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Department staff and the County’s engineering consultant have studied options to address the structurally deficient status of the bridge, and have engaged the community to gauge support for various alternatives. Board direction is desired before returning in the fall with a recommendation for the type and alignment that will be submitted to Caltrans for funding approval.
BACKGROUND:
The Rumsey Bridge is located on County Road 41, and provides the only all-weather access to properties on the east side of Cache Creek near Rumsey. (See Attachment A) The arch portion of the bridge was built in 1930, and after a major flood event damaged the northeastern abutment, the bridge was lengthened in 1949. Highlighting the unpredictable nature of Cache Creek, the southwestern approach was nearly destroyed in the 1995 flood events, and the bridge was out of service until repairs could be made.
Caltrans inspects the bridge every two years. Since the 1960s, Caltrans inspection reports have noted problems with concrete spalls and exposed reinforcing steel on the arch bridge, attributed to poor concrete quality and construction. The latest inspection report classifies the bridge as structurally deficient, with a ‘sufficiency rating’ of 37.7 out of 100. As a result of this classification, the bridge is eligible for rehabilitation or replacement under the Highway Bridge Program (HBP) administered by Caltrans.
Under current funding rules, approved HBP projects on local roads such as County Road 41 are effectively 100% funded, though this has only been the case since 2010. Before 2010, HBP projects required an 11.47% local match. In the 1990’s the local match requirement was 20%. In the early 1990’s the County requested and received HBP funds to repair the bridge, but had to abandon the effort because of insufficient local match funds. The current funding rules represent a significant opportunity for the County to address the ongoing risks of maintaining the serviceability of this bridge in the long term.
The County retained Quincy Engineering, Inc. to analyze the existing bridge and study alternative solutions. Their modeling has determined that the bridge is not seismically stable, nor is it able to resist scouring events that creek flows could produce. Staff has held several informational public meetings with local residents about the potential repair or replacement options, and most recently Quincy’s draft June 2014 Feasibility Study was presented at a public meeting at the Rumsey Town Hall. It is also posted on the County website. (Attachment D) The community provided feedback on this work, and there was strong community sentiment to save the existing bridge, although doing so was not the most cost effective solution. The bridge is a beautiful structure, considered to be a landmark by many in Rumsey.
In the past, Caltrans has only approved HBP funding for the most cost effective solution that corrects all of a bridge’s deficiencies, and the solutions studied in the draft feasibility study were limited. Following the July 2014 Town Hall meeting, County staff met with Caltrans HBP management staff to discuss the project and the community’s concerns with the lowest cost ‘freeway style’ bridge. Somewhat surprisingly, there was an indication that alternative designs for a new bridge that incorporated elements that would perpetuate some of the historical attributes of the existing arch bridge might be considered for funding, including a replacement arch. This led to the development and initial analysis of 3 additional arch-style bridge designs, all of which are shown in Attachment B. Quincy’s estimates indicate that any of the arch style bridges would be less expensive to build from scratch, as compared to rehabilitating the existing bridge. Any of the arch style bridges are more than twice the cost of the least expensive box girder option. Due to the historical nature and aesthetics of the existing bridge, the environmental clearance process is likely to be less onerous if replaced with an arch style bridge. Of these alternatives, one must be selected to be incorporated into a final Feasibility Study. Once the Study is finalized, a formal request can be made to Caltrans for funding.
As one measure of public opinion, a survey was mailed to 108 property owners of record in the Rumsey area in April 2015, with postage-paid return envelopes. Only 38 surveys (35%) were returned. 58% of the respondents showed an affinity for one of the arch bridge variants, and 39% favored the more cost effective box girder alternatives. The arch design alternative with the most support (47%) was replacement in-kind. The survey results and the mailed survey are shown in Attachment C.
Aside from the bridge type selection, there is also the question of alignment. The bridge layouts shown in Attachment B all assume a new alignment, however to an extent, the type selection decision affects the alignment decision. Alignment decisions are affected by historical and cultural considerations, as well as the cost of a temporary bridge, if the existing alignment is to be maintained. Once the preferred type of bridge has been determined, an analysis of the costs of different alignment scenarios can be completed, to support the alignment decision. Staff envisions returning to the Board later this fall to finalize the selection of bridge type and alignment. |