SUBCHAPTER 2K ‑ DAM SAFETY
SECTION .0100 ‑ GENERAL PROVISIONS
15A NCAC 02K .0101 DEFINITIONS
15A NCAC 02K .0102 DAM SAFETY ORDERS
History Note: Authority G.S. 143‑215.25; 143‑215.32;
143‑215.34;
Eff. January 22, 1977;
Amended Eff. November 1, 1978;
Repealed Eff. June 15, 1980.
15A NCAC 02K .0103 PURPOSE
The rules and regulations contained in this Subchapter are
intended to carry out the purposes of the Dam Safety Law of 1967, as expressed
in G.S. 143‑215.24 which authorizes the implementation of a dam
inspection and certification program in the interest of public health, safety
and welfare.
History Note: Authority G.S. 143‑215.31; 143‑215.34;
Eff. June 15, 1980.
15A NCAC 02K .0104 DEFINITIONS
As used in this Subchapter, the following terms have their
stated meaning:
(1) "Applicant" means any person who has
notified the department that he or she desires to construct, repair, alter, or
remove a dam and requests approval by the department.
(2) "Appurtenance" means an accessory or
integral subordinate structure associated with a dam, such as a spillway,
conduit, walkway, valve, control gate, etc.
(3) "Articulation" means provisions for safe
movement at the joint or juncture of sections of conduit.
(4) "As‑built plans" means drawings,
photographs, test data, and descriptions that clearly and accurately define the
dam and its appurtenances after all construction is completed.
(5) "Conduit" means a natural or artificial
channel or pipe through which water or other fluid is conveyed.
(6) "Critical circle" means the circle with
the lowest factor of safety against mass movement in a circular arc analysis of
slope stability.
(7) "Critical failure wedge" means the mass
or block having the lowest factor of safety against mass movement in an
analysis of slope stability along planar surfaces.
(8) "Director" means the Director of the Division
of Energy, Mineral, and Land Resources, North Carolina Department of Natural
Resources and Community Development.
(9) "Equipotential lines" means lines which
represent points of equal energy level or head in a flow net.
(10) "Factor of safety" means the ratio of the
forces or moments resisting mass movement to the forces or moments tending to
produce mass movement.
(11) "Flow lines" means lines which represent
the direction of flow in a flow net.
(12) "Flow net" means a graphical
representation of flow lines and equipotential lines.
(13) "Hazard potential" means the probable
damage that would occur if the structure failed, in terms of loss of human life
and economic loss or environmental damage.
(14) "Maintenance plan" means written
instructions prepared by the engineer that prescribe the proper servicing and
repair of mechanical equipment, appurtenances, spillways, vegetative cover, and
other aspects related to the safety of the dam.
(15) "Owner" means the individual or
association of individuals owning the property on which the dam exists or is to
be constructed, and the persons financially responsible for the construction.
(16) "Phreatic surface" means the free‑water
surface of a zone of seepage; it is represented by the uppermost flow line, or
seepage line, in a flow net.
(17) "Qualified engineer" means a professional
engineer legally qualified to practice in North Carolina pursuant to Chapter
89C of the General Statutes of North Carolina, and having appropriate specialty
expertise for the particular dam engineering problem with which he is involved.
(18) "Qualified geologist" means an earth scientist
experienced in applied geology with respect to the interaction of lithologies,
soils, and geologic structures with dams and impoundments, who can provide
professional credentials such as certification by the American Institute of
Professional Geologists or registration as a geologist in the United States.
(19) "Quality control" means that combination
of testing, observation, and monitoring provided during construction to confirm
that requirements stated or depicted in the plans and specifications are being
achieved.
(20) "Rapid drawdown" means removal of liquid
from a reservoir at a rate that is significantly faster than the rate of
drainage of the materials composing the portions of the reservoir exposed by
the fluid removal.
(21) "Seepage" means the movement of water in a
porous material and the water exiting at the visible surface of the material.
(22) "Sliding base analysis" means an analysis
of the safety of a structure against lateral movement along its foundation.
(23) "Waste treatment and mine refuse dam"
means a structure for impounding, restraining, storing, or disposing of
liquids, slurries, or materials capable of liquification, produced from
industrial, commercial, municipal, agricultural, or mining activities.
(24) "Construction" means any action, other
than by natural causes, that creates a structure capable of impounding water or
other liquids, or which increases the impoundment capacity of an existing
structure. For the purposes of 15A NCAC 2K .0222, it shall also mean the
reduction of the height or impoundment capacity of a dam when the effect of
such reduction will be to exempt the dam from the North Carolina Dam Safety Law
of 1967.
History Note: Filed as a Temporary Amendment Eff.
November 1, 1990 For a Period of 180 Days to Expire
on April 29, 1991;
Authority G.S. 143‑215.25; 143‑215.31;
Eff. June 15, 1980;
Amended Eff. July 1, 1988; November 1, 1984;
ARRC Objection Lodged November 14, 1990;
ARRC Objection Removed December 20, 1990;
Amended Eff. August 1, 2012 (see S.L. 2012-143, s.1.(f));
January 1, 1991.
15A NCAC 02K .0105 CLASSIFICATION OF DAMS
(a) For the purposes of this Subchapter, dams shall be
divided into three classes, which shall be known as class A (low hazard), class
B (intermediate hazard), and class C (high hazard):
(1) Class A includes dams located where failure
may damage uninhabited low value non‑residential buildings, agricultural
land, or low volume roads.
(2) Class B includes dams located where failure
may damage highways or secondary railroads, cause interruption of use or
service of public utilities, cause minor damage to isolated homes, or cause
minor damage to commercial and industrial buildings. Damage to these
structures will be considered minor only when they are located in back water
areas not subjected to the direct path of the breach flood wave; and they will
experience no more than 1.5 feet of flood rise due to breaching above the
lowest ground elevation adjacent to the outside foundation walls or no more
than 1.5 feet of flood rise due to breaching above the lowest floor elevation
of the structure, the lower of the two elevations governing. All other damage
potential will be considered serious.
(3) Class C includes dams located where failure
will likely cause loss of life or serious damage to homes, industrial and
commercial buildings, important public utilities, primary highways, or major
railroads.
(b) Classifications shall be proposed by the design
engineer and are subject to approval by the Director.
(c) Probable future development of the area downstream from
the dam that would be affected by its failure shall be considered in
determining the classification.
(d) Dams will be subject to reclassification if the
Director determines that the hazard potential has changed. Non‑structural
provisions of adequately demonstrated effectiveness and reliability such as
flood plain zoning, and early warning systems may be considered by the Director
in making this determination.
(e) When dams are spaced so that the failure of an upper
dam would likely fail a lower dam, the consequence of the lower dam's failure
shall be a determining factor for the upper dam's hazard classification.
(f) In assigning a hazard classification where a bridge or
roadway is the only damageable property below a dam, consideration shall be
given to the possibility of loss of human life, indirect economic impact
through loss of service, and direct cost of damage to the bridge or roadway.
History Note: Authority G.S. 143‑215.31; 143‑215.34;
Eff. June 15, 1980.
SECTION .0200 ‑ OBTAINING APPROVAL FOR DAM CONSTRUCTION:
REPAIR:OR REMOVAL
15A NCAC 02K .0201 APPLICATIONS
(a) Any person(s) who proposes to construct, repair, alter
or remove a dam must file with the Director a statement concerning the location
of the dam, including the name of the stream and county, height, purpose, and
impoundment capacity, 10 days before start of construction. If the Director
determines that the proposed dam is exempt from the law, the applicant will be
notified and he may then proceed with the construction.
(b) If the Director determines that the proposed dam is not
exempt from the Dam Safety Law of 1967, the applicant will be so notified
within 10 days of receipt of the statement described in (a) of this Rule and
construction may not commence until a full and complete application has been
filed and approved. This application must be filed at least 60 days before the
proposed start of construction:
(1) When an application to construct a dam has
been completed pursuant to Subsection (a) of this Rule, the department shall
refer copies of the completed application papers to the Department of Human
Resources, the Wildlife Resources Commission, the Department of Transportation,
and such other state and local agencies as it deems appropriate for review and
comment.
(2) Before commencing the repair, alteration,
or removal of a dam, application shall be made for written approval by the
department, except as otherwise provided by this Subchapter or in accordance
with G.S. 143‑215.27(b). The application shall state the name and
address of the applicant; shall adequately detail the changes it proposes to
effect; and shall be accompanied by maps, plans, and specifications setting
forth such details and dimensions as the department requires. The department
may waive such requirements in accordance with G.S. 143‑215.27(a). The
application shall give such other information concerning the dam and reservoir
required by the department concerning the safety of any change as it may
require, and shall state the proposed time of commencement and completion of
the work. When an application has been completed, it may be referred by the
department for agency review and report as provided by G.S. 143‑215.26(b)
in the case of original construction.
(c) The application for any dam shall include a preliminary
report. (Filing of the preliminary report prior to filing the final design
report, early in the site investigation and design schedule, is encouraged to
assure the state's concurrence with the hazard classification, site
investigation, and design concept. This is especially encouraged for class C
dams.) The preliminary report shall be filed with the application and shall
include the following information:
(1) a general description of the dam and
appurtenances and a proposed classification as set forth in Rule .0105 of this
Subchapter; The description shall include a statement of the purpose for which
the dam is to be used;
(2) a description of properties located below
the dam including number of homes, buildings, roads, utilities, and other
property that, as determined by the engineer, would be endangered should
failure of the dam occur;
(3) maps showing the location of the proposed
structure that include the county, location of state roads, access to site, and
outline of the reservoir; aerial photographs or USGS maps may be used;
(4) preliminary drawings or sketches that
include cross‑sections, plans and profiles of the dam, proposed pool
levels, and types of all spillways;
(5) preliminary design criteria and basis for
selection including a description of the size, ground cover conditions, and
extent of development of the watershed, drainage area, spillway design storm,
geology and geotechnical engineering, assumptions for the foundation and
embankment materials, and type of materials to be used in the principal
spillways(s).
(d) The Final Design Report. A "Certificate of
Approval" to construct will not be issued until the final design report is
received and approved. The preliminary report as described in (c) of this Rule
and the final design report may be submitted as one document. The final design
report shall include:
(1) a report of the investigation of the
foundation soils or bedrock and the borrow materials, including the location of
borrow areas, that are to be used to construct the dam;
(2) criteria to indicate that the dam will be
stable during construction and filling and under all conditions of reservoir
operations;
(3) computations indicating that the dam is
safe against overtopping during occurrence of the inflow design flood and wave
action; Wave action need not be considered when the design flood is based on
the probable maximum precipitation (pmp);
(4) criteria, design data or references to
indicate that seepage flow through the embankment, foundation, and abutments
will be controlled so that no internal erosion will take place and so there
will be no sloughing in the area where the seepage emerges;
(5) calculations and assumptions relative to
design of the spillway(s);
(6) provision to protect the upstream slope,
crest, and downstream slope of earth embankments and abutments from erosion due
to wind and rain;
(7) other design data, assumptions, and
analysis data pertinent to individual dams and site conditions;
(8) a proposed construction schedule;
(9) a proposed filling schedule for the
reservoir;
(10) a maintenance and operation plan;
(11) the estimated design life of the dam and the
reservoir;
(12) provision for maintaining minimum stream
flow requirements.
(e) The Plans and Specifications. Five sets of plans and
specifications must be submitted. The plans shall be a detailed engineering
design that consists of drawings and specifications and that include the
following as a minimum:
(1) Sheet one shall show the name of the
project; name of owner; hazard classification of the dam; designated access to
the project; and location with respect to highways, roads, streams, and any
dam(s) that would affect or be affected by the proposed structure;
(2) Maps shall be included showing the drainage
area and outline of the reservoir and the ownership of properties covered by
the reservoir or flood pool;
(3) Geologic investigation, cross‑section,
profiles, logs of borings, location of borrow areas, drawings of principal and
emergency spillways, and other additional sheets shall be included and drawn in
sufficient detail to clearly indicate the extent and complexity of the work to
be performed; The degree of detail required shall be determined by the
applicable provisions of Rules .0204 through .0212 of this Section;
(4) The technical provisions, as may be
required, to describe the method of construction and quality control for the
project;
(5) Special provisions, as may be required, to
describe technical provision needed to ensure that the dam is installed
according to the approved plans and specifications;
(6) General provisions that specify the rights,
duties, and responsibilities of the applicant, applicant's engineer and builder
and the prescribed order of work.
(f) The Director, within 60 days following receipt of a
completed application, shall notify the applicant, by mail, that the
application is either approved or disapproved. An approved application shall
conform to the requirements of Rule .0202 of this Section.
History Note: Authority G.S. 143‑215.26,
143-215-2; 143-215.31;
Eff. June 15, 1980.
15A NCAC 02K .0202 CERTIFICATE OF APPROVAL
(a) Approval of construction, repair, alteration, or
removal of a dam will be contained in a certificate called a "Certificate
of Approval" to be issued by the Director. A Certificate of Approval is a
letter from the Director constituting approval subject to written general
stipulations and specific written stipulations deemed necessary by the Director
on a case by case basis.
(b) No construction shall be performed until the
certificate is issued. The Certificate of Approval period shall be valid for
the construction schedule specified in the approved final design report.
Construction must commence within one year after the certificate is issued.
(c) Notice by registered or certified mail shall be given
to the Director at least 10 days before construction is commenced. When
repairs are necessary to safeguard life and property, they may be started
immediately; but the department shall be notified forthwith of the proposed
repairs and of the work under way, and they shall be made to conform to its
orders.
(d) If construction does not commence within one year after
the certificate of approval is issued, the certificate shall expire and a new
application shall be submitted. Upon written application and for good cause
shown, the Director may extend the time for commencing construction.
(e) Certificates of Approval are revocable in the event
that the terms of the certificate, including the written stipulations and those
terms stated in G.S. 143‑215.23, are violated or in the event that
conditions develop during construction that are hazardous to life and
property. If the certificate is revoked due to development of hazardous
conditions, the Director will issue an order requiring the owner or owners of
the dam to make at his or their expense maintenance, alterations, or removal as
deemed necessary within a time limited by the order; provided, any dam covered
by a certificate issued under this Rule is considered to be within the
definition of dams in G.S. 143‑215.25 and .0104 of this Subchapter.
(f) Certificates of Approval are revocable in the event
that the approved construction schedule is deviated from without prior written
approval of a substitute construction schedule submitted in writing. Such
approval of a substitute construction schedule shall be in the form of an
Addendum to the Certificate of Approval to be issued by the Director.
History Note: Authority G.S. 143‑215.26,‑27,‑31;
Eff. June 15, 1980.
15A NCAC 02K .0203 PROFESSIONAL ENGINEER REQUIREMENTS
The design, preparation of the plans and specifications,
inspection of the construction of or on the dam, and certification that the dam
was constructed, repaired, altered, or removed according to the plans approved
by the Director and that the dam or its remains are safe shall be done by a
legally qualified engineer and shall bear his professional seal unless exempted
under the provisions of G.S. 89C‑25.
History Note: Authority G.S. 143‑215.29,‑31;
Eff. June 15, 1980.
15A NCAC 02K .0204 INVESTIGATIONS
(a) General. The applicant shall be required to complete
all investigations prior to submission of the final plans and application. The
scope and the degree of precision that will be required for a specific project
will depend on the conditions of the site and the hazard created by the
proposed structure.
(b) Foundations and Abutments. The foundation and
abutments investigation shall consist of borings, test pits, and other
subsurface exploration necessary to assess the soil, rock, and groundwater
conditions. Geologic profiles and a geologic report prepared by a qualified
geologist may be required for class B dams and shall be required for class C
dams.
(c) Construction Materials. Specifications for
construction materials shall establish minimum acceptance criteria so that
design properties are achieved. If the use of on site borrow materials is
specified, exploration, testing, and calculations should be performed to
indicate that there are sufficient quantities of material available that meet
the design criteria.
(d) Surveys. Surveys shall be made with sufficient
accuracy to locate the proposed construction and to define the volume of the
storage in the reservoir. The downstream area shall be investigated in order
to delineate the area of potential damage in case of failure. Locations of
centerlines, and other horizontal and vertical control points, shall be shown
on a map of the site.
(e) Hydrologic Investigation. The drainage area shall be
determined. Both present and projected future land use shall be considered in
determining the runoff characteristics of the drainage area. The most severe
of these two conditions shall be used in the design. All hydrologic
assumptions and design calculations shall be included in the report.
History Note: Authority G.S. 143‑215.26,‑27,‑31;
Eff. June 15, 1980.
15A NCAC 02K .0205 SPILLWAY DESIGN
(a) All dams shall have a spillway system with capacity to
pass a flow resulting from a design storm indicated in (e) of this Rule for a
hazard classification appropriate for the dam, unless the applicant provides calculations,
designs, and plans to show that the design flow can be stored, passed through,
or passed over the dam without failure occurring.
(b) A vegetated earth or unlined emergency spillway will be
approved when computations indicate that it will pass the design storm without
jeopardizing the safety of the structure. The risk of recurring storms,
excessive erosion, and inadequate vegetative cover will be considered
acceptable in such a spillway when its average frequency of use is predicted to
be no more frequent than once in 25 years for existing class B and for class A
dams except for small class A dams designed in accordance with all design
criteria established by the U.S.D.A, Soil Conservation Service, and as
contained in Engineering Standard 378 of the U.S.D.A., Soil Conservation
Service; once in 50 years for new class B, small and medium new class C, and
existing class C dams; and once in 100 years for large and very large new class
C dams. The dam sizes referred to in this Subsection are defined in (e) of
this Rule.
(c) Lined Spillways and Channels. The design report shall
include design data criteria for open channel, drop, ogee, and chute spillways
and other spillway types that include crest structures, walls, channel lining,
and miscellaneous details. All masonry or concrete structures shall have
joints that are relatively water‑tight and shall be placed on foundations
capable of sustaining applied loads without undue deformation. Provisions must
be made for handling leakage from the channel or underseepage from the
foundation which might cause saturation of underlying materials or uplift
against the undersurfaces.
(d) Within 15 days following passage of the design storm
peak, the spillway system shall be capable of removing from the reservoir at
least 80 percent of the water temporarily detained in the reservoir above the
elevation of the primary spillway.
(e) It is recognized that the relationships between valley
slope and width, total reservoir storage, drainage area, other hydrologic factors,
and specific cultural features have a critical bearing on determining the safe
spillway design flood. Rational selection of a safe spillway design flood for
specific site conditions based on quantitative analysis is acceptable. The
spillway should be sized so that the increased downstream damage resulting from
overtopping failure of the dam would not be significant as compared with the
damage caused by the flood in the absence of dam overtopping failure. A design
storm more frequent than once in 100 years will not be acceptable for any class
C dam. In lieu of quantitative analysis, the following tables shall be used as
criteria for spillway design storms and permissible velocities for vegetated
earth spillways:
CRITERIA FOR
SPILLWAY DESIGN STORM
SIZE CLASSIFICATION
Size
Total Storage (Ac-Ft)1
Height (ft)1
Small
less than 750
less than 35
Medium
equal to or greater than 750
and less than 7,500
equal to or greater than 35
and less than 50
Large
equal to or greater than
7,500 and less than 50,000
equal to or greater than 50
and less than 100
Very Large
equal to or greater than
50,000
equal to or greater than 100
1 The factor determining the largest size shall
govern
MINIMUM SPILLWAY DESIGN STORMS
Hazard
Size
Spillway Design Flood (SDF)
Low (Class A)
Small
Medium
Large
Very Large
Medium
50 year
100 year
1/3 PMP
1/2 PMP
1/3 PMP
Intermediate (Class B)
Small
Large
Very Large
100 year
1/2 PMP
3/4 PMP
High (Class C)
Small
Medium
Large
Very Large
1/3 PMP
1/2 PMP
3/4 PMP
PMP
PERMISSIBLE VELOCITIES FOR VEGETATED EARTH SPILLWAYS
Permissible velocity1 feet per second
Erosion resistant soils
Easily erodible soils
Slope of exit channel
Percent
Slope of exit channel
Percent
Vegetation
0 to 5
5 thru 10
0 to 5
5 thru 10
Bermuda Grass
Bahia grass
8
7
6
5
Tall fescue
Kentucky bluegrass
Reed canary
7
6
5
4
Sod forming
grass mixture
5
4
4
3
Lespedeza sericea
Weeping lovegrass
Alfalfa
Crabgrass
3.5
Do not use
2.5
Do not use
2 Increase values 10 percent when the anticipated
average use of the spillway is not more frequent than once in 50 years or 25
percent when the anticipated average use is not more frequent than once in 100
years.
History Note: Authority G.S. 143‑215.26; 143‑215.27;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0206 CONDUITS
(a) A conduit shall be provided to drain each reservoir.
The conduit design shall include the computation of the minimum time required
to drain the reservoir.
(b) All pipe conduits shall convey water at the design
velocity without damage to the interior surface.
(c) Protection shall be provided to prohibit unsafe seepage
along conduits through the dam, abutments, and foundation. The specific design
for seepage protection along conduits shall be shown in the drawings and specifications.
(d) Adequate allowances shall be incorporated in the design
to compensate for differential settlement and possible elongation of the pipe
conduit.
(e) Trash racks shall be installed at the intake of
conduits to prevent clogging the conduit.
(f) Pipe Conduit Spillway Materials
(1) Pipe conduits shall be designed to support
the total external loads in addition to the total internal hydraulic pressure
without leakage.
(2) Reinforced or Prestressed Concrete Pipe
Conduits
(A) All conduits are to be designed and constructed to
remain watertight under maximum anticipated hydraulic pressure and maximum
probable joint opening, including the effects of joint rotation and
extensibility.
(B) Provisions for safe movement of the barrel are to be
provided at each joint in the barrel and at the junction of the barrel and
riser or inlet. Cradles are to be articulated if constructed on a yielding
foundation.
(C) The engineer shall submit the final design details
of the proposed pipe to be used for all class A dams where the height of the
dam exceeds 35 feet and all class B and C dams.
(3) Corrugated Metal Pipe Conduits
(A) Corrugated metal pipe shall not be used in class A
dams over 35 feet high or in class B and C dams, except for special cases when
the design engineer can adequately demonstrate satisfactory performance.
(B) Corrugated metal pipe may be used in class A dams
which are less than 35 feet high.
(C) Corrugated metal conduits shall have watertight
connecting bands designed and installed to remain watertight under maximum
anticipated hydrostatic head and joint rotation.
(D) Flange type couplings shall not be used for
corrugated metal pipe or corrugated steel pipe where the diameter exceeds 12
inches unless the applicant produces computations to verify that the flanges
and the pipe conduit are of such design to safely support the total external
loads in addition to the total internal hydraulic pressure without leakage.
(g) Dissipating Devices. All gates, valves, conduits and
concrete channel outlets shall be provided with a dissipator designed and
constructed to control erosion and prevent damage to the embankment or the
downstream outlet or channel.
(h) In the case of repair to an existing dam, the engineer
may determine that the conduit should not be repaired or replaced and shall
submit reasoning to support this determination in the application for the
Certificate of Approval to repair. The Director shall approve, disapprove, or
approve in part this determination.
History Note: Authority G.S. 143‑215.26; 143‑215.27;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0207 SEEPAGE CONTROL
(a) All dams shall be designed and constructed to prevent
the development of instability due to excessive seepage forces, uplift forces,
or loss of materials in the embankment, abutments, spillway areas, or
foundation. Seepage analysis for design shall identify areas having high
internal uplift or exit gradients.
(b) The design may include an embankment internal drainage
system, a zoned embankment, a foundation cut‑off, an upstream blanket, a
sufficiently wide homogeneous section, or other methods to protect against
instability from excessive seepage forces or high hydraulic gradients.
(c) For class C dams, a flow net analysis shall be made to
determine the location of the phreatic surface, flow lines, and equipotential
lines within the embankment and its foundation. This analysis may be based on
graphical construction, electrical or liquid analogs, soil prototype methods,
or other accepted methods. The flow net and stability analysis shall use the
maximum operating pool level with not less than five feet of clear water at the
surface. Possible fluctuations in tail water elevation shall be included in
the analysis. The flow net and seepage analysis shall be documented in the
final design report, as required by .0201(d)(4) of this Section.
(d) Piezometers for confirming the location of the phreatic
surface assumed for seepage and slope stability analyses should be considered
by the design engineer for class A and class B dams and shall be required for
class C dams. Where piezometers are required, their design, depths, and
locations shall be provided as required in .0201(d) and .0212(b) of this
Section.
History Note: Authority G.S. 143‑215.26; 143‑215.27;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0208 STRUCTURAL STABILITY AND SLOPE
PROTECTION
(a) Design and construction of dams to assure structural
stability shall be consistent with modern engineering practice. The scope and
degree of precision that will be required for a specific project will depend on
the conditions of the site and the damage potential of the proposed structure.
Consideration in design for structural stability shall include, but are not
necessarily limited to, the following:
(1) the hazard potential of the dam under
present downstream conditions and under conditions which would likely develop
during the life of the reservoir;
(2) foundation bearing capacity,
compressibility, and permeability; the extent and reliability of the site
investigation; and the predictability of the site and foundation conditions;
(3) the reliability of construction materials,
such as borrow soils, in terms of sufficient volume to complete construction
without unanticipated interruption and in terms of predictability of physical
properties such as strength, permeability, and compressibility;
(4) durability of construction materials;
(5) construction conditions at the site;
(6) the degree of quality control to be
exercised during construction;
(7) pore pressure build‑up during
construction;
(8) the rate of filling the reservoir and the
rate of possible reservoir drawdown;
(9) tailwater conditions and the impact of
tailwater drawdown;
(10) possible effects of landslides and
subsurface solution activity on the structural stability of the dam and
spillway structures;
(11) the extent of piezometers and other devices
which will be used to monitor the completed dam and the degree of access for
inspections.
(b) Slope stability analyses should be considered by the
design engineer for all embankment dams and may be required for class B and
class C dams. Where slope stability analyses are required, documentation in the
final design report shall include the design cross section(s) showing the soil
parameters assumed for analysis, the location of the phreatic surface assumed
for analysis, stability computations, and the location and computed safety
factor(s) for the most critical circle(s) or failure wedge(s). A minimum
factor of safety of 1.5 for slope stability for normal loading conditions, and
1.25 for quick drawdown conditions and for construction conditions, shall be
required unless the design engineer provides a thoroughly documented basis for
using other safety factors.
(c) Foundation bearing capacity and sliding base analyses
should be considered for all dams and may be required for class B and C dams.
Where bearing capacity or sliding base analyses are required, documentation of
assumptions, computations, and safety factors shall be included in the final
design report. A minimum factor of safety against bearing capacity and sliding
wedge failure of 2.0 shall be required unless the design engineer provides a
thoroughly documented basis for using other safety factors.
(d) Resistance of appurtenant structures against flotation
uplift shall be provided for all dams. If the structures are anchored by dead
weight alone, the buoyant weight shall be used for analysis and the minimum
factor of safety shall be 1.15. If the structures are anchored to soil or
rock, the minimum factor of safety for that portion of the resistance provided
by soil or rock anchorage shall be 2.0 unless the design engineer provides a
thoroughly documented basis for using a lower safety factor.
(e) For concrete, masonry, or other similar dams of
relatively narrow cross section, resistance against overturning under maximum
design loading conditions shall be considered; overturning stability
computations shall be required for class B and class C dams. Where overturning
analyses are required, the computations shall be included in the final design
report. The minimum safety factor against overturning under maximum design
loading conditions shall be 1.5 unless the design engineer provides a
thoroughly documented basis for using a lower safety factor.
(f) The anticipated reservoir and tailwater drawdown
conditions shall be considered in all stability computations and shall be
included in the design documents provided in the final design report.
(g) The slopes must be protected against erosion by wave
action, and the crest and downstream slope must be protected against erosion
due to wind and rain. Riprap and other erosion protection shall be provided
over the full range in stage between the lowest drawdown elevation and at least
two feet above full normal pool. Exceptions for slowly rising reservoirs, such
as waste storage facilities, may be approved in writing by the Director.
History Note: Authority G.S. 143‑215.26; 143‑215.27;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0209 DESIGN LIFE OF A DAM AND RESERVOIR
(a) The selection of materials and equipment to be used in
a dam and all of its appurtenant features shall either be based on sufficient
quality and durability to satisfactorily function throughout the design life or
shall provide for safe and economical replacement within the design life span.
(b) The design life of a dam and reservoir is the period of
time the dam and reservoir can be expected to perform effectively as planned.
The design life of a dam shall be determined by the following:
(1) the time required to fill the reservoir
with sediment from the contributing watershed,
(2) the durability of appurtenances and
materials used to construct the dam,
(3) the time required to permanently fill a
waste treatment or storage facility with waste,
(4) the time required to perform the specific
function for which the dam was designed.
History Note: Authority G.S. 143‑215.27; 143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0210 SEDIMENT CONTROL
Sediment control related to earth moving activities involved
in construction or repair of dams shall be provided in accordance with the
North Carolina Sediment Pollution Control Act of 1973 (G.S. 113A‑50
through 113A‑66). Devices for sediment control during drainage of a
reservoir shall be provided; exceptions for emergency drainage of a reservoir
may be approved by the Director.
History Note: Authority G.S. 143‑215.31, ‑113A‑54;
Eff. June 15, 1980.
15A NCAC 02K .0211 WASTE TREATMENT AND MINE REFUSE DAMS
(a) Waste treatment and mine refuse dams and reservoirs
shall conform to all requirements of this Subchapter. In addition to the
requirements of Rule .0105 of this Subchapter, a waste treatment or mine refuse
dam may be classified A, B, or C on the basis of potential environmental
damage.
(b) Mine refuse dams that are designed to be constructed in
stages shall include an emergency spillway system that is capable of safely
passing the required storm frequency below the top of the dam for each stage of
construction. The refuse facility shall not be used until each stage of
construction is completed and approved by the Director.
History Note: Authority G.S. 143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0212 ADDITIONAL DESIGN REQUIREMENTS
(a) All elements of the dam and reservoir shall conform to
good engineering practice. The safety factors, design standards, and design
references that are used shall be included with the final design report.
(b) Monitoring or inspection devices may be required by the
Director for use by inspectors or owners in the inspection during construction
and filling and after completion of construction. The Director may also
require that such monitoring or inspection devices, existing or installed by
requirement, be read and documented at specified intervals and that copies of
such be forwarded to his office.
(c) The plans, construction schedule, and construction
specification shall assure that the downstream flow satisfies minimum quality
and quantity standards as defined in G.S. 143‑215.25(4) during the period
of construction, filling, and life of the dam and reservoir.
History Note: Authority G.S. 143‑215.26; 143‑215.27;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0213 CONSTRUCTION SCHEDULE
The applicant shall submit a construction schedule that
includes:
(1) Techniques and work force to be used to insure that
the dam is constructed according to the plans and specifications;
(2) A construction schedule that includes the estimated
time to complete the construction activities;
(3) Techniques to be used to divert the stream flow to
prevent interference with construction and hazard to life, health, or property;
(4) The extent and method of quality control shall be
subject to approval of the Director.
History Note: Authority G.S. 143‑215.26; 143‑215.27;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0214 PROPOSED CHANGES IN DESIGN
The owner shall notify the director of any proposed changes
in design, plans, and specifications that will affect the stability of the dam.
Approval must be obtained from the Director prior to installation. This
approval shall be in the form of a written addendum to the Certificate of
Approval.
History Note: Authority G.S. 143‑215.26; 143‑215.27;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0215 AS‑BUILT PLANS
Two complete sets of as‑built plans shall be submitted
to the Director within 30 days of completion of the project.
History Note: Authority G.S. 143‑215.30; 143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0216 ENGINEER'S CERTIFICATION
The engineer who has inspected the construction of or on the
dam shall submit written certification bearing his professional seal, unless
exempted under the provisions of G.S. 89C‑25, that the dam and all appurtenances
have been built, repaired, altered, or removed in conformance with the plans,
specifications, and drawings approved by the Director and that the dam is safe.
History Note: Authority G.S. 143‑215.30; 143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0217 AUTHORITY FOR INSPECTION
Authorized personnel of the department may make inspection
during construction as deemed necessary to ensure that the structure is being
built in conformance with the Certificate of Approval issued. Said inspections
do not relieve the engineer in charge from the responsibility of providing
adequate inspection of the work.
History Note: Authority G.S. 143‑215.29; 143‑215.30;
143‑215.31;
Eff. June 15, 1980.
15A NCAC 02K .0218 EXEMPTIONS
History Note: Authority G.S. 143‑215.21; 143‑215.31;
Eff. June 15, 1980;
Amended Eff. November 1, 1985;
Repealed Eff. July 1, 1988.
15A NCAC 02K .0219 ACCEPTABLE DESIGN: PROCEDURES AND
TECHNICAL REFERENCES
The following represent acceptable design procedures and
references:
(1) the design procedures, manuals, and criteria used
by the United States Corps of Engineers;
(2) the procedures, manuals, and criteria used by the
United States Soil Conservation Service;
(3) the procedures, manuals, and criteria used by the
United States Department of Interior, Bureau of Reclamation;
(4) other procedures that are approved by the Director.
History Note: Authority G.S. 143‑215.31; 143‑215.34;
Eff. June 15, 1980.
15A NCAC 02K .0220 GRANTING OF FINAL APPROVAL
(a) Unless the Director has reason to believe that the dam,
as completed, is unsafe or not in compliance with any applicable requirement,
regulation, or law, the Director, upon completion of construction and upon
receipt of the engineer's certification pursuant to Rule .0215 of this Section,
shall grant final approval of the work in accordance with the certificate,
subject to such terms as he/she deems necessary for the protection of life and
property.
(b) Pending issuance of final approval, a new dam or the
addition to an existing dam shall not be used except on written consent of the
Director and subject to conditions he/she may impose relating to safety of life
and property and the satisfaction of minimum stream flow requirements.
History Note: Authority G.S. 143‑215.3; 143‑215.30;
Eff. June 15, 1980.
15A NCAC 02K .0221 DELEGATION OF AUTHORITY
The Director has the authority to:
(1) issue approval, disapproval, or approval subject to
conditions for proposed construction, repair, alteration or removal of dams;
(2) require progress reports, issue notices of non‑compliance
and orders to comply, order a halt in construction in the event of non‑compliance;
(3) receive notices of completion, specify details of
description, grant final approval;
(4) assess civil penalties; and
(5) perform other related functions.
History Note: Authority G.S. 143‑215.3; 143‑215.3(a)(4);
143‑215.28; 143‑215.29; 143‑215.30;
143‑215.36(b);
Eff. June 15, 1980;
Amended Eff. November 1, 1982.
15A NCAC 02K .0222 APPLICATION PROCESSING FEES
(a) A nonrefundable minimum application processing fee, in
the amount stated in Paragraph (d)(1) of this Rule, shall be paid when an
application for construction or removal of a dam is filed in accordance with
15A NCAC 2K .0201. Each application for construction or removal of a dam shall
be deemed incomplete and shall not be reviewed until the minimum application
processing fee is paid.
(b) A nonrefundable additional application processing fee,
in the amount stated in Paragraph (d)(2) of this Rule, shall be paid when the
as‑built plans are submitted to the Director in accordance with 15A NCAC
2K .0215. Final approval to impound, pursuant to 15A NCAC 2K .0220, shall not
be granted until the owner's certification and the accompanying documentation
are filed in accordance with Paragraph (e) of this Rule, and the additional
processing fee is paid.
(c) The application processing fee for the construction or
removal of a dam shall be based on the actual cost of construction or removal
of the applicable dam.
(1) The actual cost of construction or removal
of a dam shall include all labor and materials costs associated with the
construction or removal of the dam and appurtenances.
(2) The actual cost of construction or removal
of a dam shall not include the costs associated with acquisition of land or
right of way, design, quality control, electrical generating machinery, or
constructing a roadway across the dam.
(d) Schedule of Fees:
(1) The minimum application processing fee
shall be two hundred dollars ($200.00).
(2) The additional application processing fee
shall be the following percentages of the cost of construction or removal:
(A) 2 percent of the actual costs between ten thousand
and one dollars ($10,001) and one hundred thousand dollars ($100,000);
(B) 1.5 percent of the actual costs between one hundred
thousand and one dollars ($100,001) and five hundred thousand dollars
($500,000);
(C) 1.0 percent of the actual costs between five hundred
thousand and one dollars ($500,001) and one million dollars ($1,000,000);
(D) 0.5 percent of the actual costs over one million
dollars ($1,000,000).
In no case, however, shall the additional application fee be
more than fifty thousand dollars ($50,000).
(e) Immediately upon completion of construction or removal
of a dam, the owner shall file with the Director a certification, on a form
prescribed by the Department, and accompanying documentation, which shows the
actual cost incurred by the owner for construction or removal of the applicable
dam.
(1) The owner's certification and accompanying
documentation shall be filed with the as‑built plans and the engineer's
certification in accordance with 15A NCAC 2K .0215 and 15A NCAC 2K .0216,
respectively.
(2) If the Director finds that the owner's
certification and accompanying documentation contain inaccurate cost
information, the Director shall either withhold final impoundment approval, or
revoke final impoundment approval, until the owner provides the accurate
documentation and that documentation has been verified by the Department.
(f) Payment of the dam application processing fee shall be
by check or money order made payable to the "N.C. Department of
Environment, Health, and Natural Resources". The payment should refer to
the applicable dam.
(g) In order to comply with the limit on fees set forth in
G.S. 143‑215.28A, the Director shall, in the first half of each state
fiscal year, project revenues for the fiscal year from fees collected pursuant
to this Rule. If this projection shows that the statutory limit will be
exceeded, the Director shall order a pro rata reduction in the fee schedule for
the remainder of the fiscal year to avoid revenue collection in excess of the
statutory limits.
History Note: Filed as a Temporary Rule Eff. November
1, 1990 For a Period of 180 Days to Expire on April 29, 1991;
Authority G.S. 143‑215.28A;
ARRC Objection Lodged November 14, 1990;
ARRC Objection Removed December 20, 1990;
Eff. January 1, 1991.
15A NCAC 02K .0223 DAM HEIGHT AND STORAGE DETERMINATION
(a) For the purpose of determining size classification, the
height of a dam shall be measured from the highest point on the crest of the
dam to the lowest point on the downstream toe.
(b) The total storage capacity of a dam shall be that
volume which would be impounded at the elevation of the highest point on the
crest of the dam.
History Note: Filed as a Temporary Rule Eff. November
1, 1990 For a Period of 180 Days to Expire on April 29, 1990;
Authority G.S. 143‑215.31;
ARRC Objection Lodged November 14, 1990;
ARRC Objection Removed December 20, 1990;
Eff. January 1, 1991.
SECTION .0300 ‑ INSPECTIONS: DAM SAFETY ORDERS
15A NCAC 02K .0301 INSPECTION BY THE DEPARTMENT
(a) Schedule of Inspections
(1) All class A and B dams shall be inspected
at least once every five years.
(2) Class C dams shall be inspected at least
once every two years.
(b) At any time an inspection indicates that a dam may not
perform satisfactorily or that the hazard classification has changed, the
Director may require a detailed investigation at the owners expense to
determine the required remedial action, if any.
History Note: Authority G.S. 143‑215.31; 143‑215.32;
Eff. June 15, 1980.
15A NCAC 02K .0302 DAM SAFETY ORDERS
(a) The Director may issue an order directing the owner(s)
of a dam to make, in not less than 90 days from issuance of the order and at
the owner(s) expense, any maintenance, alteration, repairs, reconstruction, or change
in construction upon a finding that the dam:
(1) is not sufficiently strong,
(2) is not maintained in good repair or
operating condition,
(3) is dangerous to life or property, or
(4) does not satisfy minimum stream‑flow
requirements.
(b) The Director may issue an order directing the owner(s)
of any dam to take such measures as may be essential, including lowering the
level of the impounded water, drainage of the impoundment, and destruction of
the dam or reservoir in whole or in part, immediately or within a time limited
by the order if the condition of the dam is found to have become so dangerous
to the safety of life or property, in the opinion of the Director, as not to
safely permit sufficient time for issuance of an order in the manner provided by
Subdivision (a) of this Rule.
(c) The Director may, if at any time the condition of any
dam becomes so dangerous to the safety of life or property, in the opinion of
the Director, as not to permit sufficient time for issuance of an order in the
manner provided by Subdivision (a) or (b) of this Rule, immediately take such
measures as may be essential to provide emergency protection to life and
property including the lowering of the level of a reservoir by releasing water
impounded or the destruction in whole or in part of the dam or reservoir.
Costs of such measures may be recovered from the owner(s) of the dam by
appropriate legal action by the Commission.
(d) Orders issued by the Director may be conditioned so as
to require the dam owner, if he is required or given the option to remove the
dam, to undertake the removal in such a manner as to minimize the amount of
sediment transported from the impoundment downstream.
(e) Dam safety orders issued by the Director in no way
relieve the owner(s) of the dam from duties and obligations imposed by
regulations in Section .0200 of this Subchapter, nor do they relieve the
owner(s) of the dam from any liabilities or other legal obligations.
History Note: Authority G.S. 143‑215.32; 143‑215.34;
Eff. June 15, 1980.
SECTION .0400 ‑ ADMINISTRATIVE HEARINGS
15A NCAC 02K .0401 OPPORTUNITY FOR HEARING
An administrative hearing before the N.C. Office of
Administrative Hearings shall be granted to any person:
(1) whose application for dam construction, repair,
alteration, or removal has been disapproved by the Director or has been
approved by the Director subject to conditions which are unacceptable to the
applicant pursuant to Rule .0202 of this Subchapter;
(2) who has been denied final approval of a completed
dam by the Director or who has been granted final approval by the Director
subject to conditions which are unacceptable to the applicant pursuant to Rule
.0219 of this Subchapter;
(3) against whom a dam safety order has been issued
requiring the maintenance, alteration, repair, reconstruction, change in
construction or location, or removal of a dam within 90 days, pursuant to Rule
.0302(a) of this Subchapter, or the lowering of the level of the water
impounded by the dam within a time period prescribed by the Director pursuant
to Rule .0302(b) of this Subchapter; or
(4) who has been assessed a civil penalty pursuant to
G.S. 143‑215.36(b) and Subchapter 2J of this Chapter.
History Note: Authority G.S. 143‑215.33; 150B‑23;
Eff. June 15, 1980;
Amended Eff. July 1, 1988.
15A NCAC 02K .0402 PROCEDURES
(a) Administrative hearings shall be conducted pursuant to
15A NCAC 1B .0200 et seq., and Chapter 150B of the General Statutes. Any
person entitled to an opportunity for a hearing by Rule .0401 of this Section
must request a hearing within ten days after receipt of the notice of the
action taken under Rule .0401 of this Section.
(b) Copies of 15A NCAC 1B .0200 may be inspected in the
offices of the Division of Energy, Mineral, and Land Resources, 512 N.
Salisbury Street, Raleigh, N. C. 27611. Copies may also be inspected in the
Division of Planning and Assessment, 512 N. Salisbury Street, 8th Floor,
Archdale Building, Raleigh, N. C. 27611. Copies may be obtained at the
previous locations or from the Rules Division of the N.C. Office of
Administrative Hearings, Blount Street, Raleigh, N.C. 27611.
History Note: Authority G.S. 143‑215.33; 150B‑23;
Eff. June 15, 1980;
Amended Eff. August 1, 2012 (see S.L. 2012-143, s.1.(f));
August 1, 1988; November 1, 1984.
15A NCAC 02K .0403 DELEGATION OF AUTHORITY: APPOINTMENT OF
HEARING OFFICERS
15A NCAC 02K .0404 NOTICE: WAIVER
15A NCAC 02K .0405 PLACE OF THE HEARING
15A NCAC 02K .0406 PROCEDURES
15A NCAC 02K .0407 HEARING OFFICERS: POWERS AND DUTIES
15A NCAC 02K .0408 FINAL DECISIONS: JUDICIAL REVIEW
History Note: Authority G.S. 143‑215.3(a)(4); 143‑215.33;
150B‑23; 150B, Article 3;
150B, Article 4;
Eff. June 15, 1980;
Legislative Objection (c) Lodged Eff. October 10, 1980;
Amended Eff. November 1, 1982;
Repealed Eff. November 1, 1984.
SECTION .0500 - MINIMUM STREAM FLOWS TO MAINTAIN AQUATIC
HABITAT
15A NCAC 02K .0501 DEFINITIONS
(a) Aquatic habitat shall be divided into three classes ‑
"poor," "moderate," and "good."
(1) Streams with poor aquatic habitat are those
which have a "poor" fish assemblage rating, and which are rated
"poor" for at least two of the following three characteristics:
(A) Substrate;
(B) Cover; and
(C) Macro-invertebrate organisms.
(2) Streams with moderate aquatic habitat are
those which exhibit physical conditions and biota which are intermediate
between the poor and good categories.
(3) Streams with good aquatic habitat are those
which receive at least two "good" ratings when the substrate, cover,
and macro‑invertebrate organism characteristics are evaluated. The fish
assemblage also must receive a "good" rating.
(b) Cover means objects within or overhanging the stream
channel which provide shelter for aquatic organisms. "Good" cover
occurs when cover is widespread and diverse. "Poor" cover occurs
when the amount of cover is small or non-existent.
(c) Substrate means the predominant particle size of the
material which makes up the stream bed. "Good" substrate is composed
of at least 50 percent silt free substrate with gravel or cobble.
"Poor" substrate is composed of at least 80 percent silt, sand, or
smooth bedrock.
(d) The macro‑invertebrate organisms of the affected
reach are rated as "good" if the affected reach is rated good or
excellent in the Division of Environmental Management's (DEM) biological monitoring
database, or by a site‑specific survey according to Standard Operating
Procedures for Biological Monitoring, 1995, Division of Environmental
Management as defined in 15A NCAC 2B .0103(b). Macro‑invertebrates are
rated "poor" if the reach is rated fair or poor in DEM's biological
monitoring database, or by a site‑specific survey according to Standard
Operating Procedures for Biological Monitoring, 1995, Division of Environmental
Management as defined in 15A NCAC 2B .0103(b).
(e) The fish assemblage rating shall be based on the North
Carolina Index of Biotic Integrity (IBI). Existing ratings from the DEM
biological monitoring database shall be used where available. If no rating
exists, then a site‑specific survey shall be conducted according to Standard
Operating Procedures for Biological Monitoring, 1995, Division of Environmental
Management as defined in 15A NCAC 2B .0103(b). The fish assemblage shall be
rated as "good" if the IBI rating is good, good‑excellent, or
excellent. The fish assemblage shall be rated as "poor" if the IBI
rating is poor or lower.
(f) The affected reach of stream means that section of a
stream downstream of a dam which experiences significant changes in hydrology.
The exact delineation of the affected reach shall be site‑specific and
depend on factors including, but not limited to:
(1) volume of storage in the impoundment;
(2) upstream and downstream hydrologic
characteristics of the stream;
(3) withdrawals from the impoundment; and
(4) downstream point source discharges to the
stream.
For the purpose of evaluating aquatic habitat, the affected
reach of a stream does not include any portion which is in the backwater of a
downstream dam when the level of that downstream impoundment is at normal pool.
(g) "Special case" streams are those which
exhibit at least one of the following characteristics:
(1) supplemental classification as an
Outstanding Resource Water as defined in 15A NCAC 2B .0101(e)(4) and .0216;
(2) populations of aquatic species listed as
threatened or endangered by the U.S. Fish and Wildlife Service, or species
which are listed as threatened or endangered by the N.C. Wildlife Resources
Commission;
(3) self‑sustaining populations of wild
trout; or
(4) exceptional non-game or fishery resources
as determined by the Wildlife Resources Commission.
(h) The use of the regression equations in Rule .0502 of
this Section shall depend on the geographic region of the state in which the
stream is located. The geographic region shall be determined from the North
Carolina Atlas, edited by Clay, Orr, and Stuart, published by the University of
North Carolina Press, 1975.
(i) A continuous stream gage record means a continuous
record of daily flows from a stream gage which:
(1) has at least 15 years of continuous daily
records;
(2) has no significant hydrological effects
caused by upstream regulation, withdrawals, or discharges;
(3) is no less than one-half and no more than
one and one-half times the drainage area of the site in question; and
(4) has low flow and average flow yields which
are comparable to the site in question.
(j) A site-specific instream flow study conducted by the
applicant or his consultants, which is subject to approval by the Department,
means a study performed according to the following conditions:
(1) A plan of study shall be developed in
consultation with the Department and submitted to the Department for review and
approval prior to commencement of the study.
(2) The plan of study shall identify the
aquatic habitat parameters to be evaluated by the study. The selection of
these parameters shall depend on factors including, but not limited to:
(A) the aquatic species being evaluated;
(B) the habitat quality of the affected reach; and
(C) existing or potential water shortages or water use
conflicts.
(3) The Department shall have the option of
participating in the collection of all field data, and shall be notified prior
to collection of any set of data.
(4) The results of the study shall accurately
determine the parameters identified during study design.
(5) The Department may review the field data
and results of these studies to determine the stream flow needed to maintain
aquatic habitat.
History Note: Authority G.S. 143-215.24; 143-215.25;
143-215.31; 143-215.32; 143-215.33; 143-215.36;
Eff. December 1, 1994;
Amended Eff. April 1, 1995.
15A NCAC 02K .0502 REQUIRED MINIMUM FLOW FOR DAMS (NOT
SMALL HYDRO PROJECTS)
(a) A dam operated by a small power producer, as defined in
G.S. 62‑3(27a), that diverts water from 4,000 feet or less of the
natural stream bed, shall be exempt from this Rule.
(b) A dam proposed for a small stream with a mean annual
daily flow less than or equal to 3.0 cubic feet per second (cfs) shall be
subject to the following review process in determining the required minimum
flow:
(1) If the mean annual daily flow is less than
or equal to 3.0 cfs and the 7‑day, 10‑year low flow (7Q10) is less
than or equal to 0.2 cfs; and if there are no existing point source discharges
of wastewater to the affected stream reach; then no minimum release will be
required.
(2) If the mean annual daily flow is less than
or equal to 3.0 cfs and the 7Q10 is less than or equal to 0.2 cfs; and one or
more existing point source discharges of wastewater enter the affected stream
reach; then the minimum release shall be equal to the 7Q10.
(3) If the mean annual daily flow is less than
or equal to 3.0 cfs and the 7Q10 is greater than 0.2 cfs, then the minimum
release shall be equal to the 7Q10.
(c) If the mean annual daily flow is greater than 3.0 cfs,
then the following procedures shall be used to determine the minimum flow
requirement:
(1) The minimum flow for a dam on a stream with
poor aquatic habitat shall be the 7Q10 flow determined by using U.S. Geological
Survey procedures.
(2) The minimum flow for a dam on a stream with
moderate aquatic habitat in the piedmont, as defined in Rule .0501(h) of this
Section, shall be determined using regression equations provided in this
Subparagraph.
(A) All flows used in regression equations shall be
measured in cubic feet per second, all drainage areas shall be measured in
square miles, and all logarithmic expressions shall refer to base 10
logarithms.
(B) The regression equation used to determine the
minimum flow for a stream in the piedmont which exhibits moderate aquatic
habitat, and for which no continuous stream gage record, as defined in Rule
.0501(i) of this Section, exists, shall be as follows:
LRF = (3.204 x M)
‑ (2.618 x D)
LRF = LOG of
regression flow
M = LOG of mean
annual daily flow
D = LOG of
drainage area
The regression
flow (RF) is calculated by raising 10 to the power of the LRF.
If the drainage area is greater
than 95 square miles, the required minimum flow is 1.4 x RF. Otherwise the
required minimum flow is equal to RF.
(C) The regression equation used to determine the
minimum flow for a stream in the piedmont which exhibits moderate aquatic
habitat, and for which a continuous stream gage record, as defined in Rule
.0501(i) of this Section, does exist, shall be as follows:
LRF = (0.812 x M)
+ (8.111 x E92)
‑ (4.806 x
E85) ‑ (3.275 x E95)
LRF = LOG of
regression flow
M = LOG of mean
annual daily flow
E85 = LOG of 85%
annual exceedance flow
E92 = LOG of
92.5% annual exceedance flow
E95 = LOG of 95%
annual exceedance flow
The regression
flow (RF) is calculated by raising 10 to the power of the LRF.
The required
minimum flow is 1.1 x RF.
(3) The minimum flow for a dam on a stream with
moderate aquatic habitat, located in a geographical region for which regression
formulas are not provided, shall be determined by a site‑specific instream
flow study, as defined in Rule .0501(j) of this Section, conducted by the
applicant or his consultants and subject to the approval of the Department.
(4) The minimum flow for a dam on a special
case stream, or on a stream with good aquatic habitat, shall be determined by a
site-specific instream flow study, as defined in Rule .0501(j). This study
shall be conducted by the applicant or his consultants, and shall be subject to
approval by the Department.
(5) If the applicant or owner disputes the minimum
flow determined by the procedures described in Subparagraphs (c)(1) or (c)(2)
of this Rule for streams with poor or moderate aquatic habitat, he may
undertake a site-specific field study, as defined in Rule .0501(j) of this
Section, subject to the review and approval of the Department. The final
minimum release required will not exceed the amount determined by the
procedures described in this Rule.
(6) The minimum release schedule for a water
supply reservoir shall include provisions for reductions in the minimum flow
which coincide with reductions in the usable water supply storage remaining in
the impoundment and with reductions in the amount of water withdrawn from the
reservoir.
(A) This system of tiered releases shall apply to new
water supply reservoirs and any existing water supply reservoirs for which the
minimum release is revised.
(B) The exact percentage of storage which triggers
reductions in minimum flow will depend on several site-specific factors,
including, but not limited to:
(i) size of the reservoir;
(ii) rate of the water supply demand;
(iii) hydrologic characteristics of the impounded
stream; and
(iv) the impoundment levels which result in local
efforts to reduce water usage through conservation measures.
(C) At least three levels of minimum releases shall be
included in the release schedule for a water supply reservoir.
(D) When usable water supply storage has been reduced to
a level which triggers the first reduction in minimum flow, then the average
daily water withdrawal shall be reduced by at least 10 percent from the average
daily withdrawal for the 60 day period immediately prior to the first reduction
in the minimum flow. The water supply operator shall accomplish this reduction
in withdrawal within two weeks of the reduction in the minimum release.
(E) When usable water supply storage has been reduced
to a level which triggers the second reduction in minimum flow, then the
average daily water withdrawal shall be reduced by at least 20 percent from the
average daily withdrawal for the 60 day period immediately prior to the first
reduction in the minimum flow. The water supply operator shall accomplish this
further reduction in withdrawal within two weeks of the second reduction in the
minimum release.
(F) The water system operator shall document reduction
in water withdrawals by submitting reports of daily water withdrawals to the
Department. These shall be submitted every two weeks for as long as the
minimum release is reduced below the amount normally required.
(G) An example is shown in the table below. (Note that
the percentages of water supply storage which trigger the changes in minimum
release are site‑specific for this example and may vary according to the
factors described in Part (B) of this Paragraph.)
REMAINING USABLE
WATER MINIMUM WATER USE
LEVEL SUPPLY
STORAGE RELEASE REDUCTION
1 between
70% and 100% A - - - -
2 between
40% and 70% B 10%
3 below
40% C
20%
A = normal
minimum release determined by a field study, regression equation, or use of the
7Q10
B = intermediate
reduction in minimum release
C = low minimum
release equal to no more than the 7Q10
(7) An existing dam which was built subject to
review under the National or the State Environmental Policy Acts, and for which
a minimum release has been established, will not have its minimum release
changed under this Rule. However, the Department may review and adjust the
minimum flow released by any other existing dam if there is evidence of any of
the following conditions downstream of that dam:
(A) water quality standards not being maintained;
(B) water quality classifications which are being only
partially supported or not being supported; or
(C) aquatic habitat not being maintained.
(8) If the minimum release required from an
existing water supply reservoir is reviewed by the Department, any increase in
minimum flow will be determined on a case‑by‑case basis in
consideration of the following factors, including, but not limited to:
(A) availability of water to meet existing demands;
(B) rate of growth in water demand;
(C) planned development of alternative sources of water
supply;
(D) structural difficulties;
(E) capital costs; and
(F) anticipated improvements in water quality and
aquatic habitat in the affected reach resulting from the proposed change in
minimum flow.
The change in minimum release
shall be set no higher than an amount which would reduce the water supply safe
yield, as determined by standard accepted engineering practices, by more than
10 percent.
(9) If a new minimum release requirement from
an existing water supply reservoir is being delayed until a new source of water
supply is developed, then this delay shall not exceed a period of five years
from the written notification that a new minimum release will be required.
This period may be extended by approval of the Environmental Management
Commission in consideration of the following factors:
(A) delays in developing a new water supply source;
(B) changes in water quality and aquatic habitat in the
affected reach; or
(C) availability of water to meet existing demands.
History Note: Authority G.S. 143-215.24; 143-215.25;
143-215.31; 143-215.32; 143-215.33; 143-215.36;
Eff. December 1, 1994;
Amended Eff. April 1, 1995.
15A NCAC 02K .0503 REQUIRED MINIMUM FLOW FOR SMALL
HYDROELECTRIC PROJECTS
(a) This Rule
shall apply only to a dam operated by a small power producer, as defined in
G.S. 62‑3(27a), that diverts water from 4,000 feet or less of the
natural stream bed. The length of the bypassed reach shall be measured from
the toe of the dam to the point where the diverted water re‑enters the
natural channel, following the centerline of the natural channel.
(b) The
minimum release for a hydroelectric project subject to this Rule shall be
determined according to the procedures described in Subparagraphs (1)-(5) of
this Paragraph. If at any time the inflow just upstream of the dam is less
than the minimum flow required in the bypassed reach, then the minimum flow may
be reduced to a level equal to this inflow.
(1) If
the aquatic habitat in the bypassed reach is rated poor, then the minimum
release to the bypassed reach shall be determined as follows:
(A) If the
7Q10 is less than or equal to 10 percent of the mean annual daily flow, then
the minimum release to the bypassed reach shall be the 7Q10 flow.
(B) If the
7Q10 is greater than 10 percent of the mean annual daily flow, and there are no
existing point source discharges of wastewater to the bypassed reach, then the
minimum release to the bypassed reach shall be 0.8 times the 7Q10.
(C) If the
7Q10 is greater than 10 percent of the mean annual daily flow, and one or more
existing point source discharges of wastewater enter the bypassed reach, then
the minimum release to the bypassed reach shall be the 7Q10 flow.
(2) If
the bypassed reach does not have an aquatic habitat rating of "poor,"
is not on a special case stream, and is located in the piedmont region, as
defined in Rule .0501(h) of this Section, then the minimum release to the
bypassed reach shall be determined as follows:
(A) If the
7Q10 is less than or equal to six percent of the mean annual daily flow, then
the minimum release to the bypassed reach shall be 3.0 times the 7Q10 flow.
(B) If the
7Q10 is greater than six percent of the mean annual daily flow, and less than
or equal to 10 percent of the mean annual daily flow, then the minimum release
to the bypassed reach shall be 2.2 times the 7Q10 flow.
(C) If the
7Q10 is greater than 10 percent of the mean annual daily flow, then the minimum
release to the bypassed reach shall be 1.2 times the 7Q10 flow.
(3) The
minimum flow determined by the procedures described in Subparagraphs (1) and
(2) of this Paragraph may be adjusted downward by the Department if that adjustment
would not result in significant loss of aquatic habitat. This adjustment may
be based on factors including:
(A) the type
of aquatic habitat present in the bypassed reach;
(B) the
length of the bypassed reach.
(4) If
the applicant or owner disputes the minimum flow determined by the procedures
described in Subparagraphs (1) and (2) of this Paragraph, he may undertake a
site‑specific field study, as defined in Rule .0501(j) of this Section,
subject to the review and approval of the Department. The final minimum
release required will not exceed the amount determined by the procedures
described in this Section.
(5) The
minimum flow for a dam on a special case stream, or on a stream located in the
mountain region, as defined in Rule .0501(h) of this Section, which does not
exhibit poor aquatic habitat; shall be determined by a site‑specific
instream flow study, as defined in Rule .0501(j) of this Section. This study
shall be conducted by the applicant or his consultants, and shall be subject to
approval by the Department.
(c) A dam
operated by a small power producer, as defined in G.S. 62-3(27a), which was
operating to produce power as of October 13, 1994, and which is not under the
jurisdiction of the Federal Energy Regulatory Commission, shall not be required
by this Rule to increase its minimum flow above the amount required on October
13, 1994.
History Note: Authority G.S. 143-215.24; 143-215.25;
143-215.31; 143-215.32; 143-215.33;
143-215.36;
Eff. December 1, 1994;
Amended Eff. April 1, 1995.
15A NCAC 02K .0504 MONITORING OF MINIMUM FLOW REQUIREMENTS
(a) An owner
of a dam with a minimum flow requirement greater than 1.0 cfs shall install,
calibrate, and maintain one or more stream staff gages following procedures
described in U.S. Geological Survey Water Supply Paper 2175, "Measurement
and Computation of Streamflow." Plans for such gages shall be submitted
to the Department for approval prior to installation. Staff gages shall be
calibrated to indicate the water surface elevations which correspond to the
required flows. Calibration shall be verified at least every two years. All
initial calibration and re‑calibration measurements, including field
data, shall be provided to the Department within 30 days of completion.
(b) If the
minimum release from a dam is less than or equal to 1.0 cfs, then an accurately
calibrated release mechanism such as a gate or pipe opening shall be acceptable
in lieu of a staff gage. Plans for making the required release shall be
submitted to the Department for review and approval prior to construction,
repair, or modification of the dam.
(c) An owner
of a dam who does not comply with a minimum flow requirement may be required to
install automated gaging which continuously monitors flow. Records from this
type of gage shall be provided to the Department upon request, for the time
period being investigated.
(d) Minimum
release requirements may be modified or suspended for a term determined by the
Department for reasons including pre‑scheduled maintenance or construction
involving the dam. The Department must approve a written request for such a
change in the minimum flow requirement prior to any change in the minimum
release.
(e) Reduction
or cessation of the minimum flow as a result of emergency conditions or equipment
failure shall not constitute a violation of the minimum flow requirement, so
long as the event is reported to the Department within 48 hours. The
Department may set forth a schedule for correcting the problem and restoring
the required minimum flow. If the schedule is not met, and the problem
continues to cause violation of the minimum flow requirement, then this
violation may be subject to enforcement action.
History Note: Authority G.S. 143-215.24; 143-215.25;
143-215.31; 143-215.32; 143-215.33;
143-215.36;
Eff. December 1, 1994.