HomeMy WebLinkAboutTAPESTRY - PDP240001 - SUBMITTAL DOCUMENTS - ROUND 1 - Variance Request (2)
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April 24, 2024
Sophie Buckingham
Engineering Development Review
City of Fort Collins
281 N. College Avenue
Fort Collins, CO 80524
Project # 473-010
Tapestry PDR210019 – Modified Minimum Tangent Length Request
Variance Description:
This is a request for variance to the standard minimum tangent length contained in Chapter 7.4.1 A of the Larimer County
Urban Area Street Standards (LCUASS Fort Collins).
Variance to this Standard will allow for the smooth transition of Buckingham’s centerline alignment to occur within the
extents of the project frontage.
Technical Design Criteria:
Public Streets to be designed to horizontal alignment criteria in the Larimer County Urban Area Street Standards (Fort
Collins). This approved requirement is stated below:
Chapter 7.4 General Design Elements – 1.A - Horizontal Alignment
2. Minimum Tangent Length.
b. Reverse Curves. The tangent between reverse curves shall be no less than the lengths shown in Table 7-3 and
Table 7-4. (Table 7-3 attached to this variance for reference)
4. Curves with Small Deflection Angles (10° or less). To reduce the appearance of kinks in the street, minimum lengths of
curve shall be designed with minimum arc lengths as shown in Table 7-5.
Identifying the issue:
The existing alignment of Buckingham Street along the northern project boundary of Tapestry is centered 9 feet north of
the section line west of the intersection with 4th Street a
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collector with a modified cross-section with a minimum centerline arc length of 300 feet and minimum tangent between
curves of 100 feet. To create a smooth transition reverse curves must be fitted to the centerline alignment starting at the
west project boundary and ending at the east project boundary. However, we are unable to fit the required two arcs and
one tangent (700 feet total) within the length of our frontage (approximately 640 feet). Additionally, LCUASS prohibits
angle point deflection changes in roadway alignments.
Alternatives Considered:
1. Alternative 1: Selected alternative. Hold criteria for minimum 300-foot arc length with a shortened tangent
length.
a. This alternative was chosen for the design; however, all three alternatives were seen as feasible options.
Maintaining minimum 300-foot arc lengths for the reverse curves resulted in two symmetric curves with
12,000-foot radiuses connected by a 60-foot tangent. Radiuses of this length and curvature to illicit 1.4°
of deflection (and then 1.4° the opposite direction) will result in a traveled way feeling approximating a
straight line.
2. Alternative 2: Hold criteria for minimum 100-foot tangent between reverse curves.
a. This alternative was a feasible option resulting in reverse curve arcs with approximate lengths of 280
feet (12,223.78-foot Radius). Radiuses of this length and curvature to illicit 1.4° of deflection (and then
1.4° the opposite direction) will result in and traveled way feeling approximating a straight line.
3. Alternative 3: Utilize angle point deflections for the
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Conclusion
We do not feel that this variance will increase risks to public health, safety, or welfare, nor will it reduce the design life of
any public roadway or cause the City of Fort Collins additional maintenance costs.
Furthermore, the proposed variance maintains a reasonable balance between compliance with regulatory standards and
practical considerations, ensuring that the development remains in harmony with the City’s objectives while still meeting
the necessary criteria for functionality and safety.
Please call if you have any questions.
Sincerely,
Cody Pape, P.E.
Project Engineer