City of Frisco Engineering Standards

Engineering Standards
5.2 Wastewater System - General
A. Design criteria for all wastewater systems shall comply with TCEQ Chapter 217 (Design Criteria
for Domestic Wastewater Systems), latest revision. Chapter 217 is included in Part 1 of Title 30
of the Texas Administrative Code.
B. Wastewater main sizes shall comply with the Wastewater System Capital Improvement Plan.
C. Wastewater mains shall be sized and extended through the limits of a development to serve
adjacent properties.
5.2.1 Wastewater Main Location
A. Wastewater mains serving subdivisions and commercial developments shall be located under
street paving along the center of the street.
B. Wastewater mains shall not be located in alleys.
C. Wastewater mains located near open waterways shall follow the alignment of the waterway along
the high bank and be located a minimum of 15’ beyond the top of bank. Wastewater manholes
shall not be located in the flow line of an existing waterway.
D. No wastewater main shall be located inside the storm sewer system.
5.2.2 Horizontal and Vertical Alignment
A. Wastewater mains shall be designed as straight as possible between manholes.
B. Wastewater mains running parallel with public right-of-ways shall match change in street
direction. When streets have horizontal curvature, curved sewers are acceptable to maintain
parallel alignment.
C. Minimum cover for wastewater main shall be 4’.
D. In general, the minimum depth for a wastewater main to serve a given residential property with a
4” lateral shall be 3’ plus 2% times the length of the house lateral (the distance from the
wastewater main to the center of the house). Thus, for a house 135’ from the wastewater main,
the depth would be 3’ plus 2% x 135’ = 3.0 + 2.7 = 5.7’. The depth of the flow line of the
wastewater main should then be at least 5.7’ below the elevation of the ground at the point where
the service enters the house. Profiles of the ground line 20’ past the building line will be required
to verify that this criteria is met.
E. No vertical bends or vertical curves shall be allowed between manholes.
F. A parallel wastewater main shall be required for wastewater lateral connections on wastewater
mains deeper than 12’.
G. Wastewater mains shall be placed on such a grade that the velocity is not less than 2 fps or more
than 10 fps at design peak flow. The following table of values may be used:
Section 5 – Water & Wastewater Design Requirements May 2012 Page 5-9