WAC 173-175-030   Definitions.  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.]