523 NATIOML PROORN FOR INSPECTION OF NON-FEDERAL DAMf iRISLEY RESERVOIR DAN (.. (U) CORPS OF ENGINEERS NLTHAN

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MICROCOPY RESOLUTION TEST CHART

NATIONAL BUREAU OF STANOARDS-1963 A

_ ( jCONNECTICUT RIVER BASIN

LnVERNON & BOLTON, CONNECTICUT

RISLEY RESERVOIR DAM

CT. 00211

PHASE I INSPECTION REPORT

NATIONAL DAM INSPECTION PROGRAM

DTWCLMJUL 2 5 19J4 L'5

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DEPARTMENT OF THE ARMYCNEW ENGLAND DIVISION. CORPS OF ENGINEERS

WALTHAM. MAS.

NOVEMBER

84 07

IItNtI A-,TEF0SECURITY CLASSIFICATION OF THIS PAGE (When Does Entered) __________________

REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM

_.REPORT NUMBER 2. GOVT ACCESSION NO.,3 RECIPIENT'S CATALOG HUMBER

4 TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED

Risley Reservoir Dam INSPECTION REPORT

NATIONAL PROGRAM FOR INSPECTION OF NON-FEDERAL a. PERFORMING ONG. REPORT NUJMBER

nAMS _ _ __ _ _ _ __ _ _ __ _ _ _

7. AUTNOR(s) 41- CONTRACT OR GRANT NUMUERqa)

U.S. ARMY CORPS OF ENGINEERSNEW ENGLAND DIVISION

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT, TASKAREA & WORK UNIT NUMBERS

11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT OATS

DEPT. OF THE ARMY, CORPS OF ENGINEERS November 1978 0 0NEW ENGLAND DIVISION, NEDED 13. NUMBER OFPAGES

424 TRAPELO ROAD, WALTHAM, MA. 02254 5r)_____________14. MONITORING AGENCY NAME & ADORESS(I difteteI lems Cemlirwe Office) 15. SECURITY CLASS. (of this ropeef)

UNCLASSIFIED* Its. OECL ASSI PIC ATION/ DOWNGRADING4

SCHEDULE

IS. DISTRIBUTION STATEMENT (of this R.11e)

APPROVAL FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

17. DIST RIUIUTION ST ATEMENT (of the .&.eeaet mntesod in Block 30. It1 d1ffer. how Pops")

18. SUPPLEMENTARY NOTES

Cover program reads: Phase I Inspection Report, National Dam Inspection Program;however, the official title of the program is: National Program for Inspection ofNon-Federal Dams; use cover date for date of report.

IS. K EY WORDS (CoiDosw,. on reverse side if 00600000 4111d 141040#11 bV blockhombee.) 0

DAMS, INSPECTION, DAM SAFETY,Conn. River BasinVernon & Bolton, Conn.Risley Reservoir Dam

* 20. ABSTRACT (CmiI9~..e an reverse aide if aioceser and #dentifY &Y block f"umber) 0

The dam is located on a tributary of the Conn. River on the town line of Boltonand Vernon, Tolland County, Conn. it is an earthfill structure approx. 625' long w tha maximum depth at its center of 26'. The-crest width varies from 12 to 15 ft. Thedam is in generally good condition. It appears to be structurally stable at thepresent time under normal conditions. Based on its small size and high hazardclassification in accordance with the Corps' guidelines, the test flood is - the 0 0PMF.

DD ,A N 7 14731 EDITION OF1 1 NOV SS IS OBSOLETE

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DEPARTMENT OF THE ARMY 00NEW ENGLAND DIVISION, CORPS OF ENGINEERS

424 TRAPELO ROADWALTHAM, MASSACHUSETTS 02154

REPLY TOATTENTION OF:

NEDED-E APR 161979 0

Honorable Ella T. GrassoGovernor of the State of ConnecticutState CapitolHartford, Connecticut 06115

Dear Governor Grasso:

I am forwarding for your use a copy of the Risley Dam Phase IInspection Report, which was prepared under the National Program forInspection of Non-Federal Dams. The report is based upon a visualinspection, a review of past performance, and a preliminary hydro- 0 4

logical analysis. A brief assessment which emphasizes the inadequacyof the project spillway under test flood conditions is included at thebeginning of the report.

The preliminary hydrologic analysis has indicated that the spillwaycapacity for the Risley Dam would likely be exceeded by floods greater 0 0than 44 percent of half of the Probable Maximum Flood (1/2 PMF), thetest flood for spillway adequacy. Screening criteria for initialreview of spillway adequacy specifies that this class of dam, havinginsufficient spillway capacity to discharge the test flood, should beadjudged as having a seriously inadequate spillway and the damassessed as unsafe, non-emergency, until more detailed studies prove0 0otherwise or corrective measures are completed.

The classification of "unsafe" applied to a dam because of a seriouslyinadequate spillway is not meant to indicate the same degree ofemergency as would be associated with "unsafe" classification appliedfor a structural deficiency. It does mean, however, that based on an 0initial screening and preliminary computations there appears to be aserious deficiency in spillway capacity. This could render the damunsafe in the event of a severe storm which would likely causeovertopping and possible failure of the dam, significantly increasing

1 6 the hazard potential for loss of life downstream from the dam.

W~~ 0 I

NEDED-EHonorable Ella T. Grasso

It is recommended that within twelve months from the date of thisreport the owner of the dam engage the services of a professional orconsulting engineer to determine by more sophisticated methods andprocedures the magnitude of the spillway deficiency. Based on thisdetermination, appropriate remedial mitigating measures should bedesigned and completed within 24 months of this date of notification.In the interim a detailed emergency operation plan and warning systemshould be promptly developed. During periods of unusually heavypreciptiation, round-the-clock surveillance should be provided.

I have approved the report and support the findings and recommenda-tions described in Section 7, with qualifications as noted above. Irequest that you keep me informed of the actions taken to implementthese recommendations since this follow-up is an important part of thenon-Federal Dam Inspection Program.

A copy of this report has been forwarded to the Department of Environ-mental Protection, the cooperating agency for the State of 0Connecticut. This report has also been furnished to the owner of theproject, Mr. John S. Risley, Lake Street, Vernon, Connecticut 06066.

Copies of this report will be made available to the public, uponrequest to this office, under the Freedom of Information Act, thirtydays from the date of this letter. S

I wish to take this opportunity to thank you and the Department ofEnvironmental Protection for the cooperation extended in carrying outthis program.

m Sincerely yours, S

Accession For I>.OHN DLERNTISolonel, Corps of Engineers

DTIC TB \~fivision EngineerDTIC TABe

UnannouncedJustirfication

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RISLEY DAN

CT00211

CONNECTICUT RIVER BASINGREENFIELD, MASSACHUSETTS

*

PHASE I INSPECTION REPORT *NATIONAL DAM INSPECTION PROGRAM

NATIONAL DAM INSPECTION PROGRAMPHASE I INSPECTION REPORT

Identificaticn No.: CTO0211Name of Dam: Risley Dam and ReservoirTown: Bolton & Vernon town line 0

State Located: ConnecticutCounty Located: TollandStream: Lydall BrookDate of Inspection: 15 December 1977

FRIEF ASSESSMENTThe dam Is located on a tributary of the Connecticut River on the townline of Bolton and Vernon, Tolland County, Connecticut. It is an earthfill

structure approximately 625' long with a maximum depth at its center of 26'.The crest width varies from 12 to 15 feet. A vertical granite masonry wallextends from the downstream side of the crest to the bed of Lydall Brookbelow. The visable part of the upstream embankment has a 1 on 2 to 1 on 3slope with a riprap face. The downstream embankment consists of cobbles andboulders piled against the face of the masonry wall on an approximate 1 on1.5 slope.

The dam is in generally good condition. It appears to be structurally 0 0stable at the present time under normal conditions. Based on its smallsize and high hazard classification in accordance with the Corps' guidelines,the test flood is 1/2 the PMF. The spillway will pass only about 44 percentof the test flood and is considered inadequate.

Recommendations tn improve dam safety are: 0 0

1. Increase spillway capacity.2. Replace 6" discharge pipe and relocate valve.3. Add riprap near the center on the downstream side.4. Divert spillway discharge away from the toe of the dam.

TEAM MEMBERS 0 0

William J. Farrell, Team Leader

James M. Aiken, Soils Engineer

Joseph A. Colucci, Structural Engineer 0 0

Robert W. Mirick, Hydraulic Engineer

WILLIAM J. FARRELL 0 0

Registered ProfessionalEngineer in theCommonwealth ofMassachusettsRegistration No. 12357

ii

. . S S U S S S S S S 0 0

. 0

This Phase I Inspection Report on Risley Damhas been reviewed by the undersigned Review Board members. In ouropinion, the reported findings, conclusions, and recommendations areconsistent with the Recommended Guidelines for Safety Inspection of 0 0Dams, and with good engineering judgment and practice, and is herebysubmitted for approval.

0 0

RICHARD F. DOHERTY, MEMBERWater Control BranchEngineering Division

* 6

JOSEPH A. MCELROY, MEMBERFoundation & Materials BranchEngineering Division 0 0

CARNEY kJ TERZIAN, CIAIRMA 0Chief, Structural SectionDesign BranchEngineering Division

* 0

APPROVAL RF.Crh IMJ)ED:

JO .FR'AR

Chief, Engineering Division

* •0

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PRE FACE

This report is prepared under guidance contained in theRecommended Guidelines for Safety Inspection of Dams, for Phase IInvestigations. Copies of these guidelines may be obtained fromthe Office of'Chief of Engineers, Washington, D.C. 20314. Thepurpose of a Ohase I Investigation is to identify expeditiouslythose dams which may pose hazards to human life or property. Theassessment of the general condition of the dam is based upon availabledata and visual inspections. Detailed investigation, and analysesinvolving topographic mapping, subsurface investigations, testing,and detailed computational evaluations are beyond the scope of aPhase I investigation; however, the investigation is intended toidentify any need for such studies.

In reviewing this report, it should be realized that thereported condition of the dam is based on observations of field conditionsat the time 'of inspection along with data available to the inspectionteam. In cases where the reservoir was lowered or drained prior toinspection, such action, while improving the stability and safety of 0

the dam, removes the normal load on the structure and may obscurecertain conditions which might otherwise be detectable if inspectedunder the normal operating environment of the structure.

It is important to note that the condition of a dam depends onnumerous and constantly changing internal and external conditions,and is evolutionary in nature. It would be incorrect to assume thatthe present condition of the dam will continue to represent thecondition of the dam at some point in the future. Only throughcontinued care and inspection can there be any chance that unsafeconditions be detected.

Phase I inspections are not intended to provide detailed hydrologicand hydraulic analyses. In accordance with the established Guidelines,the Spillway Test flood is based on the estimated "Probable MaximumFlood" for the region (greatest reasonably possible storm runoff), orfractions thereof. Because of the magnitude and rarity of such a stormevent, a finding that a spillway will not pass the test flood shouldnot be interpreted as necessarily posing a highly inadequate condition.The test flood provides a measure of relative spillway capacity andserves as an aide in determining the need for more detailed hydrologicand hydraulic studies. considering the size of the dam, its generalcondition and the downstream damage potential.

iv

TABLE OF CONTENTS. Paqe

COL'S SIGNATURE PAGENED TRANSMITTAL LETTER 0

BRIEF ASSESSMENT'

REVIEW BOARD PAGE

PREFAC E iv

TABLE OF CONTENTS V, Vi

LOCATION MAP Vii

REPORT

SECTION 1 -PROJECT INFORMATION1

1.1 General11.2 Description of Project11.3 Pertinent Data 2

SECTION 2 - ENGINEERING DATA 5

2.1 Design 52.2 Construction52.3 Operation 52.4 Evaluation 5

SECTION 3 - VISUAL INSPECTION 63.1 Findings 63.2 Evaluation7

SECTION 4 - OPERATIONAL PROCEDURES 8 0

4.1 Procedure 84.2 Maintenance of Dam 84.3 Maintenance of Operating Procedures 84.4 Description of Any Warning 8

System in Effect.4.5 Evaluation 8

SECTION 5 - HYDRAULIC AND HYDROLOGIC 9EVALUATION OF FEATURES

5.1 Evaluation of Features 0

V

Page

SECTION 6 - STRUCTURAL STABILITY 11

6.1 Evaluation of Structural Stability 11

SECTION 7 - ASSESSMENT, RECOMMENDATIONS 12& REMEDIAL MEASURES

7.1 Dam Assessment 127.2 Reconmmendations 127.3 Remedial Measures 13 0

APPENDIXES

APPENDIX A - Visual Inspection 0

Check List With Commnents

APPENDIX B -

1. Inspection Report May 1969 0by John J. Mozzochi and Associates

2. Report on Maintenance and Repairsby Henry Souther Engineering Co.

g3. Plan, profile and partial 0sections of Risley Dam fromfield observations andprevious reports.

4. Plan and Elevation

5. Typical Dam Sections

APPENDIX C -

1. Photographs

APPENDIX D

1. Hydrologic Computations

APPENDIX E-

1. Information as contained in theNational Inventory of Danis

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PLATE I

PHASE I INSPECTION REPORT

RISLEY DAM CTO0211

SECTION 1 0 0

1. Project Information.

1.1 Generil.

a. Authority. Public Law 92-367, August 8, 1972, authorized the 0 •

Secretary of the Army, through the Corps of Engineers, to initiate anational program of dam inspection throughout the United States. TheNew England Division of the Corps of Engineers has been assigned theresponsibility of supervising the inspection of dams within the NewEngland Region. 0 0

b. Purpose.

(1) Perform technical inspection and evaluation of non-Federaldams to identify conditions which threaten the public safety and thuspermit correction in a timely manner by non-Federal interests. 0 •

(2) Encourage and assist the States to initiate quickly effectivedam sdfety programs for non-Federal dams.

(3) To update. verify and complete the National Inventory of Dams.

1.2 Description of Project.

a. Location. The dam is located on a tributary of the Connecticut Riveron the town line of Bolton and Vernon, Tolland County, Connecticut. Itcan be located on a U.S.C.G. survey map at Latitude 410 -48'-00" and 720 -28'-20".

b. Description of Dam and Appurtenances. The dam is an earthfillstructure approximately 625' long with a maximum depth at its center of 26'.The crest width varies from 12 to 15 feet (See photos Appenaix C). Avertical granite masonry wall extends from the downstream side of the crestto the bed of Lydall Brook below (See photo #4 Appendix C). The visable partof the upstream embankment has a 1 on 2 to I on 3 slope with a riprap face(See photo #1 Appendix C). The downstream embankment consists of cobblesand boulders piled against the face of the masonry wall on an approximateI on 1.5 slope (See photos 1,7,8 Appendix C). A 6-inch outlet pipe runsthrough the dam and discharges in the vicinity of the downstream toe. Therock slope is steeper in the vicinity of this pipe discharge. The pipe isthe only means of lowering the water level and is controlled with a 6-inchgate valve on its downstream end.

The concrete spillway (See photos 8,9, 10 Appendix C) is a broadcrested weir with a trapezoidal cross section. It is 42 feet in length, 16feet in width, with a 28 foot bottom and 1 on 5 side slopes. The crest ofthe spillway is about 2 feet below the crest elevation of the dam.

V V V V V V V V V V V V V V V 0 0 6

c. Size Classification. The Risley Dam with its maximum height of26 feet and maximum storage capacity of 226 acre feet is classified it thesmall category.

d. Hazard Classification. Because of the existence of residences,a condominium complex and a church on the flood plain of Lydall Brook down-stream of the dam, the structure has been placed in the high hazard classification.

e. Ownership. The dam is currently owned by Mr. John S. Risley S Sof Lake St., Vernon, Ct. The Manchester Water Company has water rightsto the reservoir.

f. Purpose of Dam. The dam was originally constructed foragricultural purposes. The Town of Manchester has water rights to thereservoir and uses it as a backup supply. 0

g. Design and Construction History. The dam was constructed in1853. There are no known design or construction records available. Dis-cussions with Mr. Risley and Water Department personnel indicated thatthe cobbles and bsulders placed on the downstream side of the verticalmasonry wall were put there in 1924 to add stability to the structure. 0Four test pits dug for the Henry Souther Engineering report on the damin 1972 indicated material in the vicinity of the existing spillway tobe silty gravel. These explorations were between 0.5 feet and 6.5 feetin depth. All but one uncovered bedrock. A copy of the Souther reportis attached as Appendix B.

h. Normal Operating Procedure. The only operational procedureconnected with this dam is the manual operation of the 6 inch gate valveto supplement water storage in the Manchester Water Department's down-stream pools. The water surface in the reservoir depends on recent rain-f.,il quantities and fire flow demands from the town. It is not uncommon,according to Water Department officials, to have the surface elevationwell below spillway crest.

1.3 Pertinent Data. The only available data in addition to theSouther report and information gleaned! from discussions with the ownerand Manchester Water Department offic ials, were acquired through visualinspections by New England Division personnel and the use of U.S.G.S. •topographic maps.

a. Drainage Area. The draiage area above the dam is approximately563 acres (0.88 sq. mi.). Lhere are two streams contributing to the reser-voir which are part of the headwaters for Lydall Brook. The area consistsof moderatly sloping forest land with a sparsely populated street runningalong the westerly side of the reservoir.

b. Dischar&e at Dansite. Discharge occurs at the spillway andthrough the 6 inch pipe tinder the dam. High rates of discharge are dis-cussed in Section 5 - Hydraulics and Hydrologic Evaluation of Features.

2

(1) Outlet works (conduit) size-6" and Invert Elev. +425.

(2) Maximum known flood at damslte. Unknown.

(3) Total spillway capacity at maximum pool elevation540 cfs @ 450+ elev. 0 0

c. Elevation (ft above MSL). The following elevations wereestimated from a U.S.C.G.S. topographic map.

1 Top of Dam ................ 450.0+2 Test Flood ... .. 450.6(3) Full Flood Control pooi ..... N/A(4) Recreation pool . . .... . N/A(5) Spillway crest (ungated) . . . 448.0 +(6) Upstream pipe invert ... ..... Unknow(7) Downstream pipe invert . . ... 425.0 +(8) Streambed at center line of dam . 424.0 i 0 S(9) Maximum tailwater ........... 424.0 +

d. Reservoir

(1) Length of maximum pool . . ... 1800 feet(2) Length of recreation pool .. .. N/A 0(3) Length of flood control pool . . N/A

e. Storage (acre-feet)

(1) Recreation pool .... ....... N/A(2) Flood control pool .. ........ N/AS3) Test flood storage ... ....... 235 '(gross)4) Top of dam .... ........... 226(5) Spillway crest storage .. ..... 190

f. Reservoir Surface (acres)

jl) Top of Dam .... .......... 19.5Maximum pool ... .......... 19.5

(3) Flood control pool ........... N/A(4) Recreation pool ... ......... N/A(fl Spillway crest ... ......... 14.7

g. Dam

(1) Type ..... .............. Earth-masonry(2) Length ...... .. .. ... 625 feet(3) Height .................... 26 feet(4) Top Width .............. +15 feet •(5) Sides Slopes . . U/S 1 on 2 or 3-D7/-S 1 on 1-1/2(6) Zoning .. ........... ... See Sections Plate 4(7) Impervious Core ... .......... Unknown(8) Cutoff ... .............. ... Unknown

* (9) Grout curtain ........... Unlikely

3

h. Spillway

(1) Type ..... .............. Concrete broadcrestedtrapazoidal weir

*(2) Length of Spillway ... ....... 42 feet(3) Crest length ... .......... 28 feet4) Crest elevation ... ........ 448.0 +5) U/S Channel .... .......... None - 0 0(6) D/S Channel .... .......... 10% slope estimated(7) Height of abutments ... ...... Sloping

above crest 1.5 feet above crest

i. Regulating Outlets. The only means of regulating flow from thereservoir is by operating the 6-inch gate valve on the downstream end of the.6-inch cast-iron pipe running under the dam.

(1) Invert .... .............. + 425(2) Size . . . . . . . . . . . . . .(3) Control Mechanism ..... .... Gate valve(4) Maximum discharge capacity .. 4.5 cfs

with water surface @ top of dam

* See Appendix D-l

4

* 0

SECTION 2 - ENGINEERING DATA

2.1 Design. There are no records of the original design available.

2.2 Construction. With the exception of the physical features

that have been measured and included as Appendix B of this report,plus the owner's recollection of riprap being added to the downstreamside in 1924, there is no construction data available. The Manchester

Water Department hired a consultant to inspect and make recommendationsfor repairs and modifications to the dam. This report is included herein 0 0as Appendix A.

2.3 Operation. Manual operation of a 6 inch gate valve on the

downstream end of the 6 inch conduit under the center of the dam.

2.4 Evaluation. 0 0

a. Availability. Not enough information available.

b. Adequacy. The lack of indepth engineering data did notallow for a definitive review. Therefore the adequacy of this dam couldnot be assessed from the standpoint of reviewing design and construction 0 0

data, but is based primarily on visual inspection, past performancehistory and sound engineering judgement.

c. Validity. Based on visual field observations, there is noreason to question the validity of the design, and construction and operationrecords.

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SECTION 3

VISUAL INSPECTION

*3.1 Findings.

a. Gene-.al. At the time of this inspection the water surfacewas about 1.5 feet from the top of the dam with the concrete spillway atits easterly end discharging approximately 10 cfs. The 6 inch conduitunder the dam was discharging water into Lydall Brook on the downstream 0side. There was no snow cover on the ground and no evidence of boils orseepage emerging in the vicinity of the downstream toe.

b. Dam. The rock-fill on the downstream side at the masonry wallwas moss covered with no evidence of displacement. Overall the rock-fillstarts about 2.5 feet below the top of the masonry wall and slopes on 01 on 1-1/2 to the downstream toe, except at the 6 inch outlet pipe in theold streambed where the rock-fill starts 8 feet below the top of the walland ends in a nearly vertical face at the outlet end of the pipe. Thistype of section extends for a length of about 20 feet in the deepestsection of the dam and was probably placed in this manner to avoid thenecessity of extending the outlet pipe. 0

Trees along the right downstream toe have re-ently been cutwithin a strip about 10 feet wide. This has hot beeu done along the leftdownstream toe.

The discharge from the spillway meanders as a natural water- 0course around trees, boulders and over ledge rock back to' the toe of thedam and then downstream. Large cobbles, boulders and ledge outcrop appearto be adequately protecting the downstream toe of dam.

The upstream slope, estimated at between 1 on 2 to 1 on 3is faced with riprap within the area visible to inspection. Several small 0areas were noted at the top of the slope where the earth fill has erodedbehind the riprap. One of the areas had been filled with crushed stone.The top width of the dam consists of a silty gravelly surface with asparse growth of grass. The crest of the dam shows no evidence of settle-ment or misalignment. No surface cracks were noted. The portion of thevertical masonry wall exposed to view showed generally rectangular shaped 0stone zhinked with rock spalls. The wall is dry wall construction withno mortared joints exposed. The cap stones are cut granite blocks as largeas 2 x 3 x 6 feet in dimension. There is no evidence of displacement ofthe masonry wall.

Visual observation of rock outcrop downstream of the dam on 0the left valley wall and the evidence of the spillway discharge channel 5flowing over shallow bedrock indicates a shallow bedrock foundation for

- . . . . .

the left half of the dam. There is no evidence of shallow rock to theright of the brook and the right half of the dam probably has a soil 0 0foundation. The masonry wall probably extends to bedrock in the left halfof the dam and probably not in the right half. Horses and cattle haveaccess to the top of the dam from the right abutment area.

c. Spillway. The spillway in combination with a low saddle atthe eastern end of the dam can discharge about 540 cfs or 44% of test flood 0 0outflow before the dam would be overtopped. It consists of a broad crested,concrete weir with a trapazoidal section. (See sheet 1, Appendix A). Theconcrete appears in good condition with no evidence of cracks and only minorspalling or deterioration. The unusually good condition of the concreteis an indication that the spillway is of more recent vintage than theremainder of the dam. There is no spillway approach channel. However, the 0 0downstream spillway channel takes a meandering aatural water course aroundledge outcropping and boulders back to the toe of the dam and into theoriginal channel.

The pertinent elevations at the dam were taken from a USGSmap. The water surface was given as 448 feet msl. This report assumes 0 0the pool surface to be at spil'way crest at this elevation. The crestof the dam is approximately two feet higher by field measurement. Boringstaken around the spillway in 1972 for the Henry Souther Report (Appendix A)show overburden to be shallow in the area. The soil was described as siltygravel.

d. Reservoir Area. The reservoir area appeared clear and freeof any floating debris that could cause an obstruction to the spillway.

e. Downstream Channel. The channel drops 90 feet in 2,500 feetor about a 3-1/2 percent channel slope. Five hundred feet downstream ofthe dam is a road with a 6-foot diameter culvert. Approximately 2,000 feet 0 0further downstream are two small retention reservoirs. Both the reservoirswould probably hold less than 40 percent of the Risley Reservoir storage.In the event of a failure at Risley Dam, the ensuing wave might rupture thedams containing these two pools with a consequent pyramiding effect thatwould send a surge of water through part of a new condominium developmentlocated 500 feet downstream. Endangered units are estimated to be less S Sthan 20.

3.2 Evaluation. The dam appears to be in generally good condition.There are some areas, however, where it is felt remedia' measures arerequired. (See Section 7)

7

V U U U U U U U U U U U U U S S

SECTION 4

OPERATIONAL PROCEDURES S

4.1 Procedures. The only operational procedure connected with thisdam is the regulation of flow through a 6" pipe under the structure witha 6" gate valve located in the vicinity of the downstream toe. The valveis operated by the Manchester Water Department to control flow to twosmall downstream ponds where the intake works for the water system arelocated.

4.2 Maintenance of Dam. Maintenance work on the dam consists ofsoae clearing and grass cutting. The Water Resources Commission of theState of Connecticut wrote to Mr. Risley in 1969 requesting him toperform the maintenance work and hire a registered engineer to make C Crecomendations for safety modifications ard repairs. Mr. Risley, whoapparently is interested in selling the dam, has not complied with theState's request.

4.3 Maintenance of Operating Facilities. The Manchester WaterDepartment provides occasional lubrication for the 6" gate valve. They S Shired the Henry Souther Engineering Company to submit a report onmaintenance and repair requirements in 1971. The report is includedherein as Appendix B. The town of Manchester is interested in acquiringthe property, but there is some reluctance because of legal ramifications.

4.4 Description of any Warning Systems. There are no warning 0 0systems at the site.

4.5 Evaluation. Maintenance and operational procedures areminimal due to the basic simplicity of the structure.

Part of the clearing operation along the downstream side should be • C

continued to avoid having the roots of trees affect the stability of thetoe. Clear*hng in the vicinity of the spillway should be initiated toavoid Gebris buildup.

8 S

8

3 • • • • • S U • •

0 0

SECTION 5

HYDRAULIC AND HYDROLOGIC EVALUATION OF FEATURES 0 0

5.1 Evaluation of Features.

a. Design Data. There is no design data or criteria availablefor the hydraulic features of this dam. 0 0

b. Experience Data. The maximum spillway overflow at the damcould have occurred in September 1938 when over 16 inches of rain fellin the area over a period of four days with 8 inches in one day. InAugust 1955, 7 inches of rain fell in one day during hurricane "Diane."

c. Visual Observations. The hydraulics of the spillway and 0 0

channel indicate they are inadequate in size and condition. The channelmeanders as a natural water course around trees, boulders and over ledgerock back to the toe of the dam. The trees immediately downstream ofthe spillway could obstruct high flows if they are left in place.

d. Overtopping Potential. Based on U. S. Geological Survey 0 0

Water Supply Paper 1887'"Maximumn Floodflows in the Conterminous UnitedStates," the Probable Maximum Flood for the inflow to Risley Reservoiris about 2,800 cfs per square mile. The spillway cannot discharge morethan 540 cfs or about 610 cfs per square mile (csm) without overtoppingthe dam. This is 22 percent of the P.M.F. The surcharge storage willhave a negligable effect on spillway outflow. 0 0

Since the size classification of Risley Dam is low with ahigh hazard potential classification, one half the P.M.F. was selectedas the spillway Design Flood, that is 1,400 csm or 1,250 cfs.

This would result in overtopping the dam by about 0.6 feet; 0 0

a full P.M.F. would overtop it by about 1.1 feet.

e. Dam Failure Analysis. A cursory analysis was made to assessthe downstream impact of a sudden dam failure. With the reservoir levelat top of dam elevation 450 feet msl, the spillway capacity would be540 cfs or about 22 percent of the Probable Maximum Flood discharge. • 0Assuming the dam failed at this level, producing a breach width of40 percent of the effective dam length at mid height and a breach depthof about 26 feet, equal to the difference in elevation between top ofdam and tailwater, the peak discharge through the breach is estimated tobe 24,000 cfs. This flow plus spillway discharge would total 24,500 cfsand would produce a flood wave in the order of 18 feet for a short distance • 0downstream washing out a 6 foot culvert under Lake St. located 500 feetdownstrea'. The discharge and wave would rapidly dissipate as it passedthrough two small water supply retention reservoirs located 2,500 feetdownstream. The height of water over the two reservoirs should be lessthan 9 feet, but they would probably fail causing a continuation of a

9

.. V V W 0 W W m W i I S i . . . . .

flood wave for another 1,000 feet to the vicinity of several condominiumbuildings. Onie thousand feet downstreami of the condominxiums, approximately 05 to 10 homes and a church could be iMpacted by water depths probably notexceeding five feet. Beyond this location flows would discharge intoflat areas where the flood wave would be largely dissipated. Based onthis assessment the hazard potential. in the event of a dam failure, inconsidered high according to present guidelines.

100

0

SECTION 6

STRUCTURAL STAB IL ITY

6.1 Evaluation of Structural Stability.

a. Visual Observations. Based on the absence of any observed 0seepage or boils downstream, no detrimental settlement or lateral dis-placement, and no observed surface cracks, an evaluation of the visualobservations indicate the dam is structurally stable at the present timeunder normal conditions. However, the structure is not considered adequateto handle emergency or abnormal conditions due to the following:

(1) The water surface in the reservoir was within 1.5 feet 0

if the top of the dam at its lowest point, while the depth of flow throughthe spillway was only 2-1/2 inches, indicating inadequate freeboard underall conditions and the possibility of overtopping during storm conditions.

(2) Facilities for emergency drawdown consist of one 6-inch 0pipe. This is considered inadequate.

(3) The 6-inch drawdown pipe has no means of emergencyclosure on the reservoir side in case of a break in the line.

Some conditions exist that could cause progressive weakening 0of the structure under normal operating conditions. These are listed below:

1. Spillway discharge flow against the toe of the embankment.2. The configuration of the rock-fill supporting the down-

stream side of the masonry wall where the dam height is a maximum.3. Trespassing of horses and cattle on the top of the dam. 04. Growth of brush and root systems near the downstream toe

of the dam.

b. Design and Construction Data. There are no design or construc-tion records available. The owner states the rock-fill on the downstreamslope was placed in 1924. 0

c. Operating Records. There are no operating records available.

d. Post Construction Changes. There are no known post construc-tion changes except for the addition of the rock-fill noted above.

e. Seismic Stability. This dam is located in Seismic Zone No. 1and in accordance witF Phase I guidelines does not warrant seismic analysis.

* 0

• S

SECTION 7

ASSESSMENT, RECOMMENDATIONS AND REMEDIAL MEASURES

7.1 Dam Assessment.

a. Condition. Visual observations indicate the dam to be in goodcondition at the present time under normal conditions. With a flood equalto 1/2 Probable Maximum Flood, the dam would be overtopped about 1/2 footbecause of inadequate spillway capacity. If the topsoil surface of the dam 0

were to wash away, any granite blocks that fell would mix with the downstreamface riprap causing any further failure to decrease. This would cause onlya partial failure not as severe as the downstream hydrograph computationswould indicate. (See Hydraulic Computations). Other areas of concern withregard to dam safety include: 0 0

(1) Inadequacy of 6-inch conduit for emergency drawdown. Itcan release about 4 cfs maximum with a full pool. Also, it is always pres-surized under the dam with no upstream shut off.

(2) The spillway discharge channel encroaches on the toe of 0 0the dam.

(3) The rock-fill on the downstream slope is at a minimumwhere the dam height is a maximum.

b. Adequacy of Information. The lack of indepth engineering data 0 0did not allow for a definitive review. Therefore the adequacy of this damcould not be assessed from the standpoint of reviewing design and construc-tion data, but is based primarily on visual inspection, past performancehistory and sound engineering judgement.

c. Urj encyj. The recommendations and remedial measures outlined below

should be implemented by the owner within one year after receipt of the Phase I

Inspection Report.

d. Need for Additional Investigation. Because of its hazard class- 0 0

ification and the lack of pertinent design and construction records, a de-tailed analysis of the structure should be made. The spillway dischargecapacity is considered inadequate. Further hydrologic studies by competentconsulting engineers are necessary to determine what alternative measuresare necessary to significantly increase the discharge capabilities at the dii. * 0

7.2 Reco!i iendtions.

a. If the dew is to remain essentially as it now stands, stabilityinvestigations should be started in the near future. Some of the followingrecommendations however, should be investigated by a qualified enqineer. *

12W W W W W W W W W W S

(1) Lower the existing spillway and its length to enable thespillway to pass the selected design flood ( PMF). 0

(2) Raise the crest of the dam 2 feet and double the lengthof the spillway. This recoimmendation was made by the Henry SoutherEngineering Company in their report to the Connecticut Water ResourcesCommnission in 1971. (See Appendix A).

7.3 Remedial Measures. 0

a. Alternatives.

(1) The spillway discharge channel should be diverted awayfrom the downstream toe. Trees should be cleared along the new route. 0

(2) Eliminate the dam and have the Manchester Water Departmentcontrol their water supply with modifications to their downstream poolsand water works.

b. Operational and Maintenance Procedures. With most of the above 0alternatives, the only operational procedure will involve the regulationof a valve on the drawdown conduit. Brush should be cleared in the vicinityof the structure. Debris buildup in the vicinity of the spillway shouldbe removed. Round the clock surveillance should be provided by the ownerduring periods of unusually heavy precipitation. The owner should developa formal warning system with local officials for alerting downstream 0 0residents in case of emergency. Institute a biennial program of periodictechnical inspections. Riprap should be added to the center of thedownstream slope to compare in section with the rest of the dam. The 6-inchconduit under the dam should be replaced with a new 18" pipe with substantialdrawdown capability.

13

* 0

0

* 0

APPENDIX A

CHECKLIST VISUAL INSPECTION 0

0 0

* 0

0 0

0 0

0 0

S S S S S S S S S S 5 0 0

APPENDIX A

CHECK LIST -VISUAL INSPECTION

AREA EVALUATED CONDITION

DAM EMBANKMENT

Surf ace Cracks None observed

Pavement Condition See spillway comments

Movement or Settlement of Crest Minor settlement - see profile

Lateral Movement None apparent

Vertical Alignment Satisfactory

Horizontal Aliga ment Satisfactory

Trespassing on Slopes Horses on crest and top of sideslopes

Sloughing or Erosion of Slopes orAbutments None observed

Rock Slope Protection - RiprapFailures None observed

Unusual Movement or Cracking at ornear Toes None observed

Unusual Embankment or DownstreamSeepage None observed

Piping or Boils None observed

Foundation Drainage Features Unknown

Toe Drains Probably none

Instrumentation System None

AREA EVALUATED CONDITION

OUTLET WORKS - CONDUIT 0 0

Excepting the spillway, the on'l.y The 6-inch conduit is probable

outlet is a 6-inch pipe under the cast iron. Its age and con-

center of the dam with a gate dition are unknown. There is 0 0

valve located in the vicinity of no seepage evident where it

the downstream toe. emerges from the downstream toe.

OUTLET WORKS - OUTLET STRUCTUREAND OUTLET CHANNEL

There is no outlet structure at Lydall Brook meanders south-

this site. The outlet channel westerly towards Manchester,

0 0is Lydall Brook. Conn. with little evidence of

bank erosion or flow obstruc-

tion along its length.

* 0OUTLET WORKS - SPILLWAY WEIR,APPROACH AND DISCHARGECHANNELS

a. Approach Channel

General Condition Good

Loose Rock Overhanging Channel None

Floor of Approach Channel Earth bottom on reservoir

b. Weir

General Condition of Concrete Some erosion at crest

Rust or Staining None

0 SSpalling Some on spillway

Any Visible Reinforcing No

Any Seepage or Efflorescence None observed

0 0Drain Holes None

I i S I .. .. . " .. . . . i i . .... .

AREA EVALUATED CONDITION

OUTLET WORKS - SPILLWAY WEIR,APPROACH AND DISCHARGE

CHANNELS

c. Discharge Channel

General Condition Good

Loose Rock Overhanging Channel None

Trees Overhanging Channel Some - Will affect flow conditionat spillway with 1/2 PMFflows.

Floor of Channel Bedrock and overburden

Other Obstructions None

4 0 0 4P 0 0 0 4• 0 0 4P 0 ••P P

APPENDIX B

1. Inspection Report May 1969by John J. Mozzochi and Associates.

2. Report on Maintenance and Repairsby Henry Souther Engineering Co.

3. Plan, profile and partialsections of Risley Dam fromfield observations and

* previous reports.

4. Plan and Elevation.

5. Typical Dam Sections.

JOHN J. MOZZOCHI AND ASSOCIATES ULAOTONOURY. CONN. 04i9

CIVIL ENGIN EKRS f17 1411Ou 9 A VW11M4P"Ong 422.0401

ASSOCIA72. .o WA'I'ER RESOURCES Iee M- wan"JON -UC. J,,. CO, IMISSION PHONI 4,-6440

* ECTOR L. GIOVANNINIE7CEIVE.)4

MA ; r 1969 MOLY To$a sto b7

ANSWERED -

Willimm H. OIarien 1U REFERRED 0 0Civil Ininm' r FILED.Water Resources CommissiomState O f e BLildingHatterds Connecticut 06115

Re 6s Risly leserolip Dm 0 0

Dear Xr. O'Broien

The referenced site was visited on April 13# 1969 aid noted 0 0several normal maintenanoe items that should be performed an followas

1. Remove trees from the channel downstreem of theconcrete principal spillvq.

2. Remove trees from the .ergea spillv ehanmel. 0

3. Remove trees a" brush from all portions of theembankment.

4, There in soe spalling af the conorete, pineipalspillvq to be repaired before fwrthw deterioration. 0 0

5. Add rip-rap (or stone paving) on the upetrem face ofdam in limited areas to proteet aginsmt wave action.

6. Area around gate value an 6P drs..dwma pipe tbrorem* da should be put in order for aseessibilitFy. 0

The capacity of the spillvay was checked as follows,

A . . 4P P.B ,).

Willi m H. O'Brien, III - 2 - M 3# 1969 6

* C

Frequenc Duration Rainfall Q Water level above

(years) (hours) (inches) (efe) spll, v (feet)

25 6 4.0 510 1.148

So 6 4.5 740 1.93 /100 6 5.1 870 2.10 -

MatoType 114 8.51 170 2.78/

WVith appra'mately tw (2) feet from spilluy crest to the top ofdimn it is evident the den could be over-topped. Either the dn should beraised a sniinum of 2' ON or additional spil1vq capacity added. Aeacbination of raising the den and adding spilvay capacity would also do C Cthe job.

Very truly 7oure, 0 •

JOHN J. MOZZOGHI AND ASSOCIATES

Joh L161" jro Assolate

File

0 C C

h 1,7*~, ~-!'x ,. / , t ,." z,;, i !l~ <.<X(,'. ..' ,Z, < 5 . '<< •

4 ,.(

• • i • • 7 • •. • •

FH-L MlrMMY SUUTH1kK LN(INILIIII. 3.AHARTFOR. CONN.

REPORT ON

MAINTENANCE -AND REPAIRS

1WRISLEY RrEZFJWOI"O 1AM AtJD SPILL"AY 0

DOLTON,. CO!"P2CTICUT

*TO

BOARD OF DIRiCTORS

NICIIESTER WATER COMPANY 0

T t

October ?CG, 1971 \ N. 2

IM 401* in o*.1I il'Per.&,$~~~~ W" Uw -I18 .nG~ 1111~~ Tp11

THE HENRY SOUTHiL LNfINL.I5M

HA R FORD. CONN.

TABLE OF CONTENTS

Authorization and Objective 0 0

Recommendation

Discussion

Design Criteria 0 0

Appendices

(1) New Spillwny (sketch)

(2) Storage and Spill-tay Discharge Curvos 0 0

(3) Plan Profile of Dam

(4) Letter frorn WaLer Resources Commission

(5) Cost Lsttmate 0 0

I 0 4

* 0 4

0 0 S

* s0p 0 S 0.ft4| lJ h ,,, :, (~ ( 5., 0 S S S ,,0 ~ Jw|,l 0, 0 J S'1 0l~ 0 0 ,Si S '

THE HENRY SOUTHER ENGINERIN

HARTFORD. CON.

AUTHORIZATTON AND OBJECTIVE 0 0

This report has been prepared for the Manchester Water

Company in accordance with their verbal authorization. 0 0

The objective of this report is to outline the work

necessary to sntisfy the Water Resources Commission requirements

for safety of this dvn. 0 0

* 0

'' 0

* S

U S ~ rc..I.c t . , f 'M ... . .. .

THIE HENRY SOUTHER ENGINEERING

HARTFORD. CONN.

PTMCOP.NMAT T1tS

The items of maintenance work mentioned in this report

should be begun immediatoly.

The design scheme for increasing the safety of the dam,

which includes lengthening the spillway by 30 feet and raising

the dam by two feet, should be presented to the State Environ-

mental Protection Agency for tlir approval prior to final design

and construction.

S

|JlbI| '| RI~iIL{I [tl Ih ~li~ll l h~(III fl~ t||{?f*||ptU C. h ,Iy t~ | l1(tl* 0~r It

• • • • • • ap • qP • * 0

- ' . . .. . . . . . . . .. . . . .. .. Il ra l 0 I n

I HL- HLNRY bQU I HLN LIH jir Lt.,11r1. I

HARTFORO. COW 1.0 6

DISCUSSIONJ

On May 1.5t t)-P t' r tor T) rouirce. Corr, ~

letter addressed to Mr. John S. Risley outlining measures to

be taken to insure the proper maintenance and safety at the

Risley Reservoir. A copy of this letter is included as Appendix • •

4 of this report.

The six maintenance items listed in this report are:

1. Remove trees from tha channel downstream of the • 0

concrete principal spillway.

* Remove trees from the emergency spillway channel.

3. Remove tr-ees and brush from all portions of the • •

embankment.

4. There is some spalliTig of the concrete principal spill-

way to be repaired before further deterioration, • i

5. Add rip-rnp (or stone pavin,) on the upstream face of

dam in limited areas to protect against wave action.

6. Area around gate valve on 6" draw-down ripe through • a

dam should be put in order for acceselbility.

The areas which required additional rip-rap and tree and

brush clearing are shown on Appendix 3. e •

The concrete repair on the emergency spillway should be

undertaken at the same ime as the construction 'of the enlarod

spillway. The specification for this work will be included wlh 0 •

the specification for t.! c spillway construction.

The area around the 6" gato valve should have improved

accessibility for gatn velve opf.-ratlon. Ie recommend a concrete 0 e

• • • • • • • •-3-• •

I m iml mmm C C'lCrCiC Cii C CC

THE HENRY SOUTHER ENGINEERIN * •

HARTFORO, CONN.

or cement block platform and steps to allow easier access and

manipulation of the 6" valve especially during ice and snow

conditions.

The Water Resources Commission letter Also montions that * S

their engineerin g consultant determined that the available

freeboard of the dam during a major storm is not sufficient to

allow adequate safety of the dam. The letter also stated that • •

two feet of freeboerd under high water conditions should be

allowed for a dam of this si.zo.

We have calculated tho wator shed run-off, resorvoir * 0

storage and the principal and emergency spillway capacities and

concur that an adequate factor of safety does not ecist. *e

have studied various schemes whereby the required freeboard and

spillway capacity might be achieved. The scheme chosen includes

widening the principal spillway and raising the top of the dam

approximately two feet. *

A sketch of the proposed spillway is shown in Appendix I

and a plan and profile of the dam showing the revised grade is

shown in Appendix 3. The estimated cost of doinq this work, 0

exclusive of the maintenance items is '9,650.00.

4 S

* S

g • • 'g • •~ ~ 4 - -

1HL HENRY bOUTHER ENGINEERINGHARTFORO. CONN. •

DESIGN CRITERIA• •

The following criteria was used in evaluation of the

spillway capacity.

Water Shed Area 579 Ac.

Reservoir Area 12.8 Ac. •

Runoff coefficient 0.40

Return Storm 100 year

Rninfall Intensities

Duration (hro.) Intensity (in/hr.)

.33 5

.50 4 •1.0 2.7P.0 1.56.o 0.68

12?.0 0.4218.0 0.3P24.0 0,27 0 •

Time of concentration - 21 minutes

Runoff formula ')ACI (A = Area in acres (Ac))C a Runoff coefficient)I = Rainfall intensity in/hr.) • •

Height of water at beginning of storm at spillway crest.

Weir coefficient (C) = 3.0

Weir formula - Q a CLH 3/2 + CZH 5/2 • 0

The storage and spillway discharge curves for the proposed

design are shown in Appendix 2.

• •

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t~JE'.~J SPILL~JAY S~T

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STATE QEF CONNECTICUTIs..WATER RhESOVUCES COMMISSION

STATE OFFICE BUILDING - HARLTFORD, CONNECTICUT, 0(6115

fa ~May L), 1'IJ69

M.r. John L.. ;hzslayL~ke 3tieet 4.

Vernon, Corinecticut.

i.ubjecta fHisley kaocrvoir Damr. iolt,&i, ConnocLicut 0A

Accordiig ,,) the ~orrnation in this Office~, Lhe SU.)jeCt udti11 i! at least 4In part, unue your owicxshif

The --;'ter fleso.urces Cuu~adssion has juxisdicLiui over all cins %-- vhichUy hreaking ,6ay or oLhort--ij.i'.o lt eriJange~r life or pr~ry- - 11pnc thej General !.tatu~xs, a copy of vwh~ch is enclosed. This Jain v.ould thervfOre coame

under the jurisdictian of the ila ter hOSOUrces CoIMAiSsOio.

We have had thir dom int~rc-ctod bjy oii cnyIincerint) consiultant lu thisGonassion Iho hawo foui&U die foilov-Ing itvat,. it) 11cd of wraninL01-nne ".urk.

1. iitonovec. ezes frx the chaniiel do.nstrari of the concrallePrincipal spilb.ay.

2. hernoVO treeS from Lho emotgency sdillv.ay chonnel.

3. honauvo troce and Iuru-h from all portion3 of the emjaitkweiCIL. 0

4. There is scmc. spallirg of the concieot. principal spillv3y

to ~o ropaireI aefore further doicerioration.

to IJ(i r ip-r .p ((,.r S '.01 i'j Uri Lil.) on~ t! up i o.'in011 faco, Ofdarni In 1imi,,ej -.reae to pfi:jkLuct arjai~iis. %--v actiki'.

6.Arec lzou,,( o.ite valve on ul, cz~cl, pIp ouch!, do,shc.jld be put In oxi~ur for accesioility.

-UL: c, .;s o~nt also has. cItetrt-irnd tii.')t the v.a CIc wokild t: L- hirt acouple of Inches Of '.! Lop of thuz. QJm in a Stormu of oilly P ' tA yC-:. 1 zCqiiinC'/.A dfaw as lirge as this rric shujild I-u've i."ich ~.~ac caCIiy VdIth 0 kC2G1IUilufxeeboard uf ijout 2 fQ~*t ujidex lLyl VAIt.~f CUIidiLioflO.

IF w w 0 w w w w M S

Mr.. John ~.itislay Ii- ay 15, 1' 6 . 0

Ilisley Reservoir Dain

We. request that itinc. I throuq.h 6 ixo takwi care of ;;t your oarliuSL con-veienco. A Co:istxuction Ivcrii~ vAil iut Uo noccasary fur thl.' tLr'~ 3adc YOU 0may procoeu i.ith tthi~ without furtwe ziuthorizatiofi from .14L, office.I

I:, rega~rd toj Lim in,-'daquOtC Sp~illway, plans must ue Gubmittcd for appruvalpxepared :)y an engineor xcgisterod in the Stato of Connecticut, providing foradditional rpl1l%.ay capacity. 0

thay vwe hcas frowa you at your oarliest co:ivniotaco as to your iribntionsin pruviding ade~uate cafety of thiG dam~?

* 0Vory Lruly yvurG,

Viillian It. O'B~rien IIICivil Engineer 0

Enc.

dIUINIlzib

cr~s M~nhester .ater Co.

HU9o jaG010ff, E~sq.

0 0

* 0

0 0

0 S

S0 0 4P S S0 40 0 SP 0 S S S 0 0

THE HENRY SOUTHER~ EN(MVEK1aiRIyc 0

COST ESTI",ATE 0RISLEyf RESCRVOIR

SPILL~I-Y AN~D FILLING

Fil Itn u-nt1y nit Price Tota I Snol 70c.y. 3.5o !3o90O.oo

Topsoil Reai4ovalRep~acement and Seeding 850) S.Y. 3.00 ?.550.ooSP121waY Excavation L.S. L&S& 200,00 0

Conret s C.y. 90.00 2,500.OOCleanup anid Misc. L.S. L.Sq.

Overhead & Profit 190:00

I * 0

0 0

10 -

10 Appendix 5* 0 0 0

0 0

S S S *!~ * S U S S S * S~*** USSUS SSW*I* US - !55* ~ S.-

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APPENDIX C

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APPENDIX D

HYDROLOGIC COMPUTATIONS

1. Stage vs. Discharge Computations.

2. Capacity Curve.

3. Spillway Elevation vs. Discharge Curve. '

4. Downstream Dam Failure Hydrographs.

Note: For outline of drainage area andaffected areas downstream, seeLocation Plan on page . •

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APPENDIX E

INVENTORY FORMS

PARTS 1 & 2

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