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HomeMy WebLinkAboutPed Bridge Re-use ReportFeasibility & Cost Analysis for Pedestrian Bridge Re-use Mounds View, Minnesota November 19, 2007 Bonestroo File No. 435-07000-0 INTRODUCTION The City of Mounds View currently has two prefabricated pedestrian bridges stored at its public works facility. The City has requested a brief report discussing the scope of work and costs that would be associated with reusing the bridges within the City. BACKGROUND The two bridges came from the former City-owned golf course near the intersection of I-35W and U.S. Highway 10. The bridges were no longer needed at that location after the site was redeveloped into an office complex by Medtronic. Bonestroo performed a cursory inspection of the bridges on November 8, 2007, and observed the following: x The two bridges appear to be identical x The bridges are prefabricated truss structures approximately 40 feet long and 10 feet wide x The bridges are made of self-weathering steel (“rusty” look, no painting needed), with timber decking x The bridges were designed for a 10,000 pound vehicle, and presumably pedestrian loads x The bridges appear to be in good condition, except for the timber decking x The bridges appear to have been manufactured by Contech (formerly Continental Bridge) in Alexandria, MN. Specific design information can probably be obtained from Contech. Mounds View, Minnesota Project No: 435-07000-0 Pedestrian Bridge Re-use Page 2 OPTIONS The two primary options for dealing with the stored bridges are 1) re-use the bridges at new locations within Mounds View, and 2) sell the bridges. Re-use of the bridges will be discussed in detail later in this report. If the City chose to sell the bridges, a rough estimate of their resale value would probably be in the range of $10,000 to $15,000 each. This resale value is based on an estimated cost of approximately $30,000 for each bridge if they were to be purchased new. There would be no guarantee of finding a willing buyer, as the geometry of the bridges would need to be an exact match for the buyer’s site requirements. RE-USE BRIDGES Re-using the bridges is feasible, provided the new locations match the bridge geometry. The process that would need to be followed involves several tasks, including both design and construction phases. The following is a brief discussion of the tasks that are typically required for the design and construction of a pedestrian bridge crossing, along with estimated costs for each task. DESIGN (PRE-CONSTRUCTION) TASKS x Site Survey. Determine topography, locate utilities and possible construction conflicts, define floodplain for hydraulic analysis. x Wetland Delineation. Determine presence and type of wetlands that could be impacted by construction. x Geotechnical Exploration. Determine subsurface soil conditions and obtain recommendations for bridge foundation support. x Hydraulic Analysis. Determine effect structure will have on channel flow, and possible impacts to floodplain zoning. x Hazardous Materials Investigation. If replacing an existing structure, conduct an investigation to determine presence and disposal requirements of hazardous materials. x Structure Design. Design concrete abutments, prepare construction plan sheets, prepare construction specifications, thorough inspection of existing bridges, coordinate inclusion of salvaged bridge superstructure. CONSTRUCTION TASKS x Deliver Bridge. Bridge must be moved from storage location to new project location. x Abutment Construction. Build new concrete abutments to support bridge, including excavation, backfill, and placement of riprap for scour protection. x Drive Piling. Mobilize pile driving equipment, furnish and drive piling (piling may or may not be required, depending on results of geotechnical exploration). x Install Bridge. Install existing bridge onto new abutments. x Redeck. Replace worn timber decking with new naturally durable timber decking. x Construction Administration. Construction survey, observe and document construction activities, review payment submittals from contractor, and coordination as necessary with the City. Mounds View, Minnesota Project No: 435-07000-0 Pedestrian Bridge Re-use Page 3 COSTS The costs for some of the tasks can be estimated fairly accurately, while other costs would be dependent on the proposed bridge location. The following breakdown gives approximate costs for the various tasks. It must be emphasized that these costs are based on averages from previous projects, and could vary significantly for a specific bridge re-use project considered. Design (Pre-construction) Costs Site Survey $ 2,000 Wetland Delineation $ 1,000 Geotechnical Exploration $ 5,000 Hydraulic Analysis $ 1,500 Haz. Materials Investigation (if required) $ 1,500 Structure Design $ 8,000 Design Subtotal $19,000 Construction Costs Mobilization $ 7,500 Furnish Bridge Superstructure $ 0 Deliver Bridge $ 2,500 Abutment Construction $25,000 Drive Piling (if required) $20,000 Install Bridge $ 7,000 Redeck $ 3,000 Construction Observation $ 4,000 Construction Administration $ 2,000 Construction Subtotal $71,000 Project Total $90,000 The costs shown are for one bridge. The cost to re-use both bridges would be approximately double the total shown, unless both bridges were used on the same project, in which case some overlap of tasks could result in a slight cost reduction. Costs could also be reduced if City staff were able to complete some of the work tasks, such as delivering the bridges to their new locations. Costs do not include any aesthetic features, such as textured or colored concrete. SUMMARY The two bridges currently being stored by the City of Mounds View appear to be in good condition and structurally adequate for re-use at new locations. While the City would not incur any costs for the bridges themselves, re-use of the bridges would result in a significant expenditure by the City due to the many tasks required in the design and construction processes.