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Home My WebLink AboutAGENDA REPORT 1995 0719 CC REG ITEM 11BTO: FROM: DATE: SUBJECT: i " .A 10 LI Ag�rida Report City of Moorpark The Honorable City Council Kenneth C. Gilbert., Director of Public Works July 7, 1995 (Council. Meeting 7- 19 -95) Consider Approval of the Conceptual Design for the Reconstruction of the Spring Road Bridge On September 21, 1994, the City Council selected the firm of Dwight French and Associates to prepare the design plans and specifications for the replacement of the Spring Road Bridge across the Arroyo Simi, A. Design Phases The contract for design services structures those services to provide for the evolution of the design using certain review benchmarks summarized as follows: • Conceptual Design: - initial hydrology analysis, - initial geotechnical analysis, - survey, - right -of -way needs, - utility relocation requirements, - bridge length, width & other design elements, - interface with future trail system, - Preliminary plan / profile, - bridge alignment, - road closure analysis, - preliminary construction cost estimate. sprgbrg8 0001019 Spring Road Bridge Design July 1995 Page 2 Preliminary Design: - final hydrology analysis, - final geotechnical and seismic analysis, - bridge widening costs (grant data), - final design for bridge alignment, length, width, approaches & other project elements; - final right -of -way requirements, - final utility relocation requirements, - draft construction staging & traffic control plan, - estimate of probable construction cost. Draft Final Design: - final r -o -w needs (legal descriptions, etc.), - final draft design plans and specifications, - final construction staging & traffic control plan, - final roadway approach design plans - final striping plans, - final bid items and estimated quantities. Construction Documents: - final plans and specifications B. Conceptual Design The engineer has completed the conceptual design. A copy of a report summarizing that work product has been placed in the City Council office for your review. C. Environmental Review Based on the above mentioned report summarizing the conceptual design, staff will proceed with the preparation of the Environmental Assessment and Environmental document for this project. If necessary, the completion of the this environmental document will be deferred until the completion of the Preliminary design phase. It is anticipated that the environmental document which will be required, will be a Mitigated Negative Declaration. D. Bridge Width On June 21, 1995, the City Council approved a change to the design width for the new bridge from sixty feet (601) to fifty feet (501). This bridge width is compatible with the design width for Spring Road south of the bridge which has been approved for construction by the developer of the proposed Carlsberg project. 9prgbrg8 00011-0 Spring Road July 1995 Page 3 E. Alignment Bridge Design One of the matters to be determined at this point in the design process is the alignment of the new bridge structure. The Engineer's report identifies two alternate summarized as follows: Alternate #1: Placement of the centerline of the bridge at the centerline of the street right -of -way. Pros: • Allows use of more of the existing paving, thus reducing the cost for street widening and realignment. • Required closure of Spring Road (see below) reduces construction time and cost. • Street curvature (see below) should have the effect of reducing speeds. • Shorter construction time (approximately 6 months).. Cons: • Requires the complete removal of the existing bridge and the closure of Spring Road. • Curvature of street aliqnment north of the bridge remains. Alternate 12: Curb at northeast corner of the bridge to align to the existing curb on the east side of the street north of the bridge. Pros: • Allows existing bridge to be used for one lane of traffic (signalized to allow only one direction at a time) during construction. • Curvature of the street. north of the bridge is reduced. Cons: • Will require the relocation (possible right -of- way acquisition) and reconstruction of the utility access road serving the pump station owned by the Calleguas Municipal Water District. • Will require the developer to the southeast (Carlsberg) to construct additional fill slope and /or retaining walls. • Increased cost (approximately $160,000) and construction time due to these additional construction requirements. • Longer construction time (approximately 8 months). sprgbrge 0009.1.1 Spring Road Bridge Design July 1995 Page 4 Four Lanes: With either alternate, the widening of only one side of the proposed bridge will accommodate four lanes of traffic. Curve South of Bridge: The Engineer has evaluated the existing curve and grade south of the bridge for the purpose of determining if any improvements to this curve could be undertaken at the time the bridge was reconstructed. "Softening" this curve would require the radius of the curve to be lengthen. This would move the roadway to the east. Moving the roadway to the east would require one or all of the following: a) the relocation of the existing water pump station, b) the import of substantial fill material, and c) the construction of a substantial amount of retaining walls. It is the opinion of the Engineer that the benefits derived do not justify the substantial costs of these additional improvements. F. Road Closure Absent the construction of a temporary bridge, the only way in which traffic can be maintained during construction will be to select the bridge alignment described in Alternate #2 above. However, even with this Alternate it will be necessary to remove a portion of the existing bridge reducing the width to only one lane. 1. One -Way Only: Traffic could be restricted to one direction only. If it is likely that construction activities would cause periodic closures, it may be preferable to designate the bridge for north bound traffic only due to the fact that there is limited vehicle storage for southbound traffic between the bridge and Los Angeles Avenue. 2. Two -Way Traffic: Two way traffic could be maintained on a one lane bridge through the installation of a demand - actuated temporary traffic signal which would allow only one direction of traffic to flow at time. It should be noted that there has been no traffic study performed to determine the degree of traffic congestion which would result from this installation, nor the amount of vehicle storage which would be required north of the bridge. sprgbrge �� Spring Road Bridge Design July 1995 Page 5 G. construction Cost Estimate The preliminary construction cost estimate for the project is as follows: Alternate 11: $1,285,000 Alternate 12: $1,440,000 Note: These costs are based on the preliminary recommended design which calls for a three -span bridge. Should the seismic analysis indicate the construction of a single span bridge, the cost estimate will be revised upward. H. Trails Due to the fact that the bridge does not cross the arroyo at a right angle, the design length for the new bridge is one hundred forty -six feet (1461). This is the minimum length necessary to accommodate the proposed one hundred twenty -five feet (125' ) width for the bottom of the future channel to be constructed by the Ventura County Flood Control District (VCFCD). This proposed bridge length will require the construction of vertical channel walls under the bridge. With this design it will not be possible to construct a future levy trail which would dip under the bridge structure. Any future trail system would have to cross Spring Road at grade. In order to accommodate a future levy trail which could be constructed under the bridge, it would be necessary to lengthen the bridge span by approximately eight feet (81). It is anticipated that this additional bridge length would increase the above mentioned estimated construction costs by approximately $50,000. 1. Survey: Completed. 2. Right -of -Way Acquisition: None required for bridge. Some may be required for utility access road relocation. 3. Utility Relocation: Scope to be determined. sprgbrge �,3 Spring Road Bridge Design July 1995 Page 6 4. Geotechnical Analysis: '2ompleted. Seismic safety analysis to be performed.. 5. Hydrology Analysis: Initial information obtained from VCFCD. Final hydrology analysis to be performed after bridge alignment and design is determined. 6. Alignment: It is recommended that design Alternate #1 (bridge at centerline of street) be selected. 7. Road Closure: It is recommended that the Spring Road be closed during construction. 8. Trails: It recommended that the bridge length be increase to accommodate possible future trials under the bridge. Staff recommends that the City Council take the following actions: 1. Approve the bridge alignment described by Alternate #1 (bridge to be located at the centerline of the street). 2. Approve the closure of Spring Road during construction. 3. Approve a bridge length which will accommodate the future construction of a trail under the bridge. 4. Approve the conceptual design for the subject project based on the Conclusions stated M this report. sprgbrgs 0001.1.4