I-275 is a north/south freeway which runs from I-75 in north Hillsborough County through Pinellas County and reconnects with I-75 in Manatee County. I-75 is a major north/south freeway which traverses the length of the state. Within the project limits, I-275/I-75 is a four-lane divided freeway which runs through a predominately undeveloped rural area. The proposed improvements to this facility will increase the operational efficiency of the freeway by adding an additional lane to the inside of the existing travel lanes in both the northbound and southbound directions. This corridor study is referred to as Section 2 and is approximately 14.8 km (9.2 mi) in length.
Study Purpose and Need
The purpose of this report was to document the engineering decisions and the design criteria used in the development of proposed improvements to Interstate 275 (I-275) [State Road 93 (SR 93)] from Bearss Avenue to the Hillsborough/Pasco County Line, a distance of 11.6 kilometers (km) [7 .2 miles (mi)] in Hillsborough County, and Interstate 75 (I-75) [SR 93] from the Hillsborough/Pasco County Line to the proposed State Road 56 (SR 56), a distance of 3.2 km (2.0 mi) in Pasco County. This report contained information regarding the development of the typical section and the alternative chosen to increase the operating efficiency of the freeway within the project limits.
The interstate system in Hillsborough and Pasco Counties was constructed in the late 1960’s and has operated for the past thirty years without any major improvements. The urban growth which has occurred in Hillsborough and Pasco Counties over the past several years has placed a heavy demand on the interstate system.
This Project Development and Environment (PD&E) Study evaluated the feasibility of providing improvements to I-275 fi·om Bearss Avenue to the Hillsborough/Pasco County Line and I-75 from the Hillsborough/Pasco County Line to proposed State Road (SR) 56. The Florida Department of Transportation (FOOT) recommends adding an additional travel lane on the inside of the existing travel lanes in both directions. The recommended improvements will increase the operating efficiency of the existing freeway. For I-275 from Bearss Avenue to the US 41/ CSX Railroad overpass, a 3.6 m (12ft) wide travel lane will be added to the median. Outside shoulders will be provided at a width of 3.6 m (12ft) with 3.0 m (10ft) of pavement. Paved inside shoulders will be provided at a width of2.92 m (9.58 ft). The median width will be 6.45 m (21.12 ft) and include a 0.61 m (2 ft) wide median barrier. Because of shoulder improvements, only minor modifications to the existing northbound entrance and southbound exit ramps are required at Bearss Avenue.
For I-275 from the US 41/CSX Railroad overpass to the Hillsborough/Pasco County Line and for I-75 from the Hillsborough/Pasco County Line to proposed SR 56, a 3.6 m (12ft) wide travel lane will be added to the median. Inside and outside shoulders will be provided at a width of3.6 m (12 ft) with 3.0 m (10ft) of pavement. The median width will be 12.3 m (40.73 ft). No changes in access to I-275/75 are recommended. No additional right of way is required for these mainline improvements. Conceptual Design Plans are in Appendix C.
Highway drainage at the Bearss Avenue interchange will be collected in a closed drainage system and conveyed to nearby stormwater management areas prior to discharge into the natural system. For I-275 from north of Bearss Avenue to the Hillsborough/Pasco County Line and I-75 from the Hillsborough/Pasco County Line to proposed SR 56, open swales and roadside ditches will be used to convey stormwater. Median mnoti will be collected by ditch bottom inlets and conveyed to existing crossdrain culverts. Design will adhere to permitting standards currently in place. Stormwater management methods, areas and locations will be determined during final design. Additional right of way may be required for stormwater treatment. Pond sites will be selected to minimize residential and business relocations.
Of the three bridge structures that cross over existing roadways within the study limits, the two bridge structures at US 41/CSX Railroad overpass do not meet current design standards regarding vertical clearance. The proposed widening of the structures will be designed to maintain existing vertical clearance. No improvements are recommended to correct existing deficiencies regarding vertical clearance. No improvements are proposed to the Cypress Creek bridge structures. All existing bridge structures which are located within the study corridor will require widening to accommodate the proposed additional travel lanes and adequate shoulders.