT SHEET

Lower Crystal Springs Dam Improvements and Skyline Bridge Replacement Projects

Highlights, Timelines & FAQs

In 2018, work was competed on several interconnected efforts by the County of San Mateo and the San Francisco Public Utilities Commission (SFPUC) to make improvements to the Lower Crystal Springs Dam and replaced the bridge on top of the dam, which allows the re-opening of Skyline Boulevard. Below are some key facts:

Lower Crystal Springs Dam Improvement Highlights (SFPUC Project):

• Doubling the width of the spillway to 200 feet
• Raising the parapet wall on top of the dam by 9 feet
• Replacing the stilling basin (which stills released water before it enters San Mateo Creek) with a new larger basin and erosion protection at the toe of the dam
• $35 million total project cost, over two years (completed December 2012)
• The new bridge is 626 feet long and 51.5 feet wide and approximately 7 feet higher than the former bridge.
• Constructing retaining walls at the Scenic Vista Point parking area due to the change in bridge elevation.
• Created a new 15-foot wide recreational trail on the west side of the bridge that is separated from vehicular traffic and providing connectivity for Crystal Springs Regional Trail users.
• Installed new split rail fencing.
• A new trail section south of the bridge allows trail users to continue along the Crystal Springs Regional Trail to the relatively new “South of Dam” trail section.
• PG&E relocated overhead 230kV electrical transmission lines to the underside of the new bridge.

Skyline Bridge Replacement Highlights (County of San Mateo project):

Timeline:

1888: Crystal Springs Dam is built by Spring Valley Water Company, the private predecessor of the SFPUC.

1890: The dam is raised.

1911: The dam is raised again.

1987: The County was approved to receive Federal Highway Bridge Replacement and Rehabilitation Program funding to replace the existing bridge.

1988: The California Division of Safety of Dams deems the dam’s existing spillway too small, leading the SFPUC to lower water levels in Crystal Springs Reservoir by approximately 3.6 billion gallons.

2002: As part of the $4.8 billion Water System Improvement Program to upgrade the Hetch Hetchy Regional Water System, the SFPUC plans to modify the Crystal Springs Dam to allow it to bring the reservoir back up to historic capacity.

2010-2011: The San Mateo County Department of Public Works closed Skyline Boulevard between Crystal

Springs Road and Bunker Hill Drive to remove the original 1920’s era bridge from the top of the dam.

2011: The SFPUC begins the dam renovations.

2012: Construction on the dam finishes in December.

2015: San Mateo County Parks completes a new “South of Dam” trail section.

2016: Construction begins on the new bridge.

2018: Major bridge construction completes.

2019: Skyline Boulevard is reopened.

January 2019

Lower Crystal Springs Dam Improvements and Skyline Bridge Replacement

Frequently Asked Questions:

Who owns the dam?

The San Francisco Public Utilities Commission (SFPUC) owns and operates the Hetch Hetchy Regional Water System, which delivers high-quality drinking water to 2.7 million customers in four Bay Area counties. THE SFPUC also owns three drinking water reservoirs, including Crystal Springs (upper and lower)

Why is the dam historical?

Spring Valley Water Company, the private predecessor of the SFPUC, built the dam in 1888. The dam was raised in 1890, and again in 1911. Lower Crystal Springs Dam is a gravity arch dam, engineered in a way that revolutionized the dam and concrete industry.

One of the first concrete dams on the West Coast, it consists of interlocking concrete blocks that were poured in place using a precise mix dictated by Chief Engineer Hermann Schussler. Each block cured before the neighboring block was poured, and the joints were sealed with cement. The result is a strong dam with vertical joints that do not align. Although located adjacent to the San Andreas Fault, the dam survived both the 1906 and 1989 earthquakes without any significant damage. This dam served as a model for Hoover Dam.

The Lower Crystal Springs Dam crosses San Mateo Creek, forming the Crystal Springs Reservoirs (upper and lower) and connects to the Hetch Hetchy Reservoir. Skyline Boulevard, also known as Highway 35, runs over a bridge on top of the dam.

Why was the dam renovated?

In 1988, the California Division of Safety of Dams reevaluated the Probable Maximum Flood for Crystal Springs Reservoir and deemed the dam’s existing spillway to be too small. Spillways are important safety features for dams and allow high water flows to safely bypass around or over a dam. Due to the new Probable Maximum Flood calculations, the SFPUC lowered water levels in Crystal Springs Reservoir by approximately 3.6 billion gallons of available storage until appropriate spillway modifications could be made.

As part of the $4.8 billion Water System Improvement Program to repair, replace, and seismically upgrade the Hetch Hetchy Regional Water System, the SFPUC began construction to modify the spillway, parapet wall, and stilling basin of Lower Crystal Springs Dam in 2011. The goal of construction was to enable the dam to be able to accommodate the new Probable Maximum Flood and allow the SFPUC to bring the reservoir back up to historic capacity. With the project now complete, the SFPUC will be able to incrementally raise the storage elevation in the reservoir as restoration commitments are achieved for native plants and animals around the reservoir in future years. The project also included new valves that release water downstream to San Mateo Creek to support steelhead and other native species.

How much did the dam renovations cost? $35 million.

Why was the bridge replaced?

To improve seismic safety and to be raised to accommodate the increased height of the SFPUC parapet wall (dam improvements).

How was the bridge replacement funded?

The bridge replacement project was predominantly funded with Federal Highway Bridge Rehabilitation and Replacement funds that will reimburse the $13.1 million approved by the Board of Supervisors. Applying for and receiving federal Funding requires many environmental studies, approvals from respective regulatory agencies as well as engineering design approvals from Caltrans, State Department of Water Resources Division of Safety of Dams and the SFPUC.

Lower Crystal Springs Dam Improvements and Skyline Bridge Replacement

What agencies were involved?

The County of San Mateo

San Francisco Public Utilities Commission

Pacific, Gas & Electric

Caltrans

Federal Highway Administration

California Department of Water Resources, Division of Safety of Dams

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Robert Riechel

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