City of Frisco Engineering Standards

Engineering Standards
Under each scenario, the water main shall be centered on the wastewater main crossing with a
minimum separation distance of 12”.
E. If the minimum separation distances cannot be achieved for crossing wastewater and water mains,
the separation distances may be reduced if the wastewater main has a pressure rating of 150 psi.
In these cases the wastewater main shall be cased for a minimum of 18’. The casing pipe shall be
centered on the water main crossing, be a minimum of two nominal pipe sizes larger than the
wastewater main and be sealed at each end with watertight non-shrink cement grout, or a
manufactured watertight seal. The minimum separation distance is 6”.
5.2.4 Wastewater Flows
If project specific wastewater flow projections or actual flow measurements are not available for
a development, the criteria in Table 5.4 shall be used to calculate average daily and peak
wastewater flows. This criteria meets or exceeds the minimum requirements as set by TCEQ in
Title 30 of the Texas Administrative Code, Part 1, Chapter 217, Subchapter C, Rule 217.32(a)(3).
Table 5.4 – Wastewater Flow Projections
Land Use Design Factors Average Daily
Wastewater Flows
• 3.0 persons/unit
Apartment
• 102 gallons per person per day
Residential/
Town Home/
Patio Home
• 3.5 persons/unit
• 102 gallons per person per day
Peak Wastewater
Flows*
306 gpd/unit 1,224 gpd/unit
357 gpd/unit 1,428 gpd/unit
Hospital (Beds) • 200 gallons per bed per day 200 gpd/bed 800 gpd/bed
Nursing Home or
Other Institution
(Beds)
Commercial/
Industrial/Office
• 100 gallons per day per bed 100 gpd/bed 400 gpd/bed
• 1 person per parking space, or
• 1 person per 400 s.f. of building
• 20 gallons per day/person
20 gpd/person 80 gpd/person
School • 20 gallons per student/day 20 gpd/student 80 gpd/student
* Peak flow is based on a peaking factor of 4.0.
5.2.5 Wastewater Main Sizing
A. Although the Wastewater System Master Plan may be used as a guide for sizing wastewater
mains, sizing should be based on an engineering analysis of initial and future flow of the total
drainage area to be served.
B. Wastewater mains shall be sized to carry the ultimate peak flow at 100% of the full flow capacity
of the pipe. A peaking factor less than 4 may be considered for wastewater mains with diameters
24” and larger.
C. Pipe capacity shall be calculated using Manning’s equation. A roughness coefficient of 0.013
shall be used.
Section 5 – Water & Wastewater Design Requirements May 2012 Page 5-11