New Jersey Administrative Code › Title 7 - ENVIRONMENTAL PROTECTION › Chapter 20 - DAM SAFETY STANDARDS › Subchapter 1 - APPLICATION PROCEDURE; DESIGN CRITERIA FOR DAM CONSTRUCTION; DAM INSPECTION PROCEDURE › Section 7:20-1.9 - Design criteria

Current through Register Vol. 56, No. 14, July 15, 2024
(a) The minimum
				design storm used to calculate required spillway capacity must be determined
				according to the following table:
Hazard
Spillway Design
						  Storm (SDS)
Class I
PMP
Class II
One-half PMP
Class III
24 hour 100 year frequency,
Type III storm[1]
Class IV
24 hour 100 year frequency,
Type III storm plus 50%[1]
[1] Any later technology adopted by the U.S. Department of
				  Agriculture, Natural Resources Conservation Service may be substituted for the
				  use of the Type III storm.
(b) For existing dams, it is recognized that
				the relationships between valley slope and width, total reservoir storage,
				drainage area, and other hydrologic factors have a critical bearing on
				determining the safe spillway design flood. When appropriate, based on the
				design of the dam, rational selection of a safe, reduced spillway design for
				specific site conditions based on quantitative and relative impact analysis is
				acceptable. The spillway should be sized so that the increased downstream
				damage resulting from overtopping failure of a dam would not be significant as
				compared with the damage caused by the flood in the absence of a dam
				overtopping failure. The minimum design storm for the dam shall be the 100 year
				storm.
(c) All Class II and III
				dams shall, where practicable, incorporate in the proposed design, the ability
				to make modifications necessary to increase the spillway capacity of the
				facility or other alternative measures if the downstream hazard potential
				increases.
(d) All dams shall have
				adequate storage for the design storm or have a spillway system which will
				safely pass the design storm without endangering the safety of the
				dam.
(e) Each spillway shall
				include a satisfactory means of dissipating the energy of flow at its outlet
				without endangering the safety of the dam.
(f) The capacity of the spillway system shall
				be equal to the peak inflow of the design flood unless the applicant
				demonstrates by flood routing procedures that the spillway system has the
				capacity to safely pass the resulting water flow.
(g) Pipe conduits may be used for the primary
				(principal) spillway. When so used, the following requirements shall be met:
1. Pipe conduits shall be of such design as
				to safely support the total external loads in addition to the total internal
				hydraulic pressure without leakage. The type of construction material used
				shall be consistent with the anticipated life of the structure. Corrugated
				metal pipe shall not be used in the construction of new dams.
i. For Class I and II dams, the minimum
				allowable inside dimension of the pipe conduit is 30 inches.
ii. For Class III dams, the minimum allowable
				inside diameter of the pipe conduit is 18 inches.
iii. For Class IV dams, the minimum allowable
				inside diameter of the pipe conduit is 12 inches.