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HomeMy WebLinkAbout10-21-2014 C5 Prado Road. Bridge WideningCity of San Luis Obispo, Council Agenda Report, Meeting Date, Item Number FROM: Darryl Grigsby, Public Works Director Prepared By: Jake Hudson, Traffic Operations Manager SUBJECT: PRADO RD. BRIDGE WIDENING, SPECIFICATION NO. 91203 RECOMMENDATION 1. Approve “Alternative 1” as the preferred conceptual design for the Prado Rd. Bridge widening project as recommended in the feasibility report by Wallace Group and Quincy Engineering, and proceed with the environmental study and engineering for the “Prado Rd. Bridge Widening, Specification 91203”. 2. Appropriate $390,000 in Transportation Impact Fee funds for continuing project study and engineering. 3. Authorize staff to pursue potential 2017 construction funding thru the Federal Local Highway Bridge Program (HBP) as administered by Caltrans. DISCUSSION Background Prado Road between Higuera Street and US 101 is currently wide enough to accommodate four lanes, sidewalks and bike lanes with the exception of the San Luis Creek Bridge. At this location the bridge accommodates one vehicle lane in each direction. This structure is identified for widening as part of the City’s Circulation Element (Both 1994 & 2014) and has been incorporated into the Transportation Impact Fee Program. The widening of Prado Road is assumed as a completed project in traffic impact analysis of several Environmental Impact Reports for projects within the vicinity, in particular, recent development activity within the Margarita and Airport Area. Widening of the San Luis Creek bridge is a prerequisite for the mitigation measures and traffic improvements associated with those projects. If the bridge is not widened in a timely manner, developers would be precluded from implementing their required mitigation. Widening is already needed to accommodate pedestrian and bicycle traffic in the area. As part of the 2013-15 Financial Plan, the Council authorized staff to begin work on the bridge, and therefore allocated funding to conduct a preliminary project study report. That report is now complete (available in Council Reading File) and a preferred alternative has been identified. Staff is now requesting the Council approve the preferred alternative and appropriate Transportation Impact Fee (TIF) funding to continue design and environmental work through the end of the fiscal year. Funding for the remaining work through 2016-17, will be requested as part of the next Financial Plan. Project Alternatives The project study evaluated three alternatives for bridge widening: 1) replacing the existing bridge with a new single span bridge, 2) replacing the existing bridge with a three span bridge, and 3) rehabilitating the existing bridge and attaching new bridge structures to either side. The 10/21/2014 C5 C5 - 1 PRADO RD. BRIDGE WIDENING, SPECIFICATION NO. 91203 Page 2 preferred alternative is to replace the existing bridge with a single span due to the improved hydraulic conveyance of the creek, reduced environmental impact, and reduced construction time and impact to surrounding businesses. A summary and graphic of these three alternatives are provided below. Alternative 1 (Preferred): Remove Existing Bridge & Replace with New Single Span Bridge This alternative involves completely removing the existing bridge and replacing it with a “single span” bridge which has no piles driven into the creek bed, the existing piles would be removed. The study shows this type of bridge will have the lowest environmental impact, the greatest improvement of the hydraulic flow under the bridge (increase of 25% for the 10 year flow and 37% for the 100 year flow), and allow for some offsite construction of bridge components minimizing construction time and impacts to surrounding businesses. This alternative also provides greater protection to water and sewer utilities attached to the existing bridge deck. This is the most expensive bridge which is estimated at $3.3 million. Figure 1: Preferred Alternative C5 - 2 PRADO RD. BRIDGE WIDENING, SPECIFICATION NO. 91203 Page 3 Alternative 2: Remove Existing Bridge & Replace with New Three-Span Bridge. Alternative 2 involves completely removing the existing bridge and replacing it with a similar type of bridge which spans the creek in three sections, each being supported by a set of 14 piles driven into the creek bed. This alternative has the thinnest bridge deck, providing the greatest clearance above the creek and improves hydraulic conveyance over the existing bridge; however the number of piles increases the expectation of debris snags and blockages during heavy storms. This type of bridge will require construction of significant temporary form work to support the construction of the actual deck, increasing the environmental impacts and construction time. This Alternative leaves the gravity sewer exposed to possible damage from high creek flows. An upstream horizontal protection member for the utility lines would need to be constructed. This element would eliminate the increased channel opening of this bridge and reduce the benefits gained from the thin deck section. Since this bridge also includes supporting piles in the channel, it has less improved flow capacity than Alternative 1. The cost of this alternative is estimated at $2.7 million. Figure 2: Alternative 2 Alternative 3: Rehab Existing Bridge & Widen to Either Side. Alternative 3 involves rehabilitating the existing bridge and constructing new bridge structures to either side. The existing bridge is over 55 years old and nearing the end of its structural life expectancy. The deck has significant cracking and exposed reinforcing steel. The bridge can provide many years of service with increased maintenance. That work however, would not equal the life span of a new structure. The City would be faced in the future with replacing the old section, in the midst of the new bridge. As with Alternative 2, this bridge will be constructed in multiple sections founded on piles driven into the creek bed, requires significant temporary form work, has a longer construction time and greater environmental impacts than Alternative 1, and will leave the gravity sewer line exposed. The cost of this alternative is the least expensive, estimated at $2.6 million. Figure 3: Alternative 3 C5 - 3 PRADO RD. BRIDGE WIDENING, SPECIFICATION NO. 91203 Page 4 Public Art Impact The preliminary project study report showed the potential need for a minor movement of the “Oh Great Spirit” public art piece at the corner of Prado Road and South Higeura, however it’s anticipated that this can be avoided thru design refinements. CONCURRENCES The Utilities and Natural Resources Departments are a part of the project working group and concur with the recommendation. ENVIRONMENTAL REVIEW The preferred alternative based on this initial assessment is projected to have the lowest impacts and greatest hydraulic improvement at the bridge. Formal environmental review will begin as part of this next phase of work. All project specific approvals based on this preferred conceptual alternative will be subject to formal environmental assessment, including, but not limited to, consideration of various mitigation measures and project alternatives that are ordinarily part of the CEQA review process.. FISCAL IMPACT The preliminary phase of project work, which includes Environmental, Right-of-Way acquisition, and Design was estimated to cost approximately $1.2 million through 2017, funded from the Transportation Impact Fee (TIF) program. The TIF account has $3.4 million in unspent revenues with $2 million appropriated to various other higher priority projects, leaving a balance of over $1.4 million not currently appropriated. This balance is sufficient to fund the requested $390,000. Budget for preparation of the final construction specifications, construction, and construction management will be submitted for approval as part of the 2015-17 Financial Plan. It’s important to note that the Transportation Impact Fee program now has an obligation of at least $250,000 per year to pay for the LOVR overpass project debt service starting this year. Staff is actively monitoring TIF revenues to ensure that this funding request or any others do not impair the TIF program’s ability to pay that $250,000 debt service obligation. Grant Funding Potential for Construction Based on the preliminary project studies, the estimate for construction of the bridge is between $2.6 million and $3.3 million (not including soft costs), currently proposed to be funded through the TIF Program. The current financial plan points out that construction funding may need to be provided by some form of debt financing or outside funding sources. Based on recent research, one potential outside funding source may be available. It has been determined that the project C5 - 4 PRADO RD. BRIDGE WIDENING, SPECIFICATION NO. 91203 Page 5 may qualify for construction funding under the Highway Bridge Program depending on an assessment from the State Office of Structures. Staff is requesting Council authorization to pursue this potential source of grant funding. ALTERNATIVES 1. Reject Alternative 1 and Select Alternative 2 or 3. The Council may choose to select alternative 2 or 3, however this not recommended as alternative 2 and 3 have greater environmental impacts and do not fully address all of the current bridge issues such as exposure of the gravity sewer and the structural life of the current bridge. 2. Defer the Project. The Council may choose to defer the project; however, this project is a prerequisite for mitigation measures of approved development and is needed already to address pedestrian and bicycle access. Delaying this project could create a situation where Margarita and Airport area development are precluded from completing traffic mitigation measures and traffic generated by those developments far exceed available capacity leading to unacceptable levels of congestion. AVAILABLE FOR REVIEW IN THE COUNCIL OFFICE Prado Road Bridge Widening: Preliminary Analysis T:\Council Agenda Reports\2014\2014-10-07\Prado Rd. Bridge Widening (Grigsby-Hudson)\Council Agenda Report Prado Bridge Widening.docx C5 - 5 Page intentionally left blank. C5 - 6