10 January 2002
c. Pre-engineered system's representative. The manufacturer is required to ensure that a qualified
direct employee of the system manufacturer is present to guarantee proper installation when the following
types of work are performed:
(1) inspection, unloading and storage of materials.
(2) inspection of trench prior to laying of casing.
(3) inspection of concrete thrust blocks.
(4) hydrostatic test of all service lines.
(5) field joint closure work.
(6) air test of casing.
(7) coating patch work.
(8) holiday test of casing coating.
(9) initial backfill up to 10 inches above the top of the casing.
(10) radiographic weld examination.
(11) startup and operation tests.
5-3. PROJECT DESIGNER'S RESPONSIBILITY.
a. Site information. As with all buried distribution systems, the site investigation is the responsibility of
the designer. As described in chapter 3 of this manual, the designer will obtain soil borings, be responsible for
designing the grading in the area, investigate all utilities for possible conflicts, and design for utility relocation as
necessary. The designer must then determine the site conditions (severe, bad, or moderate) before a system
type (DDT or WSL) is selected. The designer will then provide plans and profiles of the Pre-engineered system
routing. The designer will show approximate slope of the system (1 inch in 20 feet is required to ensure
drainage). This slope must be maintained in the entire system including through each leg of each expansion
loop to ensure proper system drainage.
b. Valve manholes. The designer will design all valve manholes for the system as described in chapter 3
of this manual. The manholes will be no further apart than 500 feet to minimize excavation if a leak in the
system must be found. The manholes will also be provided at all high (vent) points and low (drain) points in the
system. The valve manholes will include ground water drainage capabilities as explained in chapter 3. Casing
vents and drains will be included for maintenance of the casing air space in DDT systems as shown in figure
c. Insulation. The insulation types used on the Pre-engineered Underground system will only be those
that are listed in the guide specification. The insulation thickness tables in the guide specification will be used
in determining required insulation thickness. These insulation thicknesses were developed using life cycle cost
d. Cathodic protection. The designer will be responsible for the cathodic protection design for all
systems with coated steel casings. The designer shall also require that dielectric flanges be provided to isolate
the system's cathodic protection system from non protected systems. These dielectric flanges shall always
be installed inside valve manholes.
e. Review. The designer will provide a detailed review of the manufacturer's shop drawings to ensure the