Washington Administrative Code › Title 173 - Ecology, Department of (See also Titles 197, 317, 372, and 508) › Chapter 173-175 - Dam safety › Part ONE - GENERA › Section 173-175-030 - Definitions

Current through Register Vol. 24-14, July 15, 2024
As used in this chapter:
"Acceptance" means acceptance by the department that the
				  proposed plan(s) will satisfactorily address issues associated with proper
				  operation, maintenance, inspection, or emergency action.
"Annual exceedance probability" means the chance that a
				  specified magnitude of some phenomenon of interest, such as a flood or
				  earthquake, is equaled or exceeded during a given year.
"Approval" means approval by the department that the proposed
				  design, and plans and specifications conform to accepted engineering practice
				  and department guidelines.
"Appurtenant works" means such structures as outlet works and
				  associated gates and valves; water conveyance structures such as spillways,
				  channels, fish ladders, tunnels, pipelines, or penstocks; powerhouse sections;
				  and navigation locks, either in the dam or adjacent thereto.
"Authorization" means written acknowledgement from the
				  department to proceed with proposed actions.
"Construction change order" means a revision to the
				  department approved plans and specifications that is initiated during
				  construction.
"Construction permit" means the permit which authorizes
				  construction and that the project's plans and specifications and construction
				  inspection plan have been reviewed and approved by the department.
"Construction permit process" means the sequence of
				  activities specified in WAC
				  173-175-110 inclusive, beginning
				  with the application for construction permit and ending with the submission of
				  a report summarizing construction records.
"Crest length" means the total horizontal distance measured
				  along the axis of the dam, at the elevation of the top of the dam, between
				  abutments or ends of the dam. Where applicable, this includes the spillway,
				  powerhouse sections, and navigation locks, where they form a continuous part of
				  the impounding structure.
"Critical project element" means an element of a project
				  whose failure could result in the uncontrolled release of the reservoir.
"Dam" means any artificial barrier and/or any controlling
				  works, together with appurtenant works that can or does impound or divert
				  water.
"Dam abutment" means that contact location at either end and
				  beneath the flanks of a dam where the artificial barrier joins or faces against
				  the natural earth or rock foundation material upon which the dam is
				  constructed.
"Dam height" means the vertical distance from the natural bed
				  of the stream or watercourse at the downstream toe of the impounding barrier to
				  the maximum storage elevation. If the dam is not across a stream or
				  watercourse, the height is measured from the lowest elevation of the outside
				  limit of the impounding barrier to the maximum storage elevation.
"Department" means the department of ecology.
"Design step level" means an integer value between one and
				  eight used to designate increasingly stringent design loadings and conditions
				  for design of critical project elements. Design steps have a range in annual
				  exceedance probability from one in five hundred at Step 1 to one in one million
				  at Step 8.
"Downstream hazard classification" means a rating to describe
				  the potential for loss of human life and/or property damage if the dam were to
				  fail and release the reservoir onto downstream areas. Downstream hazard
				  classifications of 3, 2 and 1C, 1B, 1A correspond to low, significant, and high
				  downstream hazard classes respectively.
"Emergency condition" means a situation where life and
				  property are at imminent risk and actions are needed within minutes or hours to
				  initiate corrective actions and/or warn the public.
"Enlargement" means any modification of a project that will
				  result in an increase in normal pool height and/or dam height.
"Exigency condition" means a situation where the dam is
				  significantly underdesigned according to generally accepted engineering
				  standards or is in a deteriorated condition and life and property are clearly
				  at risk. Although present conditions do not pose an imminent threat, if adverse
				  conditions were to occur, the situation could quickly become an
				  emergency.
"FERC exempted project" means a project that is classified as
				  exempt by the Federal Energy Regulatory Commission (FERC) under provisions of
				  the Federal Power Act.
"FERC licensed project" means a project whose operation is
				  licensed by the Federal Energy Regulatory Commission (FERC) under provisions of
				  the Federal Power Act.
"Freeboard" means the vertical distance between the dam crest
				  elevation and some reservoir level of interest.
"Hydrograph" means a graphical representation of discharge,
				  stage, or other hydraulic property with respect to time for a particular
				  location on a watercourse.
"Impounding barrier" means the structural element of the dam
				  that has the primary purpose of impounding or diverting water. It may be
				  constructed of natural and/or man-made materials.
"Incident" means the occurrence of any dam-related event
				  where problems or conditions arise which may have posed a threat to the safety
				  or integrity of the project or which may have posed a threat of loss of life or
				  which resulted in loss of life.
"Inflow design flood (IDF)" means the reservoir inflow flood
				  hydrograph used for sizing the spillways and for determining freeboard. It
				  represents the largest flood that a given project is designed to safely
				  accommodate.
"Maintenance" means those tasks generally accepted as routine
				  in keeping the project and appurtenant works in a serviceable condition.
"Maximum storage elevation" means the maximum attainable
				  water surface elevation of the reservoir pool that could occur during extreme
				  operating conditions. This elevation normally corresponds to the crest
				  elevation of the dam.
"Miscellaneous construction elements" means a variety of
				  construction elements or activities such as, but not limited to: Reservoir
				  linings; parapet walls or low berms for wave containment; minor reconstruction
				  of isolated portions of the impounding barrier; internal drainage improvements;
				  and erosion protection.
"Modification" means any structural alteration of a dam, its
				  reservoir, spillway(s), outlet(s), or other appurtenant works that could
				  significantly influence or affect the project safety.
"Normal pool height" means the vertical distance between the
				  lowest point of the upstream toe of the impounding barrier and the normal
				  storage elevation.
"Normal storage elevation" means the maximum elevation to
				  which the reservoir may rise under normal operating conditions. Where the
				  principal spillway is ungated, the normal storage elevation is usually
				  established by the elevation of the spillway crest.
"100-year flood plain" means the area inundated during the
				  passage of a flood with a peak discharge having a one percent chance of being
				  equaled or exceeded in any given year at a specified location on a
				  watercourse.
"Outlet" means a conduit and/or channel structure for the
				  controlled release of the contents normally impounded by a dam and
				  reservoir.
"Owner" means the person holding lawful title to the dam or
				  any person who owns or proposes to construct a dam.
"Periodic inspection" means a detailed inspection of the dam
				  and appurtenant works conducted on regular intervals and includes, as
				  necessary, associated engineering analyses to confirm the continued safe
				  operation of the project.
"Person" means any individual, firm, association, county,
				  public or municipal or private corporation, agency, or other entity
				  whatsoever.
"Plans and specifications" means the detailed engineering
				  drawings and specifications used to describe the layout, materials,
				  construction methods, etc., for assembling a project or project element. These
				  do not include shop drawings or other drawings prepared by the construction
				  contractor for temporary construction support systems.
"Population at risk" means the number of people who may be
				  present in areas downstream of a dam and could be in danger in the event of a
				  dam failure.
"Project" means a dam and its reservoir either proposed or
				  existing.
"Project engineer" means a professional engineer licensed in
				  Washington, having direct supervision, as defined in WAC 196-24-095, in
				  managing the engineering aspects of the project as representative of the
				  owner.
"Reservoir" means any basin that contains or will contain the
				  water impounded by a dam.
"Reservoir routing" means the procedures used to determine
				  the attenuating effect of reservoir storage on a flood as it passes through a
				  reservoir.
"Rule curve" means the rules and procedures used to regulate
				  reservoir levels and project operation for various reservoir inflows and for
				  both normal and unusual seasonal conditions.
"Significant enlargement" means any modification of an
				  existing dam that results in the dam height or normal pool height being
				  increased by an amount greater than 5.0 feet, and which also represents a ten
				  percent or greater increase in dam height or normal pool height over that which
				  existed prior to the modification.
"Spillway" means a channel structure and/or conduit for the
				  safe release of water or floodwater.
"Stop work order" means an administrative order issued to
				  temporarily halt construction work until a problem can be resolved.
"Substantially complete" means that a plan, action, or
				  project element requires only minor additions to be complete, and in its
				  present state will perform the necessary functions for its intended use.
"Surficial inspection" means a visual inspection conducted to
				  identify obvious defects or changed conditions.
Statutory Authority:
					 RCW
					 43.21A.064,
					 43.21A.080,
					 86.16.061,
					 90.03.350 and [90.03].470.
					 04-16-122 (Order 03-08), § 173-175-030, filed 8/4/04, effective 9/4/04.
					 Statutory Authority: 1995 c 8. 95-22-030 (Order 94-15), § 173-175-030,
					 filed 10/24/95, effective 11/24/95. Statutory Authority:
					 RCW
					 43.21A.064, [43.21A].080 and 86.16.061.
					 93-01-090 (Order 92-35), § 173-175-030, filed 12/16/92, effective 1/16/93;
					 92-12-055 (Order 91-17), § 173-175-030, filed 6/1/92, effective
					 7/2/92.