AD-AI57 517 NATIONAL PROGRAM FOR INSPECTION OF NON-FEDERAL DAMS L/1-1 COLCHESTER POND DAM (..(U) CORPS OF ENGINEERS UALTIIAMUNCLSSIIEDMR NEW ENGLAND DIV OCT 80 / 3/3 NNlAIomsII

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I COLCHESTER POND DAMVT 00056

PHASE I INSPECTION REPORT

NATIONAL DAM INSPECTION PROGRAM

DTIC~JUL 1 9 985

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DEPARTMENT OF THE ARMY

NEW ENGLAND DIVISION, CORPS OF ENGINEERSWALTHAM, MASS. 02154

rusTnIBUTIONSTATEmmlTAApproved for public release#

OCT., 1980 Distribution Unlimited-.

FILE COPY 85 7 01 157

.

IINCI ASSIT~Dn~SECURITY CL ASSI FICATION OF THIS PAGE (IWhen Doe Entered)

REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM1. RIFPO"T NUMBER 2. GoVT ACCESSION NO, I. RECIPIENT'S CATALOG NUMBER

VTnnf4. TITLE (and Subelf~s) S. TYPE OF REPORT 6 PERIOD COVERED

Colchester Pond Dam INSPECTION REPORT

NATIONAL PROGRAM FOR INSPECTION OF NON-FEDERAL .PArneG.ROTMEDAMS

?. AUTHOR(*) I.CONTRACT OR GRANT NUMBER(s)

U.S. ARMY CORPS OF ENGINEERSNEW ENGLAND DIVISION

9. PERFORMING ORGANIZATION NAME AND ADDRESS i0. PROGRAM ELEMENT. PROJECT. TASKARELA 6 WORK UNIT NUMBERS

I I. CONTROLLING OFFICE NAME AND0 ADDRESS Ia. IRPORT CATS

DEPT. OF THE ARMY, CORPS OF ENGINEERS Ortnhiar 19RnNEW ENGLAND DIVISION, NEDED is. NUMBER OF PAGES

424 TRAPELO ROAD, WALTHAM, MA. 02254 4714. MONITORING AGENCY NAME 6 ADDRESS(If diferent ifte CenfrdliMj Office) Is. SECURITY CLASS. (of this 0ter)

UNCLASSIFIEDIt*. OECL.ASSIFICAIIONIDOWNGRACINEG

ACM EDULE

j 16. DISTRIBUTION STATEMENT (of this Reprt)

* APPROVAL FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

17. DISTRIBUTION STATEMENT (ci the abstract anteredd AtleIek"*. idlemit *f)

16. SUPPLEMENTARY NOTE[$

Cover program reads: Phase I Inspection Report, National Dam Inspection Program;however, the official title of the program is: National Program for Inspection of

* Non-Federal Dams; use cover date for date of report.

19, KEY WORDS (Coneenus on reverse aide ii a*e..wr and 1060#11y by bi..b mmber~)

DAMS, INSPECTION, DAM SAFETY,Richelieu River BasinColchester, VT.Pond Brook

20. ABSTRACT (Contlnue a rover&* side It nceseemYg ad IdeattlY by black 09100660

-The dam is a reinforced concrete gravity structure about 40 ft. long and 25 ft.high. The damn is considered to be in goad condition. No evidence of structuralinstability was observed, but a slight steep was noted at the ledge contact ofthe right abutment, which, if allowed to persist, could eventually become greatenough to erode the adjacent concrete. It is intermediate in size with a sig-nificant hazard pk' r.tial.

DD 147.3 EDITION OF I -IOV 65 1* OBSOLETE

DISCLAIMER NOTICE

THIS DOCUMENT IS BEST QUALITYPRACTICABLE. THE COPY FURNISHEDTO DTIC CONTAINED A SIGNIFICANTNUMBER OF PAGES WHICH DO NOTREPRODUCE LEGIBLY.

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DEPARTMENT OF THE ARMYNEW ENGLAND DIVISION. CORPS OF ENGINEERS

424 TRAPELO ROADWALTHAM, MASSACHUSETTS 02254

REPLY TOATTENTION OF:NEDED

MAR 0 6 1961

Honorable Richard A. SnellingGovernor of the State of VermontState CapitolMontpelier, Vermont 05602

Dear Governor Snelling:

Inclosed is a copy of the Colchester Pond Dam (VT-00056) Phase IInspection Report, which was prepared under the National Program forInspection of Non-Federal Dams. This report is presented for your useand is based upon a visual inspection, a review of the past performanceand a brief hydrological study of the dam. A brief assessment is in-cluded at the beginning of the report. I have approved the report andsupport the findings and recommendations described in Section 7 and askthat you keep me informed of the actions taken to implement them. Thisfollow-up action is a vitally important part of this program.

A copy of this report has been forwarded to the Department of WaterResources, the cooperating agency for the State of Vermont. Inaddition, a copy of the report has also been furnished the owner,Colchester Fire District #3, Colchester, Vermont 05446.

Copies of this report will be made available to the public, uponrequest, by this office under the Freedom of Information Act. In thecase of this report the release date will be thirty days from the dateof this letter.

I wish to take this opportunity to thank you and the Department ofWater Resources for your cooperation in carrying out this program.

Sinc 1

Incl C. E. EDGAR, IIIAs stated Colonel, Corps of Engineers

Division Engineer

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COLCHESTER POND DAMVT 00056

RICHELIEU RIVER BASINCOLCHESTER, VERMONT

PHASE I INSPECTION REPORTNATIONAL DAM INSPECTION PROGRAM or--

Accession F or

NTIS GRA&IDTIC TABunannouncedjustificatio

By

DistributiOn_ -

AvailabilitY CodeS

Ai~ and/Or

Di t sp.cia.

BRIEF ASSESSMENTPHASE I INSPECTION REPORT

NATIONAL PROGRAM OF INSPECTION OF DAMS

Identification Number: VT 00056Name of Dam: COLCHESTER POND DAMTown: COLCHESTERCounty and State: CHITTENDEN COUNTY, VERMONTStream: POND BROOKDate of Inspection: MAY 6, 1980

The dam, constructed in 1965, is a reinforced concrete gravity structureapproximately 40 feet long and 25 feet in height. The upstream face isvertical; the downstream face is sloped at 3 horizontal to 4 vertical. The damincludes a 30 foot ogee crested spillway, of which about 9 feet is renderedineffective by an adjacent upstream bridge abutment. The reinforced concreteoutlet structure at the right abutment contains a valved 6 inch diameter lowlevel drain, two gated 12 inch inlet ports at higher elevations, and a 12 inchvalved outlet which originally fed the water system. All gates and valves arereported to be operable.

The dam impounds Colchester Pond and the discharge, Pond Brook, flows in anorthwesterly direction approximately 4.2 miles to its mouth at Lake Champlain.Originally constructed as a water supply facility, the structure is now used tomaintain the level of Colchester Pond. The pond is 5500 feet in length with asurface area of 182 acres. Normal storage capacity is about 2350 acre-ft.

Based on the visual inspection and the review of available data regardingthis facility, the dam is considered to be in GOOD condition. No evidence ofstructural instability was observed, but a slight seep was noted at the ledgecontact of the right abutment, which, if allowed to persist, could eventuallybecome great enough to erode the adjacent concrete.

In accordance with the Corps of Engineers Guidelines and the size(INTERMEDIATE) and hazard (SIGNIFICANT) classification of this dam, the TestFlood selected was equivalent to one-half the Probable Maximum Flood (PMF).Peak inflow to Colchester Pond is 2000 cfs; routed peak outflow from the dam is550 cfs with the water elevation 1.25 feet below the top of dam. The spillwaycapacity is 850 cfs or about 155 percent of the routed Test Flood outflow fromthe dam.

. . . .. . . I

It is recommended that the owner engage a qualified registered engineer toaccess the necessity and means to stop the seepage at the right abutment. Thisand remedial measures which are discussed in Section 7 should be institutedwithin two years of the owner's receipt of this report except as otherwise noted.

Step en D. Murra,-P. .Project Manage -

James W. Sewal Company /

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This Phase I Inspection Report on Colchester Pond Dam (VT-00056)has been reviewed by the undersigned Review Board members. In ouropinion, the reported findings, conclusions, and recommendations areconsistent with the Recommended Guidelines for Safety Inspection ofDams, and with good engineering judgement and practice, and is herebysubmitted for approval.

ARAMAST HAHTESIAN, MEMBERGeotechnical Engineering BranchEngineering Division

CARNEY M. TERZIAN, MEMBERDesign BranchEngineering Division

Jos W. FINEL(JR CHAIRMANWat Control Bran cEngineering Division

APPROVAL RECOMMENDED:

JOE B. FRYARChief, Engineering Division

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PREFACE

This report is prepared under guidance contained in the RecommendedGuidelines for Safety Inspection of Dams, for Phase I Investigations. Copiesof these guidelines may be obtained from the Office of Chief of Engineers,Washington, D.C. 20314. The purp5ose of a Phase I Investigation is toidentify expeditiously those dams which may pose hazards to human life orproperty. The assessment of the general condition of the dam is based uponavailable data and visual inspections. Detailed investigation, and analysesinvolving topographic mapping, subsurface investigations, testing, and de-tailed computational evaluations are beyond the scope of a Phase I investi-gation; however, the investigation is intended to identify any need for suchstudies.

In rev iewing this report, it should be realized that the reported con-dition of the dam is based on observations of field conditions at the timeof inspection along with data available to the inspection team. In caseswhere the reservoir was lo ,ered or drained prior to inspection, such action,while improving the stability and safety of the dam, removes the normal loadon the 'structure and may obscure certain conditions which might otherwise bedetectable if inspected under the normal operating environment of the struc-ture.

It is important to note that the condition of a dam depends on numerousand constantly changing internal and external conditions, and is evolutionaryin nature. It would be incorrect to assume that the present condition of thedam will continue to represent the condition of the dam at some point in thefuture. Only through continued care and inspection can there be any chancethat unsafe conditions be detected.

Phase I inspections are not intended to provide detailed hydrologic andhydraulic analyses. In accordance with the established Guidelines, the Spill-way Test flood is based on the estimated "Probable Maxinum Flood" for the re-gion (greatest reasonably possible storm runoff"), or fractions thereof. Be-cause of the magnitude and rarity of such a storm event, a finding that aspillway will not pass the test flood should not be interpreted as necessarilyposing a highly inbdequate condition. The test flood provides a measure ofrelative spillway capacity and serves as an aide in determining the need formore detailed hydrologic and hydraulic studies, considering the size of thedam, its general condition and the downstream damage potential.

The Phase I Investigation "does not include an assessment of the need forfences, gates, no-trespassing signs, repairs to existing fences and railingsand other items which may be needed to minimize trespass and provide greatersecurity for the facility and safety to the public. An evaluation of the pro-ject for compliance with OSIIA rules and regulations is also excluded.

TABLE OF CONTENTS

SECTION PAGE

Letter of Transmittal

Brief Assessment

Review Board Page

Preface i

Table of Contents ii-iv

Overview Photo v

Location Map vi

REPORT

1. PROJECT INFORMATION 1-1

1.1 General 1-1

a. Authority i-1b. Purpose of Inspection Program 1-1

1.2 Description of Project 1-1

a. Location 1-1b. Description of Dam and Appurtenances 1-1c. Size Classification 1-2d. Hazard Classification 1-2e. Ownership 1-2f. Operator 1-2g. Purpose of Dam 1-2h. Design and Construction History 1-2i. Normal Operational Procedures 1-3

1.3 Pertinent Data 1-3

a. Drainage Area 1-3b. Discharge at Dam Site 1-3c. Elevation 1-4d. Reservoir 1-4e. Storage 1-4f. Reservoir Surface 1-4g. Dam 1-5h. Diversion and Regulating Tunnel 1-5i. Spillway 1-5j. Regulating Outlets 1-6

ii

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Section Page

2. ENGINEERING DATA 2-1

2.1 Design 2-1

a. Available Data 2-1b. Design Features 2-1c. Design Data 2-1

2.2 Construction 2-1

a. Available Data 2-1b. Construction Considerations 2-1

2.3 Operation 2-1

2.4 Evaluation 2-1

a. Availability 2-1b. Adequacy 2-1c. Validity 2-1

3. VISUAL INSPECTION 3-1

3.1 Findings 3-1

a. General 3-1b. Dam 3-1c. Appurtenant Structures 3-1d. Reservoir Area 3-1e. Downstream Channel 3-2

3.2 Evaluation 3-2

4. OPERATIONAL AND MAINTENANCE PROCEDURES 4-1

4.1 Operational Procedures 4-1

a. General 4-1b. Warning System 4-1

4.2 Maintenance Pocedures 4-1

a. General 4-1b. Operating Facilities 4-1

4.3 Evaluation 4-1

5. EVALUATION OF HYDRAULIC/HYDROLOGIC FEATURES 5-1

5.1 General 5-1

iii

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ection Page

5.2 Design Data 5-1

5.3 Experience Data 5-1

5.4 Test Flood Analysis 5-1

5.5 Dam Failure Analysis 5-2

EVALUATION OF STRUCTURAL STABILITY 6-1

6.1 Visual Observation 6-1

6.2 Design and Construction Data 6-1

6.3 Post-Construction Changes 6-1

6.4 Seismic Stability 6-i

ASSESSMENT, RECOMMENDATIONS AND REMEDIAL MEASURES 7-1

7.1 Dam Assessment 7-1

a. Condition 7-1b. Adequacy of Information 7-1c. Urgency 7-1

7.2 Recommendations 7-1

7.3 Remedial Measures 7-1

7.4 Alternatives 7-1

APPENDIX

PPENDIX A - VISUAL CHECK LIST WITH COMMENTS A-1

PPENDIX B - ENGINEERING DATA B-1

PPENDIX C - DETAIL PHOTOGRAPHS C-1

PPENDIX 0 - HYDRAULICS/HYDROLOGIC COMPUTATIONS 0-i

PPENDIX E - INFORMATION AS CONTAINED IN THE E-1NATIONAL INVENTORY OF DAMS

iv

.5 DAM FAILURE ANALYSIS

Utilizing the April, 1978, "Rule of Thumb Guidance for Estimating Downstreamani Failure hydrographs", the peak failure outflow with the pool initially athe top of the dam (el. 388.0 NGVJ) woulo be approximately 2800 cfs. Storageownstream of the dam woula not significantly attenuate the peak failureischarge until flow reached the relatively flat area downstream of U.S. Route 2/7ome 2.5 miles from the dam.

The prefailure flood would produce a substantial pool upstream of the 35 footentral Vermont Railroad embankment located 2000 feet downstream of the dam, and'ould overtop two town roads I and 2 miles from the dam. The failure flood,ould overtop the railroad embankment by 0.7 feet causing damage to the track.nd the fill, resulting in possible derailment with consequent damage to rollingtock and hazard to passengers and crew. Further downstream, the failure floodould overtop the two town roads, assumed washed out by the prefailure flood, bybout 2.4 feet and likely cause some damage to U.S. Route 2/7 about 2.5 milesrom the dam. There would be substantial agricultural flooding along the entire:ourse of Pond Brook. Damage to the railroad creates the potential for loss ofiot more than a few lives. Thus Colchester Pond Dam has been classified as aSignificant Hazard" dam.

5-2

CTION 5: EVALUATION OF HYDRAULIC/HYDROLOGIC FEATURES

.1 GENERAL

The project is basically a low surcharge storage-high spillage gravity dam,'iginally constructed for public water supply.

The tributary watershed consists of 1.85 square miles of relatively undevel-ped terrain, approximately 70% wooded and containing no significant storagether than Colchester Pond. Colchester Pond has a surface area of 182 acresDnstituting about 15% of the total drainage area. NGVD elevations within theatershed range from 380 feet to over 700 feet. Average watershed slope isbout 9.5%, which in the absence of significant storage would be consioeredountainous. Because of the relatively large pond area, however, the watershedas considered rolling for hydrologic purposes.

Adjacent to and upstream of the dam, a roadway bridge crosses the approachhannel with its bottom steel about 8.6 feet above the spillway crest and itsbutments contacting the upstream dam face.

Hydraulics computations indicate that the dam would control the outflowt elevations below the bridge steel; at higher elevations the bridge and adja-ent roadway would act as a weir controlling outflow to Pond Brook. Thepillway would accommodate 100% of the routed Test Flood outflow from the damith an average surcharge above the spillway crest of 3.75 feet. With surchargeo the top of dam, the spillway would accommodate 155% of the routed Test Flood,utflow from the dam.

.2 DESIGN DATA

No design data are known to exist for this project.

.3 EXPERIENCE DATA

No information on serious problem situations arising at this dam was foundLnd it does not appear that the water level has ever reached sufficient eleva-ion to overtop the dam or create a hazard to any dam component.

.4 TEST FLOOD ANALYSIS

The Test Flood for this significant hazard, intermediate size dam rangesrom one-half of the Probable Maximum Flood (Pi4F) to the Probable Maximum Flood.ine-half of the PNF was selected as the Test Flood since Colchester Pond Dam isit the lower end of the intermediate size classification and poses a relativelyow risk to populated areas.

Peak inflow to Colchester Pond is 2000 cfs and was determined using theRolling" guide curve of the "Preliminary Guidance for Estimating M~aximumrobable Discharge", dated march, 1978. Peak outflow is 550 cfs with the waterlevation 1.25 feet below the top of dam and the initial reservoir level assumedit the crest of the spillway (el. 383.0 NVD). Based upon hydraulics con-,utations, the maximum spillway capacity is 850 cfs, or approximately 155% ofhe routed Test Flood outflow.

5-1

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SECTION 4: OPERATIONAL AND MAINTENANCE PROCEDURES

4.1 OPERATIONAL PROCEDURES

a. General - This dan is no longer used for water supply and no operatingprocedure, as such, is known to exist.

b. Warning System - No warning system is known to exist.

4.2 MAINTENANCE PROCEDURES

a. General - The dam receives no regular maintenance and is not visitedfrequently.

b. Operating Facilities - No formal plan for the maintenance of operatingfacilities is known to exist. Tle gate stands and operating handwheels appearin good condition and show no sign of misuse.

4.3 EVALUATION

The operation and maintenance procedures at this dam are inadequate toensure that all problems encountered can be remedied within a reasonable periodof time. The owner should establish a written operation and maintenance proce-dure as well as a downstream warning system to follow in the event of anemergency at the dam.

4-1

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e. Downstream Channel - The channel directly below the dam is heavilywooded with steep sides and bottom as shown in Photo 10. Pond Brook flowsthrough the wooded area from the center to the upper right of Photo 9. A 35foot high Central Vermont Railroad embankment 2000 feet downstream, beneathwhich the brook passes, is also visible in this photo. The 5 foot culvert underthe embankment is shown in Photo 11.

Further downstream, the brook passes under two Town roads 1 and 2 miles fromthe dam, and the channel banks remain primarily wooded. The upstream Town roadcrossing is shown in Photo 12. About 2.5 miles downstream from the dam, thebrook passes under U.S. Route 2/7, receiving flow from three tributaries fromthere to its mouth at Lake Champlain, about 4.2 miles downstream of the dam.

3.2 EVALUATION

On the basis of the visual examination the dam is considered to be in goodcondition.

The minor leakage on the downstream face at the right abutment, ifuncorrected, could develop into a future erosion problem.

The handrail around the operating platform, if allowed to deteriorate, couldcreate a safety hazard to operating personnel.

The heavily wooded condition of the downstream channel reduces the hydraulicefficiency of the channel and could result in downstream blockages and con-sequent damage during flood flows.

3-2

SECTION 3: VISUAL INSPECTION

3.1 FINDINGS

a. General - The visual inspection of the dam was conducted on May 6, 1980.At that time, the water level of the reservoir was about I inch above the spill-way. The weather was sunny and mild. The general condition of the dam is good.

b. Dam - The dam is a reinforced concrete gravity structure with anoperating platform at the right abutment 5 feet above the crest. The operatingplatform is shown in Photo 1. All visible concrete components of the dam appearin good condition.

There is a minor amount of clear leakage coming from the downstream contactof the right abutment with the ledge as shown in Photo 2.

A roadway bridge, visible in Photos 3 and 4 and in the Overview Photo,exists directly upstream from the dam with its concrete abutments immediatelyadjacent to the dam.

c. Appurtenant Structures

Spillway

As shown in Photo 4, the major portion of the dam consists of the 30 footlong spillway section with the 10 foot long gate structure to the right of thespillway. The spillway has an ogee crest and a downstream slope of 3 horizontalto 4 vertical. Very minor erosion of the downstream face has made theconstruction joints visible as shown in Photos 5 and 6. The left abutment ofthe upstream roadway bridge obstructs flow to a portion of the spillway as shownin Photo 7.

Outlet Structure

A 6 inch low level drain shown in Photo 8, exits at the bottom of the damabout a foot above the stream channel. This outlet is sufficiently low torelieve hydrostatic pressure from the dan and to facilitate dam repair, and ispiped through the outlet structure. The outlet structure is equipped with two12 inch intakes, the lowest being I foot above the 6 inch pipe. These serve thevalved 12 inch outlet which formerly supplied the water system, and which, it ispresumed, could be used as an auxiliary pond drain. The gate and valve mechan-isms, so far as are visible, appear in good condition and are reported operable.The handrail around the operating platform of the outlet structure is in goodcondition with some minor rusting as shown in Photo 1.

d. Reservoir Area - The area surrounding the reservoir is essentiallyrural with a mixture of woods and open fields as shown in Photo 9. There are noindications of instability along the banks of the reservoir in the vicinity ofthe dam.

3-1

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SECTION 2: ENGINEERING DATA

2.1 DESIGN

a. Available Data - The available data consists of sheets 1 and 2 of ori-ginal contract drawings by Whitman and Howard, Inc., Engineers, dated March,1960.

b. Design Features - The drawings, computations and inspection reportsindicate the design features stated in Section 1.

c. Design Data - Design data consists of information on the two contractdrawings by Whitman and Howard as listed in "Available Data".

2.2 CONSTRUCTION

a. Available Data - Information as contained in any plans, drawings, orspecifications previously listed in "Design Data" or Appendix B.

b. Construction Considerations - Some variations were noted in the dam asbuilt compared to the original contract drawings. The original plans providedfor the gate structure to be near the center of the dam and to be served by asteel service bridge from the left abutment. This gate structure was moved tothe right abutment to take advantage of a ledge projection and to eliminate theservice bridge. The crest of the spillway was raised to elevation 383.0 rather thanelevation 380.0 shown on the original contract drawings.

2.3 OPERATION

Pond level readings are not taken on any regular schedule. This dam andreservoir are not currently being used for water supply and no formal operatingprocedures are known to exist.

2.1 EVALUATION

a. Availability - Existing data was provided by the State of VermontAgency of Environmental Conservation, and Colchester Fire District No. 3 (theowner).

b. Adequacy - Detailed hydrologic/hydraulic data were not available.Design data and field measurements were utilized in conjunction with New EnglandDivision - Army Corps of Engineers "Preliminary Guidance for Estimating MaximumProbable Discharges" to perform the computations of outflow capacity.

The detailed engineering data required to perform an in-depth stability ana-lysis of the dam was not available. The final assessment of the dam, therefore,must be based primarily on visual inspection, performance history, and spillwaycapacity computations.

C. Validity - A comparison of records, data, and visual observationsreveals no significant discrepancies, other than those noted above betwiendesign and as-built dimensions.

2-1

j. Regulating Outlets

1. Invert: 366.75

2. Size: 6 inch diameter

3. Description: Cast iron waste pipedischarging to downstreamchannel

4. Control mechanism: Gate operated by hand-wheel at control structure

5. Other: 12 inch increasing to16 inch gated cast ironwater supply pipe dis-charging to chlorinationstation - not currently inuse

1-6

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4. Test flood pool: 182 acres

5. Top of dam: 182 acres

g. Dam

1. Type: concrete gravity

2. Length: 40± ft

3. Height: 25± ft

4. Top Width: 2.5 ± ft

5. Side Slopes: 3H to 4V D/SVertical U/S

6. Zoning: N/A

7. Impervious'core: N/A

8. Cutoff: N/A

9. Grout curtain: N/A

10. Other: N/A

h. Diversion and Regulating Tunnel N/A

i. Spillway

1. Type: concrete ogee

2. Length of weir: 30± ft

3. Crest elevation: 383.0

4. Gates: N/A

5. Upstream channel: 31 ft span betweenbridge abutments

6. Downstream channel: original streambed

7. General: 9 feet of spillwayineffective - located

behind bridge abutment

1-5

c. Elevation (Feet, NGVD)

1. Streambed at toe of dam: 363 ±

2. Bottom of cutoff: N/A

3. Maximum tailwater: 366.8 ±

4. Recreation pool: N/A

5. Full flood control pool: N/A

6. Spillway crest (ungated): 383.0

7. Design surcharge: N/A

8. Top of dam: 388.0

9. Test flood surcharge: 386.75

d. Reservoir

1. Length of normal pool: 5500 ft

2. Length of flood control pool: N/A

3. Length of spillway crest pool: 5500 ft

4. Length of pool at top of dam: 5500 ft

5. Length of test flood pool: 5500 ft

e. Storage

1. Normal pool: 2350 acre-ft

2. Flood control pool: N/A

3. Spillway crest pool: 2350 acre-ft

4. Top of dam: 3260 acre-ft

5. Test flood pool: 3030 acre-ft

f. Reservoir Surface

1. Normal pool: 182 acres

2. Flood control pool: N/A

3. Spillway crest: 182 acres

1-4

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i. Normal Operational Procedures - All gates in the outlet structure arenormally tightly closed and locked and all four hand-wheels are reportedoperable. There are no regular operational procedures other than occasional

O checking.

1.3 PERTINENT DATA

a. Drainage Area - 1.82 square miles of moderately steep, relatively unde-veloped terrain which is about 30% open and 70% wooded.

b. Discharge at Dam Site - Discharge is over the spillway and through twogated cast iron outlet pipes. one is a 6 inch low level drain and the other a12 inch water supply conduit which increases to 16 inches just downstream of thedam. Elevations are in feet referenced to NGVD datum.

1. Outlet works (conduits) capacityat top of dam el. 388.0:

One 6" cast iron pipe

@ invert el. 366.75 2+ cfs

r One 12" increasing to 16"

cast iron pipe@ invert el. 367.0 N/A

2. Maximum known flood at damsite: N/A

3. Ungated spillway capacityat top of dam el. 388.0: 850+ cfs

4. Ungated spillway capacityat test flood el. 386.75: 550+ cfs

5. Gated spillway capacityat normal pool el. 383.0: N/A

6. Gated spillway capacityat test flood el. 386.75: N/A

7. Total spillway capacityat test flood el. 386.75: 550+ cfs

8. Total project dischargeat top of dam el. 388.0: 852+ cfs

9. Total project dischargeat test flood el. 386.75: 552+ cfs

1-3

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* 6 inch diameter valved low level drain with a center line elevation of 367.5.All three inlets are equipped with trashracks and screens. As the dam is nolonger used for water supply, the 12" diameter valved outlet which originallyfed the water system remains permanently closed. Access to the hanowheel gatecontrols is via the right embankment.

Elevations are in feet referenced to NGVD datum.

No instrumentation exists at this dam.

I c. Size Classification - INTERMEDIATE - The dam impounds approximately3260 acre-feet with the pond level at the top of the dam, which at elevation388 is 25 feet above the streambed. According to the Recommended Guidelines,the dam is classified as intermediate in size since its impoundment is between1,000 and 50,000 acre-feet.

d. Hazard Classification - SIGNIFICANT - If the dam were to be breached,there is potential for considerable downstream damage and loss of no more than afew lives. The Central Vermont Railroad tracks cross Pond Brook on a 35 foothigh embankment about 2000 feet downstream of the dam. This embankment would beovertopped by about 0.7 feet resulting in damage to the track and a possibleserious derailment. Considerable flooding of agricultural land, both upstream

P and downstream of the railroad embankment, would ensue. Two town roads, 1 and 2miles downstream of the dam, presumably washed out by the pre-failure flowbecause of the relatively small bridges under them, would receive further damagefrom the approximate 5 foot submergence resulting from the breach. U.S. Route7, about 2.5 miles downstream of the dam, would likely receive relatively minordamage.

e. Ownership - Colchester Fire District #3K *: Colchester, Vermont 05446

(802) 658-6616

The dam was built for its present owner.

* f. Operator - Clifford Morrie1 Wintergreen DriveColchester, Vermont 03446Home (802) 879-0969Office (802) 655-0813

g. Purpose of Dam - The dam was originally constructed for water supplyand was used as such for 12 years. The area is now served by the ChamplainWater District. As there is no public access to the pond, except at the damsite, recreational use is minimal. Except for maintenance of pond level for

* local asthetic purposes, the dam now serves no function.

h. Design and Construction History - The following information is* "believed to be accurate basea upon available plans and correspondence and con-

versations with persons familiar with the history of the dam. The dam wasdesigned in 1960 by Whitman and Howard Engineers, Inc. for Fire District No. 3,Colchester, Vermont. A public hearing as required by the state was held onMay 19, 1960 and a Hearing Order was issued on July 15, 1960, allowing the pro-ject to proceed to construction. The dam was completed in 1965.

1-2r.

....................... . . . . . . . . ..........................................................

PHASE I INSPECTION REPORT

COLCHESTER POND DAM

SECTION 1 - PROJECT INFORMATION

1.1 GENERAL

a. Authority - Public Law 92-367, August 8, 1972, authorized theSecretary of the Army, through the Corps of Engineers, to initiate a National

S Program of Dam Inspection throughout the United States. The New EnglandDivision of the Corps of Engineers has been assigned the responsibility ofsupervising the inspection of dams within the New England Region. James W.Sewall Company has been retained by the New England Division to inspect andreport on selected dams in the State of Vermont. Authorization and notice toproceed were issued to James W. Sewall Company under a letter of April 2, 1980from William E. Hodgson, Jr., Colonel, Corps of Engineers. Contract No. DACW33-80-C-0051 has been assigned by the Corps of Engineers for this work.

b. Purpose of Inspection Program - The purposes of the program are to:

1. Perform technical inspection and evaluation of non-federal dams toidentify conditions requiring correction in a timely manner by non-federal interests.

2. Encourage and prepare the States to quickly initiate effective daminspection 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 the headwaters of Pond Brook about 4.2miles upstream from Lake Champlain in a rural area of the Town of Colchester,County of Chittenden, State of Vermont. The dam is shown on the Colchester,VT. USGS Quadrangle Map having coordinates latitude N 440-32.9 ' and longitude W730-07.5 '. The dam is also known as Pond Brook Reservoir Dam.

b. Description of Dam and Appurtenances - The dam, completed in 1965, isa concrete gravity structure built on exposed bedrock, having a total length of40 feet. This includes a 30 foot long spillway section on the left of the damand a 10 foot long gate structure on the right.

The ogee crest spillway has a top elevation of approximately 383 and adownstream slope of 3 horizontal to 4 vertical. Immediately upstream of the damis a rc- way bridge with a 31 foot span. The left bridge abutment blocks anydirect )w to the leftmost 9 feet of the spillway section.

The !ate structure has a top elevation of approximately 388, a maximum of25 feet in height above the streambed. The structure has two gated inlet ports,12 inches in diameter with center line elevations of 370 and 377. There is a

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SECTION 6: EVALUATION OF STRUCTURAL STABILITY

6.1 VISUAL OBSERVATIONS

Visual inspection did not disclose any immediate stability problems.The minor seepage observed at the contact of the concrete dam and bedrock onthe right abutment does not indicate immediate stabilityproblems.

6.2 DESIGN AND CONSTRUCTION DATA

m No original design and construction data are available for this dam.

6.3 POST CONSTRUCTION CHANGES

There is no record of post construction changes.

6.4 SEISMIC STABILITY

The dam is located in Seismic Zone 2, and in accordance with the recom-mended Phase 1 guidelines does not warrant seismic investigation.

6-1

. ... . . . . . .

. . .. . . . . . . . . . . . . . . . . . . . .

SECTION 7: ASSESSMENT, RECOMMENDATIONS AND REMEDIAL MEASURES

7.1 DAM ASSESSMENT

a. Condition - Based upon the visual inspection, the dam is judged to bein good condition.

* b. Adequacy of Information - Due to the lack of design and construction• -data for this dam, the assessment of safety is based on the visual inspection.

M c. Urgency - Except as noted, the remedial measures and recommendationspresented below should be implemented by the owner within two years afterreceipt of this Phase I Inspection Report.

7.2 RECOMMENDATIONS

The owner should engage a qualified registered engineer to assess thenecessity and means to stop the seepage at the right abutment.

The owner should implement all recommendations by the engineer.

7.3 REMEDIAL MEASURES

a. A program of biennial technical inspection, with repairs asnecessary, should be institutea by the owner.

b. A formal downstream warning system to be implemented in the event ofan emergency at the dam should be develbped by the owner within one year ofthe receipt of this report by the owner.

-.. c. A formal program of operation and maintenance procedures should be-. instituted and fully documented to provide accurate records for future

reference.

d. The owner should arrange for the removal of trees from the downstreamchannel within 50 feet of the dam toe.

e. The handrail around the operating platform should be painted andmaintained.

7.4 ALTERNATIVES

Removal of this dam may be a practical alternative to the above recommen-* .. dations.

7-1

APPENDIX A

VISUAL CHECK LIST WITH COMMENTS

V]SUAL ]IISPECTION 0IFCKLISTPARlY ORGAIJIZATION

TIMEPRJEL.. . • .. , . -., DATE /,V&i. , / L .

ST]IME" //I ,*' '

WEATHER /--"

W.S. ELEV.. U.S. DN.S.

PARTY:

.] --' .... - ." . . ,; 6.

3- 8 .' • , .. 8Ii

.,2r C7-

-. .__- :,_-I,

7. 9.

5.

6..

7..-.A-]

- , , ._... (-. .-.,,.. ,.. . . . . . . .

. . . . . . . .. . . . . . . . . . . . . . . . . . . .

PROJECT j , -",-DAT E, - " - I .... -

PROJECT FEATURE AM -----------,

D]SC]PL] E ,. .INE NAIIE F/, -.

O.-

AREA EVALUA%.ED COtD]T1OM _

"*" DAM :tM3A'K,1UT .

Crest Elevation C. ..

Current Pool Elevation ... .

Maximum Impoundment to Date

Surface Cracks - - .*;r

Pavement Condition

Movement or. Settlement of Crest ., .

Lateral Movement

Vertical Alignment C- o, -

Horizontal Aliqnment UC

Condition at Abutment and at Concrete -, -.- '.-.-, o- -."

Structures ,-o- . , - - "

Indications of Movement of StructuralItems on Slopes ''-' > r'

Trespassinq on Slopes 7-

Slbughina or Erosion of Slopes or '. ,

Abutments

Rock Slope Protection - Riprap Failures

Unusual Movement or CrackinQ at or Near o ,... oz'. '-- L4

Toe

Unusual Embankment or DownstreamSeepage

Pipinq or Boils

Foundation Drainage Features -

Toe Drains

Instrumentation System

Veoetation

- A-2

* - - *rrzt~jU)j L JNJ5JLL I iW LMIILKLJI

PROJECT -- ~ 'DAl E i

PROJECT FEATURE ______________ NAME _____

DICPIE--- NAHE

2AREA EVALUATED COtJDIT IONJ

DIKE EME;ANKHENT

Crest Elevation 7-. 5' K~

* Current Pool -Elevation

Maximum Impoundment to Date

Surface Cracks

Pavement Condition

Movement or Settlement of Crest

Lateral Movement

r Vertical Alignment

* Horizontal Alignment

Condition at Abutment and at ConcreteStructures

IIndications of Movement of St ructuralItems on Slopes.

Trespassing on Slopes

*Sloughing or Erosion of Slopes orAbutments

*Rock Slope Protection - Riprap Failures

Unusual Movement or Cracking at or* Near Toes

Unusual Ebankment or Do%'jns trearn* Seepage

* Piping or Boils

* .Foundation Drainaoc Features

Toe Drains

Instrumentation System

Vegetation

A-3

PROJECT. -_ __- DA rE

PROJECT F[AIURE NAME ____--"I /

DISCIPLINE____ __-_:. NAIFVE " • --,_7(0 C : - r. 2 ". r' t .: ." ,'

AREA EVA LUAIED CoNDI T I ON

OUTLET WORKS - INTAKE CHANNEL ANDINTAKE STRtUC TURE

a. Approach Channel r" 7,- ,. ' -

.Slope Conditions / . :, e, - - " .

Bottom Conditions

Rock Slides or Falls

Loq Boom.

Debris

Condition of Concrete Lining

Drains or Weep Holes

b. Intake Structure

Condition of Concrete

Stop Logs and Slots

A-4

o ~~~~~ ~~ ~~~ ~~~... . ... . . . ..... . . . . . . . . -.. .... . . ,. ..... .. .. . . • ,.. .. . .

fT L. MI Vw.~-r W I J 11 1tL - 1 UIIr.[L

PROJECT C -/ D _ ,ATE '__

PROJECT FEATURE NA- ME..: UAri_ ."-

D]SCIPLINE . _ _ _ '. NAME .2/" .9<-

AREA EVALUATED CONDITION

OUTLET WORKS - CONIROL TO1ER

a. Concrete and Structural

General Condition

Condition of Joints n 0

Spalling ,

Visible Reinforcing

Rusting or Staining of Concrete , ,, ' .

Any Seepage or Efflorescence r -' f

Joint Aliqnment .Y/, '-)

Unusual Seepage or Leaks in GateCha ber

Cracks

Rusting or Corrosion of Steel /"',, K-- .- ,, ,--.

b. Mechanical and Electrical

Air Vents , ,-,

Float Wells A/. A>

Crane Hoist /V, /.

Elevator Al, 6

Hydraulic System /V /.

Service Gates

Emergency Gates o q

Lightning Protection System

Emergency Power System - •

Wiring and Lightinq System

A-5

.. -. . , ,. . . , . , . - - .N°- ,- , - - - . - . • , . . " . . " . , ' . , ' ." . - . - . ,. - . " , ' . , ' . .

PROJECT ,r 1 DAl. E

PROJECT FEATURE NNE

DISCIPLINE A.'M . , N-,E _-," '

AREA EVALUATED CONDT] I ]ON

OUTLET 14ORKS - TRANSITION AND CONDUIT

General Condition of Concrete

Rust or Staining on Concrete

Spalling"

Erosion or Cavitation

Cracking"

Aliqcnment of Monoliths

Ali(nment of Joints

Numberinq of Monoliths

Qt ,* o /

P7

A-6

_----:: :-."''"':> :' ::':/ : : " ":1 ' ,:.: ' "" " " " " - - ': -" -":' " :q ':'

I" L... .1\ j t. L I i U I| i r - I, I u I

PROJECT ____-_-_ " 'DAl E;f__

PROJECT FEAlURE ,, _... . -. "

DSC PL 1 fiz IN NAME ___

'--_-,,, ,. .

AREA EVALUATED CONDIl ION

OULT ET POCFS - OUTLET SIRUCTURE ANDUll.I_ CHANINL " ,.- ,

General Condition of Concrete

Rust or Staining

Spalling

Erosion or Cavitation

Visible Reinforcing

Any Seepage or Efflorescence

Condition at Joints

Drain holes

Channel , _, ,, , .,," , -= .. : -,' ,' -

Loose Rock or Trees Overhanging .- tChannel '•"- "

Condition of Discharge Channel ...- c, c:,,u-" Is -

A-7

.- "-•.-."-.-

PERIODIC INSPECT ION CHECKL]ST"

PROJECT __ ," ..... DATE

PROJECT FEATURE N . ., NAME ._ ,. , _- ,".",,

DISC]PL]NE ,__." __ .,, NAME , , -NAME

AREA EVALUATED CONDIT]ON

OUTLET WORKS - SPI[LWAY WEIR, APPROACHAND D]S CHARGE CHANNELS

a. Approach Channel - -

General Condition

Loose Rock Overhanging Channel

Trees Overhanging Channel

Floor of Approach Channel

b. Weir and Triining.Walls-

General Condition of Concrete ,

Rust or Staining /,,, c,- ' ., .

Spalling , , . . ,

Any Visible Reinforcing

Any Seepage or Efflorescence "o',' /';/'

Drain Holes

c. Discharge Channel eec -, c7 e 7, I

General Condition

Loose Rock Overhanging Channel

Trees Overhanging Channel

Floor of Channel

Other Obstructions

A-8

... .. .............-. -....... ,.. ...

. .. . . .. r_. .....- - .... .'v ... .• - "r L'\I *U L) t-, J I L.i I~~ I

OJECT o E ' - : m L. ........

O]ECT FEAURE URENAME

SCIPLINE ,_____ . . - NAME .

AREA EVALUAIED CONJD] T ]N

JTLET WORKS - SERVICE BRIDGE -%2., - . .. *,

Super Structure

Bearings

Anchor Bolts

Bridge Seat

Longitudinal ltnbe rs

Underside of Deck

Secondary Bracing

Deck

Drainage System

Rail ings

Expansion Joints

Paint

Abutment & Piers

General Condition of Concrete

Alignment of Abutment

Approach to Bridge

Condition of Seat , Backwall

A-9

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APPENDIX B

ENGINEERING DATA

' I

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APPENDIX C

DJETAIL PHOTOGRAPHS

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* . C

The concix-te, In ti' Onm. v:aItl have a riinIlzicorramvrtren-gth of 2,C-,)o pouf 13 per rqwirc inch, anid An thei ga~ ctru cturcof 3,000 pound: .

The rwim-i rAurip -hall be 4-112 inchos.

Test clir-krs will be, t, -tcd for co7,rennivc vItrengtlh An

~ccrc~~nc wih AT~ '!39"

All concr te .'7hal'. be Ocroritcd b, rin 'ens of a . r cc'to b, cc-ot.

Usrc of ch, tcs .1 not bc Ae~P~)

The mwiximu' ]ih of ai-:T. po~ur !7hall bl 5 feet. A 6',?lay offive days In pc-i.rin~ a accnt norol.1ths.

One vcrtlc-l conzn ructlc'n jolint will he? requIT'ed a-t f~ho,'1n ontho e ra ~ 'lie Con'ractor Its to drill holes fcr Lgroot1nr asdirected by the En-ine rs. Grc'lut pipos to extend one foot intoli(-t- and th-rou ;h form,- o gro,.i tlrg may be done aftcy, lc-w r .--cct~cn3of dam have beei poure'-.

-7:

B-11

The reservoir E itc ohall bt cleared of all te , bi-uc.h andbushcs to rithix 6-1-ncl s of th'-round. These matferlal's, alongwith all slash, are to be disposed of by burning.

The propos:d flow line of' th2 rescrvolr is elevation ?'O.O.The limit of cl, aring Chall b2 elevation 381.0 with a mJnarmir-1distance of 10 i'eet ho'izontally from, the flow lIne.

2. Strippin7

All overbu-.6i:n at the dam site including loose or pc.tially1oo3e or sea:ny 1cOige tiat can be rcyoved with bars, picks, pavingbreakers, etc. rh.-all b(- removed an d the solid ledge tl]oroug;hlycleaned with co proascC( air and water. The ledge foundation sbhallbe approved by !he -nf, neers a rx1nirrm of 12 hours before conmence-ment of concrut ,- operal ons. /

3. 1-Useellaneo , T TetaP s

- The- footbr'dgc be1 d-gshaeL-bh ntandard-6-inch- wide -flangebeams .

The floor -hall bi, type M l"x 3/16" galvanized bars - subwaygrating.

The pipe r1l fen,'e shal be 2-inch otandard genuine wrought

iron.

The ladder rungs hall be stainless steel.

The intake racks hall be of stainless steel.

The fine Enreen saall be either stainless steel or aluminum.

It. Sluice Gatc';

The sluice gates rjhall be cast iron, bronze -Mounted Rodney Huntor equal. The f'loor stands vIhall have Timk1en bearings. The stemschall be steel -ith th-caded sections of bronze.

5. Concrete

The cement shall 'c a Portltnd ce:ient, meeting all the require-nents of the It tc-t r-',ision A"T -C 150 and clm1l be Type II.

Air cntraf:lng ac ,nt --hall 1,e used. The m-axirium percent of airentrainin7 ch& 1 be 3 porcent by volume.

B-10

• i l'll i l l/ll~~~~~ill.. . .m. . . . . . . . . . . . . . . . . . . . .... .. . .. ..' ' ' - t -,' .7 ." . .' '< ."

oPECIT'1C ATiIO0, FORl

COV:;'TPIJCTI'lG TrjolAGE RE7.ERVOIfl AND FAl

- )!IRE. DISTRICT NO. 3

,,OLcWSr.lT--lR, VFIL ONT

1IITMAN ?z EOVIAYD, INC.

89 Broad St'eetJBortons 14333.

M 1ARCH, 1960

B-9

.1* ' A

LFT- I1i{9 INC I'24

[-NGINI f1S

C .1( N I. 89i~fl. 01 ,L I, L It nN 1" A,,co .zI 6 - 16,3 3

C v.Ii< ,I .W )N

I M P,1 lt LNL PE

March 17, I60

Mr. Reinhold W. ThierneCorrmnisslon of ,later ResourcesWater Consei-vation BoardMontpeller, Vermont

Dear Mr. Thleme:

We are enclosing two sets of plans and

specifications for the proposed dam for Colchester

Fire District No. 3. The District Is sending you the

application and copy of letter to the Selectmen.

Yours very truly,

WHITMAN & HOWARD, INC.

By "

c/c Mr. A. Grant Kennedy, ChairmanPrudentlal Committee , I ,N G

Fire Distric' No. 3 , - -

Colchester, Vermont ,A CT.j , 7 3 - 19. c.- . "-' ',

01, ,) T);,, , , Z

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SIO AND, INC.SI869 INC 'I24

F___NG1N1_EPS..... ,,, , .S eet, R o,,. 514 /3&s:'on /0, l/,,.facholu s

PAUL F NCIAROcc." IN U 'OAgtD

"", C cc r.OG£ PC ON HAncock 6-1632" C R W, C[PSON

L M P,7|NODkEI-H

Ap'i-l 28, 1960U

Mr. Reinhold W. ThiemeCommissioner of Water ResourcesWater Conservation BoardMontpelier, Vei'mont

Dear 1r. Thieme:

We are enclosing two sets of revi:,ed Plans for theproposed Darn for Fire District No. 3, Colchester, Vermont.

1. Detailed surveys since the snr.w has meltedindicate the ledge to be higher and the crest of the Damhas been raised to 383.0. No change was made in the typical

K section of the Dam. The higher elevation also will eliminatesome low areas in the Reservoir.

2. The Intake Structure was moved to the North endof the Dam to take advantage of a ledge projection and thuseliminate a foot-bridge and pier.U

Yours very truly,

WHITMAN & HOWARD, INC.

By /'- " ..-

T " -----

' '-

c/c Mr. Daniel HealeyColchester, Vermont t 3r S"

J 10

"" " "B-6

" . % %'~~~~~~.."..' % ".. .... ....,-- i..,.o.-......- .. . . , . . . ..

State of Verniiont

AGENCY OF ENVIRONMENTAL CONSERVATION

MARTIN L. JOlINSON, Sccrctary

Deparlment of Fish and Came Montp!ier, Vermont 05602Department of ForUsts and Parks

* Department of Water Re'ources DEPARTMENT OF WATER RESOURCES.- En' ironmental Board- " Divi sion of Enironrnontal Protection August 29, 1974

Di sion of Recreation*Diwicion of Planning

Natural Resources Consenation Council

COLCHESTER PONDTOWN OF COLCHESTERCHITTENDEN COUNTY

Colchester Pond is located in the Eastern corner ofthe town. Access to the pond area is by town highways 15,17, and.23, the latter of which is also called Lost NationRoad and leads to the East shore of the pond and the landsthe Wheelocks have offered the state.

* The original pond surface area was 97 acres. In 1965* • a dam was built on Pond Brook about 2000 feet downstream of

the natural outlet of the pond. This dam raised the pond* Wlevel approximately 17 feet to elevation 383 and increased

I the surface area to 182 acres. The date of the Water Re-sources Board order of permission was 7/15/60.

The Pond has a maximum length of 5500 feet, a maximumwidth of 2000 feet, a mean width of 1400 feet, and a shore-

*I line length of 14,500 feet.

The watershed area is 1.8 square miles and the drainage" area to surface area ratio is 6.3. The area is about 70%

* " forests.

The dam is a concrete structure, 42 feet long, 17 feethigh with an Ogee crest spillway 34 feet in length. Thedam was constructed on exposed ledge formations and from asite visit on 8/27/74 it appears to be very good condition.

The pond and 25 feet back from the shoreline is ownedby Colchester Fire District #3. The surrounding acreage isowned by seven individuals, with Wheelocks owning about one

-" third of this.

The pond is no longer used as a water supply as the areais now served by the Champlain Water District. Public accessSr is not provided, however, according to Mrs. Wheelock, there is

some unauthorized recreational use of the pond.

Colchester pond is a Class "A" water.

LRF/stt Enclosure

B-5

""" " " :"'-'" ""'"'""-"- "•'" -" -.. . . . . . .. . . . . . .. -.-.-. . . -..--.... .-.. ". . .- --... .,....... .... . ...- ". '-, L_ '_'. -"

• .. " " . -. , .'. '- " .'

VERR!-ONT D'IPARTP1T OF "ATEP. R.SOURCES

am IT.:1FOR'"ATIONJ S"ET

Name of r)am C,/ (*f. . Town___,. _______/

Owner C , /1 e f- ,," , , 4. Nam e of Stream n , ,

Address C./c.r, _s4er /j n, Classification_ _ _

U.S.,.S. Coordinates: Lat. Lonc. 7,0 2'- J/M

U.S.G.S. Man C:. . .C , Aerial Dhotos J/- ?, -2a/ ea2

U.S.C.S. Elev. 9 Snillway

Total Length of nam 4 "& Crest 1-,idth of Fhoeraency F.Snil iwavZ3

Width of Ton 21 17- Taximum Heicht__ _

Snillway Capacity: Principal F, merqencv

Pond Area / Ai n ( eiL_ Drainae Area_ / . M,

Pond Volume: , orrnal 'Tater Level26koA 11 Desicin IHich Water Level

1aximum ;Water Depth: Normal 'later Level /5- DesHian !ih WaterLevel

* Storage Ilefore Emerqencv Spillwav is Used_ J

- Use of Reservoir rV/4 -- c ' L,

Description of Darn: C, 1 3 ,-4 e- - *' "

. Description of Spillway(s): 0

Designed by _ , year Puilt i___"__",

11carinr Dot- .. ./_jyo ('rrler r)ate *fL/,, .. /9 O

Additional RTemarks:

**. B-4

SUMMARY OF DATA AND CORRESPONDENCE

DATE TO FROM SUBJECT PAGE

File Vermont Dept. of Water B-4Resources InformationSheet

n 8-29-74 Dept. of Water Description of Pond and B-5Resources Dam

4-28-60 R.W. Thieme Whitman & Transmittal letter - B-6Howard revised plans

3-17-60 R.W. Thieme Whitman & Transmittal letter - B-8Howard revised plans and

specs

3-60 Whitman & Specifications B-9Howard

3-60 Whitman & Design Plans - B-12Howard Reduced in size

I

U

.!.*

.- ............................ *~* . ** - * .- ... p£ *- -... , . . _#. .. . . . .......-.-..... .. ,

COLCHESTER POND DAM

EXISTING PLANS

On file with Vermont Department of Water Resources:

. 1. Details of Dam - Pond Brook ReservoirFire District No. 3 - Colchester, VermontWhitman and Howard, Inc., Engineers - Boston, Mass.March, 1960 - Sheets 1 and 2Marked - "Revised, see sheets of April 29, 1960

2. Proposed Water SystemFire District No. 3 - Colchester, VermontScale 1" = 2000' - November, 1959Whitman and Howard, Inc., Engineers - Boston, Mass.

On file with Fire District No. 3:r

3. Details of Dam - Pond Brook ReservoirFire District No. 3 - Colchester, VermontWhitman and Howard, Inc., Engineers - Boston, Mass.March, 1960 - revised sheets 1 and 2

B-2

. .. . ..

(1) operating Platform

* (2) Seepage at Right Abutment

. . ... ... .. ... . . A

U.S.ARMY ENGINEER DIV. NEW ENGLAND VoT ese Pond0D6CORPS OF ENGrNEERS NATIONAL PROGRAM OF V O$

*WALTHAM, MASSACHUSETTS INSPECTION OF Col chester, Verront

* ~JAMES W. SEWALL COMPANY NOt~NI~D DM a , 1CONSULTANTS C- 2

* OLD TOWN, MAINE I__________________

(3) Bridge Abutment DirectlyUpstream of Left Abutment

(4) Spillway Crest and Gate Structure, WithRoadway Bridge Abutments at Right

U.SARMY ENGINEER DIV, NEW ENGLAND Colchester Pond Dam*CORPS OF ENGINEERS NATIONAL PROGRAM OF VT 00056

*WALTHAM, MASSA CH U SETTSCocetrVrmn

* JAMES W. SEWALL COMPANY IMayC O OFC 6he, r8onCONSULTANTS NON-FED. DAMSMa6,98

OLD TOWN, MAINE C-3______________

(5) Downstream Face of Concrete (6) Spillway and Gate StructureOgee Spillway

- U.S.ARMY ENGINEER DIV, NEW ENGLAND Colchester Pond Dam*CORPS OF EN~GINEERS NATIONAL PROGRAM OF VT 00056

*WALTHAM, MASSACHUSETTS Clhse emnINSPECTION OFCocstr VemnJAMES W. SEWALL COMPANY NON-FED. DAMS may 6, 1980r CONSULTANTS

* OL01 TOWN, MAINE C-4

(7 plwyCetwt rde(8 1 o ee ri tLf

Abumen n Lef Bakron of Splla Bas

A buten in LeftL Backgroun of-FD DAMSMay B ,ase 8

CONSULTANTS C-5OLO TOWN, MAINE __________________

(9) Overview of Reservoir and Downstream Area

(10) Downstream Channel Immediately Below Dam

U.SARMY ENGINEER DIV, NEW ENGLAND Colchester Pond Dam* CORPS OF ENGINEERS NTOA PRG MOF VT 0005)6

WALHA, ASSCHSEISINSPECTION OF Colchester, Vermont

JAMES W. SEWALL COMPANY NON-FED. DAMS -May 6, 1980* - CONSULTANTS

OLD TOWN, MAINE c-6

(11) Culvert Under Central VermontRail road Embankment

(12) Culvcrt Under Town Road, One Mile Downstream of Dam

U.S.ARMY ENGINEER DIV, NEW ENGLAND Colchester__ Pond DamCORP OF ~3INERS ATIONAL PROGRAM OF VT 00056 ___

WALTHAM, M.SSACHU$ETTS INSPECTION OF czl-Jhsier, Vermont

JAMES W. SEWAL.L COMPANY NON-FED. DAMS May 6, 1980OLD TOWN, M.AINE __________C-

.....................~..............................

APPENDIX D

HYDRAULIC/HYDROLOGIC COMPUTATIONS

I

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. " CCHE:STER'POND DAMJ /

AREA.

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EUSGS QUADRANGES

•.'' -- ;':ESSEX CEN'IIER, VT 1948,, ,- ,(PHOTO REVISED

1972)

"".:COLCHESTER, VT. 1948

. (PHOTO REVISLD 1972) .

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Civil and Sanitary Engineer3 Sheet of

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Civil and Sanitary Engineers Sheet of

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W..W

AkXDTM PROBABLE LOWS

BASED ON TW-ICE THE

STAND RD PROJECT FLOOD

(Flat and Coastal Areas)

River SPF tLA.

Csq. cfsls . mi.)River ~(cfs) (sq. mi.) (fls.m.

1. Pavtuxet River 19,000 200 190

2. MIIi River (R.I.) 8,500 34 500

S . Peters River (R.I.) 3,200 13 490

4. Kettle Brook 8,000 30 530

5. Sudbury River. 11,700 86 270

6. Indian Brook (Hopk.) 1,000 5.9 340

7. Charles River. 6,000 184 65

8.. Blackstone River. 43,000 416 200

9. Quinebaug River 55,000 331 330

* .

D-20.

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- .- XIMJh PROBABLE FLOOD INFLOWS

NED RESERVOIRS

Project .D.A.

- . (cfs) (sq. mi.) cfs/sq. mi.

1. Hall Meadow Brook 26,600 17.2 1,546

2. East Branch 15,500 9.25 1,675

3. Thomaston 158,000 97.2 1,625

4. Northfield Brook 9,000 5.7 - 1,580

5. Black Rock 35,000 20.4 1,715

6. Hancock Brook 20,700 12.0 1,725

7. Hop Brook 26,400 16.4 1,610

8. Tully 47,000 50.0 940

9. Barre Falls 61,000 55.0 1,109

10. Conant Brcok 11,900 7.8 1,525

. 11. Knightville 160,000 162.0 987

12. Littleville 98,000 52.3 1,870

13. Colebrook River 165,000 118.0 1,400

14. Mad River 30,000 18.2 1,650

15. Sucker Brook 6,500 3.43 1,895

16. Union Village 110,000 126.0 873

17. North Hartland 199,000 220.0 90418. North Springfield 157,000 158.0 994

19. Ball Mountain 190,000 172.0 1,105

20. Townshend 228,000 106.0(278 total) 820

21. Surry Mountain 63,000 100.0 630

22. Otter Brook 45,000 47.0 957

23. Birch Hill 88,500 175.0 50524. East Brimfield 73,900 67.5 .1,095

25. Westville 38,400 99.5(32 net) 1,200

26. West Thompson 85,000 173.5(74 net) 1,15027. Hodges Village 35,600 31.1 1,145

' 28. Buffumville 36,500 26.5- 1,37729. Mansfield Hollow 125,000 159.0 . 78630. West Hill 26,000 28.0 928

31. Franklin Falls 210,000 1000.0 210

32. Black.ater 66,500 128.0 520* 33.. Hopkinton .. 135,000 426.0 316

34. Everett 68,000 64.0 1,062

35. MacDowell • 36,300 44.0 825

D-19

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.--

PRELIMINARY GUIDANCE

FOR EST114ATING

""AXIYUM PROBABLE DISCHARGES

* IN

PILASE I DAM SAFETY

* IVESTIGATIONS "

New England DivisionCorps of Engineers

March 1978

lo

Do

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Civil and Sanitary Engineers Sheet of

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JAMES W. SEWALL COMPANY, OLD TOWN, MIINE

Civil and Sanitary Engineers Sheet of

Subject !'"r-' ' -

I ,..S.... ' , :. -'t 'Z " ,i, . .. ... ': Job No. z. .. .Computation .... . .. i " . , " o. ..

Computed by ?2/ Checked by _ ' , Date - ,'7.

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ESTIMATI1N G EFFECT OF SURCHARGE STORAGE

0O 1 X I NX U [A PIZO BA BIE DI SC HA RGES

JNLO

QQ

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STEP 1: Determine Peak Inflow (Qpi) f romr GuideK . Curves.

*STEP. 2.: a. D e terrm in e Surcharge Height* To- P a'ss

6. Determine Volume of Surcha'rge(STO D. In Inches of Runoff.

c. Maximum Probable Flood Runoff In- N e* England equals App rox. 19"', Therefore

* Qp2 pi x - STORJ)

19

* STEP 3: a. Determine Surcharge Height a nd**** 'STO R2' To Pass ''Qp2

bAverage 'STORi" and "'STOR2z" dnd

Deiermine Average Surcharge and

*Resuling P e ak O Ut flo0W Q p 3

D-22

"RULE OF THUMB" GUIDANCE FOR ESTIMATING• DOWNSTREAM DAM FAILURE HYDROGRAPHS

or - .- . -."

'S' S -T , - -: .G " : . . . , . ". .

T3

*STEP I I DETERMINE OR ESTIMATE RESERVOIR STORAGE (5) IN. AC-FT AT TIME OF FAILURE.

STEP 2: DETERIlNE PEAK FAILURE OUTFLOW p)o-' 37 b

b BREACH WIDTH - SUGGEST VALUE NOT GREATER THAN 40% OF DAM*LENGTH ACROSS RIVER AT MID HEIGHT.

Yo I OTAL*HEIGHT FROM RIVER BED TO POOL LEVEL AT FAILURE.

STEP 3 USING USGS TOPO OR OTHER DATA, DEVELOP REPRESENTATIVE STAGE-DISCHAGERATING FOR SELECTED DOWNSTRCAM RIVER REACH.

*STEP 4: ISTIMATE REACH OUTFLOW *(Qp2) VSING FOLLOWING ITERATION.A. APPLY QjTO STAGE RATING, DETERMINE STAGE AND ACCOPMANYING

VOLUME (VI) IN REACH IN -AC-FT. (NOTE:. IF VI EXCEEDS 1/2 OF S,

* . SELECT. SHORTER REACH.)

B. DETERMINE TRIAL 0 p27

p2 (TRIAL) = Qps I-~L"-C. COMPUTE V2 USING (TRIAL).

S D. AVERAGE V1 AND V2 AND COMPUTE Q 2

0 0P 2 = QP1( ~

STEP 5:. FOR SUCCEEDING REACHES REPEAT STEPS 3 A 4..

APRIL 1978

D-23

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I

APPENDIX E

INFORMATION AS CONTAINED IN

THE NATIONAL INVENTORY OF DAMSIK

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