AD-Ri44 747 NATIONAL PROGRAM FOR INSPECTION OF NON-FEDERAL DAMS i/1IRIGHTS POND DAM (CT..(U) CORPS OF ENGINEERS WALTHAM MANEW ENGLAND DIY AUG 81

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U- CONNECTICUT RIVER BASIN

WESTBROOK, CONNECTICUT

WRIGHTS POND DAM

CT 00393 --4

PHASE 1 INSPECTION REPORT __

NATIONAL DAM INSPECTION PROGRAM

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LAUG 2 7 1984L4-'

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DEPARTMENT OF THE ARMYNEW ENGLAND DIVISION, CORPS OF ENGINEERS

WALTHAM, MASSDISTRIBIMON ISTA 'fIAUGUST, 1981 Approved for p.bh:- a.o;

Distribution J.II,2,-

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*It ASSE7r

SECURITY CLASSIFICATION OF THIS PAGE (When Data Enteed)

REPORT DOCUMENTATION PAGE BEFORE COMPLETING FR

1. REPORT NUMBER A OA CESO E4 IPI EN T'S CAT ALOG NUMBER

CT 00393 (1'V #""Y' 74. TITLE (andSubtldte) S. TYPE OF REPORT & PERIOD COVERED

Wrights Pond Dam INSPECTION REPORT

NATIONAL PROGRAM FOR INSPECT ION OF NON-FEDERAL 6. PERFORMING ORG. REPORT NUMBER

DlAMS7. AUTHOR(a) 8. CONTRACT OR GRANT NUMMERt(s)

U.S. ARMY CORPS OF ENGINEERSNEW ENGLAND DIVISION

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASKCAREA & WORK UNIT NUNSERS

11. CONTROLLING OFFICE NAME AND ADORESS 12. RSPORT OATS

DEPT. OF THE ARMY, CORPS OF ENGINEERS August 1981NEW ENGLAND DIVISION, NEDED IS. NUMBER OP PAGES

424 TRAPELO ROAD, WALTHAM, MA. 02254 7014. MONITORING AGENCY NAME A ADDRESSI different tem Cani~*mifti116) IS. SECURITY CLASS. (01 thl. raporf)

UNCLASSIFIEDIto. DIECLASSIFICATIONIDOWNGRADING

SCHEfDU LE

IS. DISTRIBUTION STATEMENT (of Ohio Report)

APPROVAL FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

17. DISTRIEUTION STATEMENT (of the. abotroct entered in 080611 20, it diflesm* ht e wa

It. 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.

It. KEY WORDS (Cmmuanmae On Parolee aide 01f nacegamy byd I.IE it'he"Atemo.,)

DAMS, INSPECTION, DAM SAFETY,Connecticut River Basin

Westbrook, Connecticut

20. A ESTRftACT (Coninume an U*vwoo aide 0I n~co*GManmd 1111001#11 6F block nmberv)

Wrights Pond Dam is an earth embankment with a masonry and concrete spillway. Itis approximately 292 feet long and 12 feet high with a top width of 9 feet. Based

on visual inspection and past operational performance, the dam is judged to be

in FAIR condition. The dam is classified as SMALL in size and a HIGH hazard pot-

ential structure. The test flood for this dam is the Probable Maximum Flood.

DD I F0R17 1473 E0ITIOM OF I NOV 65 IS OBSOLCIE

DEPARTMENT OF THE ARMY 0NEW ENGLAND DIVISION. CORPS OF ENGINEERS

424 TRAPELO ROAD

WALTHAM. MASSACHUSETTS 02254

REPLv T,0

LATTE\IC,,% G;7! AUG~ s3~NEDED

Honorable William A. O'NeillGovernor of the State of ConnecticutState CapitolHartford, Connecticut 06115

S

Dear Governor O'Neill:

Inclosed is a copy of the Wrights Pond Dam (CT-00393) Phase IInspection Report, prepared under the National Program for Inspectionof Non-Federal Dams. The report is based upon a visual inspection, areview of past performance, and a preliminary hydrological analysis.

The preliminary hydrologic analysis indicated that the spillwaycapacity for the Wrights Pond Dam would likely be exceeded by floodsgreater than 12 percent of the Probable Maximum Flood (PMF). Ourscreening criteria specifies that a dam classified as high hazard with - 4

a spillway capacity insufficient to discharge fifty percent of the PMFbe judged as having a seriously inadequate spillway. As a result,this dam is assessed as unsafe, non-emergency, until more detailedstudies prove otherwise or corrective measures are completed.

The term "unsafe" applied to a dam because of an inadequate spillwaydoes not indicate the same degree of emergency as that term would if 4 1

applied because of structural deficiency. It does indicate, however,that a severe storm may cause overtopping and possible failure of thedam, with significant damage and potential loss of life downstream.

We recommend that within twelve months from the date of this reportthe owner of the dam engage the services of a qualified registeredengineer to determine further the potential of overtopping the dam andthe need for and the means to increase project discharge capacity.Based on this determination, appropriate remedial mitigating measuresshould be designed and completed within 24 months of this date ofnotification. In the interim a detailed emergency operation plan andwarning system should be promptly developed and round-the-clocksurveillance should be provided during periods of heavy precipitationor high project discharge.

L

AUG 2!5 -.

NEDEDHonorable William A. O'Neill

I approve the report and support the findings and recommendationsdescribed in Section 7, with qualifications as noted above. I requestthat you keep me informed of the actions taken to implement these

w recommendations since this follow-up is an important part of theprogram.

Copies of this report have been forwarded to the Department of Environ-mental Protection and to the owner, Pine Lake Club, Inc., Ansonia, CT.Copies will be available to the public in thirty days.

I wish to thank you and the Department of Environmental Protection foryour cooperation in this program.

Sincerely,

C. E. EDGAR, IIIColonel, Corps of EngineersCommander and Division Engineer

2L

' Accessior,NTIS QRA&DTIC TABUnannounced [Justificatio

Distribution/S- Avallability Codes

* Avail and/or CONNECTICUT RIVER BASINDist Special

, WWESTBROOK, CONNECTICUT

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WRIGHTS POND DAM

CT 00393

PHASE 1 INSPECTION REPORT

LNATIONAL DAM INSPECTION PROGRAM

DTICT 0ELECTE

AUG 2 7 1984

App:ovOd ,,or ,ub:i, *, .. D

NATIONAL DAN INSPECTION PROGRAM

* PHASE I - INSPECTION REPORT

Identification No.: CT 00393

* Name of Dam: Wrights Pond Dam

Town: Wes tbrook

County and State: Middlesex, Connecticut

Stream: Falls River •

Date of Inspection: June 5, 1981

BRIEF ASSESSMENT

Wrights Pond Dam (also known as Pine Lake Dam) is an earthembankment with a masonry and concrete spillway. A vertical stonemasonry wall forms the downstream face of the entire dam. It isapproximately 292 feet long and 12 feet high with a top width of 9feet. The dam was probably built around 1890 with improvementsmade in 1972. It is presently owned by the Pine Lake Club, Inc. Sand its purpose is and has always been recreational andaesthetics.

Based on the visual inspection and past operational performance,the dam is judged to be in FAIR condition. Seepage, brush, looseand missing stones were noted on the spillway. Brush and trees •are growing on the embankments. Seepage was noted along thedownstream toe of the eastern embankment. Riprap along theupstream face of the embankments is in need of repair.

The dam is classified as SMALL in size and a HIGH hazard potentialstructure in accordance with the Recommended Guidelines for SafetyInspection of Dams, by the Corps of Engineers. The impoundmentstorage at the top of the dam is 200 ac.-ft. and the maximumheight of the dam is 12 feet. Failure of the dam could result inthe loss of more than a few lives and damage to eleven houses.The depth of inundation at these homes would be 0 to 1 feet beforeand 1 to 2 feet after dam failure. _S

The test flood for this dam is 1/2 the Probable Maximum Flood(PMF). The test flood has an inflow equal to 4220 cfs and anoutflow discharge equal to 4160 cfs with a stillwater elevation of131.4 which will overtop the dam by 2.1 feet.

,, :. ,. ...

The maximum outflow capacity of the spillway with the water sur-face at the top of dam is 1060 cfs which is 25 percent of the testflood outflow.

It is recommended that the following actions be carried out by aqualified registered engineer. Conduct a detailed hydrologic/-hydraulic investigation to further assess the potential for over-topping the dam and the need for increasing the height of the damor increasing the discharge capacity or a combination of both.Design measures for the removal of the trees and their respectiveroot systems on the embankments and within 30 feet of the toe andbackfilling with suitable compacted material; for the removal ofvegetation from and the repointing of the joints on the downstreamface of the spillway and embankments; and for the replacement ofmissing stones on the spillway. Investigate and monitor the see-page along the downstream toe of the eastern embankment. Designrepairs to the riprap along the upstream face of the embankments.Inspect the downstream face of the spillway when water is notflowing over the spillway and make any required recommendations.

V The following remedial measures should be taken by the owner: Theremoval of brush from the embankments and within 30 feet of theembankments, the placing of a permanent walkway on the frameworkfrom the spillway to the valve stem, insure the operability of theoutlet works on an annual basis and development of a downstreamwarning plan and an annual inspection program.

Km Recommendations and remedial measures that should be implementedwithin one year of receipt of this Phase I Inspection Report arefurther described in Section 7.

a iJAMES P. PURCELL ASSOCIATES, INC.

Sudhir A. Shah, P.E. T,Director of EngineeringConnecticut P.E. No. 8012 No. d012 *.4,,

4** A, /, )#SE ' s

. . ION. 0

This Fhs.. I Inspection Report on Wrights Pond Dam (CT-00393)

has been woweved by the undersigned Review Board mebers. to outoplato. the reported fiuding$, couclusions, and recomumdatious areconisteat with the Itecomended Guidelines for Safety Iuspection ofLaw,. and vith good engineering Judgment end practice, and is herebysubmtted for approval.

CARNEY M. TERZIA, MEMBERDesign BranchEngineering Division

JOSE', FINEGAN, MEM BER

Wate r\ontrol Branct'-JEngineering Division

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ARAMAST AIrTESIAN, CAIRNAN

Geotechnical Engineering BranchEngineering Division

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A113.OYAL &CoOgDEDs

Chief. °agimseri Division

Fhooh-lNfN ILLJ~

PREFACEU

This report is prepared under guidance contained in the Recommended Guidelines forSafety Inspection of Dams, for Phase I Investigations. Copies of these guidelines maybe obtained from the Office of Chief of Engineers, Washington, D.C. 20314. The pur-pose of a Phase I Investigation is to identify expeditiously those dams which may pose

u hazards to human life or property. The assessment of the general condition of the damis based upon available data and visual inspections. Detailed investigation, andanalyses involving topographic mapping, subsurface investigations, testing, anddetailed computational evaluations are beyond the scope of a Phase I Investigation.However, the investigation is intended to identify any need for such studies.

In reviewing this report, it should be realized that the reported condition of the dam isbased on observations of field conditions at the time of inspection along with dataavailable to the inspection team. In cases where the reservoir was lowered or drainedprior to inspection, such action, while improving the stability and safety of the dam,removes the normal load on the structure and may obscure certain conditions whichmight otherwise be detectable if inspected under the normal operating environment ofthe structure.

It is important to note that the condition of a dam depends on numerous and cons-tantly changing internal and external conditions, and is evolutionary in nature. It wouldbe incorrect to assume that the present condition of the dam will continue to representthe condition of the dam at some point in the future. Only through continued care andinspection can there by any chance that unsafe conditions be detected.

Phase I inspections are not intended to provide detailed hydrologic and hydraulicanalyses. In accordance with the established Guidelines, the spillway test flood isbased on the estimated "Probable Maximum Flood" for the region (greatest reasona-bly possible storm runoff), or fractions thereof. Because of the magnitude and rarity ofsuch a storm event, a finding that a spillway will not pass the test flood should not beInterpreted as necessarily posing a highly inadequate condition. The test flood pro-vides a measure of relative need for more detailed hydrologic and hydraulic studies,considering the size of the dam, its general condition and downstream damage poten-tial.

The Phase I Investigation does not include an assessment of the need for fences.gates, no-trespassing signs, repairs to existing fences and railings and other itemswhich may be needed to minimize trespass and provide greater security for the facilityand safety to the public. An evaluation of the project for compliance with OSHA rulesand regulations is also excluded.

TABLE OF CONTENTS

I .

Section Page

- Letter of Transmittal

Brief Assessment

Review Board Page

Preface i

Table of Contents ii-iv

Overview Photo v

Location of Map vi

REPORT

1. Project Information

1.1 General 1

a. Authorityb. Purpose

1.2 Description of Project 1

a. Locationb. Description of Dam and Appurtenancesc. Size Classificationd. Hazard Classificatione. Ownershipf. Operatorg. Purposeh. Design and Construction Historyi. Normal Operational Procedure

1.3 Pertinent Data 4

2. Engineering Data

2.1 Design 8

22.2 Construction 8

ii

S

TABLE OF CONTENTS (CONTINUED)U

Section Page

2.3 Operation 8

2.4 Evaluation 8

a. Availabilityb. Adequacyc. Validity

3. Visual Inspection

3.1 Findings 9

a. Generalb. Damc. Appurtenant Structuresd. Reservoir Areae. Downstream Channel

3.2 Evaluation 11

4. Operational and Naintenance Procedures

4.1 Operational Procedures 13

a. General

b. Description of Any Warning System in Effect

4.2 Maintenance Procedures 13

a. Generalb. Operating Facilities

4.3 Evaluation 13

5. Evaluation of Hydraulic/Hydrologic Features

5.1 General 14

5.2 Design Data 14

5.3 Experience Data 14

5.4 Test Flood Analysis 14

iii

TABLE OF CONTENTS (CONTINUED)

Section Page

5.5 Dam Failure Analysis 15U

6. Evaluation of Structural Stability

6.1 Visual Observations 17

6.2 Design and Construction 17

6.3 Post-Construction Changes 17

6.4 Seismic Stability 17

7. Assessment, Recomendations and Remedian Measures

7.1 Dam Assessment 18

a. Conditionb. Adequacy of Informationc. Urgency

7.2 Recommendations 18

7.3 Remedian Measures 19

g a. Operation and Maintenance Procedures

7.4 Alternatives 19

iv

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NATIONAL DAM INSPECTION PROGRAM

PHASE I - INSPECTION REPORT

MAME OF DAM: WRIGHTS POND DAM

SECTION 1

3 PROJECT INFORMATION 0

1.1 General

a. Authority:

Public Law 92-367, August 8, 1972, authorized theSecretary of the Army through the Corps of Engineers toinitiate a national program of dam inspections throughoutthe United States. The New England Division of the Corpsof Engineers has been assigned the responsibility ofsupervising the inspection of dams within the New England 0Region. James P. Purcell Associates, Inc. has beenretained by the New England Division to inspect andreport on selected dams in the State of Connecticut.Authorization and notice to proceed was issued to JamesP. Purcell Associates, Inc., under a letter from WilliamH. Hodgson, Jr., Colonel, Corps of Engineers. ContractNo. DACW33-81-C-0009 has been assigned by the Corps ofEngineers for this work.

b. Purpose:

1. Perform technical inspection and evaluation ofnon-federal dams to identify conditions whichthreaten the public safety and thus permit correctionin a timely manner by non-federal interests.

2. Encourage and prepare the States to initiate quickly,effective dam safety programs for non-federal dams.

3. To update, verify and complete the National Inventory

of Dams.

1.2 Description of Project

a. Location:

The Wrights Pond Dam (also known as the Pine Lake Dam) islocated in the Town of Westbrook approximately 2 milessouthwest of the village of Ivorytown, Connecticut (See

1

Plate No. 1). This dam impounds water from Falls Riverand is located approximately six miles upstream of the

U confluence with the Connecticut River.

Wrights Pond is situated in a northwest/southeast direc-tion with the dam at the southeast end. The dam islocated at latitude 410-191-49.6" and longitude720-281-09.5 " .

* All elevations used in this report are based on the 0National Geodetic Vertical Datum (NGVD).

b. Description of Dan and Appurtenances:

The dam consists of a 192 foot long earth embankment with 0a masonry wall along the downstream face. This embankmentis 12 feet high at the spillway end and tapers uniform-ally to zero at the abutment end. It is nine feet wideat the top with a vertical downstream face and a slope ofapproximately 1 1/2 horizontal to 1 vertical along theupstream face.

The upstream face of the west embankment is riprappedwith 1-2 inch stone at the normal pool elevation. Theupstream face of the east embankment is protected withlarge (3-5 foot) stones. This protection extends forapproximately 55 feet east of the spillway.

The 100 foot long masonry and concrete spillway is lo-cated near the western end of the dam. It is 10 feethigh and 11 feet wide with concrete wingwalls at each

* end.

The outlet works consist of a single 18 inch pipe throughthe center of the spillway section. The invert of theinlet of the 18 inch pipe is 8.5 feet below the spillwaycrest. The outlet opening is at the base of the spill-way. Flow into the outlet is regulated by a valve whichis operated from a valve stem located in the pond 10 feetupstream of the spillway.

c. Size Classification:

The size classification of this dam is SMALL as per thecriteria set forth in the Recommended Guidelines forSafety Inspection of Dams, by the Corps of Engineers.The impoundment storage at the top of the dam is 200ac.-ft. (within the range of 50 to 1000 ac.-ft.) and themaximum height of the dam is 12 feet (range of 25 to 40feet). This size classification is based on the storagecriteria.

2

K%d. Hazard Classification:

The hazard classification of this dam is HIGH as per thecriteria set forth in the Recommended Guidelines forSafety Inspections of Dams, by the Corps of Engineers.The dam is located upstream of eleven houses where fail-ure discharge could cause the loss of more than a fewlives. The estimated water depth due to the assumed damfailure may range from 8 feet at the dam to 1 foot, 1500

* feet downstream at Pond Hill Road. The depth of inunda-tion at the homes would range from 0 to 1 foot before andrange from I to 2 feet after dam failure. The homes areestimated to range from approximately 0 to 2 feet abovethe normal brook level.

e. Ownership:

Wrights Pond Dam is presently owned by the Pine LakeClub, Inc., c/o Mr. David A. Einbinder, Trustee, 497 MainStreet, Ansonia, CT 06401. Telephone (203) 734-9246.

f. Operator: 0

The Town of Westbrook has been given authority by theowners to operate the outlet works of the dam as it deemsnecessary.

Mr. John Riggio, Foreman 4

Highway DepartmentTown of WestbrookHall of RecordsBoston Post RoadWestbrook, CT 06498Telephone: (203) 399-9723

g. Purpose:

The former and present purpose of the dam is recreation,fishing and aesthetics.

h. Design and Construction History:

Wrights Pond Dam was probably built around 1890. In1972, the spillway was enlarged to twice its originalsize and the spillway wingwalls were added.

i. Normal Operating Procedure:

The outlet valve is normally closed and all flow is dis-charged over the spillway.

3

- - .. - - - - .. I l .

1.3 Pertinent Data

a. Drainage Area:

The Wrights Pond drainage basin is roughly rectangular inshape with a length of 3.8 miles and an average width of1.3 miles resulting in a total drainage area of 5.0square miles (see drainage basin map in Appendix D). Thetopography is generally rolling terrain with elevationsranging from a high of 430 feet to a low of 127.0 at thespillway crest. Stream and basin slopes are moderate,1.5 percent to 10 percent, respectively. This reservoirhas a normal surface of 30 acres which is 0.9 percent ofthe watershed. The upstream Messerschmidt Pond has anormal surface area of 80 acres which is approximately2.5 percent of the watershed. Eighty percent of thewatershed drains into the Messerschmidt Pond.

b. Discharge at Dam Site:

Listed below are calculated discharge values for thespillway and outlet works (18 inch outlet): 0

1. Outlet Works: An 18 inch pipe with an intake atelevation 118.5 and a discharge capacity of 27 cfsat elevation 129.3.

2. Maximum known discharge at dam site: Unknown. There i

are no specific discharge records available for thisdam.

3. Ungated spillway capacity at top of dam: 1060 cfs at* elevation 129.3.

4. Ungated spillway capacity at test flood elevation:2850 cfs at elevation 131.4.

5. Gated spillway capacity at normal pool elevation:N/A

6. Gated spillway capacity at test flood elevation: N/A

7. Total spillway capacity at test flood elevation:2850 cfs at elevation 131.4.

8. Total project discharge at top of dam: 1090 cfs atelevation 129.3.

9. Total project discharge at test flood elevation:4160 cfs at elevation 131.4.

4

c. Elevation (Feet Above NGVD)

1. Stream bed at toe of dam 117.3

2. Bottom of cutoff Unknown

3. Maximum tailwater Unknown

* 4. Normal pool 127.0

5. Full flood control pool N/A

6. Spillway crest 127.0

7. Design surcharge (Original Design) Unknown

8. Top of dam 129.3 (ExistingEmbankment)130.5 (1972 Design)

9. Test flood level 131.4 0

d. Reservoir (Length in Feet):

1. Normal pool 3400

&2. Flood control pool N/A 5

3. Spillway crest pool 3400

4. Top of dam 3500

* 5. Test flood pool 3600

e. Storage (acre-feet):

1. Normal pool 131

2. Flood control pool N/A

3. Spillway crest pool 131

4. Top of dam 200

5. Test flood pool 264 I

f. Reservoir Surface (acres):

1. Normal pool 30

2. Flood control pool N/A I

5

T I-

3. Spillway crest 30

4. Test flood pool 30

5. Top of dam 30

g. Dan:

1. Type Earth embankmentwith vertical stonemasonry wall alongdownstream face.

2. Length 292 feet

3. Height 12.0 feet

4. Top width 9.0 feet

5. Side slopes Upstream - l.5H:lVDownstream - Verti-cal Stone Wall

6. Zoning tnknown

7. Impervious core Unknown

8. Cutoff Unknown

9. Grout curtain Unknown

10. Other

h. Diversion and Regulating Tunnel: N/A

i. Spillway

1. Type Broad crested over-flow. Concrete andstone masonry.

2. Length of weir 100.0 feet

3. Crest elevation 127.0

4. Gates None

5. U/S Channel Natural bed

6. D/S Channel Overgrown graveland stone channel

6

7. General

j. Regulating Outlets:

Refer to Paragraph 1.2b - "Description of Dam and Appurten-

ances" for description of Outlet Works.

1. Invert and size 18 inch pipe -

118.5 feet

2. Description Unknown

3. Control Mechanism Valve with a handoperated valve stemin center of

spillway section

4. Other

70

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SECTION 2

ENGINEERING DATA

2.1 Design

There are limited available records presenting designinformation for the construction of Wrights Pond Dam. A plansheet showing the 1972 modifications to the dam has beenincluded in Appendix 8 of this report.

2.2 Construction

There are no available records of the original constructionof this dam.

2.3 Operation

No formal records of operation are kept for this dam. 0

2.4 Evaluation

a. Availability:

The information noted above for this facility is avail-able in the files of the Department of EnvironmentalProtection, Water Resources Unit, Dam Safety Engineers,State Office Building, Hartford, Connecticut, and thePine Lake Club, Inc., Ansonia, Connecticut.

b. Adequacy:

The lack of indepth engineering data did not allow adefinitive review. Therefore, the adequacy of this damcould not be assessed from the standpoint of reviewingdesign and construction data alone, but is based primar-ily on the visual inspection, the dam's past performance,and sound engineering judgment.

c. Validity:

The validity of the limited information available couldnot be verified.

8

8

SECTION 3

VISUAL INSPECTION

3.1 Findings

a. General:

The visual inspection of the Wrights Pond Dam was con-ducted on June 5, 1981 and a copy of the visual inspec-tion check list is contained in Appendix A of thisreport.

The following procedure was used:

1. Inspection of the upstream area of the pond which isimpounded by the dam.

2. Visual inspection of the face and top of the dam andspillways for cracks, loose stones, seepage, etc.

3. Inspection of the outlet works and other appurten-ances as to their existence, location, and oper-ability.

4. Review of procedures that could be utilized in theevent of an emergency situation.

5. A check of the downstream area for seepage, piping,boils or other indications of abnormal conditions.The downstream hazard potential in the event of dam _

failure was investigated.

6. Photographs of the general area of the dam and spe-cific items of note were taken and are included inAppendix C of this report.

Before the inspection, the available existing data wasstudied and reviewed.

b. Dam:

1. Crest: The top of the dam to the east of the spill-way is approximately 9 feet wide and extends approx-imately 160 feet to natural ground. This crest eleva-tion is non-uniform and is approximately one footlower than the 1972 design elevation (top of spillwaywingwall). It is vegetated with brush and smalltrees and contains a footpath (Photo C-l). There is

9

erosion of the top of the embankment immediatelybehind the spillway wingwalls. These eroded areasvary in depth up to approximately one half foot. Tothe west of the spillway, the top of the dam extendsapproximately 32 feet and is grassed (Photo C-3). Itis also approximately one foot lower than top of theadjacent spillway wingwall (Photo C-1).

2. Upstream Face: The eastern upstream face is an earthslope at 1.5H:lV and is heavily vegetated with brushand small trees (Photo C-5). Boulder riprap extendsalong the waterline 55 feet east from the spillway.There is some minor erosion near the spillwaywingwall. A good grass cover extends to the water-line at the western end of the dam (Photo C-3). Theriprap at the waterline is showing signs of minorerosion (right side of Photo C-3).

3. Downstream Face: The downstream face of the entiredam is a vertical stone masonry wall (Photo C-6).This wall varies in height from 12 feet at the spill-way to zero at the abutments. No seepage wasobserved on the wall, however, a seepage stream(approximately 5 GPM-clear) was observed flowing fourfeet downstream of the stone wall beginningapproximately 90 feet east of the spillway (See PlanPage B-13). There are rust colored deposits wherethis stream joins the downstream channel. Thisseepage has existed at least since 1970 as indicatedby a state order to repair dams of March, 1970.

c. Appurtenant Structures:

1. Spillway: The spillway is a 100 foot long by 11 footwide stone masonry and concrete structure near thewestern end of the dam. (Photos C-1, C-2). Theeastern half of the spillway is the original spillwayfor the dam. It is constructed of stone masonry witha concrete covering (Photos C-4, C-8). This coveringis spalled but still adequate and there are many miss-ing and loose stones, seepage and brush along thedownstream face (Photos C-8, C-9). Because of flowover the spillway, the rate of seepage between thestones in the downstream face could not bedetermined. No evidence of fines was noted in theseepage. The outlet of the 18 inch pipe is at thebase of this spillway section (Photo C-1l). Aconcrete wingwall was added in 1972 and is in goodcondition (Photo C-4). There is a void under the

10

downstream end of the spillway wingwall apparentlydue to an incomplete concrete pour duringconstruction.

The western half of the spillway was built in 1972and consists of reinforced concrete over earth fillwith the original stone masonry downstream face(Photo C-3). Brush is growing from some of thejoints (Photo C-7) and some large voids were observed

in between the stones (Photo C-11). Water was flowingover this half of the spillway during the inspectionand the existence of seepage could not be determined.The concrete portion of the spillway and wingwall isin good condition (Photo C-3).

2. Outlet Works: An 18 inch pipe extends from a valveapproximately 10 feet upstream of the spillway,through the original spillway section to a squaremasonry opening on the downstream face (Photo C-11).An angle iron framework, in good condition, extendsfrom the spillway to the valve stem (Photo C-10).This valve is usually closed and was last opened in1972 to drain the pond prior to modifying the dam.It is not known if the valve is presently operable.The wrench for opening the valve is kept at the Townof Westbrook's Highway Department.-L

d. Reservoir Area:

The pond is formed by the flooding of a portion of theFalls River Valley. The sides of the forested valleyhave gentle slopes bordering the pond. No unusual geo-

* logic features were noted that could be expected to ad-versely affect the dam or appurtenant structures.

Trespassing on the dam is not permitted.

e. Downstream Channel:

The downstream channel is an overgrown gravel and stonestreambed (Photo C-12). A house is located approxi-mately 300 feet downstream along the west bank of thestream. The basement floor of this house is approxi-mately one foot below the spillway crest elevation.

3.2 Evaluation

Based on visual inspection, the Wrights Pond Dam appears tobe in fair condition overall and there were no major areas ofdistress noted. Specific areas of concern that were noted

are as follows:

11

a. The presence of seepage and brush on the downstream faceof the spillway.

b. Missing and loose stones on the downstream face of thespillway.

c. Brush and trees on the embankments.

d. The irregularity of the top of the embankments and theirbeing one foot lower than their design elevation.

e. Seepage near the downstream face of the eastern embank-ment.

f. Erosion of the riprap along the upstream face of theembankment.

g. The outlet works should be tested for operability.

12

SECTION 4

OPERATIONAL AND MAINTENANCE PROCEDURES

4.1 Operational Proceduresa. General:

The pond is presently used solely for recreation and allflow is discharged over the spillways.

b. Description of Any Warning System in Effect:

No formal emergency or contingency plan is in effect toreduce or minimize downstream damage in emergency situ-ations.

4.2 Maintenance Procedures

a. General:

There is no regular maintenance schedule for this dam.

b. Operating Facilities:

No regular maintenance of the outlet works was reported.

4.3 Evaluation

To insure the safety of the residents downstream, a regularinspection and maintenance program and a formal downstreamwarning plan should be developed and implemented.

13

SECTION 5

EVALUATION OF HYDRHJLIC/HYDROLOGIC FEATURES

5.1 General

The Wrights Pond Dam creates an impoundment with a totalSI storage capacity of 131 ac.-ft. at elevation 127.0, the

spillway crest elevation. Each foot of depth in the reser-voir above the spillway crest can accommodate approximately30 ac.-ft. The spillway is a 100 foot long by 11 foot widebroad crested uncontrolled weir. Eighty percent of thedrainage area drains to the upstream Messerschmidt Pond.Messerschmidt Pond may have an effect on the flows intoWrights Pond depending on conditions in Messerschmidt Pondand of its outlet works. Stream and basin slopes aremoderate, 1.5 percent and 10 percent, respectively.

• 5.2 Design Data

a. No specific design data is available for this watershedor the structures of the Wrights Pond Dam. In lieu ofexisting design information, USGS topographic maps (scale1"-20001) were utilized to develop hydrologic parameterssuch as drainage area, basin length, time ofconcentration, and other runoff characteristics.Elevation-storage relations for the reservoir were approx-imated. Reservoir surface area and surcharge storagewere computed using the USGS maps. Some of the pertinenthydraulic design data was obtained and/or confirmed byactual field measurements at the time of visualinspection.

b. Outflow values (routing procedures) amd dam overtoppinganalysis were computed in accordance with the guidelinesdeveloped by the Corps of Engineers. Judgment was usedin calculating final values outlined in this report,which are quite approximate and should not be considereda substitute for actual detailed analysis.

5.3 Experience Data

Historical data for recorded discharges is not available forthis dam.

5.4 Test Flood Analysis

Recommended Guidelines for the Safety Inspection of Dams bythe Corps of Engineers were used for the selection of the

14

"Test Flood". This facility is classified as a HIGH hazardand SMALL size structure. Guidelines indicate that the rangeof 1/2 the Probable Maximum Flood (PMF) to the PMF be used asthe "Test Flood" for these classifications. A test flood of1/2 PMF was chosen due to the small size of the dam. Thewatershed has a total area of 5.0 square miles. Snyder's lagwas calculated to be 3.7 hours and a Snyder peakingcoefficient of 0.625 was used. The 200 square mile - 24 hourProbable Maximum Precipitation (PMP) is 22.0 inches. The

- flood hydrograph package, HEC-I computer program, developedby the Corps of Engineers was utilized to develop the inflowhydrograph, route the flood through the reservoir, and forthe dam overtopping analysis. A test flood inflow equal tothe 1/2 PMF was calculated to be 4220 cfs (845 CSM).

This test flood analysis assumes that the outlet works areclosed. This analysis was conducted with the embankment atits present elevation, which is approximately one foot lowerthan the 1972 design elevation. It was also assumed thatthere is no retention in the upstream Messerschmidt Pond.

The spillway capacity is hydraulically inadequate to pass thetest flood (1/2 PMF) and overtopping of the dam will occur.The maximum outflow capacity of the spillway withoutovertopping the dam is 1060 cfs. This corresponds toapproximately 25 percent of the test flood outflow. Themaximum outflow discharge value for the test flood is 4160cfs corresponding to a depth of flow over the top of the damof 2.1 feet. A spillway rating curve, an outlet ratingcurve, and a reservoir stage-capacity curve, are included inAppendix D of this report.

At the spillway elevation of 127.0, the capacity of the 18inch outlet structure is 24 cfs. It will require approxi-mately 24 hours to lower the water level the first footassuming a water surface area of 30 acres, normal inflow con-ditions, and use of the outlet works to regulate the waterlevel for expected inflows.

5.5 Dan Failure Analysis

This dam is classified as a HIGH hazard structure. Failuredischarge could cause the loss of more than a few lives anddamage due to high velocities, impact from debris, and flood-ing to eleven homes along the downstream channel.

The calculated dam failure discharge is 3300 cfs due to anassumed breach width of 32 feet and a pre-failure pool levelequal to the top of the dam. At this level the prefailureflow in the downstream channel will be equal to the full

15

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

spillway's capacity of 1060 cfs corresponding to a depth flowof approximately 1 foot throughout the impact area. Failurewill produce a water surface level of approximately 8 feetimmediately downstream from the dam. Eleven homes within theimpact area may be inundated by 0 to 1 foot before and 1 to 2feet after dam failure. These homes are estimated to rangefrom 0 to 2 feet above the normal brook level. The failuredischarge can affect downstream areas for a distance of 1500feet from the dam. At this distance, the water surface level

- will be approximately at prefailure conditions as Falls Rivercrosses Pond Hill Road. Water surface elevations due to thefailure of the dam are listed on Page D-21. Probableconsequences including the prime impact areas are listed onPage D-25.

The Messerschmidt Pond Dam is located approximately 5000 feetupstream of the dam and failure of this upstream dam wouldcreate a potential hazard at the Wrights Pond Dam.

16

SECTION 6

aD EVALUATION OF STRUCTURAL STABILITY

6.1 Visual Observation

The visual inspection revealed no signs of major physicaldistress in the structure. The most significant items notedrelative to the stability of the dam are: the seepage alongthe toe of the east embankment and through the downstreamspillway face; the low areas in the embankments behind thespillway wingwalls; the elevation of the east embankmentbeing one foot below top of dam which could result in thisarea being overtopped in high flows; and the loose andfalling stones in the downstream face of the spillway whichcould lead to the structural instability of the spillway.

The seepage conditions have reportedly existed for at least10 years (refer to past inspection reports, Appendix B-2),however, no estimates of seepage flows are available and itis not known if this condition has been changing. Althoughthe seepage condition does not appear to immediately affectthe stability of the dam, it should be monitored andinvestigated further with repairs being made as necessary.

I Other minor deficiencies such as brush growth on the

embankments and minor erosion are noted in Section 3.

6.2 Design and Construction

There is insufficient design and construction data to permitI a formal evaluation of stability.

6.3 Post-Construction Changes

In 1972, the spillway was enlarged and the spillway wingwallswere added.

6.4 Seismic Stability

The dam is in Seismic Zone 1 and hence does not require evalu-ation for seismic stability according to the Corps ofEngineers Recommended Guidelines.

17

SECTION 7

ASS8SSMENT. RECOMMENDATIONS AND REMEDIAL MEASURES

7.1 Dam Assessment

a. Condition:

Based on the visual inspection, past performance andhydraulic/hydrologic evaluation, the Wrights Pond Dam andappurtenances are judged to be generally in FAIRcondition. Items of concern that should be addressed asa result of this inspection are listed in Sections 7.2and 7.3.

b. Adequacy of Information:

The limited engineering data did not allow for a defini-tive review. Therefore, the adequacy of the dam is basedon visual inspection, past performance history, andengineering judgment.

c. Urgency:

The recommendations and remedial measures described belowshould be implemented by the owner within one year afterreceipt of this Phase I Inspection Report.

7.2 Recommendations

It is recommended that the owner engage a qualified regis-tered engineer to carry out the following actions and thathis recommendations be implemented.

a. A detailed hydrologic/hydraulic investigation be per-formed to further assess the potential for overtoppingthe dam and the need for increasing the height of the damor increasing the project discharge capacity or acombination of both.

b. Design measures for the removal of the trees and theirrespective root systems on the embankments and within 30feet of the downstream toe and the backfilling with suit-able compact material.

c. The vegetation should be removed from the joints and thejoints repointed on the downstream face of the spillwayand embankments.

d. The missing stones should be replaced on the spillway.

18

J

e. Inspect the downstream face of the spillway when no wateris flowing over the spillway and make any required

ii recommendations.

f. Investigate and monitor the seepage through the spillwayand along the downstream toe of the eastern embankment.

g. Design repairs to the riprap along the upstream face ofthe embankments.

* 7.3 Remedial Measures

a. Operation and Maintenance Procedures:

1. Clear the brush from the embankments and within 30feet of the downstream toe of the embankments.

2. Place a permanent walkway on the existing angle ironframework from the spillway to the valve stem.

3. Develop a surveillance and downstream warning plan,including round-the-clock monitoring during heavyprecipitation.

4. Institute a program of annual and periodic technicalinspection.

S. Insure the operability of the outlet works on an

annual basis.

7.4 Alternatives

There are no practical alternatives to the above statedrecommendations.

19

IL

APPENDIX A

9 INSPECTION CHECK LIST

I1

ILI

INSPECTION CHECK LIST

PARTY ORGANIZATION

PROJECT Wrights Pond Dam DATE June 5, 1981

TIME 1:00 - 4:00PM

WEATHER Sunnyl.W.S. ELEV. U.S. DN.S.

PARTY:

1. R. Johnston, JPPA 6. D. Kreiger, Pine Lake ClubInc.

2. J. Hewes, JPPA 7.

3. J. Walsh, Baystate 8.pnvironmentai consultants

4. 9.

5. 10.

PROJECT FEATURE INSPFCTED BY RFMARKS

1. Hydraulics R. Johnston

2. Structural J. Hewesii3. Geotechnical

J. Walsh

4.

5.

6.

7.

8.

9.

10.

A-ii Ii ,

INSPECTION CHECK LIST

PROJECT Wrights Pond Dam DATE June 5,.1981

PROJECT FEATURE NAME

DISCIPLINE NAME .

AREA EVALUATED CONDITION

DAM EMBANKMENT p

Crest Elevation 129.3 Grass and brush

Current Pool Elevation 127.0 Spillway crest

Maximum Impoundment to Date Unknown

Surface Cracks N/A

Pavement Condition N/A

Movement or Settlement of Crest Crest is non-uniform

Lateral Movement None observed

Vertical Alignment Irregular crest surface

Horizontal Alignment Good

Condition at Abutment and at Erosion behind spillwayConcrete Structures training walls

Indications of Movement of N/A*Structural Items on Slopes

Trespassing on Slopes Footpath along crest.Vegetation on Slopes Grass-west, brush & trees - eastSloughing or Erosion of Slopes Minor erosion along upstream face.or Abutments Erosion behind training walls.

Rock Slope Protection - Riprap Thin riprap along west upstreamFailures face. Boulders along east up-

stream face.Unusual Movement or Cracking ator near Toes None observed

Unusual Embankment or Downstream Seepage along toe of east embank-

Seepage ment 4 feet below toe. Seepagethru masonry spillway.

Piping or Boils None Observed

Foundation Drainage Features None Observed

Toe Drains None Observed

Instrumentation System None Observed

A- _____________________________

INSPECTION CHECK LIST

PROJECT Wrights Pond Dam DATE June 5, 1981

PROJECT FEATURE NAME

DISCIPLINE NAME _

AREA EVALUATED CONDITION

Outlet works 18" pipe outlet through spillwaysection

a. Approach channel Entire pond bed - underwater

b. Intake Structure Assumed free intake

c. Transition and conduit Valve stem is located in pond up-stream of spillway. Last opened in1972 during dam repairs.

A 18 inch pipe extends through thebase of the older spillway section.

d. Outlet Structure A 3 foot wide by 1.5 foot high open-ing at the base of the downstreamface of the spillway section

e. Outlet Channel Spillway discharge channel

f. Service Bridge An angle iron framework extends fronthe spillway to the valve stem.Surface rust visible.

A-3

9

INSPECTION CHECK LIST

PROJECT Wrights Pond Dam DATE June 5, 1981

PROJECT FEATURE NAME

DISCIPLINE NAME ,

AREA EVALUATED CONDITION

OUTLET WORKS - SPILLWAY WEIR,APPROACH AND DISCHARGE CHANNFLS

a. Approach Channel Pond Bed - underwater

Western half of spillway sectioncontains a 4H:lV slope into the 0pond. Eastern half of spillway sec-tion contains a nearly verticle up-stream face.

b. Weir and Training Walls

General Condition of Concrete Training walls - goodWeir - fair

Rust or Staining N/A

Spalling Concrete spalling. Some loose masonry

Any Visible Reinforcing One re-bar exposed on east traininwall

Any Seepage or Efflorescence Seepage through masonry along down-stream face of spillway.

Drain Holes None Observed

c. Discharge Channel

General Condition Overgrown

Loose Rock Overhanging Channel None Observed

Trees Overhanging Channel Yes

Floor of Channel Sand, gravel and stone

Other Obstructions Woods

A-4 _

i-

tI. 5

*

SU

APPENDIX B

ENGINEERING DATA

* S

* S

* S

- S

S

S

APPENDIX B- 1

DESIGN, CONSTRUCTION AND MAINTENANCE RECORDS

Location Items

Mr. Victor J. Galgowski "1. Plan of 1972 RepairsD Dam Safety Engineer 2. Certificate of Approval for 1972Water Resources Unit RepairsDepartment of Environmental Protection "3. Past Inspection ReportsState of Connecticut 4. State Order to Repair Dam (1970)State Office Building 5. Miscellaneous CorrespondenceHartford, Connecticut 06115

Pine Lake Club, Inc. "1. Plan of 1972 Repairsc/o Mr. David Einbinder, Trustee 2. Miscellaneous Corres-

497 Main Street pondenceAnsonia, CT 06401

Indicates material contained in this Phase I Inspection Report.

B-1

APPENDIX B-2.

COPIES OF PAST INSPECTION REPORTS

B- 2

MACCHI & HOFFMAN ENGINEERSEXECUTIVE OFFICES 44 GILLETT STREET * HARTFORD. CONN., 06105 * PHONE (203) 549-6190

* A. J. MACCHI. P.E.JOSE H. COSIO. P.E.MICHAEL GIRARO, P.1.

* ASSOCIATE CONSULTANTPROF. C. W. DUNHAM

- November 10, 1972

Dept. of Environmental ProtectionWater & Related Resources165 Capitol Avenue WATER & RELATEa 0Hartford, Connecticut RESOURCE

Attention Mr. William H. O'Brien III

Re: Wright's Pond Dam

Westbrook, Connecticut ANSV;E-O__ __

REFERRED ..- --Gentlemen: FILED

On Friday, November 10, 1972 Mr. William H. O'Brien of theDepartmentof Environmental Protection and myself inspectedthe above-reverenced dam.

The owner of the dam is Pine Lake Club Inc., c/o DavidEinburder, 497 Main St., Ansonia, Connecticut.

-- Attorney for the owner is Arthur Abeshouse, 35 Elm St., New Haven,* 06510.

- Professional Engineer representing the owner is Anthony Giordano,541 Washington Avenue, West Haven, Connecticut.

->Contractor for the owner is Ivan Sachs, 102 Cherry Hill Road,Branford, Connecticut.

The dam is constructed of a large masonry wall topped withconcrete in the spillway and gravel sand over the main portionremaining. The dam is in a generally good state of repair,however, some leaks and seepage were noted which are of noconsequence. The following is to be corrected: 0

1. At the North end of the dam - trees are to be removed andupstream faced with placed field stone to avoid erosion.

2. At the North end of the dam - new spillway endwall presentlybackfilled with sand and gravel is to be removed and back-filled with large masonry and grout joints upstream to avoid

"piping".

B-3/ o

-2-

Dept. of Environmental ProtectionWater & Related Reso4rcesHartford, Connecticut November 10, 1972

3. Surface to be topped with loam and seeded.

4. At the South wing wall of the spillway, remove end ofprojecting stone.

S5. Plank walkway presently in spillway to be removed includingsupport pins.

Very truly yours,

MACCHI & HOFFMAN, ENGINEERS

K

S --

I".-

/ B-4

NoWveme 2, 1972

Ur. Axthu A. AbeshoausAttorney at Law35 Elm Street

n Now Haven, Connecticut 06510

Res Pine Lake Club, Inc.Wrights Pond Dame Westbrook

Dear Attorney Abeshouset

In reply to your letter of October 11, 1972 addressed toMr. William H. O'Brien# I regret a Certificate of Approval fromthis department for the subject dom can not be Issued at thepresent time*

An inspection of this site was conducted on October 27p1972 by the undersigned which revealed the following areas ofconczne

1. Considerable water flow through the stones on theface of the dam in an area approximately fivefeet west of the abutment of the added section of

*I the spillway.

2. Seepage at the toe of the eastern end of the dame

3. An Improperly designed access to the gate controlstem*

We will schedule a meeting at the site with your client'sengineer and our consultant to resolve these deficiencies as soonas possible.

Very truly yours

Victor Fe GalgowskSupt. of Dan MaintenanceWater S Related Resources

Vl~osljg

ct David A. linbindes B-5-/ Anthony V. Giordano

INI.RDEPARTMENT MESSAGE SAVE TIME: lmje,.tur f rire ec tiable.,_ OTo-tol 'a-sez, Use car,e if yo really need eoj.,. I I, cr;ttc, ignorc fa;na i;,,es.

T"AGEN-Cly 'ATs'To File ...... Water Resources Commission - arch 29._. 71 -

FROM William H. O'Brien, III AGENCY Water Resources Commission TELEPHONE

Civil Engineer_ _SUBJECT Wrights Pond Dam, Westbrook

.. On March 9, 1971 the undersigned inspected the

----------. subject dam.

-.------ ------- The following work had been done..

... ... ........... ... - a) a large flat rock approximately 3'x2'x6" had..... been placed over the spot where water had been

flowing thru the top of the dam. From the down-

I......................... .~a.I AUU .a u~I&7A I... had reduced the leaks thru the dam* But it could

not be determined if water was flowing down thzu

the top of the dam beneath the rock.

............. b) trees had been removed on the earth embankment on

.. .. the west side of the spillway.

.- ---- )- soil had been placed on the downstream side of the

.... . ..... .... masonry wall at the extreme west and (apparently a

surplus from d)

d) soi'l had been placed on the top west of the spill-

way to dress it off.

Civil Engineer

WHOslig J/gj

B-6

a-

*1- doht )'hvi dxnl ThKon' Tru-ll

co',tr if tcIj vc.-lrd -,,: of~' Pc...- tin d-'.i ton -if~

,ohlelz b,#' o t ":i.'I - 'rn 1:17. or ;cOprr"'i~ ;t*,-! fellutra '.UC th-i: wo, en

tho Igt'narl'. 'Ils n1:ihs b~o 0 iec l ~ .:d r ~ to

at siPl or to rcoovmv it, caad shal Itx {ta tLc.t3 wit1-A -11ich

1969s 'Do ob(,r ? 1 c; :tnd I'ru' I1 1970m ha.ve not been !insworod.

* tasod cm~ 1%.L: i. -'azct'':i r av~r theo i.-- :ti-r kc. -'%ladstt-a . ~z'.iz.:~~~~ci~VJ ~b -i: an

Unsaf'e 30-ri'Uzt.il. 1.'d %;).--o rl."Es ft-i at o .'tn i'opcv.r. oz- altOr'2tionatare naEco3ssry I.-) nla~o tLe. stvictvro Inl a. .. fe con,"itiron.

Pb

-2-

F ine Lake Club# Inc. .4zrch 18# 1970

I. Repaiir t~ho' upstre&'i misonry wall and top of damn west of thespill.;y l Ni er'oded nwiay.

2. 110-3air voids In tha dam caused by v~atar flowing throughfromi the top.

3. 'to, oi- i-odutc to an acoptab-bl l'w ll-le.-ils throu-4i* the dart.

Do~rln 1_ ourco of :oun1 3o'n ath 'Uo lvntroon~ tccv ofthe dan cal t":a a!r:t and rid correoct.

6. omvo r-Al troas on or vdtldn 20 foo'. of the d-:a

7. ' Ta-i-U~t tc-tin ,.aiy ~ziur to oll!inatu or "joatlrXUC 4'1 V37.1.-:3 !-' f!C'; . IO~- 1-I.'tLa y yLf 6 , Liam unlJ.1 ofL- -i t

ropairz can 5o i.

* In tacr-q-nc- -lh 7o.-ti-n ?5-111 )1' th 1963 'u, Potto theG on3:,l ~n't-,;u~~&yon.oezd to In: VID z'~iSrs aind

* rocdiriczd.Ucns 1-:±j o pL iti-x *tAuctuea in a afo cate~nry orto reriova tloa stuuro.

f'.~r ~~t'i:,r 11oc4 c n I-Acn to t:, vit-'-ture, or its roriov7Ashe.ll b:: n-irot i In ceord!1ni -*ith. sr*'~ :'d3o5~1aif3 i e-

nae y -n uirv!irc,tr 1e 1 in o.to to o 0., ao tOl,0icut and1- berrida?; his cart 'icatvioar v-cv1 -on. 3tc~)Tl~rh;Al be subrnittei* to this ouiico Cor npprov-*i rnd for Tlhey Ir..uurco of R Pornit

prior to n'ny coni-trxict1on or, 1.innlition vor. in raccord!tnce wtSection 25-112 of L~ Jono0ral StAttas.

The Cot-.isnon oshall ha iotifio.) In virttn batoro ApDril 15,1970 ti t~o xat ona :ou hsvo talcon or -;M '1 to a- ply wit -this

0 RD' -lans for . ,a r± r nfir nr remial of this dam slill* be ai.i..ittad prior' 14o Juas 159 1910'. The por.nont vorkc indicnro'td

B- 8

-.3-

fl Pine Lakce Club, Ina. 2-arch .10a 1970

s~zall be couiplotod. b7 Septomibor 15# 1970. The tompu. try work (item-"7) shvall be under the direction or an ansinoer re,-.1.tered in the-Str-to of lorniticutv and with the approv3I of the Water Rasources

* 3O~MM13SIon and shaLl ba completed bilAril 30# 1970.

Vei'y truly7 yours 0

John J. - urryDira3otor

B-9

I..APPENDIX B-3

RECORD DRAWINGS AND SKETCHES

IB

B-bO

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p* V" :!Wvwrovr:vr r.

______________________________________________________ ________r ____

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WAI WA. t0'*;p'.A "FP

-,1 vr.1 r APPROVEDI STArg OF CONNECTICUTof O M-MD.ILP. iCi

OW ANTHONY V. GIORDANO- -s CONSUL r,,to ENCINEER

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L.PROS

APPENDIX C.

PHOTOGRAPHS

I

IL

1i

I

4a0-0O0

I-I

(~cJ

. ..........

C-1 SPILLWAY LOOKING EAST

C-2 SPILLWAY LOOKING NORTH

C-1

C-0ETR RIIGWL

C- ESTERN TRAIN SINGWALYNEER SPILLWAY SECTION

4c-

C-5 UPSTREAM FACE OF EARTHPORTION OF DAM AT EASTERN END

C-6 DOWNSTREAM FACE OF

.I EARTH PORTION OF DAMAT EASTERN END

C-3

C-7 DOWNSTREAM FACE OF SPILLWAY-LOOKING WEST

C-8 DOWNSTREAM FACE OF SPILLWAY-LOOK ING EAST

0~c- 4

C-9 LOOSE AND MISSING STONESAND SEEPAGE ON DOWNSTREAMFACE OF SPILLWAY AT EASTERNEND

Mi I-

C-10 VALVE STEM AND ANGLEIRON WALKWAY

C- 5

C-11 MASONRY OPENING AT THE BASEOF THE DOWNSTREAM FACE OFTHE SPILLWAY SECTION

C-12 DOWNSTREAM CHANNEL

V

C-6

II

APPENDIX D

HYDROLOGIC AND HYDRAULIC COMPUTATIONS

in

I

I-

2* -

lie, V1 11"

- lling

1

orth

ReservoirN

<~ ~ ~ ~ K Ond ) \

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IT\ OF IMATAE

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I.,..

DAIPAGT AREAAN

'~2 4~i ~ DATUM: NOVO~RIGTS PND AM )~ '. 3. ~ .QUADRANGLE SHEETS:

4. CLINTON. CT~ .. Z. ,4~B ('~JYESSEX. CT

r' .- " '' ~SCALE: 1:24000

,~py .J~j~ _ PLATE NO.D0J

j.

woo

HYDROLOGIC AND HYDRAULIC ANALYSISSUMARY SHEET 0

Dam Wrights Pond Dam

Test Flood 1/2 PMF

INFLOW HYDROGRAPH DEVELOPMENT

Drainage Area 5.0 sq. mi. 0

Probable Maximum Precipation24 hour - 200 square mile PMP 22.0 inches

Initial Rainfall Loss 0 InchUniform Rainfall Loss TT Inch S

Snyder's Lag 3.7 hours

Snyder's Peaking Coefficient .625

Test Flood Inflow 4220 CFS

PMF Inflow 8440 CFS

RESERVOIR ROUTING AUD DAM OVERTOPPING

Test Flood Outflow 4160 CFS

Spillway Capacity at Top of Darr 1060 CFS25 % of Test Flood

Flow Over Spillway at Test Flood 2850 CFS S

Spillway Crest Elevation 127.0 FeetTop of Dam Elevation L9.i FeetTest Flood Elevation 1 Feet

D-2

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WRIGHTS POND DAM

Dam Failure Analysis

1. Failure discharge with pool at Top of Dam (elev.129.3 )= 3300* CFS

2. Depth of water in reservoir at time of failure = 12.0 ft.

3. Maximum depth of flow downstream of dam = 12.0 ft.

4. Water surface elevation just downstream)of dam at time of failure ) 129.5 S

The failure discharge of 3300 CFS will enter and flow down-

stream 5500 feet until the brook Joins Mine Swamp Brook *

Valley storage in this 5500 feet length of brook is significant in

reducing the discharge. Also due to roughness characteristics,

obstructions and frictional losses, it is very likely that the

unsteady dam failure flow will dissipate its wave and kinetic P

energy and thus convert to steady and uniform flow obeying Manning's

formulae 5500 feet downstream. The failure profile will have

the following hydraulic characteristics: S

DISTANCE FROM THE DAM WATER SURFACE REMARKSELEVATION IDEPTH (ft.)

0 129.3 12.0 at dam500 122.3 2.3

1500 121.2 1.23000 111.2 1.24500 111.1 1.15500 111.0 1.0 confluence with

I-ine Swamp BrookA.-

NOTES:Including prefailure spillway flow of 1060 cfs.

** At this point, the failure discharge has disipated with only the prefailure spillwayflow remaining.

D

D- 21

I.-

r

"Rule of Thumb"Guidance for EstimatingDownstream Dam Failure Analysis

DATA

Name of Dam Wrights Pond Dam

Location Westbrook, Conn. 0

Drainage Area 5.0 sq. mi., Top of Dam 129.3

Spillway Type Broad , Crest of Spillway 127.0

Surface Area @ Crest Elev. -a-Acres = .05 sq. mi.

Pool Bottom Hear Dam = 118.0

Assumed Side Slopes of Embankments = 2:1

Depth of Pool at Dam (Yo) = 12.0 Feet

Mid-Height Elev. 122.5

Length of Dam at Crest = 160 Feet (Earth portion only)

Length of Dam at Mid-Height = 80 Feet

40% of Dam Length at Mid-Height = Wb = -Feet

Step 1

Storage (S) at time of failure 200 Ac-FT

Step 2

Peak Failure DischargeQpI = 8/27 Wb Vi Yo 3/2

A-

= (1.68) (Wb) (Y.) 3/2= 2240 cfs*

Failure is assumed to coincide with pool elevation at top of dam

NOTES: 0

*The total discharge is 3300 cfs which includes the prefailure spillway flow of1060 cfs.

SD -

D- 22

oA~g.4 L& CT *umjgc SKEET NO.. / O -cwxo --- --- ---- --- --- ---- --- --- --- --- - ----------- - - - - O O

A.*? ocqle- ve- q AoAe *.. PURCELL ASSOCIATES---- --- --- --- ---- --- ------ ---- --- --- --- - 'NGINEERS *AMC"' tECTS - PLANNERS

$eA*7 4r~~ Ai

USIA' C~:~- A R__SA n

200-

v op c cp 2zq 16/Cc , AC-Plr'

330: VAO VC?7

? 1_ --- -

A ~ ~ ~ V _____A-F

1*c I S

D- 23

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P7 -A

'32-,

16oUIS0OeZ S.~AA'cc2' Ip CA s70 M 5 r eS-0 0lc ,lp

-- 4---AREA 64t--.--.- p E P714----

*VI

VA --/725

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NCO

D-24

-

Wrights Pond Dam

A. Size Classification

Height of dam = 12.0 ft.; hence small

I Storage capacity at top of dam (elev. 129.3 )= 200 AC-FT.; hence small

Adopted size classification: small

B.i) Hazard Potential

* While depth of flooding is relatively shallow, it affects a large

area encompassing eleven homes. The potential exists for the

loss of more than a few lives.

Adopted hazard classification: High 0

ii) Impact of Failure of Dam with oool at top of dam.

It is estimated from the 'rule of thumb" failure hydrograph,that the following adverse impacts are a possibility by the failureof this dam. 0

a) Loss of homes 11b) Loss of buildings 0c) Loss of highways or roads 0d) Loss of bridges 0

The failure profile can affect a distance of 5500 feet

from the dam.

C. Hazard Potential Classifications

* HAZARD SIZE TEST FLOOD RAIGE

High Small 1/2 PMF to PMF

Adopted Test Flood = 1/2 PMF = 844 CSM

= 4220 CFS S

D. Overtopping Potential

Drainage Area -- = 5.0 sq. miles

Spillway crest elevation = 127.0 3

Top of Dam Elevation = 129.2

Maximum spillway dischargeCapacity without overtopping of dam = 1060 CFS"test flood" inflow discharge = 4220 CFS S"test flood" outflow discharge = 4160 CFS

D-25L

RATING CURVE DEVELOPMENT

WRIGHTS POND DAM

3/2Spillway Q=C L H

C= 3.05

L = 100.0 feet1/2

18 Inch Outlet Q= c a (2 g h)

c = 0.6

a = 1.77 square feet

D-26

L D-26

i. ac

i hi -

II-

LL.

4W>

0 0

IL

X ~ ~~~ 09 -I c li

('NO') 133.I N1 N011VA313

WRIGHTS POND DAM,D-27 SPILLWAY RATING CURVE

F

N

Uf) 0

I 0

I--x

o

-- in

01

g

_ 0

q. __ _ N _w

_ ( '~~O ' ' N ) 1I3 3 A 1 N I N O II V A 3 I3 L

WRIGHTS POND DAMIS INCH OUTLETD-28 OUTLET WORKS RATING CURVE

Ll

I :

u00

r=r

-.- J

w0

, ,'

-R OG PV(GA N13I NOIA1

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"a-- ON.D DAM

D- 09 REEVI TG-CPCT UV

am~

APPENDIX E

INFORMATION AS CONTAINED IN THE

NATIONAL INVENTORY OF DAMS

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NOT AVAILABLE AT THIS TIME

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