210.1r-94 compendium of case histories on repair of

ACI 210.1 R-94

Compendium of Case Histories on Repair of Erosion-Damaged Concrete in Hydraulic Structures

Reported by ACI Committee 210

(Reapproved 1999)

Stephen B. TatroChairman

Patrick J. Creegan Angel E. HerreraJames R. Graham Richard A. Kaden

This report is a companion document to ACI 210R. It contains a series ofcase histories on hydraulic structures that have been damaged by erosionfrom various physical mechanical and chemical actions. Many of thesestructures have been successfully repaired. There were many examples toselect from; however, the committee has selected recent, typical projects,with differing repair techniques, to provide a broad range of current exper-ience. These case histories cover only damage to the hydraulic surfaces dueto the action of water, waterborne material or chemical attack of concretefrom fluids conveyed along the hydraulic passages. In addition to repairsof the damaged concrete, remedial work frequently includes design modi-fications that are intended to eliminate or minimize the action that pro-duced the damage. This report does not cover repair of concrete damagedby other environmental factors such as freeze-thaw, expansive aggregate, orcorroding reinforcement.

Keywords: abrasion; abrasion resistance; aeration; cavitation; chemical attack;concrete dams; concrete pipes; corrosion; corrosion resistance; deterioration;erosion; grinding (material removal); high-strength concrete hydraulic structures;maintenance; outlet works; penstocks; pipe linings; pipes (tubes); pittings; polymerconcrete; renovating; repairs; sewers; spillways; tolerances (mechanics); wear.

James E. McDonaldErnest K. Schrader

CONTENTS

Chapter l-Introduction, p. 210.1R-1

Chapter 2-Cavitation-erosion case histories, p. 210.1R-2Dworshak DamGlen Canyon DamLower Monumental DamLucky Peak DamTerzaghi DamYellowtail Afterbay DamYellowtail DamKeenleyside Dam

ACI Committee Reports, Guides, Standard Practices, andCommentaries are intended for guidance in designing, plan-ning, executing, or inspecting construction and in preparingspecifications. References to these documents shall not bemade in the Project Documents. If items found in thesedocuments are desired to be part of the Project Docu-ments, they should be phrased in mandatory language andincorporated into the Project Documents.

210.1R

Chapter 3-Abrasion-erosion case histories, p. 21O.lR-13Espinosa Irrigation Diversion DamKinzua DamLos Angeles River ChannelNolin Lake DamPine River Watershed, Structure No. 41Pomona DamProvidence-Millville Diversion StructureRed Rock DamSheldon Gulch Siphon

Chapter 4-Chemical attack-erosion case histories, p.210.1R-25

Barceloneta Trunk SewerDworshak National Fish HatcheryLos Angeles Sanitary Sewer System andHyperion Sewage Treatment FacilityPecos Arroyo Watershed, Site 1

Chapter 5-Project reference List, p. 210.1R-32

CHAPTER 1-INTRODUCTION

This compendium of case histories provides informa-tion on damage that has occurred to hydraulic structuresand the various methods of repair that have been used.ACI Committee 210 has prepared this report to help oth-ers experiencing similar problems in existing work.Knowledge gained from these experiences may help

ACI 210.1R-94 became effective Nov. 1.1994.Copyr ight 8 1994, American Concrete Institute.Al l rights reserved including rights of reproduction and use in any form or by

any means, including the making of copies by any photo process, or by any elec-tronic or mechanical device, printed, written, or oral, or recording for sound orvisual reproduction for use in any knowledge or retrieval system or device, unlesspermission in writing is obtained from tbe copyright proprietors.

-1

210.1R-2 ACI COMMITTEE REPORT

avoid oversights in design and construction of hydraulicstructures and provide guidance in the treatment offuture problems.

Erosion of concrete in hydraulic structures may occuras a result of abrasive action, cavitation, or chemicalattack. Damage may develop rapidly after some unusualevent such as a flood or it may develop gradually duringnormal continuous operation or use. In most cases wheredamage has occurred, simply replacing the eroded con-crete will ensure immediate serviceability, but may notensure long-term performance of the structure. There-fore, repair work usually includes replacing erodedconcrete with a more resistant concrete and additionalsurface treatment, modifying the design or operation ofthe structure to eliminate the mechanism that producedthe damage, or both. A detailed discussion of mechan-isms causing erosion in hydraulic structures, andrecommendations on maintenance and repair, is con-tained in ACI 210R.

When damage does occur to hydraulic structures,repair work poses some unique problems and is oftenvery costly. Direct access to the damaged area may notbe possible, or may be limited by time, or other con-straints. In some cases, such as repair to spillway stillingbasin floors, expensive bulkheads and dewatering arerequired. It may not be possible to completely dry thearea to be repaired or maintain the most desirabletemperature. A great deal of planning and scheduling forrepair work are normally required, not only for therepairs and access, but also for control of water releasesand reservoir levels. If time permits, extensive inves-tigation usually precedes planning and scheduling todetermine the nature and extent of damage. Hydraulicmodel studies may also be necessary to evaluate possiblemodifications in the design or operation of the facility.

This compendium provides the history on 21 projectswith hydraulic erosion damage. They vary in size andcover a variety of problems: 8 with cavitation damage, 9with abrasion-erosion damage, and 4 with erosiondamage from chemical attack. Table 1.1 summarizes the
projects. Each repair was slightly different. Each historyincludes background information on the project or facil-ity, the problem of erosion, the selected solution to theproblem, and the performance of the corrective action.Histories also contain references and owner informationif further details are needed.
CHAPTER 2-CAVITATION-EROSIONCASE HISTORIES

DWORSHAK DAMNorth Fork, Clearwater River, Idaho

BACKGROUNDDworshak Dam, operational in 1973, is a straight-axis

concrete gravity dam, 717 ft high, 3287 ft long at the

crest, and contains 6,500,000 cubic yards of concrete. Inaddition to two gated overflow spillways, three regulatingoutlets, 12 ft wide by 17 ft high, are located in the spill-way monoliths. The inlet elevation for each regulatingoutlet is 250 ft below the maximum reservoir elevation.Each outlet jet is capable of a maximum discharge of14,000 fij/s.

Outlet surfaces are reinforced structural concreteplaced concurrently with adjacent lean, large aggregateconcrete. Coatings to the outlet surfaces were appliedduring the original construction. In Outlet 1, the wall andinvert surfaces from the tainter gate to a point 50 ftdownstream are coated with an epoxy mortar having anaverage thickness of % in. The same area of Outlet 2 wascoated using an epoxy resin, approximately .05 in. inthickness. Outlet 3 was untreated.

The outlets were operated intermittently at variousgate openings for a period of 4 years between 1971 and1975, resulting in a cumulative discharge duration ofapproximately 10 months. The three outlets were notoperated symmetrically; outlets 1 and 2 were used pri-marily.

PROBLEMInspection in 1973 showed minor concrete scaling of

the concrete wall surfaces of Outlets 1 and 2. One yearlater, in 1974, serious erosion had occurred at wallsurfaces of both outlets immediately downstream of thewall coatings, 50 ft from the tainter gate. Part of this wallarea had eroded to a depth of 22 in., exposing and evenremoving some No. 9 reinforcing bars. In the wall sur-faces downstream of Outlet 1 medium damage, up to 1in. depth of erosion, also occurred in over 60 squareyards of surface, bordered by lighter erosion. Everyhorizontal lift joint (construction joint) along the path ofthe jet, showed additional cavitation erosion.

SOLUTIONRepairs were categorized as three types:

l Areas with heavy damage, with erosion greater than2 to 3 in., were delineated by a 3-in. saw cut andthe interior concrete excavated to a minimumdepth of 15 in. (Fig. 2.1 and 2.2). Reinforcement
was reestablished and steel fiber-reinforced con-crete (FRC) was used as the replacement material.
l Areas with medium damage, where the depth oferosion was less than 1 in., were bush-hammered toa depth of % to 1 in. and dry-packed with mortar.The mortar, if left untreated, would easily havefailed when subjected to the high velocity discharge.

l Areas with minor damage, surfaces showing a sand-blast texture, were not separately treated prior topolymer impregnation. The entire wall surfaces ofOutlet 1 were then treated by polymer impregna-tion from the downstream edge of the existingepoxy mortar coating to a distance 200 ft down-stream.

REPAIR OF EROSION DAMAGED HYDRAULIC STRUCTURES 210.1 R-3

TABLE 1.1 - SUMMARY TABLE OF PROJECTS COMPRISING THIS REPORT

Reference

page

210.1R-2

Yearcompleted Location Owner Problem Repair type

1974 Gravity dam Idaho Corps of Cavitation PolymerEngineers impregnation

1964 Arch dam Arizona Bureau of Cavitation AerationReclamation

Project nameDworshak Dam

Glen Canyon Dam 210.1R-5

Lower MonumentalDam

210.1R-661969

1956

1960

1966

Navigation lock washington Corps of Cavitation EpoxyEngineers

Outlet structure Idaho Corps of Cavitation variousEngineers

Outlet structure British Columbia B.C. Hydro Cavitation HydraulicAuthority redesign

Stilling basin Montana Bureau of Cavitation Various overlaysRecIamation

1966

1968

Stilling basin Montana Bureau of Cavitation Aeration andRecIamation overIays

IOutlet structure

IBritish Columbia B.C. Hydro

ICavitation High-strength

Authority I I concrete

Lucky Peak Dam 210.1R-8

Terzaghi Dam 210.1R-9

Yellowtail AfterbayDam

210.1R-11

Yellowtail Dam 210.1R-11

210.1R-12Keenleyside Dam

Espinosa IrrigationDiversion Dam

1984 Diversion dam New Mexico

1965 Stilling basin Pennsylvania

Soil Conser-vation Service

Corps ofEngineers

Abrasion

Abrasion

Steel plate armor

Silica fumeconcrete

210.1R-13

210.1R-15Kinzua Dam

Los Angeles RiverChannel

210.1R-1771940s Channel California

1963 Stilling basin Kentucky

Proposed Channel Colorado

Corps ofEngineers

Corps ofEngineers

SoiI Conser-vation Service

Abrasion

Abrasion

Abrasion

Siiica fumeconcrete

Hydraulicredesign

High-strengthconcrete

NoIin Lake Dam 210.1R-18

Pine River Watershed,Structure No. 41

210.1R-19

Pomona Dam 1963

1986

1969

1991

1976

1960s

Varies

Stilling basin Kansas

Diversion dam Utah

Stilling basin Iowa

Syphon outlet Wyoming

Pipeline Puerto Rico

Concrete tanks Idaho

Sewerage Californiastructures

Corps of Abrasion variousEngineersSoil Conser- Abrasion Surface hardenervation ServiceCorps of Abrasion UnderwaterEngineers concreteSoil Conser- Abrasion Polymer-modifiedvation Service mortar

Puerto Rico Chemical attack PVC liningAqueduct &Sewer Authority

Corps of Chemica l attack LiningsEngineers

City of Los Chemical attack Shotcrete andAngeles PVC liners

210.1R-20

210.1R-22Providence-MillvilleDiversion Structure

Red Rock Dam 210.1R-23

Sheldon Gulch Siphon 210.1R-25

210.1R-25

210.1R-26

Barceloneta TrunkSewer

Dworshak NationalFish Hatchery

Los Angeles SanitarySewer System andHyperion SewageTreatment Facility

Pecos ArroyoWatershed, Site 1

210.1R-27

1988I

Outlet conduitI

New Mexico Soil Conser-I

Chemical attack HDPE liner andvation Service I hydraulic redesign

210.1R-30

Damage to the epoxy mortar was minimal and located PERFORMANCEnear the outlet gate. This area was repaired with newepoxy.

The polymer impregnation process involved drying allthe surfaces to a temperature up to 300 F to drive offwater and then allowing the surface to cool to 230 F.Monomer was then applied to the surface using a verticalsoaking chamber. Excessive monomer was drained andthe surface was polymerized by the application of approx-imately 150 F water.

Operation of the outlets from the time of repair in1975 until 1982 has been minimal averaging 1400 ft3/sper outlet with peak discharges of 3600 ft3/s per outlet.Durations of usage are not known. After 1982 outlet dis-charges increased, with durations exceeding 50 days.

Inspections performed in 1976, the year after therepairs, showed no additional concrete damage except forsome minor surface spalling adjacent to a major pre-existing crack in an area of dry-packed mortar. The

210.1R-4 ACI COMMlTTEE REPORT

Fig. 2.1-Dworshak Dam. Detail showing depth of erosion behind reinforcing steel

Fig. 2.2-Dworshak Dam. Extent of outlet surface preparation prior to concrete and mortar placements

spalled area was patched with epoxy paste, except thatthe epoxy paste did not bridge the crack this time. Epoxyresin coating repairs applied to Outlet 2 showed somefailures,

Inspections in 1983 and 1988 showed that epoxy mor-tar coatings in Outlet 1 continued to perform well. Smallareas of damage, typically spalls, are periodically repairedwith a paste epoxy. Epoxy resin coatings in Outlet 2 arerepaired more frequently but are performing adequately.Surfaces repaired with FRC and mortar and subsequentlypolymer-impregnated showed negligible damage. Poly-mer-impregnated parent concrete shows a typical matrixerosion around the coarse aggregate to a depth of 1/4-in.,and lift joints exhibit pitting up to 3/8-in. deep. Surfaces

along lift joints not polymer-impregnated show erosionup to 3/4-in. in depth and a general surface pitting greaterthan the companion polymer-impregnated surfaces,

DISCUSSIONBecause of variation in the operation of these outlets,

both in flow rate and duration, exact time-rate erosionconclusions are difficult to make. Recent outlet dischargehas fluctuated annually from moderate flows to none. Ingeneral, surfaces that received replacement materials andwere subsequently polymer-impregnated have performedwell. Original concrete and new polymer impregnatedconcrete is showing evidence of deterioration, but at arate that is less than the unimpregnated surfaces. The


best performance was by the original epoxy mortar coat-ing. The epoxy mortar in Outlet 1 continues to display anexcellent surface condition, with no cavitation-generatedpitting. The epoxy resin coating in Outlet 2 displays goodperformance.

In 1988, outlets were modified by adding aeration de-flectors, wedges 27 in. wide by 1.5 in. high, to the sidesand bottom of each outlet. These deflectors were de-signed to increase the aeration of the discharge jet andfurther reduce the cavitation erosion of the outlet sur-faces. Subsequent deterioration of the outlet surfaces hasnot been observed.

The polymer impregnating of the concrete surfaces ofthe outlets was a very complex system of operations. Suc-cess requires continual evaluation of application condi-tions and flexibility to react to changes in those condi-tions. Issues relating to safety, cost, and field engineeringadd significant challenges to a polymer impregnation pro-ject. It is doubtful that this process would be attemptedtoday under similar circumstances. It is more likely thatthe aeration deflectors would be the first remedy con-sidered since they provide a positive solution to theproblem without the higher risks of a failure inherent inthe polymer impregnation process.

REFERENCESSchrader, Ernest K., and Kaden, Richard A, “Outlet

Repairs at Dworshak Dam,” The Military Engineer, TheSociety of American Military Engineers, Washington,D.C., May-June 1976, pp. 254-259.

Murray, Myles A, and Schultheis, Vem F., “Polymer-ization of Concrete Fights Cavitation,” Civil Engineering,V. 47, No. 4, American Society of Civil Engineers, NewYork, April 1977, pp. 67-70.

U.S. Army Engineer District, Walla Walla, “PolymerImpregnation of Concrete at Dworshak Dam,” WallaWalla, WA, July 1976, Reissued April 1977.

U.S. Army Engineer District, Walla Walla, “PeriodicInspection Reports No. 6, 7, and 8, Dworshak Dam andReservoir,” Walla Walla District, Jan. 1985.

CONTACT/OWNER

Walla Walla District, Corps of EngineersCity-County AirportWalla Walla, WA 99362

GLEN CANYON DAMColorado River, Northeast Arizona

BACKGROUNDGlen Canyon Dam, operational in 1964, is a concrete

gravity, arch structure, 710 ft high with a crest length of1560 ft. The dam is flanked on both sides by high-headtunnel spillways, each including an intake structure withtwo 40- by 55-ft radial gates. Each tunnel consists of a41-ft diameter section inclined at 55 percent, a vertical

bend (elbow), and 985 ft of near horizontal length fol-lowed by a deflector bucket. Water first flowed throughthe spillways in 1980, 16 years after completion of thedam.

PROBLEMIn late May 1983, runoff in the upper reaches of the

Colorado River was steadily increasing due to snowmeltfrom an extremely heavy snowpack. On June 2,1983, theleft tunnel spillway gates were opened to release 10,000ft3/s. On June 5 the release was increased to 20,000 ft3/s.On June 6 officials heard loud rumbling noises comingfrom the left spillway. Engineers examined the tunneland found several large holes in the invert of the elbow.This damage was initiated by cavitation, triggered by dis-continuities formed by calcite deposits on the tunnelinvert at the upstream end of the elbow. In spite of thisdamage, continued high runoff required increasing thedischarge in the left spillway tunnel to 23,000 ft3/s. byJune 23. Flows in the right spillway tunnel were held at6000 ft3/s. to minimize damage from cavitation. Spillwaygates were finally closed July 23, and engineers made athorough inspection of the tunnels.

Extensive damage had occurred in and near the lefttunnel elbow (Fig. 23). Immediately downstream from
the elbow, a hole (35 ft deep, 134 ft long, and 50 ft wide)had been eroded in the concrete lining and underlyingsandstone foundation. Other smaller holes had beeneroded in the lining in leapfrog fashion upstream fromthe elbow.
SOLUTIONThe repair work was accomplished in six phases: 1) re-

moving loose and defective concrete lining and founda-tion rock; 2) backfilling large cavities in sandstone foun-dation with concrete; 3) reconstructing tunnel lining; 4)grinding and patching of small defective areas; 5) remov-ing about 500 cubic yards of debris from lower reaches oftunnel and flip bucket; and 6) constructing an aerationdevice in the lining upstream of the vertical elbow.

Sandstone cavities were filled with tremie concrete be-fore the lining was replaced. About 2000 cubic yards ofreplacement concrete was used. The aeration slot wasmodeled in the Bureau of Reclamation Hydraulic Labor-atory to ensure that its design would provide the per-formance required.

The aeration slot was constructed on the inclined por-tion of the tunnel approximately 150 ft upstream fromthe start of the elbow. A small 7-in-high ramp was con-structed immediately upstream of the slot. The slot was4 by 4 ft in cross section and extended around the lowerthree-fourths of the tunnel circumference (Fig. 2.4). Allrepairs and the slot were completed in the summer of
1983.
PERFORMANCEBecause of the moderate runoff in the Colorado River

since completion of the tunnel repairs, it has not been


Fig. 2.3-Glen Canyon Dam. Erosion of spillway tunnel invert and sandstone foundationrock downstream of the elbow

necessary to use the large spillway tunnels. However,shortly after completion of the work, another high runoffperiod permitted performance of a field verification test.This test lasted 72 hr with a maximum flow during thattime of 50,000 ft3/S. The test was conducted in twophases with several interruptions in each for examinationof the tunnel Offsets were intentionally left in place toevaluate whether the aeration slot would indeed precludecavitation and attendant concrete damage. The tunnel re-pairs and air slot performed as designed. No sign of cavi-tation damage was evident anywhere in the tunnel. Aera-tion has decreased the flow capacity of the spillwaytunnels by approximately 20 percent of the original flowcapacity.

REFERENCESBurgi, P.H., and Eckley, M.S., “Repairs at Glen Can-

yon Dam,” Concrete International, American ConcreteInstitute, MI, V. 9, No. 3, Mar. 1986, pp. 24-31.

Frizell, K.W., “Glen Canyon Dam Spillway TestsModel - Prototype Comparison,” Hydraulics and Hydro-logy in the Small Computer Age, Proceeding of the Spe-cialty Conference, Lake Buena Vista, Florida, Aug.

12-17, 1985, American Society of Civil Engineers, NewYork, 1985, pp. 1142-1147.

Frizell, K.W., “Spillway Tests at Glen Canyon Dam,”U.S. Bureau of Reclamation, Denver, CO, July 1985.

Pugh, C.A., “Modeling Aeration Devices for GlenCanyon Dam,” Water for Resource Development, Proceed-ings of the Conference, Coeur d’Alene, Idaho, Aug.14-17, 1984, American Society of Cii Engineers, NewYork, 1984, pp. 412416.

CONTACT

U.S. Bureau of ReclamationP.O. Box 25007, Denver Federal CenterDenver, CO 80225

LOWER MONUMENTAL DAMSnake River, Near Kaloutus, Washington

BACKGROUNDLower Monumental Dam, operational in 1970, consists

of a concrete gravity spillway and dam, earthfii em-

210.1R-7

Original tunnel surfac

Aeration slot

.I8

SECTION A-A

Fig. 2.4-Glen Canyon Dam. Diagram of new tunnel spillway air slot

bankments, a navigation lock, and a six-unit powerhouse.The 86-ft wide by 675-ft long navigation lock chamber,

with a rise of 100 ft, is filled and emptied by two galleriesor culverts, landside and riverside of the lock structure.The landside culvert, which supplies five downstream lat-erals, crosses under the navigation lock to discharge intothe river. The riverside culvert supplies and dischargeswater to the upstream five laterals. Each lateral consistsof 10 portal entrances approximately 1.5 ft wide by 3 fthigh. Plow velocities in excess of 120 ft/s occur in severalof the portals entrances. A tie-in gallery exists betweenthe two main culverts, near the downstream gates, thatequalizes the pressure between the two culverts.

PROBLEMInspections as early as 1975 revealed that the ceiling

concrete of the landslide culvert was spalled at somemonolith joints to depths of 9 in. This may have been ini-tiated by differential movement of adjacent monolithswhen the lock chamber was filled and emptied. Damageto the invert, at several locations, was irregular, witherosion a maximum of 18 in. deep at the monolith joint,decreasing to 1 in. at a point 10 ft upstream of the joint.Reinforcing steel was exposed. Other areas of erosion inthe invert and on wall surfaces were observed, measuring2 ft square and 2 in. deep.

Later inspections revealed that portal surfaces nearestthe culverts of the most downstream laterals were show-ing signs of concrete erosion (Fig. 2.5). By 1978, the por-tal walls, ceiling, and invert had eroded as deep as 3 in.

over an area of 5 square ft, exposing reinforcing steel.All four corners of the tie-in gallery experienced ob-

vious cavitation damage. The damage varied from minorpitting to exposure and undercutting of the 11/2-in. aggre-gate.

SOLUTIONIn 1978, the navigation lock system was shut down for

two weeks for repairs. The major erosion damage to thelandslide culvert was repaired by mechanically anchoredsteel fiber-reinforced concrete. The smaller areas ofdamage received a trowel application of a paste epoxyproduct. Ceiling damage was backfilled with dry-mixshotcrete. Portal and tie-in gallery surfaces receivedapplication of a paste epoxy, troweled to a feather edgearound the perimeter.

PERFORMANCEThe mechanically anchored fiber-reinforced concrete

has performed well to date. No additional erosion hasbeen observed. Shotcrete patches to the ceiling adjacentto the joints show continued spalling, but to a lesserextent than prior to repairs.

The repairs to the portal surfaces and tie-in gallerysurfaces performed poorly. After 1 year of service, ap-proximately 40 percent of the epoxy paste had failed; andafter 3 years, nearly 100 percent has failed. Concreteerosion in these areas has subsequently increased todepths of 6 to 8 in. in the tie-in gallery and up to 5 to 6in. on the two most downstream portal surfaces.


DISCUSSIONRecent inspections have shown that the rate of erosion

has decreased. The accumulated erosion of concrete fromcertain surfaces is significant; however, subsequent ero-sion is almost negligible. Consequently, repair schedulesare not critical.

Paste epoxy was applied to the concrete surfaces tran-sitioning to feather edges along the perimeter of thepatches. Cavitation eroded the concrete adjacent to thefeather edges as weIl as eroding the thin epoxy edges(Fig. 2.5). These new voids undermined the new, thickerepoxy, and at some point caused another failure of theleading edge. As the leading edge void increased in size,the failure progressed until little epoxy was left in therepaired area. After erosion of the epoxy patch material,no further concrete erosion has occurred. It appears thatthe eroded configuration of the surface is hydraulicallystable.

Patch-type repair procedures are not sufficient for thisstructure because erosion is initiated at the edge of thenew patch. Eventual repairs will replace larger areas ofthe concrete flow surfaces and will include substantialanchoring of new materials.

U.S. Army Engineer District, Walla Walla, “PeriodicInspection Report No. 6, Lower Monumental Lock andDam,” Walla Walla, WA, Jan. 1977.



CONTACT/OWNER


LUCKY PEAK DAMBoise River, Near Boise, Idaho

BACKGROUNDLucky Peak Dam, operational in 1955, is 340 ft high

with a crest length of 2340 ft. The dam is an earth androckfill structure with a silt core, graded filters, and rockshells. The ungated spillway is a 6000-ft-long ogee weirdischarging into an unlined channel. The outlet worksconsists of a 23-ft-diameter steel conduit that deliverswater to a manifold structure with six outlets. Each outletis controlled by a 5.25-ft by 10-ft slide gate. Individualflip lips were constructed downstream from each slidegate. Downstream of the flip lips is the plunge pool, ex-cavated into the basalt rock, with bottom areal dimen-sions of 150 by 150 ft. The outlet alignment and designwere determined by hydraulic modeling. The sir outletsoperated under a maximum head of 228 ft with a designdischarge of 30,500 ft3/S and a maximum discharge vel-ocity ranging between 88 ft/s and 124 ft/s.

PROBLEMThe steel manifold gates have a long history of cavi-

tation erosion problems. The original bronze gate sealswere seriously damaged by cavitation after initial use.Flow rates across the manifold gate frames in excess of150 ft/s for many days were common. The gate seals werereplaced with new seals made of stainless steel andaluminum-bronze. The cast-steel gate frames requiredcontinual repair of cavitated areas. In 1975 alone, over2000 pounds of stainless steel welding rod was manuallywelded into the eroded areas and ground smooth. Neatcement grout was pumped behind the gate frames to re-establish full bearing of the gate frames with the concretestructure.

The concrete invert and side piers, which separateeach of the six flip lips suffered extensive erosion soonafter the start of operations in 1955 (Fig. 2.6). 3/4-in.-thick
steel plates were anchored to the piers and invert areasjust downstream of the manifold gates. These steel wallplates became severely pitted, as did the downstreamconcrete flip lip invert surfaces. In 1968, the damagedplates were again repaired by filling the eroded areaswith stainless steel welding, and grouting behind theplates Deteriorated concrete on the flip lips was re-moved and additional steel plates were installed overthose areas. This also failed and repairs commencedagain. Deep areas of cavitation damage in the invert andpiers were filled with concrete. New 1/2-in.-thick plateswere installed. These were stiffened with steel beams,welded on 5-ft centers in each direction. Deep anchor

REPAIR OF EROSlON DAMAGED HYDRAULIC STRUCTURES 210.1R-9

-- -----

Fig. 2.6-Lucky Peak Dam. Cavitation erosion of flip lipsurface

bars were welded to the plate material to hold them inplace. Again, the voids under the plates were grouted.But during the next two years, these repairs also failed.

In 1974, it was recommended that the outlet be re-studied hydraulically. That year, remaining plate materialwas removed. Cavities were found penetrating the invertand through the piers and into the adjacent outlet invert.These voids were crudely filled with FRC in a “fieldexpedient” manner. Much of this FRC was placed instanding water with little quality control, while adjacentbays were discharging.

SOLUTIONThe side piers were redesigned and replaced to pro-

vide vents that would introduce air to the underside ofthe jet just downstream of the gates. This modificationwas intended to prevent additional invert erosion. How-ever, major modifications to the gates and gate frameswere necessary if cavitation erosion was to be eliminatedThese modifications were not made since future power-house construction would reduce and nearly eliminatethe need to use the outlet, reserving the structure foremergency and special operations use only. Steel liningon the piers was strengthened and replaced. Stiffenedsteel plates, 11/4-in. thick, were installed on the piers andinvert. Mortar backfill was pumped behind the invertplates and new concrete placed between pier plates.

PERFORMANCEAfter one year of above average usage on bays 3 and

4, cavitation was again observed. The side piers justdownstream of the gates showed areas of 1 to 2 squareft that had eroded through the steel plate and into theconcrete about 6 in. No erosion of the invert plates orthe “field expedient” FRC occurred. Use of these bayshas almost stopped since the new powerhouse becameoperational.

DISCUSSIONThe introduction of air beneath the jet appears to

have cushioned the effects of cavitation on the flip lipinvert. However, pier walls continue to erode at an extra-ordinary rate. The cause lies with the design of the gatesand gate frame. It is evident that satisfactory perfor-mance of the structure can never be achieved until thegates and frames are redesigned and reconstructed toeliminate the conditions that cause cavitation.

REFERENCESU.S. Army Engineer District, Walla Walla, “Lucky

Peak Lake, Idaho, Design Memorandum 12, Flip BucketModifications,” Supplement No. 1, Outlet Works, SlideGate Repair and Modification, Walla Walla, WA, July1986.

U.S. Army Engineer District, Walla Walla, “PeriodicInspection Report No. 6, Lucky Peak Lake,” WallaWalla, WA, Jan. 1985.

U.S. Army Engineer District, Walla Walla, “Periodic

Inspection Report No. 7, Lucky Peak Lake,” WallaWalla, WA, Jan. 1989.

CONTACT/OWNER


TERZAGHI DAMBridge River Near Lillooet, British Columbia, Canada

BACKGROUNDTerzaghi Dam, operational in 1960, is 197 ft high with

a crest length of 1200 ft. The earth and rockfill embank-ment consisting of an upstream impervious fill, clay blan-ket, sheet pile cutoff, and multiline grout curtain, isfounded on sands and gravels infilling a deep river chan-nel. The dam impounds Bridge River flow to form theCarpenter Lake reservoir, from which water is drawnthrough two tunnels to Bridge River generating stations1 and 2, located at Shalalth, B.C., on Seton Lake.

Terzaghi Dam discharge facilities are composed of asurface spillway consisting of a 345 ft long free overflowsection; and a gated section with two 25 ft wide by 35 fthigh gates. Two rectangular low level outlets (LLO), each


8 ft wide by 16 ft high are subject to a maximum heat of169 ft. These outlets were constructed in the top half ofthe concrete plug in the 32 ft, horseshoe-shaped diversiontunnel.

PROBLEMThe LLOs were operated in 1963 for about 23 days to

draw down Carpenter Lake to permit low-level embank-ment repairs. Severe cavitation erosion of the concretewall and ceiling surfaces downstream of bulkhead gateslots was observed in the north LLO after the water re-lease.

Dam safety investigations in 1985 identified that theLLOs were required to permit emergency drawdown ofCarpenter Lake for dam inspection and repair, and toprovide additional discharge capacity during large floods.

SOLUTIONThe repair consisted of three main categories of work

- repair of damage, improvement to reduce cavitationpotential, and refurbishing gates and equipment.

Repair of cavitation damage in the north LLO in-

cluded repair of the walls, crown, and gate slots.Improvements to reduce cavitation potential included

1) installing 9-in. deep rectangular constrictor frames(Fig. 2.7) immediately downstream of the operating gates

Fig. 2.7-Terzaghi Dam. Downstream detail of constrictorring

to increase pressures in the previously cavitated area, 2)backfilling old bulkhead gate slots and streamlining theexisting LLO invert entrances, and 3) installing piezo-meters in the north LLO to provide information on flowcharacteristics of the streamlined LLO during dischargetesting.

Refurbishing gates and equipment included 1) re-placing leaking gate seals on closure gates; 2) sand-blasting and repainting gates, guides, head covers, and airshafts, 3) cleaning gate lifting rods and replacing bonnetpackings; 4) replacing ballast concrete in north LLOgates and installing ballast cover plates on all gates; and5) refurbishing hydraulic lifting mechanisms of gates.

Repair concrete was designed to fully bond withexisting concrete. Surface preparation included; sawcutting around the perimeter of the damage, chipping toexpose rebar, and installation of grouted dowels. Latex-modified concrete was used for all repair work, with steelfiber reinforcement for the cavitation-damaged areas.

A total of 26 cubic yards of 3000 psi ready-mixed con-crete was placed by pumping. Maximum aggregate sizesof 3/8-in. and 3/4-in. were used for general repair and in-vert entrance backfill, respectively.

The constrictor frames were made from 1/2-in. and3/4-in. steel plate. They were installed in the LLOs bymeans of the following: 1) bolting the constrictor frameto the existing concrete with a double row of l-in.diameter adhesive anchors at 12-in. spacing 2) keying theconstrictor infill concrete into the existing concrete; 3)welding the constrictor frame to the existing gate metal-work in the walls and soffit; and 4) embedding the con-strictor sill shear bar into the existing concrete invert(Fig. 2.7).

PERFORMANCEA test with a full reservoir and a peak discharge of

7000 ft3/S, with both gates opened 7 ft, verified that theconstrictor frames and concrete repairs, downstream ofthe closure gates, performed as designed No cavitationerosion of the wall and ceiling surfaces was observed.

DISCUSSIONPiezometer readings confirmed that the constrictor

frames in the LLOs helped maintain pressures above at-mospheric, indicating that cavitation should not be aproblem in the future.

REFERENCESB.C. Hydro, “Terzaghi Dam, Low Level Outlet Re-

pairs-Memorandum on Construction,” Report No. EP6,Vancouver, B.C., Dec. 1986.

B.C. Hydro, “Terzaghi Dam, Low Level Outlet Tests,”Report No. H1902, Vancouver, B.C., Mar. 1987.

REPAIR OF EROSION DAMAGED HYDRAULIC STRUCTURES 210.1R-11

CONTACT/OWNER

British Columbia HydroHydrotechnical Department, HED6911 Southpoint DriveBurnaby, British Columbia, Canada V3N 4X8

YELLOWTAIL AFTERBAY DAMBighorn River, Montana

BACKGROUNDYellowtail Afterbay Dam, operational in 1966, is a

33-ft-high concrete gravity diversion type structure, 300ft long, located about 1 mile downstream from YellowtailDam. In 1967 following a heavy winter/spring snowpackin the upstream drainage basin, flood flows passedthrough both Yellowtail Dam and the Afterbay Dam.

PROBLEMDivers examined the Afterbay Dam sluiceway and still-

ing basin after the flood flows had passed. They foundcavitation damage on the dentates (baffle blocks) andadjacent floor and wall areas in the spillway stilling basin.Although the cavitation damage was moderate, repairswere necessary to lessen the likelihood that futurecavitation damage would occur.

Damage to the dentates and floor in the sluiceway wascaused by abrasion. The relatively low sill at the down-stream end of the sluiceway was permitting downstreamgravel and sand to be drawn into the stilling area, wherea ball mill-type action ground away the concrete surfaces.

In the stilling basin downstream of the reverse ogeesection, cavitation severely eroded the sides of the den-tates and the adjacent floor areas. A similar conditiondeveloped in the sluiceway except that it was caused byabrasion erosion. Since the damage from the two causesoccurred essentially side by side, the situation graphicallyillustrated the dissimilar types of erosion resulting fromcavitation and abrasion.

SOLUTIONFollowing the flood, low flows at the dam could be

maintained for only one month. That situation requiredthat all repairs be completed quickly and concurrently. Inaddition to repairing damaged areas, the downstream sillin the sluiceway was raised about 3 ft to stop rivergravels from being drawn into the sluiceway. Repairswere completed using a combination of bonded concrete,epoxy-bonded concrete and epoxy-bonded epoxy mortar,depending upon thickness of the repair. Epoxy used inthis repair was a polysulfide-type material. After repairedmaterials had been placed and cured, they were groundto provide a smooth, cavitation-resistant surface.

PERFORMANCEThe dam has now been in service about 23 years since

the repairs were made. With the exception of a minor

number of spalls, the performance of the repairs hasbeen excellent.

REFERENCESGraham, J.R., “Spillway Stilling Basin Repair Using

Bonded Concrete and Epoxy Mortar,” Proceedings, Irri-gation and Drainage Specialty Conference, Lincoln, NE,Oct. 1971, pp. 185-204.

Graham, J.R., and Rutenbeck, T.E., “Repair of Cavita-tion Damaged Concrete, a Discussion of Bureau ofReclamation Techniques and Experiences,” Proceedings,International Conference on Wear of Materials, St.Louis, MO, April 1977, pp. 439-445.

CONTACT

Bureau of ReclamationP.O. Box 25007, Denver Federal CenterDenver, CO 80225

YELLOWTAIL DAMBighorn River, Montana

BACKGROUNDThe dam, operational in 1966, is a concrete arch struc-

ture 525 ft high with a crest length of 1480 ft. Normalflow through the dam occurs in two 84-in. outlet pipesand through the turbines of the powerhouse. Flows ex-ceeding the capacity of these facilities are routed througha high-head spillway located in the left abutment. At thisspillway, water enters through a radial-gated intake struc-ture, then passes into an inclined section of tunnel vary-ing in diameter from 40.5 ft at the upper end to 32 ft atthe beginning of the vertical elbow. Thereafter, flow fol-lows the 32-ft-diameter tunnel through the elbow and1200 ft of near horizontal tunnel, exiting into a combina-tion stilling basin-flip bucket, then into the river.

During the spring of 1967, heavy rains in the water-shed area of the Bighorn River resulted in high inflowsinto Bighorn Lake behind Yellowtail Dam. A total of650,000 acre-ft of flood waters was released through thespillway over a period of 30 days. Maximum flow was18,000 ft3/S.

PROBLEMDuring the 1967 spill, severe damage occurred to the

concrete tunnel lining and underlying rock in the elbow,as well as upstream and downstream. After the flows intothe river had subsided sufficiently for a temporary shut-down of the tunnel, divers made an examination. Majordamage was found in the near-horizontal section of thetunnel lining and in the elbow. Failure occurred alongthe tunnel invert in a leapfrog fashion, typical of cavi-tation damage. The largest cavity was about 100 ft long,20 ft wide and 6 to 8 ft deep. After the tunnel was de-watered, it was found that a small concrete patch placedduring construction had failed. therebv causing the dis-


continuity in the flow that triggered the cavitation.

SOLUTIONThe tunnel liner was repaired using several systems

depending on the size and depth of the damage. Areaswhere the damage extended through the lining into thefoundation rock were repaired with high quality replace-ment concrete. Major areas of damage where the erosiondid not penetrate through the concrete lining wererepaired with bonded concrete. Shallow-damaged con-crete was repaired with epoxy-bonded concrete andepoxy-bonded epoxy mortar. Surfaces were ground wherenecessary to bring tolerances into conformance withspecifications requirements. Finally, tunnel surfacesbelow spring line were painted with an epoxy-phenolicpaint, to help seal the surface and bond any aggregateparticles that may have been loosened

In order to avoid recurring damage, an aeration devicewas model tested in the laboratory and then constructedin the tunnel a few ft upstream of the point of curvatureof the vertical elbow. This aeration slot measured 3 ftwide and 3 ft deep and extended around the lower threequarters of the tunnel circumference. It was designed toentrain air in the flow for all discharges up to 92,000ft3/S, without the slot filling with water. A 27-in-longramp was constructed upstream of the slot which raisedthe upstream face of the slot 3 in. at the tunnel invert.Under most flow conditions the bottom of the jet wasforced away from the tunnel floor surface. The jet re-mained free for a considerable distance downstream, allthe while drawing air into the jet from the aeration slot.Aeration has reduced the discharge capacity by approxi-mately 20 percent.

PERFORMANCEIt has now been 23 years since the tunnel was repaired

and the aeration slot installed, but flows in the river havenever been sufficient to require use of the spillway. How-ever, a controlled prototype test with flows to 16,000 ft3/swas conducted in 1969 and 1970. As a result of this test,less than one percent of the concrete repairs failed andno cavitation damage was observed, even in areas down-stream from discontinuities. To ensure that the tunnelwill always be ready for the next flow, there is a regularmaintenance program to repair ice damage and removecalcium carbonate buildups.

REFERENCESBorden, R.C., et al., “Documentation of Operation,

Damage, Repair, and Testing of Yellowtail Dam Spill-way,” Report No. REC-ERC-71-23, Bureau of Reclama-tion, Denver, CO, May 1971.

Colgate, D., and Legas, J., “Aeration MitigatesCavitation in Spillway Tunnel,” Meeting Preprint 1635,National Water Resources Engineering Meeting, Jan.24-28, 1972, Atlanta, GA, American Society of CivilEngineers, New York, NY, 29 pp.

CONTACT

U.S. Bureau of ReclamationDenver Office, Code D-3700P.O. Box 25007, Denver Federal CenterDenver, CO 80225

KEENLEYSIDE DAMColumbia River, near Castlegar, B.C., Canada

BACKGROUNDThe dam, operational in 1968, consists of an earthfill

embankment 1400 ft long and about 171 ft high and aconcrete gravity section about 1180 ft long and 190 fthigh. The concrete section contains four 55 ft widesluiceways, eight 20 by 24 ft high low level ports, and anavigation lock.

The sluiceway downstream of the gate slot has an ogeesection designed very conservatively for 65 percent of thedesign head. Upstream of the gate sill the profile is afairly broad three-radius compound curve. Accordingly,no negative pressures should occur anywhere on the crestunder free discharge operation.

PROBLEMCavitation damage has occurred on the sluiceway crest

near the gate slots on all four bays. The damage ex-tended from inside the upstream portion of the gate slotto a point about 4 ft downstream, extending at an angleof about 30 degrees to the direction of flow (Fig. 2.8).

All attempts to repair the eroded concrete with epoxymixtures and steel fiber-reinforced concrete (FRC) in1973, 1975, and 1977 were unsuccessful. Continued cav-itation soon pitted the repaired areas which later pro-gressed to development of major voids. By 1980 approxi-mately 80 percent of the previous repair had eroded.During a high water inspection in 1986, sluiceway No. 2was flow tested for 4 hr at gate openings of 4, 8, 12 and16 ft and full opening. Characteristic noises of cavitationbubble collapse could be heard intermittently at all gatesettings. The highest rate of cavitation activity wasobserved to be with gate openings from 4 to 12 ft.

The deepest erosion usually occurred just outside thegate slot with depths ranging from about 8 to 14 in.Downstream of the badly eroded area, the concrete atthe invert was observed to be roughened for another 2 ft.The maximum width of the eroded area varied from 18to 24 in.

The cavitation erosion at the foot of the gate slotdamaged not only the concrete invert but also the lowerpart of the steel liner within the gate slot and an area ofthe wall immediately downstream of the liner. The 1986study concluded that the severe concrete erosion at andjust downstream of the gate slots was due to 1) cavitationcaused by vortices originating in the upstream corners ofthe gate slots at small, part-gate operation; and 2) lack ofrounding and lack of offset of downstream edge of gateslot.


Fig. 2.8-Keenleyside Dam. Cavitation erosion of concreteinvert and adjacent damage to steel liner. Maximum depthapproximately 9 in.

SOLUTIONInitially, it was recommended that 1) eroded areas

should be filled with concrete and armored with steelplates, and; 2) field tests should be conducted to identifycavitation zones. Later, the recommendation was changedto backfill cavitated areas with aggregate, highstrength (6000 psi) concrete. The bond between the back-fill and the original sluiceway concretes was enhanced byepoxy bonding agent. The top surface of the new patchand the surrounding original concrete were coated withan acrylic latex selected through an extensive laboratoryscreening process.The work was carried out in the sum-mer of 1990.

PERFORMANCEIn order to test the effectiveness of the repairs, during

the following year it was decided to operate the sluicegates mostly in the worst range. A year later, the re-paired and coated surfaces began to show signs of pitting.The performance of the repair still did not appear satis-factory. It became obvious that besides repairing theeroded areas other initiatives were needed to alleviaterecurrence of the problem.

DISCUSSIONBased on the observations of the effect of gate open-

ing on cavitation, it was decided to limit gate operationto that outside of the destructive range. Gate operatingorders were rewritten to require “passing over” the roughzones as quickly as possible without any sustainedoperation in those zones.

REFERENCESB.C. Hydro, Hydroelectric Engineering Division,

“Hugh Keenleyside Dam, Cavitation Damage on Spill-way,” Report No. H1922, Vancouver, B.C., Mar. 1987.

B.C. Hydro, Hydroelectric Engineering Division,“Keenleyside Dam, Comprehensive Inspection and Re-view 1986,” Report No. H1894, Vancouver, B.C., May1987.

B.C. Hydro, Hydroelectric Engineering Division,“Hugh Keenleyside Dam, Cavitation Damage on Spillway,Field Investigation of Cavitation Noise and ProposedGate Operating Schedules,” Report No. 2305, Vancouver,B.C., June 1992.

CONTACT/OWNER

British Columbia Hydro Structural DepartmentHED6911 Southpoint DriveBumaby, British Columbia, Canada V3N4X8

CHAPTER 3-ABRASION-EROSIONCASE HISTORIES

ESPINOSA IRRIGATION DIVERSION DAMEspBnola, New Mexico, on the Santa Cruz River

BACKGROUNDThe diversion dam is a reinforced concrete structure

that is capable of diverting up to 13 f& in the EspinosaDitch for irrigation purposes. A 50-ft-long reinforced rec-tangular concrete channel, sediment trap, and sluice gatestructures were constructed between the headgate andthe ditch heading. A sidewall weir notch is provided inthe rectangular ditch lining to allow emergency dischargeof flood flows back to the river. A 24-in.-round sluicegate at the right side of the dam was placed at the slabinvert elevation, to sluice sand and cobbles through thedam and to prevent these materials from entering the ir-rigation ditch head gate. The dam is tied back into theriverbanks on either side with small earthen dikes thatprotect theft3/s or less.

surrounding land against flood flows of 1000

PROBLEMDebris plugged the sluice gate, preventing the diver-

sion of the bedload from the irrigation ditch. The struc-ture experienced severe erosion damage to the apron and

ACI COMMITTEE REPORT

floor blocks (Fig. 3.1) due to impact and abrasion by the

Fig. 3.1-Espinosa Irrigation Diversion Dam. Erosion damage to the floor blocks

bedload. The bedload consists of gravels and bouldersranging up to 24 in. in diameter. The concrete in theapron in the impact area was abraded to a depth of 6 in.Except for very low flows and flows diverted for irri-gation, the bedload is carried over the weir.

SOLUTIONRepairs were made by extensive structural modifica-

tions. These modifications included the following (Fig.3.2): 1) removing and replacing the top layer of rein-forcement in the apron; 2) removing and replacing thetop 6 in. of concrete; 3) protecting the apron with a ?&n.

Fig. 3.2-Espinosa Irrigation Diversion Dam. Steel plate protection added to floorblocks and endsill


steel plate; and 4) replacing the 24-in-round sluice gatewith a 36-in. square sluice gate.

PERFORMANCEThe structure has been operating satisfactorily since

rehabilitation in 1982.

DISCUSSIONFive alternatives were evaluated for the placement of

the diversion dam back into service. The ones notselected as the solution are as follows:

1. Install a reinforced concrete lining inside the wallsand apron of the existing structure.

2. Protect the apron with a 1/2-in. steel plate.3. Remove the entire apron of the structure and re-

place it with one that is adequately reinforced. Addthe liner inside the structure.

4. Remove the entire structure and replace it with anew one.

REFERENCESU.S. Department of Agriculture, “Espinosa Diversion

Dam, Report of Investigation of Structural Failure,” SoilConservation Service, Albuquerque, NM, Nov. 1980.

U.S. Department of Agriculture, “Espinosa DiversionDam, Design Engineer’s Report," USDA, Soil Conserva-tion Service, Albuquerque, NM, Sept. 1982.

CONTACT/OWNER

State Conservation EngineerU.S. Department of Agriculture Soil Conservation

Service517 Gold Avenue, SW, Room 3301Albuquerque, NM 87102

KINZUA DAMAllegheny River, Warren County, Pennsylvania

BACKGROUNDKinzua Dam became operational in 1965. The stilling

basin consists of a horizontal apron, 160 ft long and 204ft wide. It contains nine 7-ft-high by l0-ft-wide baffles,located 56 ft upstream from the end sill. The vertical-faced end sill is 10 ft high and 6 ft wide. The basin slabwas constructed of concrete with a 28-day compressivestrength of 3000 psi.

The outlet works consists of two high-level and sixlow-level sluices. A maximum conservation flow of about3600 ft3/s is supplied by the high-level sluices. The low-level sluices with flared exists containing tetrahedraldeflectors are located 26 ft above the stilling basin slab.Bank-full capacity, 25,000 ft3/s, can be discharged throughthese sluices at reservoir elevation 1325. The maximum24,800-ft3/s record discharge was discharged through thesluices in 1972. The maximum velocity at the sluice exitwas 88 ft/s.

PROBLEMBecause of the proximity of a pumped-storage power-

plant on the left abutment and problems from spray,especially during the winter months, the right side sluiceswere used most of the time. Use of these sluices causededdy currents that carried debris into the stilling basin.The end sill was below streambed level and contributedto the deposition of debris in the basin.

Divers reported erosion damage to the basin floor asearly as 1969. Also, piles of rock, gravel, and other debrisin the basin were reported. About 50 cubic yards ofgravel and rock, ranging up to 8 in. in diameter, wereremoved from the basin in 1972. Abrasion-erosion dam-age reached a depth of 3.5 ft in some areas before initialrepairs were made in 1973 and 1974.

These repairs were made with steel fiber-reinforcedconcrete. Approximately 1400 cubic yards of fiber con-crete was required to overlay the basin floor. From thetoe of the dam to a point near the baffles, the overlaywas placed to an elevation 1 ft higher than the originalfloor.

In April 1975, divers reported several areas of abra-sion-erosion damage in the fiber concrete. Maximumdepths ranged from 5 to 17 in. Approximately 45 cubicyards of debris were removed from the stilling basin.Additional erosion was reported in May 1975, andanother 60 cubic yards of debris were removed from thebasin. At this point, symmetrical operation of the lowersluices was initiated to minimize eddy currents down-stream of the dam. After this change, the amount ofdebris removed each year from the basin was drasticallyreduced and the rate of abrasion declined. However,nearly 10 years after the repair, the erosion damage hadprogressed to the same degree that existed prior to therepair.

SOLUTIONA materials investigation was initiated prior to the

second repair, to evaluate the abrasion-erosion resistanceof potential repair materials. Test results indicated thatthe erosion resistance of conventional concrete contain-ing a locally available limestone aggregate was not accep-table (Fig. 3.3). However, concrete containing this same
aggregate with the addition of silica fume and a high-range, water-reducing admixture exhibited high compres-sive strengths (approximately 14,000 psi at 28 days’ age)and very good resistance to abrasion erosion. Therefore,approximately 2000 cubic yards of silica-fume concretewere used in a 12-in. minimum thickness overlay whenthe stilling basin was repaired in 1983 (Fig. 3.4).
Construction of a debris trap immediately downstreamof the stilling basin end sill was also included in therepair contract. Hydraulic model studies showed thatsuch a trap would be beneficial in preventing downstreamdebris from entering the stilling basin. The trap was 25 ftlong with a 10-ft-high end sill that spanned the entirewidth of the basin.


10.0

9.0

8 . 0

2 . 0

1.0

I -

I -

1 I I I I

0A -STEEL FIBER REINFORCED CONCRETEREMOVED FROM THE KINZUA DAM STILL-ING BASIN.

0B -CONVENTIONAL CONCRETE, PENN-SYLVANIA LIMESTONE AGGREGATE, 5710PSI (39 MPa)

0C -CONVENTIONAL CONCRETE, LOS AN-GELES AGGREGATE, 7470 PSI (52MPa).

0D -SILICA-FUME CONCRETE, LOS AN-GELES AGGREGATE, 11,500 PSI (79MPa)

0E -S IL ICA-FUME CONCRETE, PENNSYL-VANIA LIMESTONE AGGREGATE, 13,850P S I (95 MPa)

OL0 12 2 4 3 6 4 8 6 0 7 2

TEST TIME, HR

Fig 3.3-Kinzua Dam. Abrasion-erosion performance of 5 materials tested using the underwater abrasion-erosion testmethod

PERFORMANCE In August 1984, after periods of discharge through the

upper and lower sluices, abrasion-erosion along somecracks and joints was reported by divers. The maximumdepth of erosion was about % in. The divers also dis-covered two pieces of steel plating that had been em-bedded in the concrete around the intake of one of thelower sluices. Because of concern about further damageto the intake, the use of this sluice in discharging flowswas discontinued. This nonsymmetrical operation of thestructure resulted in the development of eddy currents.

The next inspection, in late August 1984, found ap-proximately 100 cubic yards of debris in the basin. InSeptember 1984, a total of about 500 cubic yards ofdebris was removed from the basin, the debris trap, andthe area immediately downstream of the trap. The rockdebris in the basin ranged from sand sized particles toover 12 in. in diameter. Despite these adverse conditions,the silica-fume concrete continued to exhibit excellentresistance to abrasion. Erosion along some joints ap-peared to be wider but remained approximately 1/2-in.

deep.Sluice repairs were completed in late 1984, and sym-

metrical operation of the structure was resumed A diverinspection in May 1985 indicated that the condition ofthe stilling basin was essentially unchanged from the pre-ceding inspection. A diver inspection approximately 31/2

yr after the repair indicated that the maximum depth oferosion, located along joints and cracks, was about 1 in.

REFERENCESFenwick, W.B., “Kinzua Dam, Allegheny River, Penn-

sylvania and New York; Hydraulic Model Investigation,”Technical Report HL-89-17, U.S. Army Engineer Water-ways Experiment Station, Vicksburg, MS, Aug. 1989.

Holland, T.C., “Abrasion-Erosion Evaluation of Con-crete Mixtures for Stilling Basin Repairs, Kinzua Dam,Pennsylvania,” Miscellaneous Paper SL-83-16, U.S. ArmyEngineer Waterways Experiment Station, Vicksburg, MS,Sept. 1983.

Holland, T.C., “Abrasion-Erosion Evaluation of Con-crete Mixtures for Stilling Basin Repairs, Kinzua Dam,


Fig. 3.4-Kinzua Dam. Typical silica-fume concrete placement operation for a stilling basin slab

Pennsylvania," Miscellaneous Paper SL-86-14, U.S. ArmyEngineer Waterways Experiment Station, Vicksburg, MS,Sept. 1986.

Holland, T.C.; Krysa, A; Luther, M.D.; and Liu, T.C.,“Use of Silica-Fume Concrete to Repair Abrasion-Ero-sion Damage in the Kinzua Dam Stilling Basin,” Fly Ash,Silica Fume, SIag, and Natural Pozzolans in Concrete,SP-91, V. 2, American Concrete Institute, Detroit, MI,1986, pp. 841-863.

McDonald, J.E., “Maintenance and Preservation ofConcrete Structures, Report 2, Repair of Erosion-Damaged Structures,” Technical Report No. G78-4, U.S.Army Engineer Waterways Experiment Station, Vicks-burg, MS, April 1980.

CONTACT/OWNER

U.S. Army Engineer DistrictPittsburgh William S. Moorhead Federal Building1000 Liberty AvenuePittsburgh, PA 15222

LOS ANGELES RIVER CHANNELLos Angeles River, California

BACKGROUNDThe Los Angeles River Channel is an improved struc-

tural channel that drains a watershed of 753 squaremiles. The majority of the channel was constructed in the

1940s. In the invert of the concrete-lined main channel isa reinforced concrete low-flow channel, This low-flowchannel is approximately 12 miles long and was originallyconstructed with an invert thickness of 12 in. Water vel-ocities in that channel range from 20 to 30 ft/s.

PROBLEMOver the years abrasion erosion has occurred to vary-

ing degrees along the low-flow channel, In some reaches,erosion had progressed completely through the concreteby the early 1980s. This erosion was the result of a com-bination of abrasion by waterborne sediment and debrispassing over the concrete, and chemical attack.

SOLUTIONPrior to repair, laboratory studies were conducted to

evaluate the abrasion-erosion resistance of concretes con-taining locally available aggregates. Typically, these ag-gregates exhibit a relatively high abrasion loss testedaccording to ASTM C 131, using the Los Angeles mach-ine. Results of the laboratory tests indicated that con-crete with a high cement content, a silica fume contentof 15 percent by mass of portland cement, and a lowwater-cement ratio would provide excellent abrasion-erosion resistance, even when produced with aggregatesthat might be marginal in durability.

Beginning in 1983, the existing concrete in the approx-imately Yknile reach of most severe damage was re-moved and replaced with reinforced, silica-fume concrete(Fig. 35). The thickness of the replacement concrete was


Fig. 3.5-Los Angeles River Channel. Concrete for a full depth replacement wasplaced with a conveyor and finished with a specially shaped vibratory screed

12 in. Subsequent rehabilitation of the remaining channelduring 1984 and 1985 was accomplished by either full-depth slab replacement or an overlay on the existing con-crete. Full-depth repairs consisted of a new, reinforcedbase slab of conventional concrete and 6-in. overlay ofsilica-fume concrete. Overlays on the existing concretewere 4- to 6-in-thick sections of silica-fume concrete.Various mixture proportions were used with compressivestrengths ranging from 8000 to 10,500 psi. Approximately27,500 cubic yards of silica-fume concrete were requiredto complete the rehabilitation. The unit costs for thesilica-fume concrete decreased with time as bidders be-came more familiar with the material. The unit cost forthe 1985 project was $154/cubic yard, which was slightlyless than twice the unit cost of conventional concrete.

PERFORMANCEScour gauges were installed to monitor long-term wear

of the silica-fume concrete. Because of the nature of themechanism causing abrasion-erosion, an evaluation ofperformance will require an extended period of time.However, the abrasion resistance of the silica-fumeconcrete, according to the laboratory tests, should be twoto four times better than the conventional concrete pre-viously used Visual inspections of the channel surfacesindicate little or no erosion of the concrete has occurredin the 8 years following repair.

REFERENCESHolland, T.C., “Abrasion-Erosion Evaluation of Con-

crete Mixtures for Repair of Low-Flow Channel, LosAngeles River,” Miscellaneous Paper SL-86-12, U.S. Army

Engineer Waterways Experiment Station, Vicksburg, MS,Sept. 1986.

Holland, T.C., and Gutschow, R.A., “Erosion Resis-tance with Silica-Fume Concrete,” Concrete International,V. 9, No. 3, Detroit, MI, March 1987, pp. 32-40.

CONTACT/OWNER

U.S. Army Engineer District, Los Angeles300 North Los Angeles StreetLos Angeles, CA 90012

NOLIN LAKE DAMNolin River, Edmonson County, Kentucky

BACKGROUNDNolin Lake Dam became operational in 1963. The

stilling basin is 40 ft wide, 174 ft long with a 7-ft-high endsill and 35-ft-high sidewalls. The basin contains a para-bolic section with an 8.4-ft drop in elevation from theoutlet tunnel invert to the horizontal floor slab. Thedesign discharge is 12,000 ft3/s with an average velocityof 61 ft/s entering the basin. The structure was built ofreinforced concrete with a design compressive strength of3000 psi.

PROBLEMThe conduit and stilling basin at Nolin were dewatered

for inspection in 1974, following approximately 11 yearsof operation. Erosion was reported in the lower portionof the parabolic section, the stilling basin floor, the lower


part of the baffles, and along the top of the end sill. Themost severe erosion was in the area between the wall baf-fles and the end sill, where holes 2 to 3 ft deep had beeneroded into the stilling basin floor along the sidewalls.

SOLUTIONThe stilling basin was dewatered and repaired in 1975.

Conventional concrete designed for 5000 psi compressivestrength was used to restore the basin slab to an eleva-tion 9 in. above the original grade. A hydraulic modelstudy of the existing basin was not conducted, but thestructure was modified in an attempt to reduce theamount of debris entering the basin. New work includedraising the end sill 12 in., adding end walls at the end ofthe stilling basin, and paving a 50-ft-long channel section.

PERFORMANCEA diver inspection in 1976 indicated approximately 4

tons of rock was in the stilling basin. The rock, piled upto 15 in. deep, ranged up to 12 in. in diameter. Also,l8-in.-deep rock piles were found on the slab down-stream from the stilling basin. Erosion, up to 8 in. deep,was reported for concrete surfaces that were sufficientlyclear of debris to be inspected.

In August 1977, approximately 1 to 11/2 tons of large,limestone rock all with angular edges, was reported inthe stilling basin. No small or rounded rock was found.Since the basin had been cleaned during the previous in-spection, this rock was thought to have been thrown intothe basin by visitors. When the stilling basin was de-watered for inspection in October 1977, no rock or debriswas found inside the basin. Apparently, the large amountof rock discovered in the August inspection had beenflushed from the basin during the lake drawdown, whenthe discharge reached a maximum of 7340 ft3/s.

Significant erosion damage was reported when thestilling basin was dewatered for inspection in 1984. Themost severe erosion was located behind the wall baffles,similar to that prior to repair in 1975. Each scour holecontained well-rounded debris ranging from marble sizeto approximately 12-in. diameter. Temporary repairs in-cluded removal of debris from the scour holes and fillingthem with conventional concrete. Also, the half bafflesattached to each wall of the stilling basin were removed.

A hydraulic model of the stilling basin was constructedto investigate potential modifications to the basin to min-imize chances of debris entering the basin and causingsubsequent erosion damage to the concrete. Results ofthis study were incorporated into a permanent repair in1987. Modifications included rebuilding the parabolic sec-tion in the shape of a whale’s back, overlaying the basinfloor, adding a sloping face to the end sill, raising thebasin walls 2 ft, paving an additional 100 ft of the retreatchannel, slush grouting all derrick stone in the retreatchannel, and adding new slush-grouted riprap beside thebasin.

The condition of the concrete was described as goodwith no significant defects when the basin was dewatered

for inspection in August 1988. The maximum dischargeto that point had been 5050 ft3/s for a period of 13 days.

REFERENCESMcDonald, J.E., “Maintenance and Preservation of

Concrete Structures, Report 2, Repair of Erosion-Damaged Structures,” Technical Report No. C-784, U.S.Army Engineer Waterways Experiment Station, Vicks-burg, MS, April 1980.

McDonald, J.E., and Liu, T.C., “Repair of Abrasion-Erosion Damage to Stilling Basins,” Concrete Interna-tional, V. 9, No. 3, American Concrete Institute, Detroit,MI, March 1987, pp. 55-61.

CONTACT/OWNER

U.S. Army Engineer District, LouisvilleP.O. Box 59Louisville, KY 40201-0059

PINE RIVER WATERSHED, STRUCTURE NO. 41La Plata and Archuleta Counties, Colorado

BACKGROUNDStructure No. 41 is a high velocity reinforced concrete

chute spillway with a St. Anthony Falls (SAF) stillingbasin. The SAF stilling basin is a design developed by theAgricultural Research Service at the St. Anthony FallsHydraulic Laboratory of the University of Minnesota.The design includes chute and floor blocks with an endsill sized by hydraulic modeling for maximum energy dis-sipation. The floor of the basin in Structure No. 41 isdepressed about 4.6 ft below the downstream channelgrade. The design wall thickness is 8 in. and the designfloor thickness is 9 in. The reinforcement is a single matof steel centered in the floor and walls.

PROBLEMFrom 1974 to 1984 the structure had displayed signifi-

cant erosion of the concrete. The most severe erosionhad occurred at the lower end of the SAF stilling basin.The stilling blocks, end sill, and reinforcement was com-pletely deteriorated. The reinforcing steel was exposed inthe floor, sidewalls (Fig. 3.6), and wingwalls from immed-
iately upstream of the end sill downstream through thestructure. The exposed reinforcement showed consider-able wear.
Erosion in the floor of the chute was limited to about% in. This erosion appeared constant throughout thelength of the chute.

During a 1984 investigation, it was concluded that thedamage exhibited the characteristics of erosion and abra-sion damage by the ball mill effect, as described on pages14 and 15 of Chapter 1 of the Bureau of ReclamationConcrete Manual. The major damage to the structure isattributed to gravel and larger sized material being intro-duced into the stilling basin from the outlet channel

210.1 R-20 ACI COMMITTEE REPORT

Fig. 3.6-Pine River Watershed, Structure No. 41. Erosion of sidewall,exposing reinforcing steel

slope protection rock.The SAF outlet channel was designed and constructed

with a 3 to 1 adverse grade from the top of the end sillto the canal invert elevation, approximately 4 ft abovethe end sill. It has a bottom width of 10 ft with 2 to 1side slopes. The entire section is lined with loose rockriprap. The rock is rounded to subrounded and is easilydislodged. Much of the rock on the adverse slope ap-pears to have been displaced and the slope eroded, sothat it is considerably steeper than originally constructed.Hydraulic transport of the smaller rock into the basinappears to be the method of debris introduction.

SOLUTIONThe investigating team made the following recommen-

dations:1. Study the hydraulics of the outlet and design an

outlet basin to fit most favorably with those pre-dicted by model studies. Minimize use of rockriprap but, if needed, grout to prevent movement.

2. Replace concrete end sill, floor blocks, and chuteblocks using high-strength concrete. The effect onhydraulic performance will need to be studied.

A model study was conducted in 1984 to determinethe design for a preshaped, riprapped energy dissipationpool. The design was recommended for the repair andrehabilitation of the structure and was also consideredappropriate information for use in the design of similarpools.

PERFORMANCENo permanent work has been completed on the repair

of the structure to date. Options for repair are beingconsidered at this time.

REFERENCESBureau of Reclamation, Concrete Manual, 8th Edition,

U.S. Department of the Interior, 1981.Rice, C.E., and Blaisdell, F.W., “Energy Dissipation

Pool for a SAF Stilling Basin,” Applied Engineering inAgriculture, V. 3, No. 1, USDA-ARS, Stillwater, Okla-homa, 1987, pp. 52-56.

CONTACT/OWNER

State Conservation EngineerU.S. Department of Agriculture, Soil Conservation

ServiceSixth Avenue Central, 655 Parfet Street, Room E200CLakewood, CO 80215-5517

POMONA DAMHundred Ten Mile Creek, Vassar, KS

BACKGROUNDThe stilling basin at Pomona Dam, operational in

1963, is 35 ft wide and 80 ft long. The reinforced con-crete transition and horizontal basin floor have a designdischarge velocity of 58 ft/s. Two staggered rows of baf-fles, 3 ft wide and 5 ft high, are spaced at 7 ft on centers.A two-step, vertical-faced end sill is 4 ft high. Fill con-crete was placed the width of the basin for a distance of20 ft downstream from the end sill.

PROBLEMThe initial dewatering of the basin in February 1968

revealed erosion damage at the downstream end of thetransition slab and on the upstream one-third of thebasin slab. This erosion, caused by the abrasive action of


rocks and other debris, had exposed reinforcing steelalong the left wall of the basin. An inspection in October1970 revealed significant additional erosion and extensiveexposure of reinforcing steel. The major damage was at-tributed to flow conditions at relatively low discharges,since approxima500 ft3/s or less.

tely 97 percent of the releases had been

SOLUTIONHydraulic model tests confirmed that severe separa-

tion of flow from one sidewall, together with eddy actionstrong enough to circulate stone in the model, occurredwithin the basin for discharges and tailwaters common tothe project. Various modifications including raising theapron, installing chute blocks, constructing interior side-walls with reduced flare, and providing a hump down-stream of the outlet portal were model tested to evaluate

their effectiveness in eliminating the undesirable sepa-ration of flow and eddy action within the basin.

Based on the model study, it was recommended thatthe most practical solution was to provide a 3-ft-thickoverlay of the basin slab upstream of the first row ofbaffles, a l?&ft overlay between the two rows of baffles,and 1 to 1 sloped face to the existing end sill. Thissolution provided a wearing surface for the area ofgreatest erosion and provided a depression at the down-stream end of the basin for trapping debris. However,flow separation and eddy action were not eliminated bythis modification. Therefore, it was recommended that afairly large discharge, sufficient to create a good hy-draulic jump without eddy action, be released periodicallyto flush debris from the basin.

The final design for the repair included 1) a minimumY%n.-thick epoxy mortar topping applied to approxi-

Fig. 3.7-Pomona Dam. Stilling basin condition several years aftercompletion of repairs


mately one-half of the transition slab; 2) an epoxy mortarapplied to the upstream face of the right three upstreambaffles; 3) a 2-ft-thick concrete overlay slab placed on theupstream 70 percent of the basin slab; and 4) a slopedconcrete end sill. The reinforced concrete overlay was re-cessed into the original transition slab and anchored tothe original basin slab. The coarse aggregate used in therepair concrete was Iron Mountain trap rock, an abra-sion-resistant aggregate. The average compressivestrength of the repair concrete was 6790 psi at 28 days.

PERFORMANCEThe stilling basin was dewatered for inspection five

years after repair (Fig. 3.7). The depression at the down-
stream end of the overlay slab appeared to have func-tioned as desired. Most of the debris, approximately 1cubic yard of rocks, was found in the trap adjacent to theoverlay slab. The concrete overlay had suffered onlyminor damage, with general erosion of about %-in. andmaximum depths of l%-in. The location of the erosioncoincided with that occurring prior to the repair. Appar-ently, debris is still being circulated at some dischargerate. Based on a comparison of discharge rates and slaberosion, before and after the repair, it was concludedthat the repair had definitely reduced the rate of erosion.The debris trap and the abrasion-resistant concrete wereconsidered significant factors in this reduction.
The next inspection, in April 1982, indicated thestilling basin floor slab remained in good condition withessentially no damage since the previous inspection. Ap-proximately 5 cubic yards of debris, mostly rocks, wereremoved from the debris trap at the downstream end ofthe basin.


Concrete Structures, Report 2, Repair of Erosion-Dam-aged Structures,” Technical Report No. C-784, U.S. ArmyEngineer Waterways Experiment Station, Vicksburg, MS,April 1980.

Oswalt, N.R., “Pomona Dam Outlet Stilling BasinModifications,” Memorandum Report, U.S. Army Engi-neer Waterways Experiment Station, Vicksburg, MS,1971.

CONTACT

U.S. Army Engineer District, Kansas City601 E. 12th StreetKansas City, MO 64106

PROVIDENCE-MILLVILLE DIVERSION STRUCTURENear Logan, Utah

BACKGROUNDThe Providence-Millville Diversion Structure is a rein-

forced 60-ft-wide concrete drop structure, with a drop of

4 ft, a weir height of 4 ft, an apron length of 10 ft, anda sill height of 15 in. Two 4-by 4-ft slide gates in the rightabutment headwall direct flow from Blacksmith Fork intothe irrigation canal.

A considerable number of reinforced concrete diver-sion structures have been constructed in mountainstreams in the Western United States. These streams areusually on a steep gradient and generally transport aheavy bedload of sands, gravels, and cobbles. Frequentlypermanent drops are incorporated in the diversion toprovide the necessary head for diverting the irrigationflow, sluicing the bedload, and stabilizing the streamgradient.

PROBLEMIn spite of engineering practices such as providing

sluiceways, using grated inlet devices, and special en-trance configuration, the transported sediment causesabrasion to the exposed concrete in the diversions. Attimes of flood flows or above normal high water, exces-sive bedload (quantity and size of particles) also impartssevere impact to the surfaces of stilling basins or apronsof drop structures. This impact as well as the grindingaction of highly abrasive aggregate causes loss of con-crete, exposure of steel reinforcement, and, if unchecked,loss of the structure.

The bedload of sand, gravel, and boulder materials inBlacksmith Fork has caused erosion of the concrete inthe apron and walls of the Providence-Millville diversionstructure and consequent exposure of the reinforcingsteel (Fig. 3.8).

SOLUTIONFollowing the extreme flooding years of 1983 and

1984, the SCS (Soil Conservation Service) in Utah wasfaced with repairing or replacing a multitude of irrigationstructures that had been damaged or lost. The decisionwas made to make the repairs or replacements, usingsome of the proprietary concrete products available toenhance durability under high bedload conditions.

The new Providence-Millville structure was one of fivein which field trials were conducted for the evaluation ofdefensive measures available. The product selected forthis site was a metallic aggregate topping. This productconsists of premixed metallic floor topping composed ofiron aggregate, high-early portland cement, and water-reducing admixtures. A surface treatment was applied tothe hardened surface.

l-in-thick metallic aggregate topping was placed overa new concrete structure substrata following applicationof an epoxy or latex bonding aid. A proprietary sealer,recommended by the topping supplier, was applied to theoverlay surface to reduce permeability.

The cost for 604 square ft of surface treated was$ll.00/square ft (1986 price level.)

PERFORMANCEHigh water preventssclose inspection of the treated


Fig. 3.8-Providence-Millville Diversion Structure. Erosion of the surface of theconcrete apron and sidewalls

areas. Inspections since the installation indicate theoverlay is still intact. High water conditions and theaccompanying abrasive bedload have been only moderatesince the repairs in September 1986.

DISCUSSIONThis metallic floor topping hardener is supplied in pre

packaged 55-lb bags, which is enough to apply a l-in.layer to a 18- to 20-square ft area. Installation must be inaccordance with the manufacturer’s directions.

The floor topping develops approximately 13,000 psicompressive strength in 3 days and is especially suited forbuilding floor slabs subjected to impact loads. While notspecifically marketed for use on hydraulic structures, itsabrasion-resistant properties are attractive. Performancein drop structures with heavy sediment bedloads has beenpositive to date.

REFERENCESU.S. Department of Agriculture, “Memorandum,

Dated April 17, 1990, to Francis T. Holt, StateConservationist, SCS, Salt Lake City, UT, from RobertA. Middlecamp, Construction Engineer, SCS, WestNational Technical Center, Portland, OR.

CONTACT/OWNER

State Conservation EngineerSoil Conservation Service, U.S. Department of

AgricultureP.O. Box 11350Salt Lake City, UT 84147-0350

RED ROCK DAMDes Moines River, Iowa

BACKGROUNDRed Rock Dam, operational in 1969, is 6200 ft long

and 95 ft high. The two rolled earth embankment sec-tions of the dam are separated by a concrete section thatserves as the outlet works and spillway. The spillway hasan ogee crest with five 41-ft-wide by 49-ft-high taintergates. The outlet works has fourteen 5- by 9-ft conduitsthrough the ogee section. Discharge from the spillwayand the outlet works passes into a 240-ft-wide by214-ft-long stilling basin, which has two rows of baffles.A minimum flow through the basin is 300 ft3/s, even indry seasons.

PROBLEMA diver inspection in 1982 detected several small areas

of eroded concrete and bedrock along the end sill Heavyprecipitation during 1983 and 1984 resulted in large dis-charges ranging up to 40,000 ft3/s compared to normaldischarges of about 3000 ft3/s. Based on the finding ofthe diver inspection and because of subsequent high dis-charges, plans for repair were initiated.

Until recently, repairs of this type generally requireddewatering of the stilling basin. Dewatering costs can ex-ceed $1 million and have averaged 40 percent of the totalrepair cost in previous repairs. Since the damage to theend sill was not very severe, the high cost of dewateringthe basin for repair was considered inappropriate.


SOLUTIONResults of laboratory tests indicated that cohesive,

flowable, and abrasion-resistant concrete could be placedunder water by available methods without use of the tre-mie seal and withminimal loss of fines if proper mater-ials were used and precautions taken. Concrete contain-ing AWA (antiwashout admixture) and a water-reducingadmixture placed at the point of use sustained only arelatively small loss of fines and bonded well to in-placehardened concrete. Consequently, underwater concretingwas selected as the most cost effective method for repairof the stilling basin.

Immediately prior to the repair in August 1988, a finalunderwater inspection of the basin indicated larger areasof erosion than in 1982, most occurring in the bedrockjust downstream of the end sill. The eroded areas ex-tended about 18 ft downstream from the end sill and hada maximum depth of 5 ft.

Construction requirements included removing looserock and debris, installing anchors and reinforcing,positioning grout-filled bags to define the placementarea, and placing concrete by a diving contractor. Theminimum flow of 300 ft3/s was discharged through thedam during the repair (Fig. 3.9).

CONCRETE WlTHANTI-WASHOUT ADMIXTURE

GROUT FILLED BAGS

#8 ANCHORS 8’ ON CENTERS

CEMENTITIOUS NONSHRINK GROUT

Fig. 3.9-Red Rock Dam. Diagram of concrete repair of stilling basin endsill

A concrete pump with a 4-in.-diameter line was usedfor underwater placement of the concrete. A diver con-trolled the end of the pumpline, keeping it embedded inthe mass of newly discharged concrete and moving itaround to completely fill the repair area. Approximately100 cubic yards of concrete were placed in about 4 hours.

The effects of the AWA were apparent; even thoughthe concrete had a slump of about 9 in., it was very co-hesive. The concrete pumped very well and, according tothe diver, self-leveled within a few minutes followingplacement. The diver also reported that the concrete re-

mained cohesive and exhibited very little loss of fines onthe few occasions when the end of the pumpline kickedout of the concrete.

The total cost of the repair was $128,000 (1988 pricelevels). In comparison, estimated costs to dewater alonein a conventional repair ranged from $500,000 to$750,000.

PERFORMANCEAlthough additional time will be required to evaluate

performance, all indications are that the repair is an eco-nomical and durable solution to the problem.


Concrete Structures, Report 2, Repair of Erosion-Dam-aged Structures,” Technical Report No. C-78-4, U.S. ArmyEngineer Waterways Experiment Station, Vicksburg, MS,April 1980.

Neeley, B.D., “Evaluation of Concrete Mixtures forUse in Underwater Repairs,” Technical Report No.REMR-CS-18, U.S. Army Engineer Waterways Experi-ment Station, Vicksburg, MS, April 1988.

Neeley, B.D., and Wickersham, J., “Repair of RedRock Dam,” Concrete International, V. 11, No. 10, Amer-ican Concrete Institute, Detroit, MI, Oct. 1989, pp. 36-39.

CONTACT/OWNER

U.S. Army Engineer District, Rock IslandClock Tower BuildingP.O. Box 2004Rock Island, IL 61204-2004


SHELDON GULCH SIPHONBig Horn County, Wyoming

BACKGROUNDThe siphon consists of 1770 ft of 27-in-diameter

reinforced concrete pipe with a flared reinforced con-crete box outlet. The siphon replaces approximately twomiles of eroding, steep gradient, canal. A wasteway, usedto discharge excess water or provide for upline systemdrainage, was established at the inlet, discharging into theabandoned canal. Rock riprap was placed at the siphoninlet by the canal company after completion of the pro-ject.

PROBLEMThe reinforced concrete basin experienced severe ero-

sion damage to the apron and wall. The damage appearsto have been caused by the introduction of rock from theriprap protection upstream from the structure. The abra-sion has the characteristics of erosion and abrasiondamage by the ball mill effect, as described by theBureau of Reclamation Concrete Manual (see refer-ences).

SOLUTIONRepairs of the apron and sidewalls were made by re-

placing the damaged area with polymer-modified port-land cement, two-component, fast-setting patchingmortar. Existing concrete in the abraded area of theapron and sidewalls was removed in accordance with pro-cedures detailed in Chapter VII of Reclamation’s Con-crete Manual. The exposed area was prepared and themortar applied as directed in the manufacturer’s productsheet.

Riprap was stabilized by placing concrete over therock riprap at the siphon inlet and outlet to preventfurther rock removal and subsequent transport into thesiphon.

PERFORMANCEThe repairs were made prior to the 1991 irrigation

season. No opportunity has occurred for an inspection ofthe repairs to date.

DISCUSSIONAn alternate repair method, considered for this pro-

ject, was to apply a thin layer of patching mortar in areaswhere concrete erosion was greater than 1 in. This alter-native was more economical but considered inferior tothe selected method because of the laminations createdin the concrete section.

REFERENCESBureau of Reclamation Concrete Manual, 8th Edition,

U.S. Department of the Interior, 1981.

CONTACT/OWNER


ServiceFederal Building, Room 3124100 East B StreetCasper, WY 82601

CHAPTER 4-CHEMICAL ATTACK -ROSION CASE HISTORIES

BARCELONETA TRUNK SEWERMunicipality of Barceloneta, Puerto Rico

BACKGROUNDThe Barceloneta Trunk Sewer, operational in 1976,

collects sewage from several pharmaceutical plants aswell as local domestic flows. It was built using regularreinforced concrete pipes conforming to ASTM C 76,with cast-in-place reinforced concrete manholes, spacednot farther than 280 ft.

The depth of the pipe invert below ground surfacevaries from a minimum of 5 ft to a maximum of 25 ft.

Flow from pharmaceutical plants is partially treated,mostly to reduce the biological oxygen demand (BOD),and remove larger solids. The pipeline is subject to awide range of pH, temperatures and chemical composi-tion, which varies frequently because of batch productionschedules for each of the pharmaceutical plants.

PROBLEMGround subsidence of the pipeline backfill appeared

along the sewer alignment. When these failures were in-vestigated, it was found that the pipe had seriouslydeteriorated. There were places where the concrete hadalmost completely disappeared.

SOLUTIONSeveral procedures to solve the problem were investi-

gated, including replacing the entire system. Replacingthe entire system was found to be costly and difficult,because the pipe runs along the shoulder of a major roadthat is the access to the pharmaceutical plants. It wasdecided to proceed with the rehabilitation of the systemusing a proprietary pipe-lining process.

This lining process is a method of installing a newsolid lining in an existing pipeline in which pipe segmentsbetween manholes are relined in a single operation. Theprocess consists of cleaning the existing pipe interiorsurfaces, then installing a flexible plastic-lined fiberglasshose impregnated with a polyester resin. The resin isactivated by circulating hot water through the hose for aperiod of time. The hose is installed by filling it withwater under limited pressure. The water pressure alsoserves to expand the hose as required and. place it inintimate contact with the pipe wall.


In order to install the hose it is necessary to tem-porarily divert the flows, bypassing the section underrehabilitation. Waste flows controlled by the bypass sys-tem during rehabilitation averaged 2100 gallons perminute at the larger pipes.

Rehabilitation of over 17,000 ft of various diameterpipeline, ranging from 18-36 in., required 7 months. Inaddition 68 manholes were rehabilitated, having diam-eters ranging from 48 to 72 in. and depths from 5 to 25ft.

PERFORMANCEAfter several years of uninterrupted use, the reha-

bilitated sewer is performing well with no evidence ofdeterioration.

DISCUSSIONThe rehabilitation process represents a cost-effective

and seemingly durable solution to chemical attack toexisting concrete sewer pipes.

CONTACT

Puerto Rico Aqueduct & Sewer AuthorityP.O. Box 7066Bo. Obrero Station SanturcePuerto Rico 00916

DWORSHAK NATIONAL FISH HATCHERYClearwater River, Near Orofino, Idaho

BACKGROUNDThe Dworshak NFH (National Fish Hatchery), opera-

tional in the late 1960s, is located at the confluence ofthe Clearwater and North Fork Clearwater Rivers, Idaho.A series of modifications and additions has brought thefacility to its present capacity of 470,000 pounds of fishper year. The hatchery was designed as a reuse waterfacility, where only a small amount of makeup water isadded to supplement the flow and distribution system.

PROBLEMThe concrete surfaces exposed to hatchery water have

experienced chemical attack and surface removal of port-land cement paste (Fig. 4.1). Particles of sand in the con-

Fig. 4.1-Dworshak National Fish hatchery. Deteriorationof concrete surface of tank Note repaired area to the left ofthe photograph

crete have become exposed due to erosion of the weak-ened paste. This phenomenon has been previously re-ported in areas where the concrete is attacked by watercontaining free CO2, flowing pure water from melting iceor condensation, and water containing little CO,. Thewater dissolves Ca(Ol$, thus causing surface erosion.The Dworshak reservoir collects snowmelt from thedrainage basin and releases the pure water during theseasonal incubational and rearing phase of fish hatcheryproduction. The following table summarizes a typicalwater analysis for Dworshak NFH.

SOLUTIONThe most likely solution was to coat the concrete sur-

faces with some type of surface treatment to preventexposure to the pure water. Epoxy coatings, polymeric,and other coatings protect the hardened portland cementpaste at exposed surfaces. Trial coatings of epoxy mortarand a urethane coating, of approximately 500 square fteach, were applied to damaged surfaces for evaluation(Fig. 4.1). After two years of exposure, the integrity ofthe coatings is intact, however, performance of thecoatings adjacent to joints and cracks is poor. An alter-nate solution may be to alter the pH of the water by ap-propriate chemical additions, such as free lime, if it istolerable to the fish.

Parameter Value Unit

pH 6.5 to 7.4Total Dissolved Solids 28-33 mg/LSpecific Conductivity 23-29 *mhosHardness 12-15 mg/L


AlkalinityChlorides, Cl-Sulfates, SOgNitrates, NO,-Sodium, Na+Potassium, K+Calcium, Ca++Magnesium, Mg++

CONTACT/OWNER

15-20 mg/LO-2-0.4 mg/L

2.0 ma0.07 ma1.44 mg/L0.55 mg/L3.75 mg/L0.70 mg/L

U.S. Fiih & Wildlife ServiceDworshak Kooskia NFH ComplexP.O. Box 18Ahsahka, ID 83520

LOS ANGELES SANITARY SEWER SYSTEM ANDHYPERION SEWAGE TREATMENT FACILITYLos Angeles, California

BACKGROUNDThe sanitary sewerage system of the city of Los An-

geles includes over 6000 miles of sewers that service anarea of over 600 square miles.

There are two upstream water reclamation plants inthe San Fernando Valley. These are the D.C. Tillmanand the Los Angeles-Glendale plants. The sewage atthose plants is treated to advanced secondary standardsand discharged to the Los Angeles River. Their solids arereturned to the sewers for transport to the Hyperionregional treatment plant on the coast of Santa MonicaBay.

All of the remaining sewers of the service area enterone of four major interceptors for conveyance to theHyperion plant. This 420 Mgal/d (million gallons perday) facility was originally designed for 265 Mgal/d toprovide primary (mechanical) treatment and a high rateactivated sludge secondary (biological) treatment to thesewage, and meet a discharge standard of 70 ppm (par-ticles per million particles) suspended solids and 70 ppmbiological oxygen demand (BOD). In 1957 the processwas modified so that 100 Mgal/d received secondarytreatment and is mixed with 320 Mgal/d that receivesonly primary treatment. This mixed plant effluent isdischarged at sea, where dilution and dispersion ulti-mately render it innocuous. The ocean outfall extends 5miles to sea, to a water depth of 235 ft. In 1986 secon-dary treatment was expanded to 200 Mgal/d, and chemi-cals were added to enhance primary treatment.

PROBLEMOver 40 years ago, the pioneer research of Dr. Rich-

ard D. Pomeroy pinpointed the shortened life of the con-crete sanitary sewers in Los Angeles as being due to hy-drogen sulfide (II& attack of septic sewage. His was theoriginal research that recognized the phenomenon.

By one definition, septic sewage is sewage that con-tains entrained Hm To be septic, the sewage in a warmclimate need only have an age of a few hours in thesewers. The H, is generated by sulfate-reducing anaer-obic bacteria confined in the slimes that line the con-tinuously wetted perimeter of the sewer, particularly inlow velocity (<2 ft/s) zones of flow. Under conditions oflaminar flow, the H= of septic sewage escapes the watersurface at moderate rates, to attack the concrete abovethe waterline. The attack is the result of the H, beingoxidized by bacterial action and combining with watervapor to form H,SO,. So, more accurately, H, attackcould be termed sulfuric acid attack on the concretesurfaces above the waterline (compare Fig. 4.2 and 4.3).
Under conditions of turbulence, caused by high velocityflow or a plunging of the flow, as in a drop manhole(Fig. 4.4), the escape of H= from the waste-water is much more rapid, and the H, attack is much moresevere.
With this as background, the engineering conclusionsdrawn by the city of Los Angeles from their experiencesof the past 45 years will be recited.

SOLUTION-THE SEWER SYSTEMThe problem of H, attack in the sewer system is on-

going, and worsening. The long distances traveled toreach the Hyperion plant account for the plant influenthaving been in the sewers for 24 to 72 hours. That meansthat hundreds of miles of sewers are transporting septicsewage. Current policy is to use acid-resistant vitrifiedclay pipe for all sewers up to 42 in. ID (inside diameter)and PVC (polyvinyl-chloride) lined reinforced concretepipe for all diameters above that.

The H= attack on the concrete pipe has become moreaggravated in recent years. Engineers have speculatedthat this aggravation is due to point-source control oftoxic producers. In conformance with EPA regulations,many industries are required to pretreat their plant ef-fluent so as not to discharge toxins into the sewer systemthat could kiIl the bacteria in the biological reactors ofthe secondary treatment facilities at Hyperion. The ironyof the situation is that whereas previously the toxicity inthe sewers had tended to keep the growth of the H,-producing bacteria under some measure of control, nowthat lack of toxicity has permitted those bacteria tothrive. Unprotected concrete pipe, subjected to this lowtoxicity effluent, has failed within 5 years due to H,attack.

The City of Los Angeles engineering policy generatedas a result of these experiences is that:

1. For all new concrete construction, protect theinside of manholes and the inside crown of pipesabove the waterline with a sheet of acid-resistantPVC, mechanically anchored to the concrete.

2. For the repair of old concrete construction, restorethe concrete surface and then protect it with an ap-plied coating or lining. It is at this point that thecity is still in the processs of setting policv. There

ACI COMMlTTEE REPORT

Fig. 4.2-Los Angeles Sanitary Sewer System. Typical new and undeterioratedcondition of concrete pipe

Fig. 4.3-Los Angeles Sanitary Sewer System. Deterioration of concrete pipe from acidH2s attack

have been some bad experiences with spray-on coatings (Fig. 4.5), resulting both from pinhole holidays and poor
quality control of the constituent materials. Roll-on plastic sheets have been successful, but the physical situation in sewers often precludes their use. Also demolition of the damaged structure or pipe and replacement with PVC-lined new construction is under con-
sideration.

SOLUTION-THE PRIMARY SETTLING TANKSThere are 12 primary settling tanks at the Hyperion

plant; 4 more are under construction. Each of the tanksis 300 ft long, 56.5 ft wide, and 15 ft deep. Of the existing12 tanks, 8 were constructed in 1950, of unprotected rein-


Fig. 4.4-Los Angeles Sanitary Sewer System. Deterioration of reinforced concretestructures from acid attack

Fig. 4.5-Hyperion Sewage Treatment Facility. Reinforced concrete sedimentation tankshowing coating failure and corrosion

forced concrete. Four were constructed in 1957 and,based on the experience of the original eight, were pro- tected against HB attack by a PVC liner, above thewaterline, for 75 ft at each end. The first 12 tanks were covered with a 15-in. reinforced concrete slab, supportedby a system of beams and columns. The four currently

under construction will be covered with an aluminumroof.

HB is stripped as the sewage enters the tanks, througha baffle system, and again as it exits over V-notch weirs.These are two regions of turbulence, where the H,levels are unusually high. In spite of the tranquil flow


between these two regions, the tank roofs have sufferedcritically through the years, due to Ha attack. This wasfirst brought to the attention of the engineering com-munity in 1964, when Jack Betz’s paper, “Repair of Cor-roded Concrete in Wastewater Treatment Plant,” waspublished in the Journal of the Water Pollution ControlFederation. By the early 1960’s, the concrete above thewaterline in the launders (the effluent channel of theprimary settling tank), and the soffit of the roof slabs,had been damaged to the point that the reinforcing hadbeen exposed The City decided to repair the damage bychipping back to sound concrete, anchoring steel meshon to the existing rebar, and applying a new concrete tothe surface. The system only lasted 20 years. By 1983, theconcrete above the waterline was in such bad shape thata second repair was initiated.

The 1983-87 repair program involved water blastingback to sound concrete, and restoring the concrete sur-face with shotcrete. This was then sprayed with a polymercoating. The system worked fairly well, but whereverthere was a pinpoint holiday in the polymer coating, theH= attack would recur. Additionally, there were caseswhere the polymer failed to stop the reflection of ex-panding cracks in the substratum. These cracks likewiseexposed the concrete to H, and water vapor.

As a result of the experiences of the design of the 8original primary settling tanks, and the 1963-67 and the1983-87 repairs of the erosion of the first 12 tanks, thecity adopted the following policies with respect to pro-tecting the concrete in the primary settling tanks:

1. For existing concrete above the waterline, removedamaged concrete back to sound concrete and re-store the surface with shotcrete. Although policy isstill not set, the current practice is to protect thelining with a roll-on sheet plastic cemented to theconcrete. Spray-on coatings are generally not con-sidered to be a long-term solution.

2. For existing concrete and new construction belowthe waterline, protect the concrete with coal-tarepoxy. This is not related to the erosion of concretedue to H, attack, but rather to the issue of block-ing chlorides from penetrating into the perviousconcrete and attacking the reinforcement.

3. For new construction above the waterline, provide100 percent protection using PVC lining systems.

REFERENCESU.S. Environmental Protection Agency, “Process De-

sign Manual for Sulfide Control in Sanitary SewerageSystems,” EPA 625/l-74-005 and NTIS PB/260/479,Washington, DC, Oct. 1974.

American Concrete Pipe Association, Concrete PipeHandbook, Vienna, VA, 1980.

American Society of Civil Engineers, “Manuals andReports on Engineering Practice, No. 60; WPCF, Manualof Practice, No. FD-5.

CONTACT/OWNER

City of Los AngelesHyperion Treatment PlantLos Angeles, CA

PECOS ARROYO WATERSHED, SITE No. 1San Miguel County, New Mexico

BACKGROUNDThe Pecos Arroyo Dam is a floodwater-retarding

structure constructed on C&ton Bonito, 5% miles northof Las Vegas, New Mexico. The dam is earthfill with aclay core and maximum height of 47 ft. It has a 600-ft-wide excavated earth spillway. The outlet consists of 304ft of 36-in-diameter reinforced concrete pipe, with anungated concrete riser inlet structure and a plunge pooloutlet.

PROBLEMThe outlet conduit concrete was severely deteriorated,

believed to be due to galvanic corrosion in combinationwith carbonic acid attack (Fig. 4.6). The apparent source
of the chemical attack was saline water seeping from thecarbonaceous shale and limestone in the right abutment.Resultant corrosion of reinforcement had been aggra-vated by local galvanic cells at the steel spigot pipe endsin the low resistivity soils. No other apparent damageshad occurred Structural failure had not occurred but aserious safety hazard existed.
SOLUTIONThe existing 36-in. I.D. reinforced concrete pressure

pipe was lined with 304 ft of 32-in. O.D. high-densitypolyethylene (HDPE) pipe. The annular space betweenthe two pipes was pressure pumped full with 2.3 cubicyards of grout. A cast-in-place cantilever outlet replaced24 ft of existing downstream 36-in. pipe and cantileversupport. The downstream outlet channel was enlarged toprevent submergence of the pipe invert during normalflows. The total cost of the contract for the performanceof this work was $126,000.

Treatment of the abutment was considered unneces-sary and was not provided.

PERFORMANCEAnnual inspections since installation have shown no

evidence of chemical attack. No flow has been observedin the drain system around the conduit. The length of theHDPE liner has stretched 1 to 2 in. longer than the con-crete conduit. This variation is in accordance with thedesign calculations.

DISCUSSIONTwo alternatives, other than lining the existing con-

duit, were considered in the design. The first was toremove and replace the existing conduit with a reinforced

REPAIR OF EROSION DAMAGED HYDRAULIC Sl?WCTURES 21 0.1 R-31

Fig. 4.6-Pecos Arroyos Watershed, Site 1. Deterioration of concrete of outlet structure

concrete prestressed cylinder pipe made with Type Vcement. The second alternative was to abandon the exist-ing conduit and install another conduit in an altenativelocation. These alternatives were estimated to be morecostIy than the repair method used.

REFERENCESU.S. Department of the Interior, “Pecos Arroyo

Watershed, Site No. 1, Preliminary Design Report,” SoilConservation Service, Nov. 17, 1986.

U.S. Department of the Interior, “Pecos ArroyoWatershed, Site No. 1, Final Design Report,” SoilConservation Service, Dec. 4, 1987.

CONTACT/OWNER


Service517 Gold Avenue Southwest, Room 3301Albuquerque, NM 87102

CHAPTER 5-PROJECT REFERENCE LIST

While compiling information on suitable projects toinclude in this compendium of case histories, many casesof erosion damage were reported. Most were not suitablefor inclusion because sufficient information on thedamage and subsequent repair was not readily available.Many other cases were similar to those cases selected forinclusion. Table 5.1 provides a listing of projects reported

to have experienced erosion damage of the type de- _scribed in this report. It is not clear if repairs have beeninitiated for all the listed projects. Additional informationon specific dams is available in the World Register ofDams, published by the International Commission onLarge Dams in 1984, 3rd Edition, and in a 1988 FirstUpdating by the same publisher.

1 in.1 ft.1 in21 ft.21 in.31 ft.31 yd31 lb.1 IbJin.2 (psi)1 ft./s1 ft?/s1 mi.1m.P1 Mgal/d

Metric Conversions

25.4 mm0.3048 m645.1 mm20.0929 m216.39 x 104 mm30.0283 m30.7646 m30.4536 kg6.894 MPa0305 m/s2832 l/s1609 m2590 km243.821 l/s

Temperature‘c = (9 - 32)/l.8

Difference in temperature‘c = tffl.8


TABLE 5.1 - REFERENCE LIST OF EROSION AND REPAIR OF CONCRETE STRUCTURES

Project name

Alcova Dam

Alder Dam

Arkabutla Lake

Arthur R. Bowman Dam

Barren River Lake

Belton Dam

Blue Mesa Dam

Blue Ridge Dam

Bonneville Dam

Bratsk Dam

Type of structure

Spillway

Plunge Pool

Type of erosion

Chemical attack

Abrasion

Bull Shoals Lake Dam

Project location

Casper, WY

ICentrailia, WA

1 Coldwater, MS

Oregon

Glascow, KY

Belton, TX

Colorado

Toccoa River, GA

Bonneville, WA

IBratsk, Irkutsk, U.S.S.R.

1 Mountain Home. AR

Stilling basin

Tunnel outlet works

Stilling basin and outlet works

Stilling basin

Diversion tunnel

Spillway and stilling basin

Stilling basin

SpillwayI

1 Sluices and stilling basin

Abrasion

Cavitation

Abrasion

Abrasion

Abrasion

Abrasion

Abrasion

CavitationI

1 Abrasion and cavitation

Burfell Dam Selfoss, Arnesssyla, Iceland

Canyon Ferry Dam Townsend, MT

Causey Dam Ogden River, UT

Cave Run Dam Farmer, KY

Center Hill Dam Carthage, TNCherokee Dam Holston River, TN

Chickamauga Dam Hamilton County, TN

Chief Joseph Dam Columbia River, WA

Conchas Dam Tucumcari, NM

Sand sluice Abrasion

Stilling basin and outlet works Abrasion

Stilling basin and outlet works Abrasion and cavitation

Stilling basin Not listed

Stilling basin Abrasion and cavitation

Spillway apron and stilling basin Abrasion

Spillway piers, weirs, and stilling Abrasionbasin


Stilling basin Abrasion

Curwensville Lake Dam

Derbendikhan Dam

Douglas Dam

Curwensville, PA

Sulaymaniya, Iraq

Sevier County, TN


Spillway

Outlet works, sluiceway, and

Abrasion

Cavitation

Abrasion and cavitation

Douglas Dam

Detroit Dam

Sevier Countv. TN

apron

Stilling basin Abrasion and cavitationI ,- I I

1 Salem. OR Stilling basin and conduit 1 Abrasion and cavitation

Echo Dam

Emigrant Dam

Enid Dam

Folsom Dam

Grand Coulee Dam

Wader River, UT

Emigrant Creek, OR

Grenada, MS

Folsom, CA

Columbia River. WA

Stilling basin

Stilling basin


Stilling basin

Spillwav

Abrasion

Abrasion

Abrasion

Abrasion

Cavitation

Guri Dam

Haystack Dam

Hiwassee Dam

Howard Prairie Dam

Ice Harbor Dam

Itha Solteira Dam

Karoon Dam

Kentucky Dam

Krasnoyarsk Dam

Lac qui Parle Dam

Libby Dam

Iindsay Creek Culverts

Little Goose Dam

Mason Dam

Mayfield Dam

McCloud Dam

McNary Dam

Venezuela

Madras, OR

Hlwassee River, NC

Beaver Creek, OR

Pasco, WA

Parana River, Brazil

Masjed Soliian, Iran

Tennessee River, KY

Krasnoyarsk, U.S.S.R.

Montevideo, MN

Kootenia River, MT

Lewiston, ID

Starbuck, WA

Baker, OR

Mayfield, WA

IRedding, CA

1 Umatilla, OR

Spillway and flip bucket

Stilling basin

Outlet works

Cavitation

Abrasion

Cavitation




3 Chute spillway cavitation

Spillway and stilling basin Abrasion

Spillway flip bucket Cavitation


Stilling basin and outlet works Abrasion and cavitation

Box culvert Abrasion

Stilling basin and navigation lock Abrasion and cavitation

Conduit cavitation

Plunge pool Abrasion and cavitation

Spillway Abrasion and cavitationt

1 Stilling basin 1 Abrasion


TABLE 5.1 (cont.) - REFERENCE LIST OF EROSION AND REPAIR OF CONCRETE STRUCTURESMica Dam British Columbia 3 Bay chute Pitting

Milford Dam Junction City, KS Stilling basin Abrasion

Navajo Dam Farmington, NM Stilling basin and outlet works Abrasion and cavitation

Nimrod Lake Dam Danville, AR Stilling basin Abrasion

Norris Dam Clinch River, TN Stilling basin and outlet works Abrasion and cavitation

Norris Dam Clinch River, TN Spillway apron Abrasion

Nurek Dam Tadjik SSR, U.S.S.R. Tunnel and chute Abrasion

Oologah Lake Dam Tulsa, OK Stilling basin Abrasion

Oxbow Dam Homestead, OR Spillway Abrasion

Painted Rock Dam Ravalli County, MT Outlet works tunnel Abrasion and cavitation

Palisades DamI

1 Irwin, EDI I

1 Outlet works chute 1 Abrasion and cavitation

Perry Dam

Pine Flat DamI Perry, KSI -

1 Fresno, CA

Redding, CA

Redding, CA

Hermitage, MO

1 Stilling basinI

I Spillway

1 AbrasionI

1 Abrasion

Pit No. 6 Dam

Pit No. 7 Dam

Pomme de terra Dam

Stilling basin and spillway

Stilling basin and spillway

Stilling basin



Abrasion

Rathbun Dam

Ririe Dam

Ruedi Dam

San Gabriel No. 1 Dam

Table Rock Lake Dam

Tarbela dam

Tiber Dam

Rathbun, IA

Ririe, ID

Colorado

Azusa, CABranson, MO

Pakistan

Montana


Stilling basin

Outlet works

Stilling basin

Stilling basin and conduit

Spillway and outlet tunnels

Outlet works

Abrasion


Cavitation

Abrasion

Abrasion


Abrasion

Tionesta Dam

Tuttle Greek Dam

Tygart DamV.I. Lenin Volga Dam

Tionesta, PA

Manhattan, KS

Grafton, WV

U.S.S.R

Stilling basin


Stilling basin

Baffle piers

Abrasion

Abrasion

Abrasion

Cavitation

Walter F. George Dam 1 Fort Gaines, GA I Stilling basin I Abrasion

Warsak Dam

Webbers Falls Dam

Wilson Dam

Wilson Dam

Pakistan

Webbers Falls, IL

Tennessee River, AL

Tennessee River, AL

Stilling basin and spillway Abrasion


Spillway apron and stilling basin Abrasion

Outlet works cavitation