City of Frisco Engineering Standards

Engineering Standards
2. The City requires a minimum of 9’ of pavement in each direction during the 100-year event
for Type A and B thoroughfares.
3. The dry lane criteria shall be met in both the interim and future conditions.
B. Parabolic Crown Streets
1. All parabolic crown street capacities shall be hydraulically designed using Manning’s
equation.
2. During a 100 year storm event, the gutter depth on Type C, D, E, F, and G thoroughfares are
required by the City not to exceed 6” or top of curb, whichever is less.
3. During a 100-year storm event, the City requires a minimum of 9’ of pavement in each
direction for Type C and D thoroughfares.
4.05 Alley Capacity
A. All alley capacities shall be hydraulically designed using Manning’s equation.
B. The 100 year storm event shall be contained within the edge of pavement.
C. In residential areas where the standard alley section capacity is exceeded, storm sewer systems
with inlets shall be provided.
D. Grate combination inlets shall be located in alleys upstream from an intersection and where
necessary to prevent water from entering intersections in amounts exceeding allowed street
capacity.
4.06 Valley Gutters
A. The use of valley gutters to convey storm water across a street intersection is subject to the
following criteria:
1. Valley gutters shall not cross Type A, B, C, and D thoroughfares.
2. At any intersection, valley gutters perpendicular to the main street will not be permitted; and
valley gutters parallel to the main street may only cross a lower classified street.
4.07 Inlet Location and Capacity
A. Gutter Flow
Curb inlets shall be placed to ensure that the 100 year flow in a street does not exceed the dry lane
requirements for straight crown streets and top-of-curb elevation for parabolic crown streets as
per Sections 4.04. The following form of the Manning’s equation should be used to evaluate
gutter flow hydraulics:
Q = 0.56
n Sx5/3 S 1/2 T 8/3
Q
S x
= Gutter flow rate (cfs)
= Pavement cross slope (ft/ft)
Section 4 – Drainage Design Requirements May 2012 Page 4-10