RD-AL56 378 NATIONAL PROGRAM FOR INSPECTION OF NON-FEDERAL DAMS 1CHASE POND DAN (NH 98..(U) CORPS OF ENGINEERS NALTHAMMA NEW ENGLAND DIV MAR 88

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NATIONAL BUREAU OF STANDAROS-1963-A

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1....MERRIMACK RIVER BASIN

-!. WILMOT, NEW HAMPSHIRE

',- CHASE POND DAM

NH 00255

NHWRB NO. 253.02

r PHASE I INSPECTION REPORT ,

: . NATIONAL DAM INSPECTION PROGRAM

* ,~DTIC

DEPARTMENT OF THE ARMYNEW ENGLAND DIVISION, CORPS OF ENGINEERS

WALTHAM, MASS. 02154

MARCH 1980 le,-

OII fIE OX86 U6 18 12

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liNri A- TTrflSECURITY CL ASSIFICATION OF THIS PAGE (When Doss kntoved)

REPORT DOCUMENTATION PAGE READ INSTRUCTIS____________________________________ BEFORECOMPLETINL_,*ORM

1 REPORT NUBE . oOVT ACCESSION NO. 3. RECIPIENT*S CATALOG N4UMBER

NH 00255-I_ _ _ _ _ _ _ _ _ _ _ _ _ _ _

*4. T IT LE (end Subo~le) S. TYPE OF REPORT & PERIOD COVERED

Chas Pon DamINSPECTION REPORT

NATIONAL PROGRAM FOR INSPECTION OF NON-FEDERAL S.EROMOO.RPOTUSR

DlAMS7. AUTHOR(a) It. CONTRACT OR GRANT NUMBER~ts)

U.S. ARMY CORPS OF ENGINEERSNEW ENGLAND DIVISION

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELRMENT. PROJECT, TASKAREA It WORK UN IT NUMBERS

ft. CONTROLLING OFFICE NAME AND ADDRESS t2. RIPORT DATE

*DEPT. OF THE ARMY, CORPS OF ENGINEERS March 1980*NEW ENGLAND DIVISION, NEDED 13. NUMBER OFPAGES

* 424 TRAPELO.ROAD, WALTHAM, MA.. 02254 8214. MONITORING AGENCY NAME ADDRESS(I differentl Uresm CmuorsUotaj Office) It. SECURITY CLASS. (of ths. rePorl)

UNCLASSIFIED164. DECLASSIFICATION/DOWNGRADING

&CmEDULE

16. DISTRIBUTION STATEMENT (of &life Aeport)

APPROVAL FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED

* 17. DISTRIBUTION STATEMENT (of the sibefroet utesod In Block 20, It diteepI ht XOPOrt)

IS. 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.

19. K EY WORDQ (Continue on fewsorsp side #0 .o..oemay and Ientify by black Muthot)

- DAMS, NSPECTION, PAM S'AFETY,Merrimack River Basin.

* Wilmot, New Hampshire- Chase Pond.*

*20. ABSTRACT (Continueon ut wswee aide ft n~ecessary and Idenify by black mbaesr)

*The dam is a rock filled log crib with timber planking overflow strucute be-tween stone and concrete embankments. The dam is 103 ft. lonf and about 12 ft.

*high. The dam is considered to be in poor condition with various major concerns.* ,~The dam is small in size with a significant hazard classification. The dam* at the outlet from Tannery Pond could be overtopped or breached. '

DD li %N7 1473 ELDITION OF I NOV Go IsOU11SOLIETE

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DISCLAIMER NOTICE

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

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Accession For"CHASE POND DAM -NTIS GRA&I

NH 00255 DTIC TAB

NHWR 253.02 Unannounced -Justification

ByDistribution/

Availability Codesr 1Avail ad/or

Dist r Special

MERRIMACK RIVER BASIN

R WILMOT, NEW HAMPSHIRE - -

PHASE I INSPECTION REPORTNATIONAL DAM INSPECTION PROGRAM

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NATIONAL DAM INSPECTION PROGRAMPHASE I - INSPECTION REPORT

BRIEF ASSESSMENT

Identification No.: NH 00255

Name of Dam: Chase Pond

Town: Wilmot Flat

County and State: Merrimack, New Hampshire

Stream: Chase Pond

Date of Inspection: November 27, 1979

Chase Pond Dam is a rock filled log crib with timber planking overflow structurer between stone and concrete embankments. The overall length of the dam is 103

feet. The timber overflow section is approximately 12 feet. high (negleatiq-llshboar s, by 50.5 feet. long and 10 feet. wide at the crest. The embankments,

* i which are approximately 5.4 feet higher than the crest of the timber overflowsection, are composed of masonry and concrete on the upstream and training wallfaces.\The downstream faces are composed of unmortared stone and boulders. Bothembanknents are earth filled. There is no emergency spillway.

The dao impounds Chase Pond and the discharge flows through an unnamed brookapproxmately 0.2 mile to Tannery Pond.The original purpose of the dam is not

wn but its present use is recreational. The pond is 0.40 mile in length witha suriface area of about 39 acres. The maximum storage capacity is about 370

! acre-feet.

\AM result of the visual inspection of this facility, the dam is considered to bein AdR condition. 'Major concerns are: considerable settlement of the log cribbingin the center of the spillway structure; subsidence and a sinkhole on the crest ofthe embankment at the left abutment; and cracking and signficiant spalling ofconcrete in the upstream face of the right abutment and the left training wall.

This dam is classified as SMALL in size and a SIGNIFICANT hazard structure inaccordance with the recommended guidelines established by the Corps of Engineers.The test flood for this dam, therefore, ranges from a 100-year flood to one-halfthe Probable Maximum Flood (1/2 PMF). The one-half Probable Maximum Floodwas selected for the test flood analysis, and the test flood inflow was estimatedto be 10,700 cfs. This test flood has an outflow discharge equal to 9,890 cfs andwould overtop the dam crest by about 3.8 feet. The maximum spillway dischargecapacity (assuming that the flashboards have washed away) with the water levelat the dam crest was estimated to be 2,230 cfs or about 21 percent of the testflood discharge. A major breach with the pond surface at the dam crest wouldincrease the stage along the immediate downstream channel by over 5 feet, possibly

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damaging two of the dwellings and a barn along this reach. Water would be nearthe sill of these two dwellings and about 4 to 5 feet above the lower foundationof the barn. A town road and bridge which cross the stream approximately 675feet below the dam could also be damaged. The increase in the volume of water

V entering Tannery Pond would significantly increase the stage of the pond approxi-mately 6 to 8 feet, such that three or four houses located near the pond would

r_ have water 1 to 2 feet above their sills. The dam at the outlet from TanneryPond could be overtopped or breached.

It is recommended that the owner engage a qualified registered professional engineerto investigate the settlement in the center of the log crib overflow section, thesubsidence and sinkhole on the crest of the embankment at the left abutment, todo a detailed hydrologic-hydraulic investigation to assess further the potential ofneed for and the means to increase project discharge capacity, and to assess theneed for and means to provide a low level regulating outlet that would allowdrawdown of the pond in an emergency. It is also recommended that the ownerrepair the cracks and spalling of concrete in the upstream face of the right

r embankment and in the left training wall, clear the embankmnents and downstreamtoe of the dam of trees and brush and establish and maintain grassy vegetationon the embankments.

The recommendations and remedial measures are described in Section 7 and shouldbe addressed by the owner within one year after receipt of this Phase I InspectionReport.

O.NNM enneth M. StewartSTRWAMProject ManagerKO. =1N.H.P.E. 3531

4 4IhONAI.$~JS E A Consultants Inc.Rochester, New Hampshire

:...'

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PREFACE

mI

This report is prepared under guidance contained in the Recommended Guidelines

for Safety Inspection of Dams, for Phase I Investigations. Copies of these guidelines

may be obtained from the Office of Chief of Engineers, Washington, D.C. 20314.

The purpose of a Phase I investigation is to identify expeditiously those dams

which may pose hazards to human life or property. The assessment of the general

condition of the dam is based upon available data and visual iispections. Detailed

'" investigation, and analyses involving topographic mapping, subsurface investigations,

testing, and detailed computational evaluations are beyond the scope of a Phase I

investigation; however, the investigation is intended to identify any need for such

studies.

r In reviewing this report, it should be realized that the reported condition of the

dam is based on observations of field conditions at the time of inspection along

with data available to the inspection team. In cases where the reservoir was

lowered or drained prior 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 which might otherwise be detectable if inspected under the

normal operating environment of the structure.

It is important to note that the condition of a dam depends on numerous and--- .. constantly changing internal and external conditions, and is evolutionary in nature. .i-.

It would be incorrect to assume that the present condition of the dam will continue

to represent the condition of the dam at some point in the future. Only through

continued care and inspection can there be any chance that unsafe conditions be

detected.

Phase I inspections are not intended to provide detailed hydrologic and hydraulic

- - analyses. In accordance with the established guidelines, the Spillway Test flood is

" - based on the estimated "Probable Maximum Flood" for the region (greatest reason-

ably possible storm runoff), or fractions thereof. Because of the magnitude and

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rarity of such a storm event, finding that a spillway will not pass the test flood

should not be interpreted as necessarily posing a highly inadequate condition. The

test flood provides a measure of relative spillway capacity and serves as an aide

in determining the need for more detailed hydrologic and hydraulic studies, con-

sidering the size of the dam, its general condition and the downstream damage

' •.potential.

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 items

which may be needed to minimize trespassing and provide greater security for the

facility and safety to the public. An evaluation of the project for compliance with

OSHA rules and regulations is also excluded.

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Vi

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TABLE OF CONTENTS

Section Page

Letter of Transmittal

Brief Assessment

FReview Board Page iv

Preface V

Table of Contents vii

Overview Photo ix

Location Map X

1. PROJECT INFORMATION 1-1.1 General

1-1

1.2 Description of Project 1-1

1.3 Pertinent Data 1-3

h2. ENGINEERING DATA 2-1

2.1 Design.

2.2 Construction 2-1 -.

2.3 Operation 2-1

2.4 Evaluation 2-1

3. VISUAL INSPECTION 3-1

-3.1 Findings 3-1

* 3.2 Evaluation3-

4. OPERATIONAL AND MAINTENANCE PROCEDURES 4-1

4.1 Operational Procedures 4-1

* .4.2 Maintenance Procedures 4-1.

4.3 Evaluation 4-1

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Section Page

5. EVALUATION OF HYDROLOGIC/HYDRAULIC FEATURES 5-1

5.1 General 5-1

5.2 Design Data 5-1

5.3 Experience Data 5-1

5.4 Test Flood Analysis 5-1

5.5 Dam Failure Analysis 5-1

" 6. 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 6-2

6.4 Seismic Stability 6-2

- 7. ASSESSMENT, RECOMMENDATIONS AND REMEDIAL MEASURES 7-1

7.1 Dam Assessment 7-1

7.2 Recommendations 7-2

1 7.3 Remedial Measures 7-2

7.4 Alternatives 7-2

APPENDICES

APPENDIX A - INSPECTION CHECKLIST A-i

APPENDIX B - ENGINEERING DATA B-i

APPENDIX C - SELECTED PHOTOGRAPHS C-i

APPENDIX D - HYDROLOGIC AND HYDRAULIC COMPUTATIONS D-i

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OVERVIEW PHOTO -CHASE POND DAM

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7-- 7

NATIONAL DAM INSPECTION PROGRAMPHASE I INSPECTION REPORT

I CHASE POND DAM

SECTION 1PROJECT INFORMATION

1.1 General

a. Authority. Public Law 92-367, August 8, 1972 authorized the Secretaryof the Army, through the Corps of Engineers, to initiate a National Program ofDam Inspection throughout the United States. The New England Division of theCorps of Engineers has been assigned the responsibility of supervising the inspectionof dams within the New England Region. S E A Consultants Inc. has been retainedby the New England Division to inspect and report on selected dams in the Stateof New Hampshire. Authorization and notice to proceed were issued to S E AConsultants Inc. under a letter of November 5, 1979 from William Hodgson, Jr.,Colonel, Corps of Engineers. Contract No. DACW33-80-C-0008 has been assignedby the Corps of Engineers for this work.

b. Purpose

(1) To perform technical inspection and evaluation of non-Federaldams to identify conditions which threaten the public safety and thus permitcorrection in a timely manner by non-Federal interests.

* (2) To encourage and prepare the states to initiate quickly effectivedam safety programs for non-Federal dams.

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

1.2 Description of Project

a. Location. Chase Pond Dam is located in the Town of Wilmot, NewHampshire, approximately 0.8 mile west from the center of town. The dam impoundswater creating Chase Pond, which after passing over the spillway flows in anunnamed brook in an easterly direction approximately 0.2 mile to Tannery Pondin Wilmot Flat, New Hampshire. The dam is shown on U.S.G.S. Quadrangle, Mt.

- Kearsarge, New Hampshire, with coordinates approximately at N 43025'00 ' , W71 54'4011, Merrimack County, New Hampshire (see Location Plan).

b. Description of Dam and Appurtenances. Chase Pond Dam is a rockfilled log crib with timber planking overflow structure between stone and concreteembankments. The overall length of the dam is 103 feet. The timber overflow

* section is approximately 12 feet (neglecting flashboards) high by 50.5 feet long.The timbers are composed of 8, 10, and 12 inch diameter round logs. The logs

- are arranged in cribs which are rock filled except for the downstream cribs whichhave several void areas. The spillway deck is composed of 2" x 8" and 2" x 6"planking, and is about 10 feet wide at the top. A 2.5 foot high flashboard acrossthe top of the spillway deck is also constructed with 2" x 6" and 2" x 8" planking.

. .]

, The embankments are composed of masonry and concrete on the upstream andtraining wall faces. The downstream faces are composed of unmortared stone andboulders. Both embankments are earth filled.

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" -. c. Size Classification. Small (maximum hydraulic height - 17.2 feet,storage 370 acre-feet) based on storage (< 1,000 acre-feet to ? 50 acre-feet) asgiven in the Recommended Guidelines for Safety Inspection of Dams.

d. Hazard Classification. Significant hazard. A major breach with thepond surface at the dam crest would increase the stage along the immediatedownstream channel by over 5 feet, possibly damaging two of the dwellings and

r -- a barn along the reach. Water would be near the sills of these two dwellings and -'1about 4 to 5 feet above the lower foundation of the barn which is constructeddirectly adjacent to the stream channel. A town road and a bridge which crossthe stream approximately 675 feet below the dam could also be damaged. Theincrease in the volume of water entering Tannery Pond would significantly increasethe stage of the pond, approximately 6 to 8 feet, such that three of four houseswould have water 1 to 2 feet above their sills. The dam at the outlet from Tanneryr- Pond could be overtopped or breached. There appears to be little potential forloss of life.

e. Ownership. No information regarding the original structure or ownerwas found. Early records indicate it was first rebuilt in 1922, the owner at the

time being N.P. Clough & Company. Ownership passed to a John and MyrtleNewcomb in the late 50's, who sold it to its present owner in 1973, that beingMrs. David Romanoff, Village Road, Wilmot Flat, New Hampshire 03287. TelephoneNo. (603) 526-6490.

f. Operator. The dam is maintained and operated by Mrs. David Romanoff,Village Road, Wilmot Flat, New Hampshire 03287. Telephone No. (603) 526-6490. " .

g. Purpose of Dam. The original purpose of this dam is not known. Duringits ownership by N.P. Clough & Company, between the 1920's and 1950's, it wasused for industrial conservation. The present purpose of the dam is recreational.

h. Design and Construction History. No information regarding the originaldesign or construction of the dam was found. Early records indicate it was firstrebuilt in 1922. The dam was completely washed out during the 1938 flood andwas rebuilt in its present form of a stone filled log crib in 1939. The log cribbingand planking was again rebuilt in 1963. In 1973, repairs were made to the concreteon the right abutment. Since that time there is no indication of any furtherconstruction being performed.

i. Normal Operating Procedures. The Chase Pond Dam is used primarilyto create Chase Pond for recreational purposes. There is no normal operationalprocedure for this dam.

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1.3 Pertinent Data

a. Drainage Area. The drainage area above the Chase Pond Dam coversnearly 13.8 square miles (8,830 acres), consisting of steep mountainous terrainsurrounding Chase Pond and Pleasant Lake, which is located upstream from ChasePond. The majority of the watershed is heavily wooded. Development within thebasin is predominantly located near either Pleasant Lake or Chase Pond, sincethese two water bodies serve as recreational areas.

t

The topography in the drainage basin ranges from about 1,950 feet (NGVD) to 704feet (NGVD). A number of small brooks are evident in the watershed, one suchbrook carries the outflow from Pleasant Lake to Chase Pond.

b. Discharge at Damsite

(1) Discharge at the damsite occurs over the 50.5 feet long timberplanking overflow structure constructed between the stone and concrete embank-ments. The reservoir is maintained at an elevation near 704 feet NGVD, byflashboards which have been installed on top of the timber planking deck. Duringlower and normal flow periods, the discharge emanates from a 5.6' x 0.84' weirsection which has been removed from the flashboard crest near the right embank-ment, as well as from a triangular shaped weir section near the left embankment.The triangular shaped discharge weir appears to be the result of a misalignment

* "in the flashboard crest, rather than a designed point of discharge.

* (2) Maximum known flood at damsite - unknown.

(3) The capacity of the overflow spillway with the flashboards removedand the water surface at the dam crest (elevation 707.8 feet) was estimated tobe approximately 2,230 cfs.

ad (4) 1 ne capacity of the overflow spillway with the flashboards removedand the water surface at the test flood elevation (711.6 feet) was estimated tobe approximately 4,400 cfs.

(5) The total flow through the rectangular weir section and thetriangular weir section was estimated to be approximately 19 cfs with the watersurface elevation at the top of the flashboards (elevation 704.0).

* (6) The capacity of the spillway structure with the flashboards stillin place was estimated to be 2,680 cfs with the water surface at the test flood

" .elevation (711.6 feet).

(7) The total spillway capacity at the test flood elevation of 711.6feet was estimated to be 4,400 cfs with the flashboards removed.

(8) The total project discharge with the water surface at the damcrest (elevation 707.8) was estimated to be 2,350 cfs with the flashboards removed.This includes a flow of 120 cfs which by-passes the spillway structure to the northof the dam.

1-3

I (9) Total project discharge at test flood elevation - 9,890 cfs at 711.6elevation.

c. Elevation (feet, NGVD) based on elevation of 704.0 shown on U.S.G.S.% -quad sheet assumed to be pool elevation at top of flashboards.

(1) Streambed at toe of dam - 690.6

(2) Bottom of cutoff - unknown

(3) Maximum tailwater - unknown

(4) Normal pool - 704.0

(5) Full flood control pool - N/A

(6) Spillway crest (flashboards in place) - 704.0

(7) Design surcharge (Original Design) - unknown

(8) Top of dam - 707.8

(9) Test flood design surcharge - 711.6

d. Reservoir (Length in feet)

(1) Normal pool - 2,100

- (2) Flood control pool - N/A

(3) Spillway crest pool- 2,100

(4) Top of dam - 2,600

- - (5) Test flood pool - 3,100

e. Storage (acre-feet)

(1) Normal pool - 190

(2) Flood control pool - N/A

(3) Spillway crest pool (top of flashboards) - 190

(4) Top of dam - 370S"(5) Test flood pool- 530

1-4

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" ° °°o.°.£"oo."°o.:,. -.. ° ..*. ' -oo'-o.-.-.. . -'....'.'."-.. . ... ." . . . .

f. Reservoir Surface (acres)

K(1) Normal pool -39

(2) Flood-control pool - N/A

(3) Spillway crest (top of flashboards) - 39

(4) Test flood pool - 75

(5) Top of dam - 57

g. Dam

(1) Type - concrete and unmortared stone embankments, earth filled;central overflow structure, rock filled log crib with timberplanking

(2) Length - 103 feet. r .- ---

(3) Height - 17.2 feet (maximum)

(4) Top width- 8.3 feet

(5) Side slopes - not applicable

(6) Zoning - not applicable

S.(7) Impervious core - unknown

(8) Cutoff - unknown

[ (9) Grout curtain - none

(10) Other - none

h. Diversion and Regulating Tunnel - Not applicable

i. Spillway

(1) Type - rock filled log crib with timber planking overflow structure

. (2) Length of weir - 50.5 feet

(3) Crest elevation - 704.0 (top of flashboards)703.2 (invert of rectangular weir section)701.2 (top of spillway deck)

(4) Gates - no gates

" 1-5

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(5) U/S Channel - Chase Pond. The banks are tree lined and thereare several summer cottages on the pond. The slopes around the pond appear tobe stable. No evidence of significant sedimentation was observed.

" (6) D/S Channel - Water over the spillway discharges into a brookwhich travels in an easterly direction for about 0.2 mile, where it discharges intoTannery Pond, in Wilmot Flat, New Hampshire. The brook is covered with bouldersand overhanging trees exist on its banks. A town road and bridge cross the brookjust before it discharges into Tannery Pond.

j. Regulating Outlets. There is no apparent low level regulating outlet" - incorporated in this dam that would allow drawdown of the pond in an emergency.

An inspection report from the State of New Hampshire Water Resources Boardmade during the 1939 reconstruction indicates provisions were made so that threesections of planking could be removed to drawdown the pond if this becamenecessary. It was not possible to determine, during the field inspection, if thisprovision still exists.

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SECTION 2ENGINEERING DATA

a No design data were disclosed for Chase Pond Dam.

2.2 Construction

No construction records were disclosed.

:!77

2.3 Operation

* - No engineering operational data were disclosed.

2.4 Evaluation

ra. Availability. No .engineering data were available for Chase Pond Dam.A search o h flsof the New Hampshire Water Resources Board and directcontact with the owner, revealed a limited amount of recorded information.

b. Adequacy. The final assessments and recommendations of this investi-gation are based on the visual inspection and the hydrologic and hydraulic calcula-

ft tions.

C. Validity. No engineering data were disclosed to validate.

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SECTION 3VISUAL INSPECTION

3.1 Findings

- a. General. Chase Pond Dam impounds a pond of small size. The watershedabove the pond consists of steep mountainous terrain. The majority of the drainagebasin is heavily wooded and predominantly undeveloped, except for the perimeterof Chase Pond and Pleasant Lake where numerous summer cottages and the townof Elkins are located. The downstream area is rocky in the bed of the brook andwooded on its banks. The area is slightly developed close to where the brookdischarges into Tannery Brook.

The field inspection of Chase Pond Dam was made on November 27, 1979. Theinspection team consisted of personnel from S E A Consultants Inc. and GeotechnicalEngineers Inc. Inspection checklists, completed during the visual inspection, areincluded in Appendix A. At the time of inspection, water was passing approximately7 inches deep over the 5.6 foot wide main overflow weir. The pool elevation wasat approximately 703.7 NGVD. The upstream face of the dam could only beinspected above this water level.

b. Dam. Chase Pond Dam is a rock filled log crib overflow sectionbetween stone and concrete embankments (See Photo No. 2). The overall lengthof the dam is 103 feet. The central timber overflow section is about 12 feet high,50.5 feet long, and 10 feet wide at the crest (See Photo Nos. 5 and 9).

A' each end of the central, log-crib overflow section, there is a vertical concrete

t ining wall which also serves as a retaining wall for the earthen embankmentsection that connects the central timber section and the abutment. The upstream

" side of both embankment sections is retained by a vertical concrete wall (SeePhoto No. 3). The downstream side of both embankment sections is retained by adry stone masonry wall (See Photo No. 11), except close to the abutment, where --

the downstream side of the embankment is an earth slope.

The center of the log-crib spillway section has deflected approximately 1.2 feetin comparison with the top of the cribbing at the training walls (See Photo Nos.9 and 12).

The downstream lower sections of the wood cribbing are absent of stone fill andmany voids exist (See Photo No. 10).

The upstream face of the right embankment has a large vertical crack in theconcrete (See Photo No. 4). The left training wall has a large horizontal crack atabout the same elevation as the spillway (See Photo No. 6). There is also significant

* spalling of the concrete at this embankment (See Photo No. 8).

3-1

* - - -,- * V . * *. ' V *. . *- -

The crest of the embankment section between the central timber section and theright abutment is practically bare of vegetation. There is a tree stump in thedry-stone-masonry wail on the downstream side of this section and there are treesgrowing at the downstream toe of this wall (See Plans and Details in AppendixB). This is no vegetation and considerable erosion of the downstream slope of thissection between the end of the dry-stone-masonry wall and the abutment. Theerosion appears to be due to trespassing. The right abutment appears to be bedrock.

The crest of the embankment section between the central timber section and theleft abutment has subsided several inches next to the concrete training wall (SeePhoto No. 7). There is also a sinkhole in the embankment next to the dry-stone-masonry wall on the downstream side of the crest (See Plans and Details in ...Appendix B and Photo No. 7). The crest is practically bare of vegetation, althoughthere are a few small trees starting to grow. Logs and timbers have been dumpedat the downstream toe of this embankment section (See Plans and Details inAppendix B). There are also some trees growing close to the downstream toe.

No evidence of seepage was observed on the downstream side of either embankmentsection.

c. Appurtenant Structures. There are no appurtenant structures for thisdam.

d. Reservoir Area. The slopes around the pond appear to be stable. Noevidence of significant sedimentation was observed.

e. Downstream Channel. The downstream channel is covered with boulders.Trees overhang the channel (See Photo Nos. 13 and 14).

3.2 Evaluation

Based on the results of the visual inspection, Chase Pond Dam is consideredto be in poor condition.

The large settlement in the center of the log crib spillway section and large voidsof stone fill in the downstream cribbing is evidence of a significant structural andstability problem.

Subsidence and a sinkhole on the crest of the embankment between the centraltimber section of the dam and the left abutment are evidence of a significantstability problem.

The lack of vegetation on the crest of both embankment sections of the damresults in relatively low erosion resistance in case of overtopping of the dam.

Erosion of the downstream slope of the embankment near the right abutment,apparently related to trespassing, could result in loss of the embankment, if notcorrected.

3-2

'I- i':

Trees growing at the toe of the embankment sections and small trees growing onthe crest of the embankment section near the left abutment will eventually attainsufficient size to be a possible cause of seepage and erosion problems if a tree

.. blows over and pulls out its roots, or if a tree dies or is cut and its roots rot.Similarly, the roots connected to the tree stump in the dry-stone-masonry wall onthe downstream side of the embankment section near the right abutment will rotI and become potential channels of seepage and erosion.

Logs and timbers dumped at the downstream toe of the embankment section nearthe left abutment make it impossible to inspect that area adequately.

i3

Io_

,I. .

rn . .".,

- ° .°°,.3-3

I"•°

SECTION 4OPERATIONAL AND MAINTENANCE PROCEDURES

4.1 Operational Procedures

-a. General. The Chase Pond Dam is used primarily to create Chase Pond.There are no written or routine operational procedures.

b. Description of any Warning Systems in Effect. No written warning

system exists for the dam.

4.2 Maintenance Procedures

a. General. The owner, Mrs. David Romanoff, is responsible for themaintenance of the dam. No formal maintenance was discussed.

b. Operating Facilities. There are no operating facilities incorporated intothis dam.

S-4.3 Evaluation

- The current operation and maintenance procedures for the Chase Pond Dam- "are inadequate to insure that all problems encountered can be remedied within a

reasonable period of time. The owner should establish a written operation andmaintenance procedure, as w.ell as establish a warning system to follow in event

i I of flood flow conditions or imminent dam failure.

ii"'i

4-1

-------------.A

SECTION 5EVALUATION OF HYDROLOGIC/HYDRAULIC FEATURES

5.1 General. The Chase Pond Dam consists of a rock filled log crib, approximately12 feet high, constructed between two stone and concrete embankments. Theoverall length of the dam is 103 feet. The central overflow spillway extends theentire 50.5 feet length of the log crib, and is formed with timber planking laidover the log crib. Flashboards have been installed to raise the reservoir level tonearly 704 feet NGVD. The dam impounds Chase Pond which serves as a recreationalsite. The Chase Pond Dam is classified as small in size having a maximum storageof approximately 370 acre-feet at the dam crest. Pleasant Lake is located in thesame watershed, approximately 6,600 feet upstream from Chase Pond. PleasantLake has a surface area about five times that of Chase Pond, and obviouslyintercepts the majority of the runoff from the watershed before it reaches ChasePond.

5.2 Design Data. No hydrologic or hydraulic design data were disclosed.

5.3 Experience Data. No experience data were disclosed. Maximum flood flowsor elevations are unknown, although it is known that the dam was washed out inthe 111938 Flood".

5.4 Test Flood Analysis. Due to the absence of detailed design and operationalinformation, the hydrologic evaluation was performed utilizing data gathered duringfield inspection, watershed size and an estimated test flood equal to one-half the

Probable Maximum Flood (1/2 PMF) Although the drainage area is mountainous,the "rolling curve" from the Corps of Engineers set of guide curves was used toestimate the maximum probable flood peak flow rate, in order to account for thepresence of Pleasant Lake.

[ L Based on an estimated maximum probable flood peak flow rate of 1,550 cfs per

square mile and a drainage area of 13.8 square miles, the test flood inflow wasestimated to be 10,700 cfs. The test flood was routed through the dam in accordancewith the Corps of Engineers procedure for Estimating Effect of Surcharge Storageon Maximum Probable Discharge. The discharge was estimated to be 9,890 cfs.This analysis indicated that the dam crest would be overtopped by approximately3.8 feet. The maximum spillway capacity (assuming that the flashboards havewashed away) with the water level at the dam crest was estimated to be 2,230cfs, which is only about 21 percent of the test flood discharge.

* 5.5 Dam Failure Analysis. The impact of dam failure with the reservoir surfaceat the dam crest was assessed utilizing the "Rule of Thumb" Guidance for EstimatingDownstream Dam Failure Hydrographs published by the Corps of Engineers. Theanalysis covered a reach extending approximately 0.4 miles downstream to TanneryPond. Based on this analysis, the Chase Pond Dam was classified as a significanthazard.

,. 5 -1. . ..

. . . . . . . . .

L. - .. ..

L-

Since the dam has a long overflow spillway, the discharge emanating from thedam with the water surface at the dam crest (elevation 707.8 feet) and with theflashboards removed would be about 44 percent of the calculated darn failurei- .-- discharge. Consequently, the impact of the tailwater resulting from the discharge

over the overflow spillway was taken into consideration when examining the stagein the downstream reaches. The various stages discussed in the remainder of thissection include the effect of the tailwater.

Failure of the Chase Pond Dam with the reservoir surface at the dam crest wouldincrease the stage along the immediate downstream channel by over 5 feet, possiblydamaging two of the dwellings and a barn located along this reach. Water would

-- be near the sill level of the two dwellings and would be about 4 to 5 feet abovethe lower foundation of the barn which is built directly adjacent to the streamchannel. A town road and bridge which cross the stream approximately 675 feet

S--. below the dam could also be damaged, since it appears that the bridge openingdoes not have the capacity to handle the dam failure discharge. The increase inthe volume of water entering Tannery Pond would significantly increase the stage

r of the pond approximately 6 to 8 feet, such that three or four houses locatednear the pond would have water 1 to 2 feet above their sills. The dam at theoutlet from Tannery Pond could be overtopped or breached. It appears that there

. .is little potential for loss of life.

5-2

E U O SECTION 6EVALUATION OF STRUCTURAL STABIITY

, .6.1 Visual Observations

The visual examination indicates the following structural problems:

(1) The large settlement in the center of the log crib overflow section andlarge voids of stone fill in the downstream cribbing is evidence of asignificant structural and stability problem.

(2) Subsidence and a sinkhole on the crest of the embankment between thecentral timber section of the dam and the left abutment is evidenceof a significant stability problem.

(3) The lack of vegetation on the crest of both embankment sections ofthe dam results in relatively low erosion resistance in case of overtoppingof the dam.

(4) Erosion of the downstream slope of the embankment near the right* - abutment, apparently related to trespassing, could result in loss of the

embankment if not corrected.

(5) Trees growing at the toe of the embankment sections and small treesgrowing on the crest of the embankment section near the left abutmentwill eventually attain sufficient size to be a possible cause of seepageand erosion problems if a tree blows over and pulls out its roots, orif a tree dies or is cut and its roots rot.

(6) The roots connected to the tree stump in the dry-stone-masonry wallon the downstream side of the embankment section near the rightabutment will rot and become potential channels of seepage and erosion.

(7) Logs and timbers dumped at the downstream toe of the embankmentsection near the left abutment make it impossible to inspect that areaadequately.

(8) Cracks and significant spalling of concrete in the upstream face of theright embankment and in the left training wall.

-- 6.2 Design and Construction Data

No information regarding the original design or construction of the dam wasfound.

6--.

. . .- . ..i

1 16.3 Post-Construction Changes

Early records indicate the dam was first rebuilt in 1922. It was completelywashed out during the 1938 flood and was rebuilt in its present form in 1939. Thewood cribbing and planking was again rebuilt in 1963. In 1973, repairs were madeto the concrete on the right embankment. Since that time, there is no indication - -

* any further construction has been performed.

6.4 Seismic Stability

.This dam is located in Seismic Zone 2 and, in accordance with the Phase Iguidelines, does not warrant seismic analysis.

r.6

.0'+

6--2

* - . .° * . . - .- . . . . . . .

SECTION 7-ASSESSMENT, RECOMMENDATIONS, AND REMEDIAL MEASURES ..

* *- 7.1 Dam Assessment

i a. Condition. Based on the results of the visual examination, Chase Pond -'

V Dam is considered to be in poor condition. The major concerns are:

(1) Considerable settlement of the log cribbing in the center of thespillway structure

(2) Subsidence and a sinkhole on the crest of the embankment section

between the central timber section of the dam and the leftabutment

(3) Lack of vegetation on the crest of the embankment sections of

the dam

r(4) Trees at the downstream toe of the embankment sections and

trees beginning to grow on the crest of the embankment sectionat the left end of the dam

(5) Roots connected to a tree stump in the downstream dry-stone-masonry wall at the right end of the dam

(6) Trees growing at the downstream toe of the dam

(7) Inadequacy of the spillway to pass the test flood.

(8) Apparent lack of a low level regulating outlet that would allowdrawdown of the pond in an emergency

b. Adequacy of Information. Logs and timbers dumped at the downstreamtoe of the embankment section at the left end of the dam make it impossible toinspect that area adquately. It should be inspected after the logs and timbers havebeen removed.

The information available from the present visual inspection is adequate to identify

the potential problems listed in 7.2. These problems require the attention of a

qualified registered professional engineer who will have to make additional engi-neering studies to design or specify remedial measures. No other engineering studiesare needed for the purposes of this Phase I inspection.

c. Urgency. The owner should implement the recommendations in 7.2 and7.3 within one year after receipt of this Phase I report.

7-1

. . -. . . . .." .. - ..... . ..-.....-...... ..-...... -.... . .... .... - -... .. .-,,..-,.....-.-.,.,- ...-. . -

7.2 Recommendations

The owner should retain a registered professional engineer qualified in thedesign and construction of dams to do the following:

(1) Investigate the settlement of the log crib spillway in the centerof the structure and design remedial measures, if necessary.

(2) Investigate the subsidence and sinkhole on the crest of the embank-ment section at the left end of the dam, and design remedialmeasures, if necessary

(3) Do a detailed hydrologic-hydraulic investigation to assess furtherthe potential of overtopping the dam, the adequacy of the spillwayto pass the test flood, and the need for and the means to increaseproject discharge capacity

(4) Assess the need for and means to provide a low level regulatingoutlet that would allow drawdown of the pond in an emergency

The owner should implement the recommendations made by the engineer.

7.3 Remedial Measures

a. Operation and Maintenance Procedures. The owner should:

(1) Repair the cracks and spalling of concrete in the upstream faceof the right embankment and in the left training wall

(2) Maintain the embankment and a zone 25 feet wide at the down-stream toe area free of trees and brush

(3) Establish and maintain grassy vegetation on the embankments

(4) Clear trees and brush from a zone 25 feet wide on either side

of the discharge channel for a distance of 100 feet downstreamfrom the dam

(5) Engage a registered professional engineer qualified in the designand construction of dams to make a comprehensive technicalinspection of the dam once every year

(6) Establish a surveillance program for use during and after periodsof heavy rainfall, and also a warning system to follow in case ofemergency conditions

7.4 Alternatives

There are no practical alternatives to the recommendations of Section 7.2

and 7.3.

7-2

APPENDIX A

INSPECTION CHECK LIST

. .-

INSPECTION CHECK LIST

PARTY ORGANIZATION

3PROJECT: Chase Pond Dam, NH DATE: November 27, 1979

TIME: 1: 15 P.M.

WEATHER: Cool, sunny

W.S. ELEV.703.7 U.S. 691.2 DN.S.U-.S.G.S. DaEu-T-

PARTY:1. Kenneth Stewart, S E A 6. Kenneth Stern, NHWHRB

2. Robert Durfee, S E A 7. Richard DeBold, NHWRB

3. Bruce Pierstorff, S E A 8. _________________

* . 4. Philip Ricardi, S E A 9.__________________

5. Ronald Hirschfeld, GEl 10. _________________

* .PROJECT FEATURE INSPECTED BY REMARKS

*1. Structural stability K. Stewart/R. Durfee

h2. Hydrology/hydraulics B. Pierstorff/P. Ricardi

3. Soils and geology R. Hirschfeld

4.

5.-

6.

* 7.

8.

10.

A- 1

INSPECTION CHECK LIST

PROJECT: Chase Pond Dam, NH DATE: November 27. 1979

PROJECT FEATURE: Dam Embankment NAME: _ _..

DISCIPLINE: NAME: -_"__.

AREA EVALUATED CONDITIONS

DAM EMBANKMENT Left End of Over- Right End ofFlow Section to Overflow SectionLeft Abutment to Right Abutment

Crest Elevation 707.8

Current Pool Elevation 703.7

Maximum Impoundment to Date Unknown

Surface Cracks None observed None observed

Pavement Condition Not paved Not paved

t Movement or Settlement of Crest General subsidence, None observed

up to 1 ft with sink-holes next to dry stonemasonry wall at d.s.edge of crest

Lateral Movement None observed None observed

Vertical Alignment See "Movement or None observedSettlement of Crest"

Horizontal Alignment Good Good

Condition at Abutment and at Subsidence next to GoodConcrete Structures concrete wall at left

end of overflow section

Indications of Movement of StructuralItems on Slopes None observed None observed

Trespassing on Slopes Timbers and logs Footpath on d.s.dumped against d.s. slope next to right end

S- toe of overflow section

Vegetation on slopes One small tree on Several trees atcrest. Several trees d.s. toeat d.s. toe

Sloughing or Erosion of Slopesor Abutments None observed None observed

* Rock Slope Protection - Riprap Failures No rip rap No riprap

Unusual Movement or Cracking at or Near T, None observed None observed• - Unusual Embankment or

Downstream Seepage None observed None observed

Piping or Boils None observed None observed

Foundation Drainage Features None observed None observed

Toe Drains None observed None observed

Instrumentation System None observed None observed

A-2

.. ,,,','- • .... ... ". -...... ................ ,,<<... ...... ...... "-." ."•""

INSPECTION CHECK LIST

PROJECT: Chase Pond Dam, NH DATE: November 27, 1979

PROJECT FEATURE: Dike Embankment NAME:

- DISCIPLINE: NAME: .-__,

AREA EVALUATED CONDITIONS

DIKE EMBANKMENTNo dike

Crest Elevation

Current Pool Elevation

Maximum Impoundment to Date

Surface Cracks

Pavement Condition

Movement or Settlement of Crest

Lateral Movement

& Vertical Alignment

. . Horizontal Alignment

- " Condition at Abutment and atConcrete StructuresI "Indications of Movement of StructuralItems on Slopes

- Trespassing on Slopes

Vegetation on Slopes

Sloughing or Erosion of Slopes or Abutments

'" Rock Slope Protection - Riprap Failures

Unusual Movement or Crackingat or near Toes

"- Unusual Embankment or Downstream Seepage

Piping or Boils

Foundation Drainage Features

• " Toe Drains

Instrumentation System

A-3

INSPECTION CHECK IST

- PROJECT: Chase Pond Dam, NH DATE: November 27, 1979

PROJECT FEATURE: Intake Channel NAME: _____________

r - DISCIPLINE: _____________ NAME: _________

AREA EVALUATED CONDITIONS

OUTLET WORKS - INTAKE CHANNEL ANDINTAKE STRUCTURE No intake channel or intake structure

a. Approach Channel

Slope Conditions

Bottom Conditions

Rock Slides or Falls

1 Log Boom

Debris

Condition of Concrete Lining

5Drains or Weep Holes

b. Intake Structure

Condition of Concrete

Stop Logs and Slots__

L

A-4

INSPECTION CHECK LIST

PROJECT: Chase Pond Dam, NH DATE: November 27, 1979

PROJECT FEATURE: Control Tower NAME:

DISCIPLINE: NAME: _..

AREA EVALUATED CONDITIONS

OUTLET WORKS - CONTROL TOWER No control tower

a. Concrete and Structural

General Condition

Condition of Joints

Spalling

Visible Reinforcing

- Rusting or Staining of Concrete

Any Seepage or Efflorescence

Joint Alignment

RUnusual Seepage or Leaks inGate Chamber

Cracks

Rusting or Corrosion of Steel

b. Mechanical and Electrical

Air Vents

Float Wells

Crane Hoist

Elevator

Hydraulic System

Service Gates

." Emergency Gates

Lightning Protection System

Emergency Power System

Wiring and Lighting Systemin Gate Chamber

PLA-5

.. . • . _ .. .. .. . .. -: .... -. .. .. .. .. -. .. " .' - . . - . . . . .. . . ° . . .. . • . .. . .

INSPECTION CHECK LIST

PROJECT: -Chase Pond Dam, NH DATE: November 27, 1979

PROJECT FEATURE: Transition and conduit NAME: ___________

" DISCIPLINE: __ _ _ _ _ _ _ _ _ _ _ _ _ NAME: _ _ _ _ _ _ _ _ _ _

*AREA EVALUATED CONDITIONS

I ~ OUTLET WORKS - TRANSITIONAND CONDUrT No transition and conduit

General Condition of Concrete

Rust or Staining on Concrete

Spelling

*Erosion or Cavitation

* r Cracking

- Alignment of Monoliths

* Alignment of Joints

~.. Numbering of Monoliths

A-6

INSPECTION CHECK LIST

PROJECT: Chase Pond Dam, NH DATE: November 27, 1979

PROJECT FEATURE: Outlet Structure NAME: -

I DISCIPLINE: NAME: -__ _"

AREA EVALUATED CONDITIONS

OUTLET WORKS - OUTLET STRUCTUREAND OUTLET CHANNEL No outlet structure, or outlet channel

General Condition of Concrete

Rust or Staining

Spalling

Erosion or Cavitation

Visible Reinforcingr

Any Seepage or Efflorescence

Condition at Joints

Drain holes

Channel

Loose Rock or Trees OverhangingChannel

| Condition of Discharge Channel

A-7

-- ~.".. -.

INSPECTION CHECK LIST

?ROJECT: Chase Pond Dam, NH DATE: November 27, 1979

VROJECT FEATURE: Spillway Weir NAME:

DISCIPLINE: NAME:

AREA EVALUATED CONDITIONS

OUTLET WORKS - SPILLWAY WEIR,

APPROACH AND DISCHARGE CHANNELS

a. Approach Channel

General Condition Good

Loose Rock Overhanging Channel None

Trees Overhanging Channel Some trees overhanging, but channel is wide

r Floor of Approach Channel Not visible beneath pond surface

b. Weir and Training Walls Wood crib weir with concrete training walls

General Condition of Concrete Fair, a few large cracks

Rust or Staining None visible

Spalling Moderate

S . Any Visible Reinforcing None

' Any Seepage or Efflorescence Moderate through 2" x 8" stop logs on topof cribbing

Drain Holes None

c. Discharge Channel

General Condition Fair

Loose Rock Overhanging Channel None observed

Trees Overhanging Channel Trees overhang channel

Floor of Channel Bedrock and large boulders

Other Obstructions None observed

A-3

INSPECTION CHECK LIST

PROJECT: Chase Pond Dam, NH DATE: November 27, 1979

PROJECT FEATURE: Service Bridge NAME: ___________

DISCIPLINE: _______________ NAME: ___________

AR;EA EVALUATED CONDITIONS

OUTLET WORKS -SERVICE BRIDGE No service bridge

a. Super Structure

Bearings

Anchor Bolts

Bridge Seat

Longitudinal Members

Under Side of Deck

Secondary Bracing

Deck

Drainage System

Railings

Expansion Joints

t Paint

b. Abutment & Piers

General Condition of Concrete

Alignment of Abutment

Approach to Bridge

Condition of Seat & Backwall.

A- 9

APPENDIX B

ENGINEERING DATA

AVAILABLE ENGINEERING DATA

No Engineering Data other than past inspection reports from the State ofNew Hampshire Water Resource Board were available.

l V

a

0iii-

•

.'- .,

*

I

.1

I

PAST TNSPECTIOI~I REPORTS

£

K

0

0'

B-2

. * . * . . ** .

MEMO

Date: November 30, 1979 6 (To: Vernon A. Knowlton, ¢ i,

Chief Engineer

From: Ken Stern,Water Resources Engineer

Subject: Chase's Pond Dam, No. 253.02, Wilmot Flat

On November 27, 1979 Dick DeBold and I accompanied the inspection team fromSEA Consultants. The dam is a log crib with timber planking between stone andconcrete abutments. It appears to be in good condition. The crest has a 6 to9 inch sag. The abutments are in good condition with the exception of a crackin the left concrete facing and some minor erosion of the right embankment.The dam is classified as a menace structure due to possible damage to a downstreambridge. The potential for loss of life is slight. There is a dam downstream atTannery Pond that has very little freeboard and would probably fail if ChasePond Dam failed.

r I believe any action on this dam can wait until the Corps' report is received.

KS:paf

40B-3

* Dam No. 253.02, Chase's Pond Dam, inspected by Ken Stern on November 27, 1979

View from upstream

YT.

View from downstream

B-4

NEW HAMPSHIRE WATER RESOURCES BOARD

I iINSPECTION REPORT

Town: W AIL4 (-.iO 1.-F Dam Number: ZS "3'. 0 Z_-

Name of Dam, Stream and/or Water Body: F-5'J--), C740 rA-4

Owner: ____________ _ _ _ _ Telephone Number:

Mailing Address: I/iLLA..c j' .'I W,.,OT FLAT-

//

Max. Height of Dam: /0 Pond Area: 7 C..-;F5 Length of Dam: )00

FOUNDATION: tQ)UI1.QAJ4" 2.- -rjutL W/' LA-C- 0ooL ---_

OUTLET WORKS:

. Ltv~- '~?~ s?'.u'"'- o'~&~~-e ~~

._ - f 11S s a r- .- .-- /T~f .f.

-tP -- ... "A'~~I,-'~~I' .DW&.- .. ~. .ij ..

* ABUTMENTS: g< t.- o,)- '-- )O 5eF7---r e

0- L -.- ,- "

EMBANKMENT: -- ,_-TW ,6r _-rDn-oJ¢ Mt- HVSS C ..

.Note: Give Sizing, Condition and detailed description for each item, if applicable.B-5 .

• . ° . . ,

-2- Dam No.

SPILLWAY: Length: Freeboard: S. ; , FZ "6-fApJV.;-r <ZE5-"-

I SEEPAGE: Location, estimated quantity, etc.

-- [~~L 6-A La .=S : T H I .oO & O :c z , .) ,-. -

I ,

Changes Since Construction or Last Inspection:

• "" Tail Water Conditions:

Overall Condition of Dam: jI- -

Contact With Owner: P-)C)

Date of Inspection: 1)/z z7 Suggested Reinspection Date '

Class of Da:

.- . . -i O d.-

- .ignature

Date___________________

B-6

K. *p- nrive Rizine. Condition and detailed description for e3ch item.if applicable.

-3- ~~Dam No._______

COlMNTS:

&LEAZ- FZ~ eL- 139-oep &J-~

-r"L-2/,5 S Q'.~ PrA teje

B-7

-4- ~~Dam No._______

SKETCH OF DAM (Show Plan, Elevation & Cross Sections)

LI

B -8

N. H. WATER RESOURCES BOARDConcord, N. H. 03301

DAM SAFETY INSPECTION REPORT FORM

Town: \__ _ _ _-_ _ Dam Number: T5 , 6

Inspected by: Date: a ,, 14

Local name of dam or water body:

Owner: PC'-) i2- Address: j; f A/~

Owner was/was not interviewed during inspection.

Drainage Area: _sq. mi. Stream:

Pond Area: Acre, Storage Ac-Ft. Max. Head Ft.

Foundation: Type , Seepage present at toe - Yes/No,

Spillway: Type , Freeboard over perm. crest: ,

* Width , Flashboard height , . -

Max. Capacity c.f.s.

Embankment: Type , Cover Width__

Upstream slope to 1; Downstream slope to 1

Abutments: Type , Condition: Good, Fair, Poor

Gates or Pond Drain: Size Capacity_ Type

. Lifting apparatus Operational condition________

Changes since construction or last inspection:

Downstream development:___ _

This dam would/would not be a menace if it failed.

Suggested reinspection date: _ _ _ _ _ _

Remarks: ea f 20 In I -',;

B--

,-.. ................-.-..- , - .. . .. - ........... ..........-...... .. -... .. .-... . -.., :

WILMOT -#253.02

NOVEMBER 22. 1974

If

* DEPARTMENT OF THE ARMYNEW ENGLAND DIVISION, CORPS OF ENGINEERS

) 424 TRAPELO ROAD

WALTHAM, MASSACHUSETTS 02154

IN REPLY REFER TO

NEDPL-P 9 August 1974

Mr. David RomnanoffVillage Road

Wilmot Fiat, N. I-. 03287 , ',...,, .._

Dear Mr. Romanoff:

This is to inform you of the results of our reconnaissance investigation

of the condition of Chase Pond Darn in Wilnot Flat, New Hampshire.f {Our study was initiated in response to a letter of Z4 April 1974 from

Congressman James C. Cleveland, on your behalf. The investigationwas conducted under authority contained in Section 205 of the 1948Flood Control Act, as amended.

Members of my staff met with you on 26 June 1974 to inspect the ..-

problem area. Our investigation disclosed that the dam is utilizedstrictly for recreation and is privately owned. In addition, the damserves no flood control purpose. Any recreational benefits, accruableto repair or reconstruction of the darn or any appurtenant structures,

coiud not balance the cost of such construction work. Therefore,

Federal assistance is not justified in either a policy or economicsense under the authority contained in Section 205 of the 1948 Flood

Control Act, as amended.

While the Corps of Engineers is unable to provide aid to you underexisting authorities, the following information may be helpful to you.

Chase Pond Dam is a rock filled, timber crib overflow structure

which impounds a pond having a surface area of 36 acres. The timber

overflow section is about 1Z feet high and 35 feet long. The timbersare composed of 8, 10, and 12-inch round logs which are in fairlygood condition. These timbers are arranged in cribs which are rockfilled except for the downstream cribs, which have several large

void areas. The spillway deck planks, composed of 2" x S" andZ" x 6" planks, are also in good condition except for a few nails whichare exposed. The deck-planking in the middle of the structure shows

signs of minor settlement.

B-i1

NEDPL-P 9 August 1974Mr. David Ronanoff

The non-overflow abutments are composed of unmnortared masonry,partially faced with concrete. and are about six feet higher than the

* overflow section, It was observed that the right abutment rests onbedrock while the left abutment foundation conditions could not be

Kaccurately determined within the scope of our study but, most likely,it is also founded on bedrock. The concrete facing on the left abut-ment showed some cracking and deterioration. A scour hole, about3 feet deep, has been formed at the downstream toe of the overflowsection. This scour hole did not appear to be under-ining the cribs.

All evidence suggests that there is no serious threat to the stabilityof the dam and overall the dam is considered safe. However, thefollowing remedial work should be undertaken to prevent futuredeterioration of the structure:

. The nails in the deck planking which are loose should beredriven."

2 The concrete facing on the left abutment shows somecracking and deterioration of the concrete. These cracks should

......- be s-ealed. This abutment will probably require a refacing, similarto that performed on the right abutment in 1973.

3. Settlement of the spillway deck planking is probably causedby minor adjustment and deterioration of the underlying timber criband support beams. A periodic measurement of the settlement couldbe made to establish a time pattern of any future movements,

The item of improved flow control at Chase Pond Darn and coordinationwith controlled discharge from upstream lakes was evaluated. However,regulation of stream flow lies within the jurisdiction of the NewHampshire Water Resources Board and you may wish to obtain infor-mation directly from them. You should address correspondence to:

Chairman, New Hampshire Water Resources Board,37 Pleasant St., Concord, N. H. 03301 (Tel. No. 603-271-3406)

3-12

~ - ,- ,.

NEDPL-P 9 August 1974I Mr. David Romanoff

Lastly, the problem of cleanup of stumps on the bottorn of thelake, in addition to cleanup of the shoreline, was considered.It is suggested tbat before you pursue any cleanup of the pond it-self, you should consult with the proper State agency that wouldhave an interest in this problem. On this matter you shouldcontact:

DirectorNew H--ampshire Water Supply and Pollution Control Commission

,105 Laudon RoadConcord, New Hampshire 03301Telephone No. 603-271-3503

6While the Corps of Engineers is unable to provide aid to you underexistin-- authorities, I hope these suggestions and referrals will

*prove to be of assistance to you.

I - Sincerely yours,

JOSEPH L. IGNAZIOChief, Planning Division

copy furnais hed:Mr. Vernon Knowlton

- N. H.L Water Resources Board37 Pleasant Street

* _Concord, N4. H.L 03301

3 3

B-.L

DATE: September 15, 1969

FROM: Francis C. Moore

SUBJECT: Chase Pond Dam, Wilmot #253.02

TO: Vernon A. KnowltonWater Resources Engineer

On September ii, 1969, In inspected Chase Pond dam in Wilmot. This dam isin good condition. The dam is rated as a potential menace if allowed to

fall into disrepair as there are bridges and roads downstream.

The owner, John G. and Myrtle Newcomb should be notified that within a fewyears the upstream wing wall to the spillway (looking downstream) should berefaced with concrete as it is deteriorating considerably.

This dam should be reinspected in 1974 to determine its safety.

FC-M/j b

I i

,

B- 14

N. H. WATER RESOURCES BOARDConcord, N. H. 03301

DAM SAFETY INSPECTION REPORT FORM

Town: / ; Dam Number: - ,--- .--

* . Inspected by: ' : . / Date: i' I /9"/Local name of dam or water body: - - ,

Ce7 ,' *. J k .4%Y '..,. Address: ,'.".,.

Owner /was not interviewed during inspection.

Drainage Area: /[', sq. ml. Stream: ._,_,_,:________

Pond Area: __ _ __ _Acre, Storage /i&-' Ac-Ft. Max. Head /1. Ft.

Foundation: Type YL-t. ! .a-, , [ Seepage pr sent toe -- Y. No, //J

Spillway: Type - , Freeboardover perm. crest: Swidth___________ __________,__,."__01

Width- Flashboard height________

Max. Capacity _ !-- c.f.s.-:rbankmet : yp id t-.!_ Type,4_____ Cover 'r"." Width /-

Upstream slope V_____ to 1; Downstream slope to I

Abut-ents: Type .t-l' , Condition: Go Fair, Poor

dates or Pond Drain: S iz e 4 S l.A'ci .4 P/. 4riType )

Lifting apparatus /Y 1 Operational condition ?#Changes since construction or last inspection: 5/M1 . 6 &- z As 1

;/ q .,!/ ;

* Downstream development:

This dam wouldyw;ld-net be a menace if it failed.

Suggested reinspection date: / -"

.* -: ,, ,. ,-,_ . :/ ,./. , -ib ! I: ; / ,.. ,.<.Remarks: "

3 /

.. _ , ., ,-V-- .-.- ".<h .,.:,- -", ..."".,%""".....

THE STATE OF NEW HAMPSHIRE

I ~~ ~ ~ ~ ~ ~ ~ Jl 12ony''--- s _________ 63.County of Merrimack ssJuly 12

STATEMENT OF INTENT TO 1)j

RECONSTRUCT A DAM AT CHASE PONl WII OT, N.H.

TO THE WATER RESOURCES BOARD:

In compliance with the provisions of ESA 482:3.

I, JOHi G. NE C IB

(Here state name of person or persons, partnership, association, corporation,

* etc.)

hereby state our intent to the Water Resources Board 1, to reconstruct, and/orto make repairs to, a dam (cross out portion not applicable) across:

The northeast corner of Chase Pond where a dam now einsts

(Here state name of stream or body of water)

At a point S.ee abo7e __..__-._I (Here give location, by distance from muth of stream, county or

municipal boundary)

in the town (s) of Wilmot (Wilmot Flat) New Hampshire _ _-___

in accordance with PRELIMMARY PLANS, and SPECIFICATIONS FILED WITH THIS STATEMENT

AND MADE A PART HEREOF.

understand that more detailed plans and specifications may be requestedby the Board in conformance with RSA 482:4 and that, if such plans are requested,-construction will not commence until such plans have been filed with and approved

by the Board.

~~~B-16 -- "

maintain Chase Pond for scenic,The purpose of the proposed construction is

(Here briefly state use to

fishing, boating and other recreation purposes.

which stored water is to be put)

The construction will consist of Io cribbing with two inch nlanks. In other(Here give brief description of

words, the existing structure will be duplicated, with the exception of a gate added to

work contemplated including height of dam)

the upper structure so that the water level can be lowered during the winter and spring

seasons. The present height of the dam, which is about 17 feet, will not be increased.

All land to be flowed is not owned by applicant.is

Address Village RoadIWilmot Flat, New Hampshire

S- Note: This statement together with plans, specifications and information anddata filed in connection herewith will remain on file in the office ofthe Water Resources Board. This statement is to be filed in duplicate.

B-17

7

NEW HAMPSHIRE WATER CONTROL COMMISSION

DATA ON DAMS IN NEW HAMPSHIRE

LOCATION STATE NO. .5.3.. ................

aTow nm ................... .W. ..Q............................................... County .................... m -rr.iM . .......................................

S a .................. B.a ia aeP..rP dm .... /...........................................................................................................................................

ocBasin-Primary am e. rixac..R ..................................... ... C1Q.a oQ ....R.. ...........................

L ocal N am e ................................................................................................................................................................................

Coordinates-Lat .L....... o .. 5 .6...t.................................. : Long .6............ U......5 ,...-0. , .t ....................................GENERAL DATA

Drainage area: Controlled ........ Sq. Mi.: Uncontrolled ......... Sq. Mi.: Total..o1..5....Sq. Mi.

Overall length of dam .... 12 .ft.: Date of Construction ......... . . 2.2.............

Height: Stream bed to highest elev .... 1.... ... ft.: Max. Structure ........... 15,4 .................... ft.C ost- D am ........................................................................ : R eservoir ................................................................................

DESCRIPTION Stone,Blo.cks,Concrete,earth,,timber /Waste Gates

T ype .......................................................... .s.t.one. .o .en jy ... ....................................................................................

N um ber ................................ : Size .............. ?........ ft. high x ............ - ........................................................ ft. w ideElevation Invert ............................................................ : Total Area ............................ sq. ft.

Hoist..............................................................................

Waste Gates ConduitN um ber .................................................... M aterials ........................................................................................................

. Size ................................ ft.: Length ................................ ft.: A rea ..................................................................... sq. ft.

Embankment

Height- ax................................ .. ft.: Min ...................................................................................Hih- a ....... ........ ft.: Mm . -................ ft.******* ..

T op- W idth ................................................................ : E lev . ................................................................................... ft.

Slopes--Upstream ........................ on ........... : Downstream ............... on......................

Length-Right of Spillway ................. Left of Spillway ............................

SpillwayM aterials of Construction ............... .1 .................................................................................................................

Length-Total .............. 50.......... ft.: Net ................................................................................ ft.

Height of permanent section-Max . ..... ft.: Min .................. . ..................... . ft.Flashboards-Type ................ None ....... ...................... Height ................................................ ft.

Elevation-Permanent Crest ........ ... ... . . . . . .... : Top of Flashboard ......................... "

Flood Capacity ............................................ cfs.: .................................................................... cfs/sq. m i.

Abutments

M aterials: ...........................................................................................................................................................................

F reeboard : M ax .............. 2 ..................................... ft.: M in . ................................................................................... ft.

Headworks to Power Devel.-(See "Data on Power Development")

OWNER .............. ..... C..... . ......... ..... .......... ...... .REMARKS"•R M.S Condition fair Dam is Uenace. Use is conservation for Ind.

T abulation B y ..................... R U ........................................... D ate ..................... 9 / 26 439 .................................. ...............R&321234 B-1"

- - - - - - . . .. . .

MMOARANDUMj

Case No.C90-C

TO: Richard S. Holmgren, Chief Engineer

RE: Case No. C90-C - Dam No. 253.02 - Chase Pond in 7ilmot Flat

Made final inspection of construction of dam at Wilmot Flat onMarch 6, 1939. 'Was accompanied by representative of N.P. Clough Company

* and Mr. Simpson, land orner on the pond.

The dam is completed as specified with the following changes:Instead of allowing for 40 inches of freeboard, there is now an allowa.ceof 54 inches of freeboard. There are at present installed 30 inches offlashboards and it is understood that another 10 inches will bring thepond to its natural high water level. No gate was incorporated in thestructure for dra own of the pond but provision was left for taking outthree sections of planking on the upstream face if this became necessary.The flashboard bays are 8.6 feet in length using 2 x 10 stop planks. Theplanks are fitted with eyes for hooking out in case removal is desiredof any number of stop planks. The standards holding the stop planks arefeathered on to the planking with braces against the downstream faceof the dam. Mr. Stanley who was present at the latter part of theinspection was of the opinion that in case of extreme head or icepressure, these members would fail, giving us a clear spillway. Thereis some bending of the stop planks due to the extreme length of the bayand subject to your approval, Mr. Stanley will cut the bay length td

4.3 feet with a weaker member in the center designed to let the stopplanks go out with a head at abutment height.

" Subject to that change, I recommend that final approval be

given to the dam, and I believe that this approval if given izediately=- would help Mr. Stanley as the group are holding up his pay subject to

final approval of the structure by the later Control Commission.

Respectfully submitted,

"Charles D. olman -

Assistant Engineer

, .8

B-19

,_ .- _ ._ -, . . _ - :. - . . . . . - ,. •.. . . v .. .' - . •.. . .. ... . .. - ,, .'.. , - ,. ...

eTATER CO'.T.RL CLO2!I SION

STATE OF . HAITPCH'IE2

Concord, N~ew Hampshire

0ctobaT 11, 1958.

N P Clough & Co.,,ilmot Flat N H

RE: Ch;se Pond Im. v. . C. poZ53.02

Gentlemen:

In order that we may determine the magnitude and ex-tent of the flood of September 21-24 just passed, we are re-questing the various dam owners In the Otate to supply us with

the folloy.ing information:

1. "Fas this dam injured? Ans.

2. If so, to rhat extent? Anis. .k

" 3. Did all flashboards Ans.___"'"_._go out?

4. TPhat was the maximum Ans.height of water over J _"

the permanent crest '_ _ _ _.

of spillway? __ _-'___

5. At what day and hour A..s.± 9did the maximum flood Iheight reach your dam? "

6. Any other interesting information regarding the floodor rain fill may be given on the back of this sheet, or atzachormsheets. s

7'ill you please return this letter with as much in-Pformation as you can ,ive us as pro nTpt! - as possible. A self-"-

Saddressed envelope is attached hereto.

.e thank you for your cooreration.

Very truly yours,_

/ Y ;/W

Richard 2. KolmCrenCDC:G1 Chief EngineerEnc .

B-20

Form WCC.17/30/37

THE STATE OF NEW H&1fPSHIRE

SoCounty ofPETITION FOR AMPR A OF THECINORRPI OF

TO THE WAIER CONTROL COMISSION;

In complianco with tho provisions of Laws of 1937, c.133, an ActcstablishinA a Water Control Comi 'ion,

Wo, cj"L \- 49I, (Hare state naMetof parson or parsons, partnership, assosia.tion,

corporation, etc.)

. . hereby petition the Wator Control Ccmission for approval to construct,to reconstruct tow r-ypaio- dom, a or (cross out portionnot applicabl f ".'-

* across* (Here state narq of stream or body of water)

aa point 1 7Z" ~ VZi~~,WJJ ' 1/(Hare give location, by distance from -of stro a,

*I county or =unicipal boundary)

in the toVw (s) c .

in accordanco with preliminary plans, and specifications filed with.this applicaticn and made a part horeofe

-0.

' ~B-21,-_.

Form WCC.3-p.27/30/37

The purpose of the proposed construction is wi, A _i (hjro briefly

oAJ4 'IA I A

state uce to which-stored wator I to lo puff)

The construction will consist of ~C ~kHoro give briof dcacription of

work contemplated including height of dam)1

r .

All land to be fl owoscd b pliateis ow~cd y appio,.

Seal" ___

Addross_

Note: This application together with plans, spocifications andinformation and data filed in connection horcwith, willremain on file in the office of the Wator Control Comris-sion.

B

B- 22 -:

NE.7 !iA~rPsi:TP f"E -:s.7:P.ES iCAAD

r EcRYOF DA:.13 A!TD VAER Pc'rr-.R

k-. ;1 CTEr2,I

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EA5 ITF:C,. V '7-~ -- T~ -Dx 65TZ 3ELC'i CRES?.

RE:VARBCS

1177: TC. HP FEET -UL E FV. !{1;

-7 _ _ _ _ _ __ _ _ __ _ _ __ _ _ __ _ _

PA -- E-

B-23

-I . _ _ _ . . . . . , . o _ . . . . . .. - : .

• ~PLANS AND DETAILS .- "

n

S °

-3-.:4

- .. - --. .

a,.. ?

' ' I*... '...

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F)' F-""'

L.i

S

APPENDIX C

SELECTED PHOTOGRAPHS

So

"i I

I -

"- >

i i-i

U,,I

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-_ ..c - : . . ;:; , : _. : . :. . .- , . . , . , . : - - :._ .: , : - . :,2 L 2: ,,.I:: :

0 "-

Photo No. 1 - General view of reservoir fromright abutment.

a -- ,

I-- L

I

Photo No. 2 - General view of dam fromreservoir.

% .. .-

Ii 2

- ,

Photo No. 5 - View of crest of dam and leftabutment from right abutment.

" .

Photo No. 6 - Closeup of spalling & cracking ofconcrete training wall at left endof overflow section (same view as 5).

3

Photo No. 9 -View of overflow section lookingupstream (Note depression of woodcrib planking).

to,-

Photo No. 10 - Closeup of wood crib overflowsection at left abutment.

5

ilk1

t Photo No. 13 -General view of dam from downstreamchannel.

* Photo No. 14 -General view of downstream channelimmrediately below dam.

7

I

II

* Photo No. 17 - View of channel and bridgelooking upstream.

* Photo No. 18 - General view of downstream areaapproximately 100 yards belowbridge (Tannery Pond).

9

APPENDIX D

HYDROLOGIC AND HYDRAULIC COMPUTATIONS

4Z

41 U

CL 0

II

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Gto

6I

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DETAIL -C . 6- ____. DATE __

Stac~e

d. Ave age ~ an'.e "7

- -- .

1

V 2

d . A v e r a g e V l a n . : - '!'

il Va.(1) Vavg - 1.+.

VavgV 'avg = 5 -4 c .-c--t--

(.2] P2 2 20 - •

Qpz ODCcT;:

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SIEIA CONSULTANTS INC. BosroN~ f"ss

iENGINjEERs/ PLANNERS ROCME 5TEMN H-

CLIENT rrm J- s Jo No3fl . 4-- PAGE- -

PROJiECT-r- N - v COMPTO. 13 0_____ DAT E-

DETrAIL 1 c 7C~C .- alcs. CK'0. BY _______ DATE_______

-- 7- P repare stage.-,-is-ha-:-

a. z:ert inent Data

(11, Reach leng7th

... annel -,..

-

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SIEIA CONSL LTAIJTF *r. ;

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CLI ENT J-m 0~ F3__ Jo INo n__ PAGE 2- --

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C. CoimuteV un-

From Figure

- ~Stage ~ -:

X-area =C.)u~.;,

d. Averagre V~ an- ,a _

V + V

(.1) Vavg - 1

V

V a g

C a2

Q ? Dc-sK

AD-A156 379 NATIONAL PROGRAM FOR INSPECTION OF NON-FEDERAL DAMS 2/12CHASE POND DAMI (NH 99 .(U) CORPS OF ENGINEERS WALTHAM

-iSIID MR NEW ENGLAND DIV MAR 88

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MICROCOPY RESOLUTION TEST CHART

NATIONAL BUREAU OF STANDARDS-1963-A

7-7

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SIEIA CONSULTANTS INC. BOSTON , MASS.

ENOINEERS / PLANNERS POCNESTER, N.H.

CLIENT Army Cores Joa No. 2%4-7901 PACE .+ -. '

PROJECT .e. , -- COMpTO. By BW)ATE '? 4""OETAIL Hydrolozic Calcs. CKCO. By OAT --

.STEP 3 Prepare stage-disclharge curie for Reach

a. Pertinent Data

(.) Reach length

(2) Channel slope =

(.3) Manning % O-"(1L Channel shape -

C51 Base width l 2 e_. -

b. See Figure 3 for stage-discharge curve

~r Z STEP ': Estimate Reach Outflow

a. Determine stage for QP3 ' \ZQ CJ from Figure 3and find volume in reach

(1) Stage (depth of flow) 0 ., -rev_ %:-

'" /~~cross-sectional ..-..(2) Volume in reach (reach length) roa of coal] 1

(~area of channel)

X-area "CI .. • ;•

Volume -V1 : -- .)

SS- \".Q -L -. l-

1 " reach length OK

b. Determine Qp (T"IAL)1.

QP4.(TRIAL) '\ - . _

- .... . . . . . . . . . .AL) : ". -- --

T~~ IF A.L'"

.. _"--..% _ "._ -"-.--_-',- " -' _' -"._.."-- ."-- '',"" "" - ': i, _t._-" -'-"_.' .:.. -. ,," -' , i' " ]''l """"" """ " " "-"-" ""-"T "

SIBIA CONSULTANTS IC OTNMS

ENGIN.EERS / PLANNYE92 ROCMESTER. N ."

CLiErwT Army Corps Je No. 2'~JI PAGE ZPaOJEcT '..CompATO. By?. DATE -

DETAIL T4tnn;ie- C~-c- CK'o. Ely k DATE

c. Compute V2 sn P~RA

From Figure 3 determin It e r P1RAL)

I aStage 3~4

X-area (0 (s4.-Q 1 --

2 r

d. Average V 1 and V 2 and c'-,n-

I Vi + V2(1) Vavg

Q~14, ~0 C A-I..l

-

Vavg

C2IQp,. aT

......................... 3

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- SIEIA CONSULTANTS INC. SIOON MASS.

ENGINEERS / PLANNERS ROCHESTER N.M.

CLIENT t- ,.. Joe No. : - " PAG E-. ..

P R O J E C T - " ; " " -' . ". " C O M P T O . B y O) A T S "_ _-, . . ..'."_

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I 31KIA CONSULTANTS INC. SOUTON *MASS.ENGINEERS PLANNERS ROCNME~Ru, N.M.

CLIENT r~ ' JOB No._______ PAGE .Z oPmojuc-r C. CompTro. By OATE --

AJ2Ai- Cgco. By - OATS ~/

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[ SIEIA CONSULTANTS INC. BOSTON~ MASS.aNGSNGERS /PLANNERS ROCH.ESTER.* N.M.

2 4-CLIENT (4vx Co.-QDc Joe______________ -:

PROJECT 5 9 .c, '~- Compiro. By _______ Alre..

DETAIL L-~.~ CSCbao. By DATE ______

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