| (iii) be installed ending one full pipe diameter above
the top of the collection system pipe, or 12 inches above the top
of the collection system pipe, whichever is greater.
(8) If a nine-foot separation distance between a manhole
and a water supply pipe cannot be achieved, the manhole must either:
(A) have no measurable leakage during a leakage test
conducted according to the requirements in §217.58 of this title
(relating to Testing Requirements for Manholes); or
(B) have all portions of the manhole within nine feet
of a water supply pipe encased in at least one foot of cement stabilized
sand that meets the requirements of paragraph (7)(D)(i) and (ii) of
this subsection.
(e) Building Laterals and Taps. Building laterals and
taps must:
(1) include a manufactured fitting that prevents infiltration
and root entrance;
(2) prevent service lines from protruding into the
collection system pipe; and
(3) protect the mechanical and structural integrity
of a collection system.
(f) Bore or Tunnel for Crossings. The spacing of supports
for carrier pipe through casings must maintain the grade, slope, and
structural integrity of the pipe as required by subsection (k) of
this section.
(g) Corrosion Potential of Collection System Pipes.
(1) The engineering report must include calculations
or other information that demonstrate the structural integrity of
a pipe during the minimum 50-year design life cycle if a pipe or an
integral structural component of a pipe has potential to deteriorate
when subjected to corrosive internal conditions, or if a pipe or component
does not have a corrosion resistant liner or protective coating installed
by the pipe manufacturer.
(2) If the corrosion analysis indicates that corrosion
will reduce the functional life of the pipe to less than 50 years
based on the structural analysis in subsection (k) of this section,
then the pipe must have a lining or protective coating that will extend
the functional life to 50 years.
(h) Odor Control. An owner shall implement odor control
measures necessary to prevent a collection system from becoming a
nuisance.
(i) Active Geologic Faults.
(1) An owner shall identify all active faults within
the boundaries of the collection system project and minimize the number
of collection system lines crossing faults.
(A) If the crossing of a collection system over an
active fault is unavoidable, the engineering report must specify design
features that protect the structural integrity of a collection system
in the event of movement of the fault.
(B) If a collection system line crosses an active fault
line, the design must specify:
(i) joints that provide maximum flexibility; and
(ii) manholes on each side of the fault that would
allow a portable pump to be used to prevent unauthorized discharge
of wastewater in the event of a collection system failure.
(2) An owner shall not install a collection system
service connection within 50 feet of an active fault.
(j) Capacity Requirements.
(1) An owner must ensure that a collection system's
capacity is sufficient to serve the estimated future population of
the area served by the project, including institutional, industrial,
and commercial flows.
(2) An owner must include calculations in the engineering
report that demonstrate the hydraulic capacity of a collection system,
accounting for the peak flow of domestic wastewater, peak flow of
wastewater from industrial sites, and maximum expected infiltration
rates.
(3) An owner must ensure that the collection system
has capacity to prevent a surcharge.
(4) An owner must ensure that a gravity pipe is at
least 6.0 inches in diameter.
(5) Any connection between a stormwater collection
system and a wastewater collection system is prohibited.
(6) An owner may use the data from an existing collection
system for design purposes. In the absence of existing data, a design
must use data from a system with similar characteristics, including:
(A) location;
(B) inflow and infiltration characteristics;
(C) peak flows;
(D) pipe materials;
(E) customer base; and
(F) any other characteristics required by the executive
director.
(7) New collection systems.
(A) The sizing of pipe for a new collection system
must be based on an engineering analysis of initial and future peak
flow of domestic wastewater, peak flow of waste from industrial sites,
and maximum expected infiltration rates.
(B) A new collection system design must be sized for
the peak flow, which is based on the estimated daily wastewater flow
contribution as shown in Table B.1. in Figure: 30 TAC §217.32(a)(3)
of this title (relating to Organic Loadings and Flows for New Wastewater
Treatment Facilities).
(k) Structural Analysis.
(1) An owner must ensure that a collection system is
designed to have a minimum structural life of 50 years.
(2) For flexible pipe used in a collection system,
which is pipe that will deflect at least 2% without structural distress,
the engineering report must include:
(A) live load calculations;
(B) allowable buckling pressure determinations;
(C) prism load calculations;
(D) wall crushing determinations;
(E) strain prediction calculations;
(F) calculations that quantify long-term pipe deflection;
(G) the method of determining the modulus of soil reaction
for bedding material and in-situ material;
(H) pipe diameter and material with reference to appropriate
standards;
(I) modulus of elasticity;
(J) tensile strength;
(K) pipe stiffness, or ring stiffness constant converted
to pipe stiffness;
(L) Leonhardt's zeta factor;
(M) trench width;
(N) depth of cover;
(O) water table elevation; and
(P) unit weight of soil.
(3) For trench installations, the design must specify
a minimum stiffness requirement to ensure ease of handling, transportation,
and construction. Pipe stiffness must be related to the ring stiffness
constant by Equation C.1. in Figure: 30 TAC §217.53(k)(3)
Attached Graphic
(4) The owner is not required to perform the structural
calculations in paragraphs (2) and (3) of this subsection, if the
pipe is installed and tested in accordance with all other requirements
of this subchapter and meets all of the following:
(A) the pipe is installed using an open trench design;
(B) the pipe is flexible pipe with a pipe stiffness
of 46 psi or greater;
(C) the pipe is buried 17 feet or less from the ground
surface;
(D) the pipe has a diameter of 12 inches or less;
(E) the modulus of soil reaction for the in-situ soil
is 200 psi or greater;
(F) there are no effects on the pipe due to live loads
from vehicles driving over the pipe;
(G) the unit weight of soil used for backfill is 120
pounds per cubic foot or less; and
(H) the pipe trench width is 36 inches or greater.
(5) A design analysis for rigid pipe installations
must be included in the engineering report. The design analysis must
include a structural analysis and all details necessary to verify
that the structural strength is sufficient to withstand the expected
stresses. For rigid pipes, the minimum strength for each class of
pipe material and the appropriate standard must be included.
(l) Minimum and Maximum Slopes.
(1) All collection systems must contain slopes sufficient
to allow a velocity not less than 2.0 feet per second when flowing
at full capacity.
(2) When site-specific data is not available, a collection
system must be designed in accordance with the minimum and maximum
slopes specified in this paragraph.
(A) The slopes shown in the following table are based
on Manning's formula with an assumed "n factor" of 0.013 and are the
minimum acceptable slopes.
Attached Graphic
(i) The minimum acceptable "n" value for design of
minimum pipe slopes is 0.013.
Cont'd... |
