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HomeMy WebLinkAbout2010-10-06 PACKET 08.A.REQUEST OF CITY COUNCIL ACTION COUNCIL AGENDA MEETING ITEM # DATE 10/06/10 Engineering ORIGINATING DEPARTMENT Jennifer Levitt STAFF AUTHOR COUNCIL ACTION REQUEST Approve the recommendation to the concrete girder bridge ravine crossing option with the recommendations from the sub - committee. STAFF RECOMMENDATION Council approve the concrete girder bridge ravine crossing option with the recommendations from the sub - committee. ADVISORY COMMISSION ACTION DATE REVIEWED APPROVED DENIED ❑ PLANNING ❑ ❑ ❑ ❑ PUBLIC SAFETY ❑ ❑ ❑ ❑ PUBLIC WORKS ❑ ❑ ❑ ❑ PARKS AND RECREATION ❑ ❑ ❑ ❑ HUMAN SERVICES /RIGHTS ❑ ❑ ❑ ❑ ECONOMIC DEV. AUTHORITY ❑ ❑ ❑ ❑ ❑ ❑ ❑ -6: e ® MEMO /LETTER: Jennifer Levitt, September 26, 2010. ❑ RESOLUTION: ❑ ORDINANCE: ❑ ENGINEERING RECOMMENDATION: ❑ LEGAL RECOMMENDATION: ❑ OTHER: Site Design Sub Committee Minutes. ADMINISTRATORS COMMENTS City Administrator Date COUNCIL ACTION TAKEN: /APPROVED ❑ DENIED ❑ OTHER CITY OF COTTAGE GROVE MINNESOTA To: Honorable Mayor and City Council Ryan Schroeder, City Administrator From: Jennifer M. Levitt, P.E., City Engineer Date: September 26, 2010 Re: Ravine Parkway — Phase 2 Ravine Crossing Options VM7 The City Council on July 7, 2010 authorized the preparation of a feasibility report for the Ravine Parkway Phase 2 extension to serve the proposed Public Safety /City Hall facility. Then on August 6, 2010 the Council approved the feasibility report and ordered the project. The feasibility report outlined different structural options to facilitate crossing the ravine. The options included a con -span arch, steel pony truss and a concrete girder bridge. The next step that is necessary to ensure that the project is completed in 2011 is the selection of a ravine crossing. Discussion The options for the ravine crossing were presented to the site design sub - committee for review and design consideration. The sub - committee received a presentation from a structural bridge engineer from S.E.H. on the three crossing options, pros and cons of each structure type, cost comparisons, maintenance concerns and architectural treatments that are available to each structure. The ravine crossing would provide for motorists and pedestrians to cross at road grade, but there would also be a trail crossing below the structure in the bottom of the ravine. The trail would be a key entry point into Cottage Grove Ravine Regional Park. Below is an outline of each structure type and specific design details related to each option. Steel Pony Truss The steel pony truss to cross the ravine would need to be 74' in clear span and would have an estimated construction cost of $780,000. The pony truss is an attractive bridge providing character, formality and grandeur for both motorists and trail users. Pros: • Creates a small foot print in contact with the ravine • Provides for an open feeling for the trail user • Attractive structure from roadway above and trail below Cons: • Structure is a fracture critical truss design and will meet with some approval resistance • High initial construction cost • Higher maintenance costs for deck (resurfacing 20 -30 years) and truss painting • Salt sensitive which will increase routine maintenance to structure in the spring • Retaining wall will be required to separate water and trail Con -Span Arch The con -span arch would have 42 feet in clear span and would have an estimated construction cost of $610,000. The con span provides for architectural enhancement of the precast span and wing walls to provide for a welcoming feel for trail users into the park. The motorist will not experience a feeling of crossing the ravine because there is no bridge deck, just a typical road surface. Pros: • Lower initial construction cost compared to the pony truss • Maintenance cost is the lowest of the three options Cons: • Large footprint of impact in the ravine (more tree loss) • More enclosed feeling for the trail users (tunnel effect) • Less attractive to motorists' vantage point on the roadway • High potential for graffiti and vandalism • There is limited view of the ravine as one is traveling down gradient Concrete Girder Bridge The concrete girder bridge would need to be 74' in clear span and would have an estimated construction cost of $580,000. The single -span pre- stressed concrete girder design helps motorists to clearly identify and experience the great views of the ravine, while at the same time allowing trail users a very open view of the ravine they are descending. Pros: Lowest initial construction cost Small footprint in contact with the ravine More open feeling for trail users Better advantage to taking in the views of the ravine Cons: Moderate maintenance (deck re- surfacing 20 -30 years) Retaining wall will be required to separate water and trail The sub - committee recommended proceeding with the concrete girder bridge with the addition of the following architectural treatments: • Provide for an arched valance treatment to the structure to enhance the aesthetic view of the bridge to trail users, while not reducing the views of the ravine • Provide for decorative rail, but keep it low to not detract from the ravine views • Provide for limestone texture finished concrete • Provide for parapets limestone entrance features • Utilize the Ravine Parkway standard decorative lighting for bridge Below is a sample of the features and style outlined by the subcommittee for the look of the bridge (replace the field stone for limestone in the figure). 3 Applying a valance or skirting to a concrete girder bridge is typical to add more character, interest and soften the lines of the bridge. Below are two recent projects that utilized a valance to give more shape and visual appeal to local bridges. The picture to the left is of the Margret Street Bridge over TH 36. The bridge design utilized an arched valance to add visual appeal in conjunction with the more formal brick pattern accents. Below is the Raymond Avenue Bridge. It utilized a simple concrete valance with the contrasting form -lined limestone pattern on the abutment and wing walls of the structure. The limestone pattern carried through on the abutment to enhance the visual experience of the pedestrian. This would be a similar design that could be used on the ravine crossing which would improve the aesthetics of the bridge for trail users and remove a flat/smooth surface for potential graffiti. 11 Since this is a MSA route and MSA funds will be utilized for the project, the bridge design will go through extensive bridge review with the Department of Transportation. The bridge is the limiting factor in ensuring that the project is completed in 2011. It is recommended that Council approve proceeding with the concrete girder bridge with the added aesthetic treatments outlined by the site design sub - committee, so that bridge design can commence. It is recommended the Council approve the concrete girder bridge ravine crossing option with the recommendations from the sub - committee. Public Safety /City Hall Site Design and Landscaping Subcommittee Thursday, September 23, 2010 - 12:30 PM Meeting Synopsis The meeting began at 12:30 PM in Room 147 at the South Washington County Service Center. Attendees were: Al Larson, Ben Pierson, Mike Coffey, Dave Shuster, Dave Olund, Jim Fohrman, Jeff Johnson of SEH Engineering, Chad Setterholm of SEH Engineering, Jennifer Levitt, and John McCool. Levitt explained that SEH Consulting will be preparing the construction plans for the northerly extension of Ravine Parkway. Levitt described elements of bridge and pedestrian crossing. Setterholm reported that the Ravine Parkway alignment is consistent with the original concepts that were discussed and considered in 2006 with the South Washington County Service Center project. Johnson described three bridge structure advantages and disadvantages. A color photograph of various bridge designs was distributed to each person in attendance. Johnson explained that state aid monies will be used to construct the bridge across the ravine and the Ravine Parkway extension. The State Aid office will review the construction plans. He described the project as the northerly extension of Ravine Parkway for motorists and pedestrians. A drainage Swale beneath the bridge structure will permit surface water drainage into the Ravine Park from Keats Avenue. Johnson explained that a pedestrian trail paralleling the drainage Swale beneath the bridge structure is proposed so that pedestrians can access the Park trail system without crossing on the Ravine Parkway road surface. Because a trail will be beneath the bridge structure, the bridge will be designed to allow maintenance and emergency vehicles. Minimum clearance between the bottom of the bridge structure and trail is ten feet. A brief description of three bridge designs and the advantages /disadvantages of each design are summarized below: Bridge Tye Advantages Disadvantages Con -Span Arch e Lower initial construction cost. e Larger "footprint" on ravine. 42 foot clear span e Lowest maintenance costs. e More enclosed feeling for trail users. $610,000 construction cost a Frost/ice on the deck may not form a Less attractive from motorist vantage point on roadway. as soon as compared to other e Potential for graffiti vandalism. bridge designs. Retainin wall needed to se arate drama ewa and trail. Steel Pony Truss e Less "footprint" contact with ravine. e Truss fracture issues. 74 foot clear span a More open feeling for trail users. e Higher initial construction cost. $780,000 construction cost a Most attractive from roadway e Higher maintenance costs for decking and truss painting. above and trail below. a Retaining wall needed to separate drainageway and trail. e Frost/ice may form earlier on the deck as compared to the con-span arch design. Concrete Girder Bridge e Lowest initial construction cost. a Moderate maintenance costs for deck. 74 foot clear span e Moderate maintenance costs. a Retaining wall needed to separate drainageway and trail. $580,000 construction cost e Less "footprint" contact with ravine. e FrosUice may form earlier on the deck as compared to the e More open feeling for trail users. con -span arch design. The group discussed the benefits of a bridge structure that will maximize pedestrian's views up and down the ravine. Views of the ravine from the bridge deck are also important. The group agreed that the con -span arch bridge design would detrimentally impact the public's view of the ravine and require more trees and vegetation to be removed. The steel pony truss design was not considered because it's higher cost and long -term maintenance. Majority of the sub - committee members recommended a concrete girder bridge that includes Site Design and Landscaping Subcommittee Meeting Synopsis September 23, 2010 Page 2 of 2 design elements that will enhance its visual appearance. These design elements pertain to limestone parapets along the sides of the bridge, decorative railing and bridge abutments, and unique street light bases at each end of the bridge. A couple members preferred the con -span arch design because of lower maintenance cost and the possibility that less salt/sand will be needed on the deck during the winter season. It was also the group's consensus that whatever the design of the bridge, construction materials and design elements should complement the South Washington County Service Center's building materials, the proposed Public Safety /City Hall facility, and enhancing the Ravine Parkway's design features. Setterholm stated that once a bridge structure type is decided, then the City can focus on design options and color scheme. Adjournment The meeting adjourned at 2:15 PM.