Glossary of Terms Specific to the Horsetooth Dams’ Modernization Project

Introduction

This glossary is designed to help interested parties better understand construction details of the Horsetooth Dams Modernization Project.

The terms below have often been used to describe work involved in the modernization of the four dams at Horsetooth Reservoir. These definitions are specific to the purposes of the U.S. Bureau of Reclamation and its related engineering projects; meaning, these definitions are not common definitions. All links (underlined and in blue) are to the U.S. Bureau of Reclamation agency Internet pages and its master glossary.

Some terms are specific to parts of a dam; others are specific to parts of the process leading up to construction. All terms here are specific to the work at Horsetooth Reservoir. Terms are arranged alphabetically. All of the terminology defined here can be found throughout the website, in related handouts, or in recent media coverage of the Horsetooth Dams Modernization Project. Terms are used in an explanatory sentence at the end of each definition.

Glossary

A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

Abutment: That part of the valley wall against which the dam is constructed. The part of a dam that contacts the riverbank. A structure that supports the ends of a dam or bridge. An artificial abutment is sometimes constructed, as a concrete gravity section, to take the thrust of an arch dam where there is no suitable natural abutment. Action or place of abutting; the part of a structure that is the terminal point or receives thrust or pressure. Defined in terms of left and right as looking away from the reservoir, looking downstream (i.e., left abutment, right abutment). "The Tropics” climbing area at Soldier Canyon Dam was located on the northern abutment of that dam.

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Berm: A horizontal strip or shelf built into an embankment or cut to break the continuity of the slope, usually for the purpose of reducing erosion or to increase the thickness of the embankment at a point of change in a slope or defined water surface elevation. A horizontal step in the sloping profile of an embankment dam. A shelf that breaks the continuity of a slope, or artificial ridge of earth. A ledge or shoulder, as along the edge of a road or canal. An artificial ridge of earth. A "stability” berm will be added to all four Horsetooth Dams for compliance with new Bureau of Reclamation earthquake requirements.

Blast: To loosen or move rock or soil by means of explosives or an explosion.

Borrow areas: Generally, surface areas, that contain borrow pits. The area from which material for an embankment is excavated. The contractor is blasting the overhangs off the northern or “left” (looking down from the dam) abutment at Soldier Canyon Dam.

Borrow: Material excavated from one area to be used as fill material in another area. The constractor will use borrow material for the stability berms at all four dams.

Borrow pits: Specific site(s) within a borrow area from which material is excavated for use. The contractor will reopen old borrow pits, or borrow areas, to access borrow material.

Boulder: A rock fragment, usually rounded by weathering or abrasion, with an average dimension of 12 inches or more: will not pass a 12-inch screen. A particle of rock that will not pass a 12-inch (300-mm) square opening. A rock which is too heavy to be lifted readily by hand. Some riprap boulders exist on the face and to the sides of the dams.

Bulkhead: A one-piece fabricated steel unit which is lowered into guides and seals against a frame to close a water passage in a dam, conduit, spillway, etc. An object used to isolate a portion of a waterway for examination, maintenance, or repair. A wall or partition erected to resist ground or water pressure. When water levels were lowered to dead storage at Horsetooth Dam in the fall of 2001, regular maintenance work was performed on the intake structure’s "bulkhead” section.

Bureau of Reclamation (USBR, Reclamation, BOR): The mission of the Bureau of Reclamation is to manage, develop, and protect water and related resources in an environmentally and economically sound manner in the interest of the American public. The USBR built and owns Horsetooth Reservoir, its four dams, one dike, and adjacent land.

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Canal: A channel, usually open, that conveys water by gravity to farms, municipalities, etc. The Hansen Supply Canal carries water from Horsetooth Dam and Reservoir to water users along the Poudre River.

Canal headworks: The beginning of a canal. The headworks for the Hansen Supply Canal are located at Horsetooth Dam.

Clay: Fine-grained soil or the fine-grained portion of soil that can be made to exhibit plasticity (putty-like properties) within a range of moisture contents, and that exhibits considerable strength when air-dry. Plastic soil which passes a No. 200 (0.075 mm) United States Standard sieve. Reclamation geologists have identified some clays in the various foundations of the Horsetooth dams.

Coarse gravel protection: Gravel generally placed in a layer upon a finished surface to protect the finished surface from deterioration or erosion. All four dams at Horsetooth have a gravel protection layer.

Core (impervious core or impervious zone): A zone of low permeability material in an embankment dam. Sometimes referred to as “central core,” “inclined core,” “puddle clay core,” and “rolled clay core.” A cylindrical piece of an underground formation cut and raised by a rotary drill with a hollow bit. All four dams at Horsetooth have an impervious core.

Cubic feet per second (cfs or ft3/s): A unit of discharge for measurement of a flowing liguid equal to a flow of 1 cubic foot per second (448.8 gallons per minute (gpm), 7.48 gallons per second, or 1.98 acre-feet per day). A rate of streamflow; the volume, in cubic feet, of water passing a reference point in 1 second. Water in and out of Horsetooth Reservoir is recorded in cfs.

Cutoff: An impervious construction by means of which water is prevented from passing through foundation material.

Cutoff trench (keyway): An excavation in the foundation of an embankment dam, usually located upstream of the dam axis or centerline crest which extends to bedrock or to an impervious stratum. The excavation is backfilled with impervious material to form a cutoff and reduce percolation under the dam. See foundation trench.

Cutoff wall. A wall of impervious material (e.g., concrete, asphaltic concrete, timber, steel sheet piling, or impervious grout curtain) located in the foundation beneath a dam and which forms a water barrier and reduces seepage under a dam or spillway. A cutoff wall or trench is being designed to stop the seepage underneath Horsetooth Dam.

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Dam: A barrier built across a watercourse to impound or divert water. A barrier that obstructs, directs, retards, or stores the flow of water. Usually built across a stream. A structure built to hold back a flow of water. Horsetooth Reservoir has four dams: Spring, Dixon and Soldier Canyon Dams and Horsetooth Dam.

Dam foundation: The excavated surface or undisturbed material upon which a dam is placed. A limestone section of the dam foundation at Horsetooth Dam is seeping.

Dam safety issue: Dam safety related issues and concerns are those which, if not adequately addressed could/would:

  1. Lead to a failure or malfunction resulting in an uncontrolled release of stored water that would place the downstream population potentially at risk or;
  2. Compromise the agency's ability to detect developing adverse dam performance and prudently respond to that performance.

The foundation seepage at Horsetooth Dam and the modernization upgrades of filter buttresses and stability berms at all four dams are considered Dam Safety issues; they are, therefore, financed in part by Reclamation’s Safety of Dams Program (see the In Depth Funding Report under "Data and Reports”)

DataWeb: DataWeb is an electronic presentation of the Bureau of Reclamation's Project Data book and contains historical, statistical, and technical information on the projects of the Bureau of Reclamation. More information on the Colorado-Big Thompson Project, of which Horsetooth Reservoir is a part, can be found on Dataweb.

Dead capacity (dead storage): The reservoir capacity from which stored water cannot be evacuated by gravity. Horsetooth Reservoir was lowered to dead storage at Horsetooth Dam once in fall 2000 in order to fill the sinkhole and again in fall 2001 for general maintenance work.

Depth of cutoff: The vertical distance that the cutoff penetrates into the dam foundation. The depth of the cutoff wall at Horsetooth Dam is still under design.

Design basis earthquake (DBE): The earthquake a structure is required to safely withstand with repairable damage. Those systems and components important to safety must remain functional and/or operable. For design purposes, the intended use of this earthquake loading is for economic design of structures or components whose damage or failure would not lead to catastrophic loss. For most usage in Reclamation, the DBE is defined to have a 90% probability of nonoccurrence in a 50-year-exposure period, which is equivalent to a recurrence interval of 474 years. Economic considerations for specific projects may lead to consideration of other values. Reclamation’s new earthquake compliances are based on DBEs.

Dewatering: As opposed to unwatering, dewatering is the removal and control of ground water from pores or other open spaces in soil or rock formations to the extent that allows construction activities to proceed as intended, including the relief of ground water pressure. Removing water by pumping, drainage, or evaporation. The removal of ground water and seepage from below the surface of the ground or other surfaces through the use of deep wells and wellpoints. All four dams at Horsetooth Reservoir must be dewatered before they can be excavated. Dams are monitored 24-7 when they are being dewatered.

Dike: A low embankment, usually constructed to close up low areas of the reservoir rim and thus limit the extent of the reservoir. Embankment for restraining a river or a stream. Embankments which contain water within a given course. Usually applied to dams built to protect land from flooding. See saddle dam. There is one dike at Horsetooth Reservoir. Satanka Dike abuts Horsetooth Dam on its western side.

District: An entity that has a contract with the Bureau of Reclamation for the delivery of irrigation water. Such entities include, but are not limited to: canal companies, conservancy districts, ditch companies, irrigation and drainage districts, irrigation companies, irrigation districts, reclamation districts, service districts, storage districts, water districts, and water users associations. The Northern Colorado Water Conservancy District is the contracting entity on the Colorado-Big Thompson Project of which Horsetooth Reservoir is a part.

Downstream face: The inclined surface of a dam away from the reservoir. See face. The downstream faces of Spring, Dixon, and Soldier Canyon Dams are all visible from the city of Ft. Collins.

Drawdown: Lowering of a reservoir's water level; process of depleting a reservoir or ground water storage. Vertical distance the free water surface elevation is lowered or the reduction of the pressure head due to the removal of free water. The difference between a water level and a lower water level in a reservoir within a particular time. The amount of water used from a reservoir. The water at Horsetooth Reservoir draws down every summer by irrigators and other water users. Horsetooth has also been drawn down to a temporary water level restriction for the duration of the construction.

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Earth dam (earthfill dam): An embankment dam in which more than 50 percent of the total volume is formed of compacted earth material generally smaller than 3-inch size. Seepage through the dam is controlled by the designed use of upstream blankets and/or internal cores constructed using compacted soil of very low permeability. All four dams at Horsetooth are earthen, earthfill, embankment dams.

Earthwork: Any one or combination of the operations involved in altering or movement of earth. Construction on the Horsetooth Dams will involve a lot of earthwork.

Easement: The right to use land owned by another for some specific purpose. Reclamation and the District have secured the proper easements to access all four Horsetooth Dams.

Economic analysis: A procedure that includes both tangible and intangible factors to evaluate various alternatives. Reclamation had to prepare an economic analysis as part of its justification of work at the Horsetooth Dams.

Environmental assessment (EA): A NEPA compliance document used to determine if an action would have a significant effect on the human environment. If not, a finding of no significant impact (FONSI) is written. If so, an environmental impact statement (EIS) is written. An Environmental Assessment was drafted and finalized prior to the final design and construction at the Horsetooth Dams.

Erosion: A gradual wearing away of soil or rock by running water, waves, or wind. Concrete surface disturbance caused by cavitation, abrasion from moving particles in water, impact of pedestrian or vehicular traffic, or impact of ice floes. Surface displacement of soil caused by weathering, dissolution, abrasion, or other transporting. The gradual wearing away of material as a result of abrasive action. Excessive recreation along the faces of the dams has caused unnecessary erosion along the abutments.

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Face: Exposed surface of dam materials (earth, rockfill, or concrete), upstream and downstream. The downstream faces of the dams at Horsetooth will be excavated so the filter can be placed.

Facilities: Structures associated with Reclamation irrigation projects, municipal and industrial water systems, power generation facilities, including all storage, conveyance, distribution, and drainage systems. Horsetooth Reservoir and its four dams are facilities on the Colorado-Big Thompson Project.

Filter (filter zone): One or more layers of granular material incorporated in an embankment dam and is graded (either naturally or by selection) to allow seepage through or within the layers while preventing the migration of material from adjacent zones. A layer or combination of layers of pervious materials designed and installed in such a manner as to provide drainage, yet prevent the movement of soil particles due to flowing water. A filter buttress is being added to all four Horsetooth Dams.

Foundation: Lower part of a structure that transmits loads directly to the soil. The excavated surface upon which a dam is placed. The foundation at Horsetooth Dam includes a layer of limestone that has been channeling water from the reservoir, under the dam, to the valley downstream of the dam.

Foundation drains: Tile or pipe for collecting seepage within a foundation. All four of the Horsetooth Dams have foundation drains. The foundation drains at Horsetooth Dam were what first indicated there was a seepage problem.

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Grader: A machine with a centrally located blade that can be angled to cast to either side, with independent hoist control on each side. An example of some of the heavy construction equipment the contractor is using at the Horsetooth Dams.

Groin: The contact between the upstream or downstream face of a dam and the abutments. The area along the contact (or intersection) of the face of a dam with the abutments. Recreation trails have caused erosion along the groin of Soldier Canyon and Dixon Canyon Dams.

Grout cap: A concrete pad or wall constructed to facilitate subsequent pressure grouting of the grout curtain beneath the grout cap. A grout cap was placed atop the sinkhole at Horsetooth Dam once the sinkhole was filled.

Grout curtain (grout cutoff): A vertical zone, usually thin, in the foundation into which grout is injected to reduce seepage beneath a dam. The cutoff wall at Horsetooth Dam will be a form of grout curtain.

Grouting: Filling cracks and crevices with a cement mixture.

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High hazard: A downstream hazard classification for dams in which more than 6 lives would be in jeopardy and excessive economic loss (urban area including extensive community, industry, agriculture, or outstanding natural resources) would occur as a direct result of dam failure. This classification also applies to structures other than dams. All four dams at Horsetooth Reservoir are considered "High Hazard" under this definition.

Human environment: Natural and physical environment and the relationship of people with that environment, including all combinations of physical, biological, cultural, social, and economic factors in a given area. The human environment will be impacted by the construction at Horsetooth Reservoir. Consequently, under NEPA, Reclamation prepared an EA.

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Instrumentation: Any device used to monitor the performance of the structure during its construction and throughout its useful life. An arrangement of devices installed into or near dams (i.e., piezometers, inclinometer, strain gages, measurement points, etc.) and used to evaluate the structural behavior and performance parameters of the structure. Reclamation has utilized a variety of instrumentation, most often piezometers, to evaluate the situations and conditions of all four Horsetooth Dams.

Intake: Any structure through which water can be drawn into a waterway. Any structure in a reservoir, dam, or river into which water can be drawn and then discharged. Both Horsetooth and Soldier Canyon Dams have an intake structure to take water out of the reservoir.

Intake structure: Concrete portion of an outlet works, including trashracks and/or fish screens, upstream from the tunnel or conduit portions. The entrance to an outlet works.

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Multiple-purpose reservoir (multipurpose reservoir): A reservoir planned to operate for more than one purpose. Horsetooth is a multi-purpose reservoir.

Multipurpose dam: A dam constructed for two or more purposes (e.g. storage, flood control, navigation, power generation, recreation, or fish and wildlife enhancement.) Horsetooth Dam is a multipurpose dam.

Multipurpose project: A project designed for irrigation, power, flood control, municipal and industrial, recreation, and fish and wildlife benefits, in any combinations of two or more (contrasted to single-purpose projects serving only one need). The Colorado-Big Thompson Project, of which Horsetooth is a part, is a multipurpose project.

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National Environmental Policy Act (NEPA): An act requiring analysis, public comment, and reporting for environmental impacts of Federal actions. See National Environmental Policy Act of 1969. An EA was prepared under NEPA for the Horsetooth Dams’ Modernization Project.

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Operations and maintenance (O&M): Operation, maintenance, repairs, replacements, and testing of Reclamation facilities. O&M responsibilities for Horsetooth Reservoir and the four dams was transferred to the Northern Colorado Water Conservancy District in the late 1980s.

Outlet: An opening through which water can be freely discharged from a reservoir to the river for a particular purpose. Horsetooth Reservoir has two outlets, one at Horsetooth Dam and one at Soldier Canyon Dam.

 

Outlet Works: A combination of structures and equipment required for the safe operation and control of water released from a reservoir to serve various purposes, i.e., regulate stream flow and quality; release floodwater; and provide irrigation, municipal, and/or industrial water. Included in the outlet works are the intake structure, conduit, control house-gates, regulating gate or valve, gate chamber, and stilling basin. A series of components located in a dam through which normal releases from the reservoir are made. A device to provide controlled releases from a reservoir. A pipe that lets water out of a reservoir, mainly to supply downstream demands. The outlets at Horsetooth and Soldier Canyon Dams have associated outlet works.

Overhang: Projecting parts of a face or bank. Overhangs have been blasted off the left abutment at Soldier Canyon Dam.

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Permeability: The measure of the flow of water through soil. The ease (or measurable rate) with which gasses, liquids, or plant roots penetrate or pass through a layer of soil or porous media. The capacity or ability of a porous rock, sediment, or soil to allow the movement of water through its pores.

Permeable: Having pores or openings that permit liquids or gasses to pass through.

Pervious zone: A part of the cross section of an embankment dam comprising material of high permeability. All four earthen dams at Horsetooth Reservoir are partly permeable.

Piezometer: An instrument which measures pressure head or hydraulic pressures in a conduit or hydraulic pressures within the fill of an earth dam or the abutment; at the foundation because of seepage or soil compression; or on a flow surface of a spillway, gate, or valve. Piezometers are used regularly for monitoring of all four dams at Horsetooth Reservoir.

Piping: The erosion of embankment or foundation material (soil) due to leakage. The action of water passing through or under an embankment dam and carrying with it to the surface at the downstream face some of the finer material. The progressive removal of soil particles from a mass by percolating water leading to the development of channels. The progressive development of internal erosion by seepage, appearing downstream as a hole discharging water. The process of conveying erodible embankment or foundation materials through a continuous, open "pipe" which is able to maintain a self-supported roof. The pipe normally begins at an unprotected exit and works it's way upstream (up gradient) along an erodible flow path until the reservoir is reached. The filter buttresses will be installed at all four dams as an improvement for preventing piping.

Probability: The likelihood of an event occurring. Reclamation had to tally probabilities in its Safety of Dams Modification Report that was presented to Congress in December 2000 as justification for the Horsetooth Dams work.

Probable maximum flood (PMF) (maximum probable flood, MPF): The largest flood that may reasonably be expected to occur at a given point on a stream from the most severe combination of critical meteorologic and hydrologic conditions that are reasonably possible on a particular watershed. This term identifies estimates of hypothetical flood characteristics (peak discharge, volume, and hydrograph shape) that are considered to be the most severe "reasonably possible" at a particular location, based on relatively comprehensive hydrometeorological analyses of critical runoff-producing precipitation (and snowmelt, if pertinent) and hydrologic factors favorable for maximum flood runoff. The maximum runoff condition resulting from the most severe combination of hydrologic and meteorologic conditions that are considered reasonably possible for the drainage basin under study. All four dams at Horsetooth Reservoir were raised in the late 1980s based on PMF calculations.

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Recreation: Recreational opportunities at more than 1,900 federal recreation sites managed by the Bureau of Reclamation and other federal agencies can be found at the interagency Recreation.Gov website (www.recreation.gov). Recreation is one of the many uses of Horsetooth Reservoir.

Regional office: Five Reclamation offices in the 17 Western States that supervise Area, Field, and Project Offices in their respective geographic locations. See Great Plains, Lower Colorado, Mid Pacific, Pacific Northwest, and Upper Colorado. Horsetooth Reservoir, the Colorado-Big Thompson Project and the Eastern Colorado Area Office are all under the Great Plains Region of the U.S. Bureau of Reclamation.

Reservoir: A body of water impounded by a dam and in which water can be stored. Artificially impounded body of water. Any natural or artificial holding area used to store, regulate, or control water. Body of water, such as a natural or constructed lake, in which water is collected and stored for use. Dam design and reservoir operation utilize reservoir capacity and water surface elevation data. To ensure uniformity in the establishment, use, and publication of these data, the following standard definitions of water surface elevations shall be used.

Reservoir capacity: The capacity of the reservoir, usually in acre-feet. Dam design and reservoir operation utilize reservoir capacity and water surface elevation data. The water level restriction in place at Horsetooth Reservoir for the duration of the construction was based, in part, on reservoir capacity.

Reservoir inflow: The amount of water entering a reservoir expressed in acre-feet per day or cubic feet per second. Inflow to Horsetooth Reservoir is near Inlet Bay.

Reservoir regulation (or operating) procedure: Operating procedures that govern reservoir storage and releases. The Bureau of Reclamation writes and updates the reservoir operating procedures for Horsetooth Reservoir. These are also known as Standard Operating Procedures.

Reservoir surface area: The area covered by a reservoir when filled to a specified level. Reservoir surface area is often used to determine how many boats can utilize the reservoir at one time. With the water level restriction in place, Horsetooth’s surface area is greatly reduced.

Riprap: A layer of large uncoursed stones, broken rock, boulders, precast blocks, bags of cement, or other suitable material generally placed in random fashion on the upstream and downstream faces of embankment dams, stream banks, on a reservoir shore, on the sides of a channel, or other land surfaces to protect them from erosion or scour caused by current, wind, wave, and/or ice action. A protective blanket of large loose stones, which are usually placed by machine to achieve a desired configuration. Riprap is usually placed by dumping or other mechanical methods but, in some cases, is hand placed. It consist of relatively large pieces as distinguished from a gravel blanket. Very large riprap is sometimes referred to as "armoring." All four dams at Horsetooth are covered with riprap. The riprap will be removed and eventually replaced as part of the construction.

Risk: The relationship between the consequences resulting from an adverse event and its probability of occurrence. The potential for losing credibility, failing to solve a problem, or getting hurt. The ability to describe potential outcomes using historic probability. The likelihood or chance of an unacceptable event occurring.

Risk assessment: As applied to dam safety, the process of identifying the likelihood and consequences of dam failure to provide the basis for informed decisions. Reclamation had to provide a risk assessment as part of its justification for the work at the Horsetooth Dams.

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Saddle dam: A subsidiary dam of any type constructed across a saddle or low point on the perimeter of a reservoir. See dike. All four dams at Horsetooth Reservoir are also saddle dams.

Seep: A spot where ground water oozes slowly to the surface, usually forming a pool. Seeps were located downstream of Horsetooth Dam near Bellvue.

Seepage: The slow movement or percolation of water through soil or rock. Movement of water through soil without formation of definite channels. The movement of water into and through the soil from unlined canals, ditches, and water storage facilities. The slow movement or percolation of water through small cracks, pores, interstices, etc., from an embankment, abutment, or foundation. Seepage was detected through the foundation of Horsetooth Dam.

Sinkhole: A steep-sided depression formed when removal of subsurface embankment or foundation material causes overlying material to collapse into the resulting void. Seepage through the limestone foundation at Horsetooth Reservoir has caused sinkholes at the south end of the reservoir near the Swim Beach and also one sinkhole near the upstream face of Horsetooth Dam. All sinkholes have been filled and capped.

Stockpile: A storage pile of materials. Dam face material stripped from the dams at Horsetooth will be stored in stockpiles near each of the dams.

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Toe (toe of dam): The point of intersection between the bottom of a slope or the upstream or downstream face of a dam and the natural ground, for example, the upstream or downstream toe of a dam or the downstream toe of a landslide or debris fan. The junction of the face of a dam with the ground surface. During construction, a lot of activity will be going on at the toe of the dams. As a result, all recreation trails and access will be closed in those areas.

Toe drain(s): Open-jointed tile or perforated pipe located at the toe of the dam used in conjunction with horizontal drainage blankets to collect seepage from the embankment and foundation and conveys the seepage to a location downstream from the dam. A system of pipe and/or pervious material along the downstream toe of a dam used to collect seepage from the foundation and embankment and convey it to a free outlet. Tile or pipe used to collect external seepage along the downstream toe of an embankment. Spring Creek starts at the toe drain of Spring Canyon Dam.

Trashrack: A metal or reinforced concrete structure placed at the intake of a conduit, pipe, or tunnel that prevents entrance of debris over a certain size. A device or structure located at an intake to prevent floating or submerged debris from entering the intake. The intake structure at Horsetooth Dam, visible at dead storage, has a large trashrack section.

Turbidity: Measure of extent to which light passing through water is reduced due to suspended materials (see nephelometric). The optical property of water based on the amount of light reflected by suspended particles. Cloudiness of water, measured by how deeply light can penetrate into the water from the surface. The cloudy appearance of water caused by the presence of suspended and colloidal matter. The scattering and absorption of light that makes the water look murky. Caused by the content and shape of matter suspended in the water. The state of having sediment or foreign particles suspended or stirred up in water. Reclamation partnered with the City of Ft. Collins to provide additional water quality monitoring equipment needed, in part, to better detect turbidity at low water levels, particularly during construction.

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Water user: Any individual, district, association, government agency, or other entity that uses water supplied from a Reclamation project. The Northern Colorado Water Conservancy District represents the majority of Horsetooth’s water users.

Water year (WY): Period of time beginning October 1 of one year and ending September 30 of the following year and designated by the calendar year in which it ends. A calendar year used for water calculations. Horsetooth Reservoir is traditionally at its lowest water level elevation at the end of each water year.

Wetlands: Lands including swamps, marshes, bogs, and similar areas such as wet meadows, river overflows, mudflats, and natural ponds. An area characterized by periodic inundation or saturation, hydric soils, and vegetation adapted for life in saturated soil conditions. A jurisdictional wetland is subject to regulation under the Clean Water Act. A nonjurisdictional is subject to consideration under the Fish and Wildlife Coordination Act. There are a few wetlands near Horsetooth Reservoir. Construction impacts to wetlands are covered in the EA.

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