Current through Register Vol. 43, No. 39, September 26, 2024
(a) Each pipe
under or through an embankment shall meet the following requirements:
(1) Be capable of withstanding the external
load without buckling, cracking, being damaged, or being deformed. The minimum
internal diameter of the pipe shall not be reduced by more than the pipe
manufacturer's stated allowable, long-term pipe deflection limit and in no case
by more than five percent;
(2) be
designed to adequately resist flotation;
(3) be impervious to water, with watertight
joints and seams;
(4) except for
drawdown pipes, be installed with sufficient slope to provide adequate
drainage, with a minimum average slope of one percent after settlement. No pipe
shall have an adverse grade through any section of pipe;
(5) if the pipe is installed in conjunction
with a riser on a high-impact dam, be placed to insure that the requirements of
paragraph (a)(4) are met and that all pipe sections are properly aligned after
settlement of the foundation and consolidation of the embankment;
(6) have the discharge end extended a
sufficient distance beyond the downstream toe of the dam to avoid erosion to
the dam;
(7) be adequately
supported at the discharge end to prevent deflection when the pipe is flowing
full; and
(8) if the pipe is a
primary spillway, be sized to evacuate 95 percent of the detention storage in
14 or fewer days.
(b)
Steel cylinder-reinforced concrete pipe shall be acceptable for use in any dam
if the design computations, plans, and specifications related to the placement
of the pipe meet the minimum requirements of the manufacturer.
(c) In applying the provisions of subsections
(c), (e), and (f), the depth of fill over the top of each pipe shall be
measured from the top of the embankment after settlement has occurred.
Reinforced concrete pipe shall be acceptable for use in a low-impact dam if
less than 30 feet of fill will be placed over the pipe and if the design
computations, plans, and specifications related to the placement of the pipe
meet the minimum requirements of the manufacturer.
(d) Each metal pipe shall be coated with a
protective coating adequate to prevent corrosion for the planned life of the
dam, or the design report shall include an estimate of the expected life of the
pipe, the expected life of the dam, and a plan for replacement of the pipe when
it no longer functions as designed.
(e) Corrugated metal pipe shall be acceptable
for use in any hazard class A or B dam if no more than 25 feet of fill is
placed over the pipe.
(f)
(1) Polyvinyl chloride pipe shall be
acceptable for use in any dam if the maximum fill over the pipe does not exceed
the depth specified in the following table:
Standard dimension ratio Maximum fill over top of pipe
(SDR) (feet)
SDR 17 and thicker 35
SDR 18 31
SDR 21 23
SDR 25 18
SDR 26 16
SDR 28 14
A pipe with walls thinner than SDR 28 shall not be used.
(2) Polyvinyl chloride
pipe shall not be placed in highplasticity soils.
(3) Each portion of polyvinyl chloride pipe
that will be exposed to sunlight shall be protected as recommended by the
manufacturer of the pipe or shall be encased in a protective material.
(g) Pipe materials
other than those described in subsections (b) through (f) may be used if the
applicant demonstrates that all of the following criteria are met:
(1) The pipe material, accounting for any
protective measures that will be taken, has a minimum expected life of 25 years
if exposed to sunlight or buried in soil with the same characteristics of the
soil to be used to construct the dam.
(2) All of the pipe manufacturer's design
recommendations are met by the plans and specifications for the dam and are
documented in the design report.
(3) All of the pipe manufacturer's
recommendations for bedding, supporting, and installing the pipe are included
in the specifications for construction of the dam, except those specifications
that are demonstrated in the design report to be inapplicable in the
construction of the proposed dam.
(4) The design report includes an estimate of
the life of the pipe, the life of the dam, and a plan to replace the pipe when
it no longer functions as designed if the design life of the pipe is less than
that of the dam.
(5) The design
report demonstrates that the proposed placement and use of the pipe will meet
the requirements of sound engineering principles and commonly accepted
engineering practices.
(h) If the estimated life of a pipe is less
than the estimated life of the dam, the permit shall contain the condition that
the pipe shall be replaced when the pipe no longer functions properly.
