25 Pa. Code § 105.97 - Stability of structures
(a) Dams
must be structurally sound and be constructed of sound and durable materials.
The structure must be stable during and at the completion of
construction.
(b) As part of the
permit application for the construction or modification of a dam, the design
engineer shall submit to the Department, under professional seal and
certification, a report entitled "Dam Stability Report" which clearly
demonstrates to the Department that the requirements of subsection (a) have
been satisfied. At a minimum, this report must address the following
considerations:
(1) The physical properties of
the materials available for construction.
(2) A stability analysis based on the
properties of the structure's materials and on the seismic forces and seepage
conditions affecting the structure.
(3) The methods of construction.
(4) The conditions of operation of the dam
and reservoir.
(c)
Earthfill dams must be demonstrated to be stable for the following conditions:
(1) Normal pool with steady-state seepage
conditions with a factor of safety of 1.5.
(2) Maximum pool with steady-state seepage
conditions with a factor of safety of 1.4.
(3) Sudden drawdown from normal pool
conditions with a factor of safety of 1.2.
(4) Normal pool with steady-state seepage
conditions under seismic forces produced by the maximum credible earthquake
with a factor of safety of 1.1.
(5)
Completion of construction with no pool with a factor of safety of
1.3.
(d) Gravity dams
must be demonstrated to be stable for the following conditions:
(1) Normal pool with appropriate uplift
pressures, ice loads and silt loads with a factor of safety of 2.0.
(2) Maximum pool with appropriate uplift
pressures and silt loads with a factor of safety of 1.7.
(3) Normal pool with appropriate uplift
pressures and silt loads under seismic forces produced by the maximum credible
earthquake with a factor of safety of 1.3.
(e) For gravity dams, the overturning
stability is acceptable when the resultant of all forces acting on the dam is
located as follows:
(1) Within the middle
third of the structure for normal pool conditions.
(2) Within the middle half of the structure
for maximum pool conditions.
(3)
Within the structure for earthquake conditions.
(f) For gravity dams, the foundation bearing
pressures must be less than or equal to the allowable for no pool, normal pool
and maximum pool conditions and less than 133% of the allowable for earthquake
conditions.
(g) The factors of
safety for earthfill dams or gravity dams must be the higher of:
(1) The factors of safety in subsections (c)
and (d).
(2) The factors of safety
in the most recent Engineering Manuals developed by the United States Army
Corps of Engineers relating to stability of dam structures.
(h) The Department may, in its
discretion, consider a revised factor of safety for a class of dams or
reservoirs when it can be demonstrated that the factor of safety provides for
the integrity of the dams or reservoirs and adequately protects life and
property.
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