Attachment_7_-_1991_RO_M_Guidelines_PDF_0001.pdf

eview of per&ion and Maintenance Field Examination Guidelines

Program

A Water Resources Technical Publication

UNITED STATES DEPARTMENT OF TH

BUREAU OF RECLAMATION

:PORT STANDARD TITLE PAGI

3. RECIPIENT’S CATALOG NO.

Review of Operation and Maintenance Program Field Examination Guidelines

1. AUTHOR(S)

9. PERFORMING ORGANlZATlON NAME AND ADDRESS

Bureau of Reclamation Denver Office Denver CO 80225

2. SPONSORING AGENCY NAME AN0 AOORESS

Bureau of Reclamation Denver Office Denver CO 80225

5. SUPPLEMENTARY NOTE5

5. REPORT DATE

October 1991

6. PERFORMING ORGANIZATION CODE

D-521 0

9. PERFORMING ORGANIZATION

REPORT NO.

Bureau of Reclamation

(0. WORK UNIT NO.

D-521 0

11. CONTRACT OR GRANT NO.

13. TYPE OF REPORT AN0 PERIOD

COVERED

14. SPONSORING AGENCY CODE

DIBR

6. ABSTRACT

Ed:RNW

The Review of Operation and Maintenance Program Field Examination Guidelines provides information useful in conducting field reviews of operation and maintenance practices of dams, canals, tunnels, pipelines, and other structures and facilities. The guidelines are not intended to replace, but complement, experience and professional engineering judgement.

7. KEY WORDS AN0 DOCUMENT ANALYSIS

I. DESCRlPTORS-- *examination/*operation and maintenance/*storage dam/diversion dam/ powerplant structures/pumping plant/canal

I. IDENTIFIERS--

:. CO.SATl Field/Group 13 COWRR: 1313 SRIM:

I). 0lSTRlB~Ti0td STATEMENT 19. SECURITY CLASS ht. NO. OF PAGE

Available from the National Technical Information Service, Operations

(THIS REPORT)

Division. 5285 Port Royal Road, Springfield, Virginia 22161.

UNCLASSIFIED

20. SECURITY CLASS 22. PRICE

(THIS PAtiE)

UNCLASSIFIED

REVIEW OF O&M

PROGRAM

FIELD EXAMINATION

GUIDELINES

Engineering Division Facilities Engineering Branch

Denver Off ice Denver, Colorado

First Edition 1991

U.S. Department of the Interior

Bureau of Reclamation

Mission: As the Xation’s principal conservation agency. the Department of the Interior has responsibility for most of our nationallv-owned public lands and natural and cultural resources.

This includes fostering wise use of our land and water resources.

protecting our fish and wildlife, preserting the environmental and cultural values of our national parks and historical places. and probiding for the enjoyment of life through outdoor recreation.

The Department assesses our energy and mineral resources and works to assure that their development is in the best interests of all our people. The Department also promotes thr goals of the Take Pride in America campaign by encouraging stewardship and citizen responsibility for the public lands and promoting citizen participation in their care. The .D epartment also has a major, rcsponsil)ilit+ for American Indian reservation communities and for people who lice in Island Territories under li.S. Administration.

Mission of the Bureau of Reclamation

The Bureau oj Reclamation oj the If..S. Deparlmertr oj Ihe Inrrrior is rc~sponsihle jk the detwlopmenr and cortsert~o~ion of the Naliorti waler resources in the Wesrrrn Unired Shades.

The Bureau% original purptp.se “to prot’idr for Ihe reclamariort t>j arid and wmiarid lands in [he We,sl” Irrday cotvrs a wide range oj inrerrelated Junctions. Thrse include prot-iding municipal and indtcs~rial water supplies; hydroelectric power gencrarion: irrigarion t4mler for aprictrlrure; waler qualify impror~ement: jlo0d c0nLrol: river rtat~iparion: ritvr regulation and control: fish and toildlije enhance-rrrc’nl: ouIdoor recrealion: and researrh on water-r&ted design.

cortstrttctiort. materials. atmospheric manapem~nt. and wind and .solar po twr.

Bureau programs most freqttentl~ are the resulr oj c1o.w cooperalion with the U.S. Congress. ofher Federal agencies. S1are.s. local gotvrnments. academic insrirurions. waler-user orpaniza~ions. and other concerned groups.

Hb!B

SI METRIC

D i i]

I d I I

PREFACE

This document presents current guidelines for conducting field examinations under the Bureau of Reclamation’s Review of Operation and Maintenance (RO&M) Program for dams, canals, tunnels, pipelines, and other structures and facilities. It is noted that the guidelines are not intended to replace experience or professional engineering judge-ment, but rather to provide the minimum observations that should be made during an RO&M examination. Addition-ally, the guidelines are intended to promote uniformity in the manner that examinations are conducted and to improve continuity in preparation of-the associated reports.

The guidelines were developed by former and present operation and maintenance personnel from Reclamation’s Denver, regional, and project offices.

a22

CONTENTS

d I I R i I I

Page

PREFACE “’

SECTION 1: RO&M PROGRAM REQUIREMENTS

A. Background B. Organizational Responsibilities C. Applicable Reclamation Instructions

SECTION 2: FIELD EXAMINATION GUIDELINES

A. Purpose and Scope of Examinations B. Preparing for the Examination C. Conducting Field Examinations D. Field Examination Observations

1. Storage Dams

a. Embankment Dams (including Spillway and Outlet Works)

b. Concrete and Masonry Dams

.2. Diversion Dams

3. Powerplant Structures

4. Pumping Plants

5. Pipelines

6. Canals and Laterals

7. Drainage Systems

8. Tunnels and Inverted Siphons

9. Regulating Reservoirs and Tanks

10. Bridges

E. Miscellaneous Areas of Examination ................................. 4 1

1. Landslides

2. Instrumentation (including Seepage Monitoring)

a. StorageDams

b. Diversion Dams

c. Other Structures (pipelines, tunnels, etc.)

3. Factors Affecting Operations

a. Access to the Site

b. Communications

c. Site Security and Attendance

d. Standing Operating Procedures

e. Logbook-Documentation

f. Dam Tender’s Training

g. Maintenance Management System

11. Emergency Reserve Fund

F. Following the Field Examination

1. Exit Conference

2. Interim Communications

3. Examination Report

GLOSSARY

BIBLIOGRAPHY

OTHERREFERENCES

APPENDIX A: Checklist for RO&M Examinations

APPENDIX B: Guidelines - Removal of Trees and Other Vegetative Growth From Earth Dams, Dikes, and Conveyance Features

APPENDIX C: Guidelines for Testing Gates and Valves at Major Facilities

Figure CONTENTS - Continued

Page

1 Major components of a typical storage dam 2 Typical spillway configurations 3 Commonly used spillway gates ....................................... 1.5 4 Typical outlet works configurations 5 Commonly used guard ptes and valve 6 Commonly used regulating gates and valves 7 Typical pumps 8 Typical bridge profile and cross sections

?I fm .1m

‘II

ia vi

SECTION 1

R08cM PROGRAM REQUIREMENTS

A. BACKGROUND

The Bureau of Reclamation (Reclamation) began constructing water resources projects in 1902 in compliance with its mission “. . . to provide for the reclamation of the arid and semiarid lands in the West.” Until 1948, the responsibility of operation and maintenance tasks at the facilities was that of the respective project office staff. Many project offices developed general operation and maintenance (O&M) guidelines to accomplish these tasks. In some cases the guidelines were not entirely satisfactory and, at times, produced a variety of results that invdlved extensive rehabilitation of structures to restore them to satisfactory condition for continued safe operation.

In recognizing this problem, Reclamation’s Commissioner (administrative directive, July 6, 1948) set into motion Reclamation’s Review of Maintenance (ROM) Program. The directive cited the following requirements from the Bureau Manual (now named Reclamation Instructions): (1) dams, reservoirs, appurtenant structures, and machinery are to be examined and the findings documented in a written report twice each year, and (2) Reclamation’s regional directors are responsible for implementing all corrective measures identified in the report.

Because it was questionable whether other manual provisions were being satisfied for all intended facilities in a consistent manner, additional paragraphs were quoted in the directive.

Accordingly, the O&M staffs in Washington and Dentier, together with the Regional Directors, were directed to develop a coordinated and comprehensive program of examinations to review the maintenance of Reclamation facilities.

In addition, periodic reports that verified the completion of this work were to be sent to the Commissioner.

The first formal examinations of both major and minor facilities under the ROM Program were made in 1948. The detail and frequency of the examinations varied greatly between the regions. In 1951, several regions decided that biennial examinations were sufficient because under normal circumstances the structural conditions of a facility had not significantly changed to warrant organizing an examination party and writing a thorough report more frequently. Accordingly, Reclamation Znstructions were changed to require regional examinations of major and minor water and power facilities every 2 years unless the respective Regional Director desired they be more frequent.

The Commissioner’s letter of March 17, 1954, created the Division of Irrigation Operations (later named the Division of Water and Land Technical Services and now the Engineering Division); the directive placed the responsibility ‘for review of maintenance of Reclamation facilities in the Denver Office. This responsibility includes direction, coordination, and supervision of the ROM Program and requires that the Commissioner be furnished an annual report on the general condition of Reclamation facilities. This report advises the Commissioner that the objectives of the program were being met, and provides a record for official use.

In January 1957, the Commissioner specified organizations responsible for program activities and established the method to finance the ROM Program.

Although Reclamation Instructions were prepared from the above considerations and have been changed little in most aspects, numerous changes in program procedures have been necessary to meet changing conditions.

The Commissioner changed the program title (memorandum, Feb. 12, 1979) from “Review of Maintenance Program” to “Review of Operation and Maintenance Program.” The title change was made because it is virtually impossible to evaluate maintenance without considering operational procedures and conditions.

B. ORGANIZATIONAL RESPONSIBILITIES

The organizational responsibilities concerning the Review of Operation and Maintenance (RO&M) Program are described below.

Zkzuer Office - The Facilities Engineering Branch, Engineering Division under the Assistant Commissioner - Resources Management (ACRM), is responsible for: (1) providing an annual RO&M Program report to the Regional Directors and the Commissioner, (2) coordinating the development of RO&M Program policy and technical criteria, and (3) promoting consistency of field examination procedures and reports, and for providing personnel for conducting the 6-year examinations of major facilities. This includes ensuring that periodic examinations are scheduled and conducted on all facilities and that technical assistance and overview are provided as needed to the regional offices. Following completion of each RO&M examination, a report of findings is prepared and transmitted to the respective regional office. In addition, the Facilities Engineering Branch, Engineering Division prepares an annual report of the RO&M Program which includes the status of all the current recommendations and is sent to the Regional Directors with a copy to the Commissioner.

Regional Off ices - The Regional Director is responsible for the satisfactory O&M of all facilities and structures under the region’s jurisdiction, including the coordination of all RO&M examinations and the monitoring and accomplishment of recommendations. Formal examinations are conducted and a report prepared by regional office personnel for all minor facilities. Major structures are examined every 3 years by regional office personnel with the Denver Office participating every 6 years. Reports are prepared by Denver Office personnel when they participate. Each region is to ensure that dam tender’s training is provided at 3-year intervals for all personnel responsible for operating major storage dams.

Regional offices are responsible for recommending and/or assisting in the development of program policy and technical criteria for the RO&M Program.

Information concerning regional RO&M activities is to be transmitted annually to the Reclamation’s Facilities Engineering Branch, Engineering Division, Denver Office. This information includes a status report of all category 2 recommen-dations on the current program records, a list of facilities where O&M responsibility is anticipated to be transferred in the upcoming year, and recommended examination schedules for both major and minor facilities for the upcoming year. In addition, regional directors are responsible for a semiannual

I

(January 1 and July 1) status report for all current category I recommendations to the Denver Office-with a copy to the Commissioner.

Project Offices - Whether or not O&M responsibility of a particular facility has been transferred to the project office or to a local water user, the area project offices are responsible for general O&M oversight and routine inspections of all facilities during the period between formal examinations. For reserved works, the project office is responsible for corrective action necessary to accomplish applicable recommendations resulting from the RO&M examinations and to provide continued O&M of the facilities. For a facility operated by water users, the project office (or regional office in the absence of a project office) will periodically monitor the condition of the facility-and any corrective action taking place-and will provide the liaison for any technical assistance requested by the water users.

Water Users - For facilities where O&M responsibility has been transferred to the water users, the water users have the responsibility to provide continued O&M of the facilities and to accomplish .any corrective action necessary for completing applicable recommendations resulting from the RO&M examinations.

C. APPLICABLE RECLAMATION INSTRUCTIONS

Reclamation Instructions, Parts 2332.1 through 233.210 [ 11,” are to be followed for the RO&M Program activities. Once the ongoing revision of the Reclamation Instructions is finalized, Parts 233.1.8 through 233.1.16 will supersede the previous instructions.

* Numbers in brackets refer to bibliography.

m -4 Jrn w ‘m

SECTION 2

RO&M EXAMINATION GUIDELINES

A. PURPOSE AND SCOPE OF EXAMINATIONS

The principal purposes of RO&M examinations are to:

l Evaluate the adequacy of the O&M program at the facility;

l Disclose conditions that might cause disruption or failure of operation;

l Determine the adequacy of the structures and facilities to serve their intended purpose;

l Note the extent of deterioration as the basis for planning maintenance, repair, or rehabilitation;

l Review current operating practices;

l Determine the degree of operational safety at the facility; and l Obtain data for improvement of design, construction, maintenance, and operating practices.

These examinations will protect the Federal investment in the facility by lengthening the service life and reducing breakdown maintenance.

The RO&M examinations are generally limited to nonpower facilities, pumping plants rated below 2,500 horsepower (1864.25 kW), and structural features of major pumping plants and powerplants. Examinations should be conducted on all of the facilities described above for which Reclamation is directly or indirectly responsible as listed below:

l Reserved works l Works transferred to water users and other interests l Works constructed under loan projects and with Rehabilitation and

Betterment (R&B) funds l Works built’by other agencies but forming an integral part of a Reclamation operating project

For works constructed under a loan to non-Reclamation entities, examinations will be conducted during the repayment period only.

Facilities examined under the RO&M Program are divided into major and minor facilities. The following is a list of major facilities:

(1) Storage dams and reservoirs

(2) Diversion dams having significant storage or where equipment and operation are complex

(3) Large pumping plants and powerplants

(4) Large canal systems

(5) Large complex closed conduit systems

(6) Class A bridges

(7) Class B bridges

The following is a list of minor facilities:

(1) Most carriage, distribution, and drainage systems

(2) Small diversion works

(3) Small pumping plants and powerplants

(4) Open and closed conduits

(5) Tunnels

(6) Siphons

(7) Small regulating reservoirs

(8) Small waterways

(9) Class C bridges

Generally, each major facility or structure should be examined in detail and reported upon separately. In conducting c>xaminations of carriage, distribution, and drainage systems, it is not expected that each lateral, drop, check, or turnout in the system be examined. However, a representative portion of the system should be examined so that the overall condition of the related facilities can be determined.

If possible, the examination of such systems should attempt to cover areas that have not been examined during previous examinations.

B. PREPARING FOR THE EXAMINATION

Preparing for the examination should be regarded equally as important as the examination itself. All documentation related to the facility should be reviewed to identify areas which need special attention during the examination. These documents include. but are not limited to:

l Technical Record of Design and Construction, l Design Summary, l Designers’ Operating Criteria (DOC) as provided for the facility, l Standing Operating Procedures (SOP), l All previous RO&M examination reports, l Safety Evaluation of Existing Dams (SEED) reports, l Structural behavior (instrumentation) summary reports, and l All related correspondence.

From the review of documentation, it is suggested that a listing of important and significant concerns be prepared for use during the examination. Such a listing can be of valuable assistance as a ready reference and reminder of items to be discussed. In reviewing past RO&M examination reports, previous recommendations which remain incomplete should be given special attention.

Any problems or deficiencies, especially when supported by photographic records, should be evaluated. Repairs or modifications anticipated by previous reports should be noted for reference during the examination. Changes in operation and maintenance practices reported in past reports also should be noted so that any related effects can be identified during the examination.

All arrangements regarding the itinerary and examination procedures should be coordinated with the appropriate offices and personnel. Ample time should be allotted for the examination without requiring the participants to work unreasonably long hours. Examiners are encouraged to request a preexamination checklist from the responsible regional or project office, as appropriate. The preexamination checklist indicates the areas that will or will not be available for examination and any special equipment needed.

Regional or project personnel should make available safety or other special equipment, such as ladders, ropes, etc., required to examine the facility. Examiners should provide safety boots and other personal gear, including hard hats, safety glasses, gloves, earplugs, etc., as needed. Project personnel may need to schedule dewatering of conduits, stilling basins, siphons, etc.; ventilation of enclosed areas;

and gate closures to allow access for examination purposes. Appropriate clearance procedures should be outlined and implemented before examining a facility.

This includes placing safety tags or locks on equipment controls or electrical switchboxes before examining an area affected by the equipment’s operation.

Special arrangements may be required for R08cM examinations conducted concurrently with SEED examinations or landslide surveys.

C. CONDUCTING FIELD EXAMINATIONS

Examination teams should consist of regional office and/or Denver Office personnel experienced in the design and O&M aspects of the facilities. The examiner is not expected to be an authority on all technical aspects of the facility.

However, he or she should have sufficient background to recognize problems and unusual conditions and recommend remedial actions or further evaluation by others. It is essential that operating personnel responsible for daily operation and maintenance of the facility also participate as team members. Where applicable, water user organization representatives (e.g., Board of Directors) should also participate in the examination. Additionally, the applicable state water resource agency may need to be advised for their possible participation in the examination.

To the extent possible, examinations should be scheduled during seasons which differ from those held previously. This will enable the structure or facility to be examined under differing reservoir, water delivery, and site conditions.

Before beginning the examination of a facility, the examination team should discuss the order in which features are to be examined for accommodating operations as well as to ensure time for the examination is appropriately allotted.

In addition, the examination team should conduct a job hazard analysis prior to the examination, whereby procedures and equipment necessary to minimize or avoid potential safety and health hazards are discussed. Of primary importance is the need for detailed clearance, lockout or “tag-out” procedures when accessing areas affected by equipment or gate operations. Basic elements of a job hazard analysis are outlined in the- Reclamation Operation and Maintenance Safety Standards [2].

It is important that the examination team stay together as much as possible during the field examination so that safety precautions, observations, deficiencies, and recommendations can be known and discussed with all interested parties.

In general, the team leader, who is responsible for writing the examination report, directs the manner in which the examination is conducted. When conducting an examination, the examiner should avoid developing an atmosphere of a formal inspection. The examiner should be considerate and helpful-keeping in mind that effective communication and good public relations are essential to the success of the examination and the program. The examiner should be complimentary, where appropriate, by recognizing improvements and good work.

D. FIELD EXAMINATION OBSERVATIONS

Appendix A is a checklist for items of special importance during KO&M examinations of concrete, embankment, and diversion dams, spillways, outlet works, powerplants, pumping facilities, pipelines, canals, and bridges.

1. Storage Dams.-These dams store water for irrigation, municipal and industrial (M&I), flood control, power generation, recreation, and fish and wildlife uses. Figure 1 illustrates major components of a typical storage dam.

Changes in the visible portions of a dam can alert the examiner of areas being subjected to elements and forces-undetected by instrumentatiotl-tl~at could adversely affect its performance. Such observations provide the basis for determining the need and/or type of remedial work or routine O&M activit) necessary to ensure the integrity of the structure.

a. Embankment Dams.-Usually embankment dams are accessible for examination due to the moderate slopes of upstream and downstream faces.

(1) Crest.-Generally, the crest width is dictated by the design of the dam.

IJsually, the crest accommodates a roadway which may be the only means for vehicle access from one side of the reservoir to the other. The crest provides access to both faces of the dam for monitoring and maintenance purposes.

The roadway surface material may consist of concrete, asphalt, gravel, rock. or native soil.

The crest should be carefully examined to note any areas of misalignment, cracking, excessive heaving or settlement, improper roadway grading practices, or deep-rooted vegetation. Movement of the crest usually can be detected by observing any horizontal or vertical irregularities in the alignment of the roadway, guardrails, curbs, or parapet walls. Although such observations may indicate movement in the embankment, the condition may be the result of original construction or maintenance work.

Cracking of the crest surface or roadway material may indicate localized thermal effects associated with the material. However, depending on the size and/or location, cracking may be an indication of changes in the structural behavior of the underlying embankment or foundation.

Longitudinal cracking, which rmis parallel to the length of the dam, could indicate a loss of embankment support due to foundation failure or uneven settlement of adjacent zones within the embankment. Transverse cracking, which runs perpendicular to the length of the dam, may indicate instability or deformation of the embankment in the immediate area ot an uneven movement in an adjacent section of the embankment. Vertical offsets associated with either type of cracking could indicate serious instability of the embankment.

Most embankment dams are designed and constructed with a cambered crest. The camber is the result of additional fill material placed in the maximum section area of the dam in anticipation of future settlement.

Therefore, embankment dams are expected to lose their camber after a number of years. Some settlement of an embankment is normal; however, evidence of localized (sinkholes) or excessive settlement (low areas in crest

P Am ‘lm -m

W

Reservoir ,,/ -- kze~a. ,“,.;> A;,,.

-- .e -z=

Left abutment

Downstream

Outlet works control house

Figure l.-Major components of a typical storage dam.

profile) may be indications of internal embankment erosion, piping along various paths within the dam, or the occurrence of foundation spreading.

Improper roadway grading may create erosion channels beginning at the edge of the crest and continuing down the embankment face. The roadway should be graded to drain toward the upstream face where better slope protection is usually provided. A windrow of the roadway material at the downstream edge of the crest is desirable to prevent runoff in that direction.

Guardrails meeting the applicable county, state, or Federal regulations should be provided where vehicular traffic is allowed on the crest. All restricted areas associated with the crest should be appropriately fenced and posted with signs as needed [3].

Vegetation can obscure signs of erosion, seepage, or other undesirable conditions that may exist. The presence of lush vegetation on the downstream face and toe and in groin areas may indicate the existence of seepage at or near the ground surface. Deep-rooted vegetation on the crest, as well as the crest and upstream and downstream faces and toe and groin areas, is undesirable because associated root systems can provide a means for shortening seepage paths within the embankment. If vegetation exists, it may be necessary, to recommend its removal as outlined in appendix B. The guidelines suggest that vegetation that is potentially detrimental to the integrity of the embankment be removed.

(2) Upstream I;ace.-The upstream face of an embankment dam usually is constructed with a slope of 2.5:l or 3:1 (horizontal:vertical) and is provided with a protective material to guard the embankment from erosion due to wave action in the reservoir. Materials used for this purpose include rock riprap with bedding, concrete, soil-cement, rock pavement blocks, and asphalt paving. Under normal conditions, reservoir levels inundate much of the face; therefore, the condition of only a portion of the protective cover material can be examined. During low reservoir levels, a thorough examination should be performed of the upstream face.

The visible portions of the upstream face should be carefully examined to note any areas of significant erosion, subsidence, cracking, loss OI deterioration of the protective material, or deep-rooted vegetation.

Evidence of cracking or subsidence of the upstream face as previously discussed relative to the crest of the dam, can indicate adverse changes occurring within the embankment. Any irregularities at the normal water surface elevation could indicate subsidence problems. However, such irregularities can be difficult to ascertain and are often relative to the condition of the protective material only.

Significant erosion or movement of protective material on the upstream face usually is associated with upstream faces having a layer of riprap.

Riprap displacement at the waterline is called “beaching” and may occut because of wave action or pressure caused by ice layers. This can result in movement of the underlying bedding-creating void areas within the riprap-thereby exposing portions of the embankment to erosion and other damage. Movement of protective material, in the form of slides and slumps, can occur because of rapid reservoir drawdowns.

Deterioration, or the gradual breakdown of protective material, will almost always be evident to some degree. Causes for deterioration include:

substandard quality of original material, poorly placed material, and weathering effects of nature. The riprap used in constructing a dam is usually selected because of its availability during construction. Therefore, the type, gradation, and quality of the material varies. Significant loss of riprap size can cause it to lose its relative position and affect the underlying embankment by subjecting it to wave action and erosion.

Because riprap deterioration can be caused by heat from fire, signs prohibiting building of fires on the upstream face should be posted where applicable. Restricted areas associated with the upstream face can be fenced and posted with signs, if necessary. The examiner should note the condition of the riprap and any needed remedial work associated with it.

(3) Downstream Fuce.-An embankment dam’s downstream face usually is constructed with a maximum slope of 2:l (horizontal:vertical) and provided with a 12-inch layer of selected material to protect the embankment from damage due to exposure. Depending on the location of the dam, protection can consist of topsoil and seeding, rock, or no specified cover on some older dams.

The examiner should carefully inspect the downstream face for any evidence of damage or irregularities. Slope damage can result from wind or surface runoff erosion, undesirable deep-rooted vegetation, rodents, pedestrian and cattle traffic, and off-road vehicles. Irregularities in the slope can consist of cracks, slides, subsidence, impairments of slope protection, natural springs, and seepage from the reservoir. Observations regarding seepage that. the examiner should make are discussed in the Instrumentation (including SeePage Monitoring) subparagraph of the Miscellaneous Areas of Examination paragraph.

As previously noted, relative to the crest and upstream face, irregularities noted on the surface of the downstream face can be reflective of changes occurring within the underlying embankment. The examiner should consider previous observations and instrumentation history relative to the affected area in determining the need for remedial work.

Maintenance related to the downstream face of a dam should consist of:

removing all trees and deep-rooted growth from the surface; limiting off-road vehicle, cattle, and pedestrian access by using appropriate measures (e.g., signing, fencing); rodent control; and erosion repair. Any means to reduce the effects of erosion damage, such as grading the crest for drainage toward the upstream face, maintaining culverts to ensure proper drainage, and encouraging the growth of natural grasses or shallow-rooted shrubbery where appropriate, should be encouraged.

(4) Toe and Groin Areas.-The toe and groin areas are the surface contacts betbveen the embankment and the original river channel and abutments, respectively. The examiner should closely examine the toe and groin areas of an embankment dam to note the specific locations of any possibly detrimental vegetation, significant erosion, and seepage exit areas.

IJsually, erosion is caused by surface runoff and can lead to undermining the embankment. To alleviate this condition, preventive measures include:

channeling runoff away from the groins, placing rock protection in the eroded areas, or otherwise providin g a suitable drainage system within the affected area.

The toe and downstream groin areas are the most common locations for reservoir seepage to exit. [Refer to the Zmtrurne~ztation (irzclzdi,zg Seepng~ Monitoring) subparagraph in the Miscellaneous Areas of Examination paragraph.]

All restricted areas associated with the toe and groin should be appropriately fenced and posted with signs as needed.

(5) Spillway.-The purpose of a spillway is to pass excess flow that ma)’ threaten the structural integrity of the dam. By using a spillway, flou is passed safely to a downstream cl~annel. Service spillways are provided at nearly all storage dams and are designed to accommodate releases up to the inflow design flood (IDF). An auxiliary or emergency spillway is also provided depending on topographic conditions and the frequency and magnitude of flooding possible. Figure 2 depicts typical spillway configurations.

Spillways may be uncontrolled or controlled. An uncontrolled spillwa) uses an ungated crest structure as a flow control section. Controlled spillways use gates on the crest structure to regulate spillway discharge.

A conveyance chute, conduit, or tunnel below the control section conveys spillway discharge to the stilling basin, where provided, or downstream channel. The conveyance chute may be an open channel cut in rock or concrete lined. The spillway design is dependent upon the inflow design flood, topography, dam location, downstream channel configuration, and hydraulic considerations.

Spillway examination is necessary to ensure its operational reliabilit) to pass flow. Because of the wide variety of types and configurations of spillways, these guidelines al-e limited to the following more common features normally examined:

(a) Inlet urea and intake structure.-The inlet area should be examined for trees or other large vegetative growth or other debris which could restrict flow through the spillway. If necessary, removal of sucl~ obstructions or installation of a log boom immediately upstream 01 the spillway crest may be appropriate measures in preventing objectionable material from entering the spillway.

Where a log boom is not needed, a safety buoy line may be net-essar) to warn recreationists of the dangers associated with a spillway intake.

The buoy line should be placed a reasonable distance upstream from the area affected by the hydraulic characteristics associated with watc’r entering the intake. Buoys should be spaced at 2.5foot (7.6-meter) centers and held in place with cable clamps. Signs prohibiting all recreational activities inside the restricted areas should be posted on every third buoy. To restrict movement of the buoy line, concrete anchors should be added to lines spanning more than 400 feet (122 meters). \Vhen necessary, posted signs and fencing should be added to the spillway intake area.

{’ ‘n’et ‘rFrCre*t of dam

Original ground surface

MORNING GLORY INLET SPILLWAY

Operating bridge

/ Radial gates

““A \

GATED CONCRETE-LINED SPILLWAY

Dumped riprap \

I-- Grout-curtain

UNCONTROLLED OVERFLOW SPILLWAY

Figure Z-Typical spillway configurations.

The intake structure should be examined for evidence of significant deterioration, settlement, or other signs of distress. If provided, the riprap or other protective material should be examined for indications of movement or deterioration.

A controlled spillway is provided with a gate(s) that regulates discharge from the reservoir through the structure. The following types of gates can be used for spillway regulation: radial gates, drum gates, ring gates, roller (Stoney, coaster, or caterpillar) or wheel-mounted (fixed-wheel) gates, and cylinder gates (see fig. 3). As compared to outlet-works gates, spillway gates are usually larger, under relatively low head, and more readily accessible for examination. The following items listed for the most commonly used spillway gates should be checked during the field examination.

Radial gates - Condition of protective coating; corrosion, buckling, cracked welds, and missing or broken rivets or bolts on the faceplate, beams, girders, and arms; trunnion pins and anchorage system for damage, proper lubrication, and loose nuts; damaged, cracked, uneven or missing seals and associated clamp bars and bolts; open drain holes;

wallplates and sill for damaged surfaces, misalignment or damage to adjacent concrete; and the interior of radial gates with downstream covers.

Drum or ring gates - Interior of the drums for water tightness, condition of protective coating, debris, cracking, corrosion, or any other signs of deterioration; clearances between walls and drum gates; the exterior surfaces of the gates for damage to the protective coating, hinge system, or concrete anchorage; the condition of inlet and outlet areas of the float chamber and the drainline from the interior of the drum; drainlines are open and flexible drainline joints are free to move; and drain holes in structural support beam webs are clear.

If possible, the spillway gates should be test operated according to instructions in appendix C. The examiner should note the operational condition of the main and auxiliary power units and recommend corrective measures if necessary. An adequate fuel supply should be available to ensure that any operations necessary during an emergency can be made using the auxiliary power unit. Storage of the fuel for the auxiliary power unit should meet all applicable regulations. Where remote operation or supervisory control is provided and conditions permit, the system should be tested during the examination to determine its operational reliability.

Hoist equipment for spillway gates can range from devices which use the reservoir water buoyancy for operation of the gates (as in the case of drum and ring gates), to the use of electrically-driven chain, wire rope, belt, or screw hoists or hydraulic cylinders. The following list identifies items for each type of hoist that should be checked for damage or malfunction during the field examination.

Hydraulic hoists - Oil leakage around piston stem, flanges, or cylinder head of the operator; loose connections; oil leakage, inadequate or excessive pressure in hydraulic system; unusual noise, vibration, or overheating of the oil pump motor.

m x 3

Wire rope hoists - Corroded, dirty, or broken components; damaged or frayed wire ropes and electrical wiring; proper lubrication of wire ropes; proper wrapping (i.e., two dead wraps and each successive wrap laying side by side) of wire ropes on hoist drums; alignment of hoist components; the presence of water or contaminants in the lubricating oil of the gear box. Proper operation of limit switches, brakes, and position indicators.

Chain hoists - Seizing of the chains; corroded, broken, deformed ot missing pins, gear teeth, or sprockets; and proper operation of limit switches, brakes, and position indicators.

Screw lift hoists - Galling of screw threads in lift nut, overheating of gear motor, alignment of stems and stem guide bearings, bent stems, and loose bolts and nuts.

(b) Conveyance chute, conduit, OT tunnel.-Unlined channels should be examined for erosion caused by surface runoff and spillway releases.

If erosion exists and has the potential to adversely affect spillway operation, additional protection or stabilization of the area may be necessary. However, it should be noted that adding riprap or other suitable material may reduce the capacity of the channel. Such channels also should be kept free of any obstructions which could significantly reduce capacity.

Concrete-lined chutes, conduits, or tunnels should be examined for evidence of spalling (due to freeze/thaw damage, rocks having been thrown in, construction imperfections, etc.), cracking (due to freeze/ thaw damage, alkali-aggregate reaction, differential settlement, etc.), and joint displacement or separation (due to differential settlement, freeze/thaw damage, or uplift pressure). The lining should be examined for signs of cavitation or erosion damage. Conditions such as imperfections in the lining or significant calcium carbonate deposits which may promote cavitation damage should be noted. These deficiencies should be evaluated and the need for remedial measures and/or periodic monitoring of the condition determined.

Fencing and posted signs should be provided along spillway chute walls as appropriate.

(c) Stilling basin.-Where provided, a stilling basin is located at the downstream end of the spillway chute, conduit, or tunnel structure.

The basin’s purpose is to dissipate energy from high velocity flow to protect the downstream channel and toe area from erosion. Usually, the stilling basin is designed with dentates and an end sill to facilitate energy dissipation. The lower portions of the stilling basin are usually submerged and cannot be observed during the examination. To determine the condition of submerged portions of the stilling basin, the basin should be dewatered or examined by divers every 6 years or more frequently if possible (e.g., stilling basins with draining capability), or as determined by a suspected or previously identified condition or past operations (e.g., following major spills). A copy of the report documenting the findings of the examination should be sent to the Facilities Engineering Branch, Engineering Division, Denver Office.

K

If possible, concrete-lined spillway stilling basins should be examined for erosion and other damage. Rocks in the stilling basin, either thrown in, or from upstream or adjacent slopes, can cause extensive damage to the concrete because they tend to be continuously churned about in the basin during discharge. This action is called “ball milling.”

Severe damage to the dentates and floor can result in ineffective operation of the basin and undercutting of the basin walls. Rocks and other debris in the stilling basin can significantly reduce the design capacity which could result in overtopping of the basin walls. High fences along the top of the basin walls and/or scaling or netting nearby slopes may help minimize the amount of rock in the basin.

Stilling basin walls should be examined for deflections, offsets at joints or cracks, plugged weepholes, and other deficiencies described previously for the spillway chute, conduit, or tunnel. The fill behind the walls should be examined for evidence of large vegetative growth, sinkholes, evidence of improper drainage, and any other undesirable conditions. If provided, the training or splitter wall should be examined to determine if any cracking or separation exists at its base. If possible, the examiner should observe the stilling basin in operation. All unusual conditions should be properly documented and any necessary corrective measures recommended.

Guardrails or fencing should be provided on top of the stilling basin walls, as appropriate, to deter unauthorized access. Signs restricting recreational activities and warning of sudden high flows should be posted in the stilling basin area. Stilling basins associated with gates that are remotely controlled or can open automatically should be provided with an alarm that warns individuals downstream of an impending release.

(cl) Discharge channel.-A discharge channel downstream from the stilling basin or conveyance chute, conduit, or tunnel (if a stilling basin is not provided) is normally provided to convey releases downstream to a river, tributary stream, or other natural water conveyance channel. Generally, a riprap protected transition area is provided immediately downstream of the stilling basin or conveyance chute, conduit, or tunnel.

If no cutoff wall or an inadequate depth of cutoff is provided immediately downstream of the stilling basin or conveyance chute, conduit, or tunnel, undercutting and collapse of the structure is possible.

If such deficiencies are evident, stabilization measures, such as placing additional riprap, should be considered.

The examiner should observe the condition and placement of riprap and any signs of erosion or backcutting in the discharge channel and transition area. Sloughing or erosion of the channel banks could be the result of inadequate riprap protection or saturation of the banks due to high tailwater levels. The channel should be free of any objectionable vegetation or debris which may restrict flow or cause undesirable flow characteristics. If deemed to cause significant adverse effects, such vegetation or debris should be recommended for removal.

Signs warning of sudden high flows should be placed in the discharge channel area as far downstream as rapid increases in water surface elevation are expected to occur. A safety buoy line placed across the discharge channel may be considered as a means of preventing boaters from entering this area.

(6) Outlet Wo&s.-The primary purpose for providing a dam with an outlet works is to provide a controlled release of water downstream fol irrigation, municipal or industrial use, fish and wildlife habitat, and recreation. The outlet works is the primary means to drawdown or evacuate the reservoir and may be designed to assist in passing floods. Each outlet works is designed for site-specific conditions, and thus dependent upon its intended purpose(s), required capacity, type of dam,. topography, and dam location.

The basic components of an outlet works are an intake structure, upstream tunnel or conduit, guard (emergency) and regulating gates and/or valves, stilling basin, and discharge channel. An outlet works can be pressurized or free-flow (open to atmosphere). A pressurized outlet works consists of a guard-gate chamber and a regulating gate or valve control house separated by a pressurized tunnel or conduit. A free-flow outlet works normally includes a gate chamber in which both the guard and regulating gates and/or valves are located upstream of a free-flow tunnel or conduit.

Figure 4 illustrates two typical outlet works configurations.

Examination of the features related to the outlet works of a dam is necessary to ensure reliable operation. Because of the wide variety of outlet works configurations, discussions will be limited to the following more common features normally addressed during field examinations:

(a) Zntakestructure and upstream conduit or tunnel.-The outlet works intake structure and upstream conduit are normally submerged during a field examination and not accessible to the examiner. As a minimum, these structures should be examined during a low reservoir level 01 when warranted by a suspected or previously identified condition as outlined in Guidelines for Determining Whether Normally Inundated Outlet Works Features Should be Examined [3]. If necessary, divers or a remotely operated underwater camera can be used for the examination. A report should dodument the findings of the special examination with copies sent to the Facilities Engineering Branch, Engineering Division, Denver Office.

During an examination of these features, it is important to check that no subsidence of surrounding material or sedimentation buildup has occurred, thereby blocking the intakes. All concrete associated with the structure should be checked for significant cracking, settlement, and deterioration. If provided, trashracks should be checked for damaged metalwork, excessive buildup of rust, and blockage by debris. For gated intake structures, the examiner should make observations similar to those described in the following subparagraph. The upstream conduit should be checked for unusual settlement, excessive cracking or seepage, and cavitation or other damage. Appropriate corrective action should be recommended if these conditions exist and threaten the structure’s integrity or quality of operation. Experience has shown that because riginal ground surface

Control house

Cutoff collars Horseshoe conduit

PRESSURIZED OUTLET WORKS

Access tunne Regulating gate

$ Intake structure, Shaft house, y Axis of dam inal ground surface

Gate chamber

Circular tunnel Guard and regula tes in tandem

FREE-FLOW OUTLET WORKS

Figure 4.-Typical outlet works configurations.

these structures are not subjected to a changing environment (constantly submerged), little damage or deterioration occurs.

If a bulkhead is provided for the intake structure, the location and condition of it should be noted and verified by the examiner, if possible.

Information relative to bulkhead location and installation and removal procedures should be outlined in the facility’s SOP.

Where deemed necessary, a safety buoy line as described in the Embankment Dams subparagraph of subparagraph Storage Dams under Spillway should be provided for the outlet works intake area.

(b) Guard gate chamber and access house and shaft.-Facilities with guard and regulating gates in tandem that discharge freely into a tunnel or conduit are normally provided with an access shaft located on the crest of the dam that leads to the gate chamber. In many instances, the shaft is located inside of an access house.

Where provided, the access house should be examined for cracking or other concrete deterioration, damage to the roof, and any movement of the structure. Settlement, deflection, or any other observed movements, may be the result of movement within the dam embankments, or inadequate compaction of material adjacent to the structure during construction.

Controls for gate operation located within the access house should have all significant components such as valves, switches, etc. clearly and correctly labeled. Posted operating instructions, a copy of the current SOP, and a current logbook (operating log) should be kept in the access house. Metalwork, susceptible to corrosion, should be protected with an adequate coating of paint.

The access…