Inter-Departmental Correspondence

Department of Public Works



October 7, 2002


October 22, 2002


Honorable Board of Supervisors


Neil R. Cullen, Director of Public Works


Crystal Springs Dam Bridge - Reduction in Weight and Speed Limits and Lane and Shoulder Widths - Hillsborough/San Mateo Area



Adopt ordinances reducing:



the weight limit to a maximum of seven (7) tons on the Crystal Springs Dam Bridge (the Bridge); and



the speed limit on the Bridge from 30 miles per hour (mph) to 25 mph.



Adopt a resolution authorizing the Director of Public Works to:



narrow the existing lanes and shoulders on the Bridge from 12-foot-lanes to 10-foot-lanes and from 3-foot-shoulders to 1-foot-shoulders; and



post the necessary signs advising the public of the narrow lanes and shoulders, as well as the load and speed limits.


Previous Board Action

Authorized various agreements since 1987, which provided for the design and the funding to replace the existing bridge on Crystals Spring Dam.


Key Facts


We have been working with the San Francisco Water Department (SFWD) over the past several years to coordinate the replacement of the Bridge with SFWD's plans to raise the parapet wall on top of the dam to improve flood control protection and provide additional water storage.



Our and SFWD's efforts to obtain approvals to have the Bridge replaced and to raise the parapet wall on the dam have been delayed by the conditions for receiving permits from the United States Fish and Wildlife Service (USFWS), as the USFWS is concerned about the California Red Legged Frog, a federal endangered species, that uses a "top of dam" pond for propagation purposes.



Our consultant recently re-evaluated the Bridge and has recommended that the Bridge be posted for reduced loads and that the lanes be narrowed due to the condition of the Bridge's substructure.




Plans for the County's bridge replacement project and the SFWD's dam project must be compatible, and both projects involve environmental issues, which must be resolved before either project can be constructed. The County's bridge project is currently on "hold" as we cannot recommend accepting the conditions imposed by the USFWS for relocating the California Red-Legged Frog (CRLF) from the "top of the dam" pond. We retained an expert on the CRLF and developed a plan to relocate the CRLF into a temporary pond on County property while a new bridge was constructed. However, USFWS rejected this idea and required the use of SFWD's property for a permanent pond, which SFWD was not willing to allow. The USFWS was also requiring the County to establish a perpetual funding source to fund the maintenance of the pond on SFWD's property indefinitely after construction. We could not recommend USFWS's conditions as it committed the County to an open-ended undetermined fiscal burden.


Subsequently, SFWD determined that they needed to find a replacement pond for the CRLF as they will have to relocate the CRLF in conjunction with proposed work in the watershed. SFWD has indicated that there will be room to relocate the CRLF from the "top of dam" pond into their proposed replacement pond and we are now waiting for SFWD to complete the study and receive approval of the replacement pond from USFWS. USFWS has been supportive of SFWD's concept.


Evaluation of the Existing Bridge

We had our structural consultant inspect and evaluate the current Bridge's substructure as several years have passed since the conclusion was reached that the Bridge needed to be replaced to improve the Bridge's seismic strength. The consultant estimates the remaining service life of the Bridge to be between 6 to 10 years if no improvements or repairs are performed, and has also recommended that weight limits be posted on the Bridge. The repairs that are needed to improve its structural capacity would impact the CRLF pond in a similar manner as the Bridge replacement project and the Bridge would still be seismically deficient.


The consultant also recommended that the County consider moving traffic loads away from the west side of the Bridge due to the condition of the most westerly girders on some of the spans.


We are therefore recommending, based on the consultant's evaluation, that a seven (7) ton weight limit be placed on the Bridge and the usable deck area of the Bridge be narrowed. We are also recommending that the speed limit be lowered on the Bridge to reduce the dynamic loading that can also occur at higher speeds. We will place the necessary signs to advise the public of the reduced load and speed limits as well as advisory signs indicating a narrower bridge if your Board approves our recommendations.


Vision Alignment

We believe our recommendations are consistent with the Shared Commitment to "ensure basic health and safety for all" and Goal Number 7 "maintain and enhance the public safety of all residents and visitors," as the proposed load and speed limit, and shoulder/lane reconfiguration will allow for the use of the current bridge while we work with SFWD to meet the conditions of USFWS to allow the bridge replacement project to go forward.


Fiscal Impact

The estimated cost for placing the weight limit signs and the associated cost for narrowing a section of the travel lane width on the Bridge is estimated to cost $16,000 which is proposed to be paid for with Road Funds. There is no impact to the General Fund.


Forms of ordinances and a resolution have been approved by County Counsel.


A copy of our staff report has been sent to the fire departments of the Cities of San Mateo and Hillsborough and to the Division of Forestry as the road may be a route for heavy fire equipment that responds to mutual aid calls.