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Debra Bloom,, P.E. July 13, 2011 City of Roseville Page 20 ROADWAY DESIGN REVIEW The following section presents a conceptual roadway design for the potential County Road C2 connection. This layout is presented for conceptual purposes only and is not intended to represent a detailed construction drawing. Furthermore, other alternatives are possible to complete this connection and the one shown in Figure 13 would require further review, comment,, data collection and development. Exiis,tiing Con iitiions, — Alignment The existing alignment of County Road C2 between Merrill Street and Griggs Street as well as the segment from the cul-de-sac to Lexington Avenue are straight and in line, and as such present no significant impacts to adjacent properties due to alignment connections. Design speed on a roadway without horizontal curves is not a factor in this case. The posted speed limit is 30 mph. Exiis,tiing Con iitiions, — Profile The existing roadway profiles of both segments referenced above were evaluated to determine adequacy of the grades and vertical curves with the 30 mph posted / design speed. In accordance with MnDOT Road Design Manual Table 2-5.06A, the design speed for a low speed collector should be 30 — 4O mph. The existing maximum grade in this segment is eight percent (8%)�, which by itself does not pose an issue with design compliance as the length is less than 500 feet and is less than the 11.(x% maximum grade suggested by MnDOT Road Design Manual Table 3- 4.0 .. However,, the combination of the rolling terrain and short vertical curves, cause deficiency in the design such that the existing configuration does not meet the design standards for 30 mph in several areas. The existing vertical curves and existing design speed standards that are met are shown in Figure 13. Within both segments there are areas with very short vertical curves (50 feet or less) or in some cases no curves at all. These areas typically have very small algebraic differences of grades and as such should not present issues with traffic at the design speed. However, the MnDOT State Aid Manual would recommend that the minimum vertical curve length be 3-times the design speed, which in this case is 90 feet. If the roadway is improved, it is recommended that the vertical curve lengths be constructed to meet current standards. Potential Roadway Cond�iitiions, — Profile In an effort to determine the approximate impacts of a proposed connection, a conceptual profile I was developed that meets a 30 mph design speed (see Figure 13). The following issues and impacts that should be resolved as part of further study or design, if the County Road C2 roadway connection is to proceed, are listed as follows.- In an effort to balance impacts across the different properties adjacent to County Road C2,, the high point of the proposed vertical curve near Merrill Street is represented further west of its current location; this was done in order to limit the amount of fill in the low area of CIS. C2 near Fernwood Street. As a result,, there are impacts to Merrill Street and driveways in the area.