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Overcrossing Alternative
The Overcrossing is a simpler alternative to provide access across I-215 in order to facilitate traffic movements to local regions in the City of San Bernardino. This design will extend the existing Campus Pkwy from Kendall Dr to Cajon Blvd and will align adjacent to Devil Creek Diversion Channel. A new intersection is included in the design at Hallmark Pkwy and Campus Pkwy in order to increase circulation to the area.
Traffic Analysis
The traffic team performed a traffic analysis for this alternative using Synchro 10 and forecasted traffic volumes from the San Bernardino County Traffic Analysis Model (SBTAM) and the Southern California Association of Governments model (SCAG) and using the Highway Capacity Manual 6th Edition standards for the level of service. Although the level of service stays the same when the overcrossing is built, the traffic delay time is reduced by almost 95 seconds with PM traffic and more than 55 seconds with AM traffic when the alternative is built. Due to the high traffic volumes at Campus Parkway and Kendall Drive, the levels of service at that intersection are unable to meet the San Bernardino County Congestion Management Plan's standard due to the study boundary of this project. Other projects pursued by the city can improve the level of service for that intersection. After the proposed intersection designs, the traffic team found layouts that produced the best levels of service for the Overcrossing alternative.
Geometric Feasibility
The overcrossing alternative that is proposed consists of a bridge that goes over I-215, two four-ways controlled intersections, and one three-ways controlled intersection. The overcrossing is a simple alternative that allows access from one side of the I-215 to the other which makes it easier for the local community to travel. It does not have any features that impede maneuverability or greatly affect the area around it so the alternative is geometrically feasible.
Impact Evaluation
The simpler design of the overcrossing reduces the costs of the right of way that would need to be purchased and the amount of retaining walls that would need to be built compared to other alternatives. The project site is alongside a channel and is located within a 100-year floodplain but to address these issues a NEPA (National Environmental Policy Act) permit is required and the first level must be constructed 2 feet above the flood plain which as been taken into account with the design. In addition, proper drainage will be implemented in the design and a Storm Water Pollution Prevention Plan as outlined by SBCFCD (San Bernardino County Flood Control District) will be created. Due to the project site located parallel to residential homes a sound wall is to be considered due to the noise that may come during and after construction along with a possible sound analysis for the area.
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There are three different particular species (shown above) that have been identified that require proper mitigation techniques. Proper mitigation techniques such as relocation of a species are thought to be the best tactic not only ensure the completion of this project, but also the safety and prosperity of the species. Some possible permits needed would be an incidental take permit for the San Bernardino kangaroo rat or a voucher collection permit for endangered plants for relocation.
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Detailed Design
The cross-section of the Overcrossing is similar to the Hook Ramp Hybrid and will have a 6’ bike lane in each direction to improve access for all users, two 12’ through lanes, and one 4’ shoulder on each side of the 16’ median with a 6’ sidewalk on the north side. Bike lanes and sidewalks were included in our bridge design to promote active transportation and to satisfy the San Bernardino Master plan.
For our project study report, an Advance Planning Study (APS) was done to define the scope of structure work and develop a reasonable cost estimate for budget purposes. APS consists of a plan sheet for each structure with basic dimensions and minimal detailing including the vertical clearance, span length, and structure type. Each plan sheet contains the plan, elevation, typical section view, and cost estimate of the structure. All these structures will be constructed out of precast concrete. The Bridge Design Aids were used for the design of the new bridges. Please refer to the Geometric Approval Drawing and Advanced Planned Study under the Deliverables tab for geometric details of this alternative.
Viability
The Overcrossing went through all steps done while reviewing possible alternatives - Alternative Scoping, Traffic Analysis, and Geometric Design. It was considered as one of the three viable alternative design through all of the aspects mentioned in detail above. It also passed the traffic analysis, geometric feasibility, and impact evaluation steps and was considered viable for detailed design. All documents and deliverables pertaining to this design can be found under the Project Deliverables Tab.