HomeMy WebLinkAboutTHE MARK - FDP240013 - SUBMITTAL DOCUMENTS - ROUND 2 - Responses (7)
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July 30, 2024
Sophie Buckingham
Engineering Development Review
City of Fort Collins
281 N. College Avenue
Fort Collins, CO 80524
Project # 24-0409
The Mark PDR240006 – Smaller K-Value for Sag Vertical Curve
Variance Description:
This is a request for variance to Table 7-3 of “Chapter 7 – Street Design and Technical Criteria” of the Larimer County
Urban Area Street Standards. The variance is for the vertical alignment of Spring Court, specifically the minimum K-
value for local connector streets.
Variance to this standard will allow for a smaller K-value for a proposed vertical curve that blends into the existing
street grade.
Technical Design Criteria:
LCUASS chapter 7, table 7-3 “Fort Collins Street Standards – Technical Design Criteria” calls for a minimum K-value
of 37 for sag vertical curves in a local connector.
Identifying the issue:
This project was approved by the City of Fort Collins on 02/25/2020 under the name of “Utility Plans for Johnson
Drive Apartments”. All of the street improvements up to the curb and gutter for both Spring Court and Johnson
Drive along with the foundation of the building have been installed. Construction came to a screeching halt after
said improvements were constructed. Because the previously approved plans have expired, the City is requiring
another entitlements process before construction can begin.
It should also be noted that the City is requiring the previously approved curb lines that are part of the project
along Johnson Dr and Spring Ct to be ripped out and replaced due to lack of concrete testing at the time of
installation.
EPS Group has since surveyed the site and the surrounding streets again in preparation for the new round of
entitlements. In the new topography survey, it was found that the intersection of Arthur Drive and Spring Court
(southeast corner of the site) is substantially steeper in grade than the original topography had shown. Centerline
grades shown in the topography go up to 8.4%.
Because the building elevation is set in stone due to the foundation already constructed, the grades between the
building and the western flowline of Spring Court need to remain the same in the new design. In order to do that,
the curve to tie into existing must be as short as possible in order to stay low enough for positive drainage away
from the building.
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Justification for Smaller K-Value for Sag Vertical Curve
Project Partially Constructed
• As mentioned in the previous section, the building footprint has already been constructed. This means that
in order to hold the previously approved grades and to keep drainage away from the building, the come
down from the existing grade must be quick to minimize disturbance and to ensure safety of the building.
Existing Flowline K-Value
• In order to minimize the impact of the new design, the original tie in point has been held. This also
happens to be a grade break point in the existing flow line. The flowline grade north of this point is only
4%. The curve has an A value of 3.55, length of 60’ and a K value of 16.9.
• If the curve were to be designed with an adequate K value, it would need to stretch much further south,
possibly into Arthur Drive. With an A value of 7.5 (8-0.5), the curve would need to be 200’ long based on a
speed limit of 25mph. That would raise the flowline that runs parallel with the building causing many more
issues with drainage and improvements that have already been constructed.
• With the horizonal length of the outside radius of the Arthur Drive and Spring Court intersection being just
under 100’, it is safe to assume that the existing K-value of the current vertical curve is less than required in
the existing condition. The proposed design is closely matching what is installed currently without
requiring substantial improvements to the road and avoiding any disturbance in drainage pathways.
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 road or cause the City of Fort Collins additional maintenance costs.
This smaller K-value for a sag vertical curve will allow for minimal disturbance to the surrounding Right-of-Way and
ensure that there is positive drainage away from the existing building.
We look forward to continuing to work with the City on solutions that provide a multitude of benefits.
Please call if you have any questions.
Sincerely,
Cody Pape, P.E.
Project Engineer