West Virginia Code of State Rules › Agency 38 - Mining And Reclamation › Title 38 - LEGISLATIVE RULE DEPARTMENT OF ENVIRONMENTAL PROTECTION MINING AND RECLAMATION › Series 38-04 - Rules For Quarrying And Reclamation › Section 38-4-7 - Design Requirements

Current through Register Vol. XLI, No. 28, July 12, 2024
7.1.
				General Hydrologic Requirements
7.1.a.
				Hydrologic Investigation: A survey shall be conducted to evaluate soil types,
				land use, and slope watershed area, runoff curve number, and any of the factors
				needed to establish watershed characteristics. A summary of all hydrologic and
				hydraulic data compiled in the initial site investigation and used in the
				analysis shall be included in table or figure form in the plan
				package.
7.1.b. A stream flow
				analysis shall be conducted to evaluate stream flow quantity and quality as it
				affects the dam and its appurtenances.
7.1.c. Design Storm Requirements:
7.1.c.1. All dams shall be designed to meet
				the following minimum hydrological criteria based upon hazard classification:
7.1.c.1.A. Class A impoundments shall be
				designed for a minimum of P100 + 0.12 (PMP-P 100) inches of rainfall in six (6)
				hours.
7.1.c.1.B. Class B
				impoundments shall be designed for a minimum of P100 + 0.40 (PMP-P 100) inches
				of rainfall in six (6) hours.
7.1.c.1.C. Class C impoundment shall be
				designed for a probable maximum precipitation (PMP) of a six (6) hour or
				greater event plus three feet of freeboard.
7.1.d. Antecedent Moisture Conditions: Where
				applicable to the development of a hydrograph, antecedent moisture condition II
				(AMC II) may be used unless a different condition class is required by the
				Secretary.
7.1.e. Flood Routings:
				An analysis shall be performed for the reservoir and spillways which includes
				inflow hydrographs, stage storage curves, stage discharge curves, and routings.
				The spillways must be able to safely discharge that portion of the design storm
				that is not stored in the reservoir. If a computer analysis is used, the input
				data and output results must be clearly labeled and identified. Trial
				calculations or intermediate results not relevant to the final results may be
				omitted from the plan package.
7.1.f. Specific Flood Routing and Storage
				Requirements:
7.1.f.1. Class A dams must be
				designed with an open channel spillway unless otherwise (90) percent of the
				stored portion of the design storm must be discharged or removed within ten
				(10) days after the storm event.
7.1.f.2. Class B dams must be designed with
				either an open channel spillway only, or with an emergency spillway and a
				principal spillway together. Ninety (90) percent of the stored portion of the
				design storm shall be discharged or removed within ten (10) days after the
				storm event.
7.1.f.3. Class C dams
				may be designed in one of three ways:
7.1.f.3.A. An impoundment designed without
				discharge structures shall be capable of storing a minimum of two (2) six (6)
				hour duration probable maximum storms. A system shall be designed to dewater
				the impoundment of the probable maximum storm in ten (10) days by pumping or by
				other means. The requirements of 25.14 shall also be met.
For existing structures exceeding the minimum 2 PMP volume
				  requirement, the dewatering system shall be installed when the containment
				  volume is reduced to 2 PMPs.
7.1.f.3.B. An impoundment designed with a
				decant or principal spillway only shall be capable of storing at least one (1)
				six (6) hour duration probable maximum storm Ninety (90) percent of the stored
				shall be discharged or removed within ten (10) days after the storm
				event.
7.1.f.3.C. An impoundment
				designed with either an open channel spillway only, or with an emergency
				spillway and principal spillway together shall be capable of discharging that
				portion of the six (6) hour duration probable maximum storm that cannot be
				safely stored in the impoundment. Ninety (90) percent of the stored portion of
				the storm shall be discharged or removed within ten (10) days after the storm
				event.
7.1.g.
				Surface Drainage Control: Surface drainage control devices (e.g., vegetated
				slopes, benches, groin ditches, and collection channels) shall be provided as
				necessary to protect the dam and its appurtenances from the effects of erosion.
				Riprap or other erosion protection measures shall be included where excessive
				velocity is anticipated or experienced. All surface drainage control devices
				must be designed to exit safely beyond the downstream toe of the embankment in
				a natural drain way and be capable of carrying the design flow without
				excessive erosion. Any open channel spillway designed for less than one hundred
				(100) percent probable maximum precipitation shall be provided with freeboard
				above the maximum water surface as determined by the equation 1 + 0.025
				vd1/3.
7.1.h. Hydraulic Considerations: Using
				standard engineering practices, a hydraulic analysis shall be performed for the
				spillways and surface drainage system. Typical cross section design techniques
				may be used where constant shapes are encountered. All hydraulic structures
				shall be designed to safely control the velocity of water in order to prevent
				excessive erosion. Accepted engineering practices shall be used to design
				riprap, non-flexible channel linings, bedding, and energy dissipaters.
7.1.h.1. Specific Hydraulic Requirements:
				Open channels, including open channel spillways, shall be analyzed for flow
				depth, velocity, non-uniform flow conditions, super-elevation, and hydraulic
				jumps.
7.1.h.1.A. Stage Discharge: Where an
				open channel is used as a spillway, a stage discharge rating shall be developed
				using standard engineering practices for the type and shape of the spillway. In
				developing the rating, increase in upstream water depth due to change in
				velocity head must be considered.
7.1.h.1.B. Water Surface Profiles: Where
				channel slopes or cross-sections vary and non-uniform flow conditions result, a
				water surface profile may be necessary in order to analyze the channel flow
				depths and the location of hydraulic jumps.
7.1.h.1.C. Hydraulic Jumps: Where hydraulic
				jumps will occur, channel sidewall height shall be sufficient to contain the
				jump. The channel lining shall be designed to withstand the hydraulic jump
				without damage.
7.1.h.1.D. Critical
				Flows: Channels shall be designed so that water will not flow at critical depth
				for extended distances. In channels of varying slope or cross-sections where
				non-uniform flow occurs, the transition through critical flow shall be as rapid
				as possible.
7.1.h.1.E. Super
				Elevation: Channel walls shall be designed to contain super elevated flows on
				curves.
7.1.i. Closed Conduit Systems: Closed Conduit
				Systems including principal spillways, risers and pipes shall be analyzed to
				determine the controlling limits for weir, orifice, and pipe flows.
7.1.j. Risers and Drop Inlets: Risers shall
				be protected with a designed trash rack and anti-vortex device. The drop inlet
				shall be sized to provide a rapid transition from partial to full pipe flow
				conditions.
7.1.k. Stage Discharge:
				When a closed conduit system is used as a principal system, a stage discharge
				rating shall be developed using standard engineering practices for weir,
				orifice, and pipe flow conditions.
7.1.l. An adequate foundation and bedding
				shall be designed for all pipes and risers.
7.1.m. All pipe spillways shall be designed
				to provide seepage control along the conduit.
7.1.n. Use of Corrugated Metal Pipes
				-Corrugated metal pipes, whether coated or uncoated, shall not be used in new
				or unconstructed refuse impoundments or slurry cells. If an existing corrugated
				metal pipe has developed leaks or otherwise deteriorated so as to cause the
				pipe to not function properly and such deterioration constitutes a hazard to
				the proper operation of the impoundment, the Secretary will require the
				corrugated metal pipe to be either repaired or replaced. Provided, however,
				sediment control or other water retention structures used for the treatment of
				effluent and designated as Class A Dams under 3.4.b of this rule are exempt
				from this prohibition.
7.1.o. The
				pipe spillway shall be of sufficient strength to withstand the maximum load of
				the fill above it.
7.1.p. The pipe
				spillway shall be of suitable material to resist deterioration for the design
				life of the facility.
7.1.q. The
				pipe spillway must be designed to avoid formation of alternating partial and
				full pipe flow conditions through proper selection of pipe slope and headwater
				or tail water conditions.
7.1.r.
				The outlet of all conduits where blockage by animals can occur must be
				protected by an animal guide.
7.1.s. Landslide Potential: When locating all
				hydraulic structures the potential for landslides or slope failures as
				determined in the initial site investigation shall be evaluated according to
				Section 10.6.