25 Pa. Code § 89.111 - Large impoundments
(a) Large
impoundments are those where:
(1) The
structures are located on a water course, and one of the following applies:
(i) The contributory drainage area exceeds
100 acres.
(ii) The greatest depth
of water at maximum storage elevation exceeds 15 feet.
(iii) The impounding capacity at maximum
storage elevation exceeds 50 acre-feet.
(2) The structures are not located on a
watercourse and have no contributory drainage, but the greatest depth of water
at maximum storage elevation exceeds 15 feet and the impounding capacity at
maximum storage elevation exceeds 50 acre feet.
(b) Large impoundments shall be designed,
constructed and maintained in accordance with the Dam Safety and Encroachment
Act (32 P. S. §§
693.1-693.27) and Chapter 105
(relating to dam safety and waterway management).
(c) If the embankment is more than 20 feet in
height as measured from the upstream toe of the embankment to the crest of the
emergency spillway, or has a storage volume of 20 acre feet or more, is located
where failure could cause loss of life or serious property damage or otherwise
poses a hazard to miners or the public, it must:
(1) Be stable under all probable conditions
of operation and be designed and constructed to achieve a static safety factor
of 1.5, or higher if required by the Department and a seismic safety factor of
at least 1.2.
(2) Have an
appropriate combination of principal and emergency spillway to discharge safely
the runoff from a 100-year, 24-hour precipitation event, or larger if required
by the Department.
(3) Have a
foundation investigation, as well as any necessary laboratory testing of
foundation material to determine the design requirements for foundation
stability.
Notes
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