City of Frisco Engineering Standards

Engineering Standards
1. Height. Any retaining wall exceeding 3-ft. in height measured from the top of foundation
and/or pier to the top of wall shall be engineered. The structural design shall be provided in
accordance with the geotechnical recommendations and minimum design criteria provided in
Section 9.03.
2. Geometry. Determine applicability of wall type - cut, cut/fill, or fill – based on geometry, site
constraints, existing and proposed topography, and wall alignment and location. Identify
available ROW and any necessary ROW or easements to accommodate the proposed
improvements and the access necessary to accommodate access for maintenance. Identify
location and type of existing and proposed utilities and drainage structures.
3. Economics. Evaluate the total installed cost of the wall and consider long-term maintenance
requirements. Identify necessary excavation requirements (including shoring), required utility
adjustments and costs, project schedule, construction phasing requirements, and these effects
on the wall design and construction.
4. Stability. The Design Engineer is responsible for the global stability of the wall. Evaluate all
walls to ensure that the minimum applicable factors of safety are a least met (see Section
9.05.C), if not exceeded depending on the Design Engineer’s judgment. When possible, avoid
placing walls on slopes. A slope in front of the wall dramatically reduces the passive earth
pressure (resistance), increasing the chance for wall failure. Additionally a slope in front of
the wall will have a significant effect on global stability of the wall and embankment in
which it resides. For situations where the walls above a slope cannot be avoided, a rigorous
slope stability analysis shall be required in accordance with these Engineering Standards.
5. Constructability. Determine whether walls are near water or subject to inundation or
groundwater. Identify access limitations for equipment both during and after construction.
Ensure adequate horizontal and vertical clearances are provided.
6. Drainage. Design the wall to prevent the build-up of hydrostatic pressure behind the wall. If
conditions warrant, the City may require the wall design to withstand full hydrostatic pressure
load. The wall design shall consider potential deleterious short and long term effects of water
inundation including scour and rapid draw down.
7. Aesthetics. Ensure that aesthetic treatments of walls complement the retaining wall and does
not interfere with the functionality of the wall. Detailed consideration shall be given to
aesthetic treatments of retaining walls that involve landscaping. Additionally, the wall’s
drainage system design shall avoid potential compromise of the wall aesthetics because of
water related damages.
8. Loading. Design loads shall be in accordance with these Engineering Standards (for building
code references, see Section 9.02), including construction loads and surcharge loads from
slopes, structures, and vehicles.
B. Analyze and design walls following accepted geotechnical engineering industry standards for the
City of Frisco area and in accordance with these Engineering Standards. In analysis, use earth
pressures that follow the requirements of the project’s geotechnical investigation specifically
addressing the retaining wall design requirements for the project’s specific location.
C. The Design Engineer must ensure that the retaining wall system is appropriate for its location and
application. The Design Engineer shall design for all potential modes of wall system failure;
Section 9 – Structural Design Requirements May 2012 Page 9-7