OHIO RIVER BASIN 9MILLER RUN, WESTMORELAND COUNTY

DERY PENNSYLVANIA

04' DERRY ROD AND GUN CLUB DAMNDI ID NO. PA-518

DEFP ID NO. 65-143

DERRY ROD AND GUN CLUB

PHASE I INSPECTION REPORT

NATIONAL DAM INSPECTION PROGRAM

Prepared ByC..) L. ROBERT KIMBALL & ASSOCIATES

CONSULTING ENGINEERS & ARCHITECTSEBENSBURG, PENNSYLVANIA 1TlC

15931 ELECTE

OC29 '1981rsFOR S LET

DEPARTMENT OF THE ARMY DBALTIMORE DISTRICT CORPS OF ENGINEERS

BALTIMORE, MARYLAND21203

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6112 444

S ~ OHIO RIVER BASIN

MILLER RUN. WESTMORELAND COUNTY

PENNSYLVANIA

DERRY ROD AND GUN CLUB DAMNDI ID NO. PA-518

DER ID NO. 65-143

DERRY ROD AND GUN CLUB

PHASE I INSPECTION REPORT

NATIONAL DAM INSPECTION PROGRAM

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S... t.nEBENSBURG, PENNSYLVANIAAvailability Codes 15931

1Avail anid/or n j Ij 3,4Ct MCW(-'1 -c C -/C12st Specialit FOR

DEPARTMENT OF THE ARMYBALTIMORE DISTRICT CORPS OF ENGINEERS

BALTIMORE, MARYLAND

21203

*ortginal oontains c0]Or DISTRIBUTION STATEMENT Aplates: All DTIC reproduot- Approved for public reoaIions will be in black and JUNE, 1981 Distributiom Unlimited

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Thsreport is prepared under guidance: conitained in the R~ecommended

Copies of these guidelines may be obtained from the Of fic~e of Chief ofEngineers, Washington, D.C. 20314. The purpose of a Phase 1 investi-gation is toidentify expeditiously those dams which may pose hazardsto human life or property. The assessment of the general condition ofthe dam is based upon available data and visual inspections. Detailed

F investigation, and analyses involving topographic mapping, subsurfaceinvesiain, testing, and detailed computational evaluations are

beyond the scope of a Phase I investigation; however, the investign-tion is intended to identify any need for such studies.

In reviewing this report, it should be realized that the reported cott-dition of the dam is based on observations of field conditions at thetime of inspection along with data available to the inspection team.In cases where the reservoir was lowered or drained prior toinspection, such action, while improving the stability and safety ofthe dam, remove* the normal load on the structure. and may obscure cer-tain conditions which might otherwise be detectable if inspected underthe normal operating environmient of the structure.

It is important to note that the condition of a dam depends onnumerous and constant~ly changing internal and external conditions, andis evolutionAry in nature. It would be incorrect to assume that thepresent condition of the dam will continue to represent the conditionof the dam at some point in the future. Only through frequent ins pec-tions can unsafe conditions be detected and only through continued :care and maintenance can these conditions be prevented or corrected.

L Phase I inspections are not intended to provide detailed hydrologicand hydraulic analyses. In accoilaace with the establishedsGuidelines, the spillway det.4a flood is based on the estimated"Probable Maximum Flood" for the region (greatest reasonably possiblestors runoff), or fractions thereof.* The spillway design flood provi-des a meassure ef relative spillway capacity and serves as an aid indetemining the need for more detailed hydrologic and hydraulicstudies, considering the size of the dam, its general condition andthe downstream damage potential.

PHASE I REPORTNATIONAL DAM INSPECTION REPORT

NAME OF DAM Derry Rod and Gun Club DamSTATE LOCATED PennsylvaniaCOUNTY LOCATED WestmorelandSTREAM Miller RunDATES OF INSPECTION March 26, 1981 and May 12, 1981COORDINATES Lat: 4Q@ 18.2' Long: 790 18.4'

ASSESSMENT

The assessment of Derry Rod and Gun Club Dam is based upon visualobservations made at the time of inspection, interviews with membersof the Rod and Gun Club, hydraulic and hydrologic computations andpast operational performance.

-The Derry Rod and Gun Club-Dam appears to be in fair condition, withthe condition of the operating facilities being considere~d as poor.The maintenance of the dam and operating facilities is consideredpoor. The condition of the principal spillway discharge line is in avisibly deteriorating condition at the outlet. The condition of thepipe through the embankment is unknown. It is unknown as to whethercutoffs were provided for the line.

A wet area was observed on the downstream slope of the dam. The conr-ditiori of the wet area did not appear to pose an immediate problemrelative to the stability of the structure. Groundwater and surfacerunoff near t~e right abutment has caused erosion gullies along thetoe of the dam, adjacent to the right abutment contact. The erosionIcould potentially erode the toe of the dam, and th'ý runoff should bediverted away from the toe of the dam. A low spot was noted duringthe inspection, and the top of dam should be filled to an elevationconsistent with the top of slope at the emergency spillway at theleft abutment. Based on information provided by the members of theDerry Rod and Gun Club, it was riported that 'the drainline valve hasnot been operated in several years. The control stem for the valvereportedly is located in the reservoir, but the stem was not visibleduring the inspection period.

The Derry Rod and Gun Club Dam is a high hazard-small size dam. Therecommended Spillway Design Flood (SDF) for a dam of this size andclassification is in the range of 1/2 PMF to PMF. Since the B~erry 'Aodand Gun Club Dam just meets the minimum size criteria; and since thedam is located in a rural area suggesting only appreciable economicloss; compliance with current practice of the Baltimore District CorpFof Engineers leads to the selection of the 1/2 PMf as the SpillwayDesign Flood (SDF). The spillway and reservoir are capable ofcontrolling approximately 19% of the PMF without overtopping the

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embankment low spot.* Based on criteria established by the Corps ofEngineers, the spillway is termed inadequate, but not seriously inadequate.

The following recommendations and remedial measures should be insti-tuted immediately.

1. A detailed hydrologic and hydraulic analysis should be corr-ducted by a registered professional engineer knowledegable in damdesign and construction to increase the spillway capacity.

2. The wet area on the downstream slope of the dam should bemonitored. If the wet area increases in size or flow is observed fromthe wet area an analysis should be made as to the effect of theseepage on the stability of the embankment. Seepage monitoring shouldbe conducted at the direction of a registered professional engineerknowledgeable in dam design and analysis.

3. It should be ascertained whether the drainline valve reportedon the upstream end of the drainline is capable of operation. If itis determined whether the valve is operable, it should be operatedand lubricated on a regular basis. If it is determined that the valveis not operable, it should be made operable or some other methoddevised to drain the reservoir.

4. The condition of the pipe through the emi'~ankment should bedetermined. Deteriorated portions of the pipe through the embankmentshould be repaired or replaced. Erosion control iteasures should beimplemented at the outlet of the pipe to prevent erosion at theoutlet.

5. Groundwater and surface runoff near the right abutment shouldbe diverted away from the toe of the dam.

6. The top of dam should be filled to an elevation consistentwith the top of slope at the emergency spillway as a temporary measureuntil the owner determines what permanent modifications will be made.

7. A regularly scheduled operation and maintenance plan shouldbe prepared and implemented to insure the continued safe operation ofthe structure. The operation and maintenance plan should include theregular operation and lubrication of the drainline valve.

8. A warning system should be developed to warn the downstreamr~esidents of imminent failure of the dam.

9. A safety inspection program should be implemented withinspections at regular intervals by qualified personnel.

DERRY ROD AND GUN CLUB DAMPA 518

SUBMITTED BY: L. ROBERT KIMBALL & ASSOCIATESCONSULTING ENGINEERS AND ARCHITECTS

OR I.- I

Date R. Jeffrey Kimball, PE...

APPROVED BY:

Date I JAMES W. PECKColonel, Corps of Engineers

\ Commander and District Engineer

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7777

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TABLE Of O)NTENTS

PAGE

SECTION I -PROJECT INFORMATION I

1.1 General 1

1.2 Description of Project 1

1.3 Pertinent Data 2

SECTION 2 - ENGINEERING DATA 5

2.1 Design 5

2.2 Construction 5

2.3 Operation 5

2.4 Evaluation 5

SECTION 3 - VISUAL INSPECTION 6

3.1 Findings 6

3.2 Evaluation 7

SECTION 4 - OPZRATIONAL PROCEDURES 8

4.1 Procedures 8

4.2 Maintenance of Dam 8

4.3 Maintenance of Operating Facilities 8

4.4 Warning System in Effect 8

4.5 Evaluation 8

SECTION 5 - HYDRAULICS AND HYDROLOGY 9

5.1 Evaluation of Features 95.2 Evaluation Assumptions 95.3 Summary of Overtopping analysis 10

5.4 Summary of Dam Breach Analysis 10

SECTION 6 - STRUCTURAL STABILITY 12

6.1 Evaluation of Structural Stability 12

SECTION 7 - ASSESSMENT AND RECOMMENDATIONS/REMEDIAL MEASURES 13

7.1 Dam Assessment 13

7.2 Recommendations/Remedial Measures 14

vi

APPEND ICES

APPENDIX A -CHECKLIST, VISUAL INSPECTION, COHSAUCEOIAPPEDIXB -CEKIT NIERN AA EIN OSRCIN

OPERATION, PHASE IAPPENDIX C - PHOTOGRAPHSAPPENDIX D - HYDROLOG11 AND HYDRAULICSAPPENDIX E - DRAWINGSAPPENDIX F - GEOLOGY

vii j

PHASE INATIONAL DAM INSPECTION PROGRAM

DERRY ROD AND GUN CL.UB DAMNDI. I.D. NO. PA 518

DER I.D. NO. 65-143

SECTION 1PROJECT INFORMATION

1.1 General.

a. Auhriy The National Damn Inspection Act, Public Law92-367, authorized the Secretary of the Army, through the Corps ofEngineers, to initiate a program of inspection of dams throughout theUnited States.

b. P~uroe. The purpose of the inspection is to determine ifthe dam constitutes a hazard to human life or property.

1.2 Description of Project.

a. Dam and Appurtenances. The Derry Rod and Gun Club Dam is anearthf ill dam, 480 feet long and 24 feet high. The crest width of thedam is 15 feet. The upstream slope of the dam is 4H: IV to 5H:LIV. The~downstream slope of the darn is 3H:17. The crest and downstream slopeof the dam are grass covered.

The principal spillway for the at' .icture consists of an 8" to 10"cast iron pipe riser. Inf low to the principal spillway is dischargedthrough a 12" diameter bituminous coated corrugated metal pipe. Anemergency spillway for the structure is located at the left abutment,

and consists of a trapezoidal shaped spillway with a concrete weir at

the crest. The crest width at the bottom of the trapezoidal channelis 28 feet long. The sideslopes of the trapezoidal channel areapproximately Ii: IV.

b. Location. The dam is located on Miller Run, which is atributary to the Loyalhanna Creek, approximately 2 miles south of theBorough of Derry, Derry Township, Westmoreland County, Pennsylvania.The Derry Rod and Gun Club Dam can be located on the Derry, U.S.G.S.7.5 minute quadrangle.

c. Size Classification. The Derry Rod and Gun Club Dam is asmall size dam (24 feet high, 54 acre-feet).

d. Hazard Classification. The Derry Rod and Gun Club Dam is ahigh hazard dam. Downstream conditions indicate that the loss of morethan a few lives is probable should the structure fail. Approximatelyfive homes are located approximately 2 miles downstream of the dam.

The Kennametal Dam is located 1 mile downstream of the dam. Theapproximate elevation of the hoses located on reach cross-sectionnumber 2 is elevation 1240.

e. Owunersh . The Derry Rod and Gun Club Dam is owned by TheDerry Rod and Can Club. Correspondence should be addressed to:

The Derry Rod and Gun ClubEast 2nd Str-eetDerry, Pe.nsylvania 15627412/694-9960

f. Purpose of Dam. The dam was constructed for the purpose ofrecreation.

g. Design and Construction History. No information is availableregarding the design and construction of the structure. The dam wasbuilt around 1952 by Graver Construction of Ligonier, Pennsylvania.No design drawings were available for review, and no construction dataare known to exist.

h. Normal Operating Procedures. No operating procedures areknown to exist for this structure. It was reported by members of theRod and Gun Club who accompanied the inspection team that thedrainline valve has not been operated in several years.

1.3 Pertinent Data.

a. Drainage Area. 0.40 square mile

b. Discharge at Dam Site (cfa).

Maximum known flood at dam site UnknownDrainline capacity at normal pooi UnknownSpillway capacity at top of dam 260

c. Elevation (M.S.L.) (feet). - Field survey based on an assumedpool elevation, 1925 interpolated from U.S.G.S. quadrangle.

Top of dam - low point 1927.1Top of dam - design height UnknownPool at time of inspection 1925.0Spillway crest 1925.0Maximum pool - design surcharge UnknownNormal pool 1925.0Upstream portal - 12" drainline UnknownDownstream portal - 12" drainline 1905.0Maximum tailwater UnknownToe of dam 1903.4

d. Reservoir (feet).

Length of maximum pool 1000Length of normal pool 900

2

a. Storage (acre-feet).

Normal pool (spillway crest) 41Top of dan 54

f. Reservoir Surface (acres).

Top of dam 7Normal pool 6.4Spillway crest 6.4

g. Dan.

Type Earthfill ILength (including spillway) 480 feetHeight 24 feetTop width 15 feetSide slopes - upstream 4H:1V to 5H:1V

- downstream 3H: IVZoning UnknownImpervious core UnknownCutoff UnknownGrout curtain Unknown

h. Reservoir Drain.

Type 12" diameterbituminous coated

corrugated metalo ipe

Length 100 feetClosure Valve on

upstream end

of pipeAccess Valve stem reported to

be on upstream slopein reservoir. Unobserved

during inspection.Regulating facilities Valve stem

Unobserved duringinspection

3

i. Spiillway.

Type Trapez~oidalwith concreteIogee crest.

Length (bottom~ width) 28 feetCrest elevation 12

Upstream channel. LakeI(unrestricted)

Downstream channel Miller Run

SECTION 2ENGIN RING DATA

2.1 Design. No information was available relative to the design ofthe dam.

2.2 Construction. No informazion exists regarding the constructionof the dam. The dam was reportedly constructed by the GraverConstruction Company of Ligonier.

2.3 Operation. No operations are conducted at the dam. No operatingrecords are maintained.

2.4 Evaluation.

a. Availability. No angineerine data were available from thePennDER, Bureau of Dams and Waterways Management. Two members of theDerry Rod and Gun Club Dam accompanied the inspection team during theinspection and were interviewed to obtain data regarding the opera-tion and maintenance of the dam. The only information the represen-tatives of the club were able to give the inspection team was inregards to the approximate date of construction (1952), and that theprincipal spillway riser was approximately 8" to 10" in diameter.

b. Adequacy. This Phase I Report is based on the visual inspec-tion, hydrologic and hydraulic analysis, and reports of past opera-tional performance. Sufficient information exists to complete a PhaseI Report.

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SECTION 3"VISUAL IhPECTIC

3.1 Findings.

a. General. The onsite inipection oi Derry Rod and Gun Club Damwas conducted by personnel of L. Robert Kimball and Associates, accoun-panted by two members of the Derry Rod and Gun Club, on March 26,1981, and May 12, 1981. The inspection consisted of:

1. Visual inspection of the retaining structure, abutments andtoe.

2. Examination of the spillway facilities, exposed portion ofany outlet works and other appurtenant works.

3. Observations affecting the runoff potential of the drainagebasin.

4. Evaluation of the downstream area hazard potential.

b. Dam. The dam appears to be in fair condition. From a briefsurvey conducted during the inspection, it was noted that a low spotexists on the crest of the dam approximately 300 feet right of thespillway. No riprap was observed on the upstream slope of the dam.The slopes and crest of the dam are grass covered. The upstream slopeof the dam was measured to be 4H:IV to 5H:1V, and the downstream slopewas measured to be 3H:1V. A wet area was observed on the downstreamslope of the dam, and the location of the wet area can be seen inAppendix A, on page A-12. No flow was visible from the wet area. Nochange was noted in the wet area during the second inspection fromthat which existed during the earlier inspection.

Groundwater and surface runoff near the right abutment has causeda small erosion gully to form near the downstr%:am toe of the dam.Surface drainage from this area ultimately disca'arges into thedrainline discharge channel beyond the toe of the dam. The runoff hasthe potential to enlarge the erosion gully and ultimately erode partof the toe of the dam.

c. Appurtenant Structures. The spillway for the dam is locatedat the left abutment of the structure. T'l.e spillway is trapezoidal inshape, with a concrete weir at the control section of the structure.The side slopes of the discharge channel in the area of the controlsection were estimated to be IH:IV. The emergency spillway extendsaround the junction of the left abutment and the flow is dischargedinto the natural stream below the dam. No obstructions were visiblein the spillway approach or discharge channel during either the March26 or May 12, 1981 inspections.

The intake for the principal spillway was barely visible duringthe inspection. It was noted during the March 26, 1981 inspectionthat the intake was surging due to the reservoir pool elevation at the

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time of inspection. During both inspection dates, it was observedthat flow was d ischarging from the principal spillway. The dischargepipe for the principal spillway and drainline consists of a 12" bitu-minous coated corrugated metal pipe. The pipe outlet is In adeteriorating condition. A major portion of the pipe at the outlethas rusted away, and flow discharges from the entire length of theexposed portion of the pipe. Discharges from the principal s~illwayand the surface runoff from the right abutment combine and flow in astream channel, which ultimately converges with the spillway dischargechannel into Miller Run. It was reported by members of the Derry Rodand Gun Club that a drainline valve exists at the upstream entranceto the principal spillway and discharge drainline. The valve isreportedly operated by a valve stem on the upstream slope in thereservoir area. The valve stem was not observed during theinspection. It wva also reported by members of the club that thevalve has not been operated in several years.

d. Reservoir Area. The watershed is covered almost entirelywith open fields. A small wooded area does exist at the headwaters ofthe watershed. The reservoir slopes are gentle to moderate and do notappear to be susceptible to landslides which would affect the storagevolume of the reservuir or overtopping of the darn by d_±qolacing water.

e. Downstream Channel. The downstream channel of the Derry Rodand Gun Club consists of Miller Run. A small unidentified dam existsdownstream of the Derry Rod and Gun Club Dam, and the KennLmetalReservoir (PA 482) is located approximately I mile downstream of theDerry Rod and Gun Club Dam. A Phase I inspection of the KennametalDam was completed by Ackenheil and Associates of Pittsburgh,Pennsylvania, around April, 1980. Five homes are located approximately1 mile downstream of the Kennametal Dam, and two miles downstreem ofthe Derry Rod and Gun Club Dam. The population of the five homes isestimated at 20 people.

3.2 Evaluation. In general, the dam appears to be in fair candition.Maintenance of the dam and operating facilities is considered poor.It was reported by members of the Derry Rod and Gun Club that thedrainline has not been operated in several years. The control facili-ties for the drainline were not observed during the inspection.

The wet area on the downstream slope of the dam should be moni-tored and if seepage becomes excessive in the area, its effects on thestability of the structure should be ascertained.

The principal spillway and drainline discharge pipe was visiblydeteriorated along the visible portion of the exposed pipe. The con-dition of the pipe through the embankment is unknown and should beinvestigated, and the deteriorated portions of the pipe replaced. Thearea. around the outlet for the drainline should be protected withriprap to prevent erosion at the outlet.

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SECTION 4OPERATIONAL PROCEDUUES

4.1 Procedures. The reservoir is maintained at the principalspillway cr@6,t during normal inflow to the reservoir. Excessive

inflow to the reservoir is discharged through the emergency spillwayat the left abutment. No operational procedures are conducted at the

dam. It was reported that the drainline valve his not been operatedin several -ears.

4.2 Mai,.tenance of the Dam. No planned maintenance schedule existsfor the dam. Maintenance of the dam is performed on an unscheduled,as-needed basis by club members. Maintenance includes mowing grass onthe crest and slopes.

4.3 Maintenance of Operati2g Facilities. No maintenance of operatingfacilities is conducted at the dam.

4.4 Warning System in Effect. There is no warning system in affectto warn downstream residents of large spillway discharges or LAminentfailure of the dam.

4.5 Evaluation. Maintenance of the dam is considered feLtr, and main-tenance of the operating facilities is considered poor. The drainlinevalvt reportedly has not been operated in several fears. The lack ofmaintenance of the operating facilities has allowed the deteriorationof the principal spillvay discharge line to deteriorate extensively atthe outlet. The emergency spillvay appears to be in fair condition.

An emergency action plan should be available for every dam in thehigh and significant hazard category. Such plans should outlineactions to be taken by the operator to minimize downstream effects ofan emergency, and should include an effective warning system. Noemergency action plan has been developed, and the owner should developsuch an action plan.

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SECTION 5ErT!. uuCC ANn' MlvzioL'rv

5.1 Evaluation of Features.

a. Desian Data. No design data relative to the hydraulic andhydrologic design of the dam were availab], for review.

b. Experience Data. No rainfall, runoff or reservoir level datawere available. The principal and emergency spillway has reportedlyfunctioned adequately in the past.

c. Visual Observations. The principal spillway reportedly con-sists of an 8" to 10" diameter riser pipe. The entrance to the prin-cipal spillway is unprotected and was disregarded during the hydraulicand hydrolo2:.c analysis.

The emergency spillway appeared to be in fair condition. Noobstructions were observed at the entrance to the spillway or in thespillway discharge channel. The emergency spillway was observed to betrapezoidal in shape, with a concrete weir at the control. Theemergency spillway was considered as providing the only dischargeduring periods of excessive inflow to the reservoir.

The low spot on the embankment crest was observed to be near midembankment. The low spot was considered to be the top of dam eleva-tion in the hydraulic and hydrologic analysis.

d. Overtopping Potential. Overtopping potential was investi-gated through the development of the probable maximum flood (PMF) forthe watershed and the subsequent routing of the PMF and fractions ofthe PMF through the reservoir and spillway.

The Corps of Engineers, Baltimore District, has directed that theHEC-1 Dam Safety Version systemized computer program be utilized. Theprogram was prepared by the Hydrologic Engineering Center (HEC), U.S.Army Corps of Engineers, Davis, California, July 1978. The majormethodologies or key input data for this program are discussed brieflyin Appendix D.

5.2 Evaluation Assumptions. To enable completion of the hydraulicand hydrologic analysis for this structure, it was necessary to makethe following assumptions.

1. The emergency spillway crest elevation was assumed to be atelevation 1925.0.

2. The pool elevation in the reservoir prior to the storm wasconsidered to be at the spillway crest elevation.

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3. The t-p of dam was considered to be the low spot elevation onthe crest, 1927.1.

4. The emergency spillway was considered as exhibiting the prop-erties of a trapezoidal channel.

5. The principal spillway was not considered during theanalysis.

6. The Kennametal Dam located downstream of the Derry Rod andGun Club Dam was assumed to fail during the breach analysis for tneDerry Rod and Gun Club Dam. The failure conditions utilized for the

Kennametal Dam were consistent with data provided in the Phase I damreport for the Kennametal Dam.

5.3 Summary of Overtopping Analysis. Complete summary sheets for thecomputer output are presented in Appendix D.

Peak inflow (PMF) 1480 cfs

Peak inflow (1/2 PMF) 740 cfsSpillway capacity 260 cfs

a. Spillway Adequacy Rating. The Spillway Design Flood (SDF)is based on the hazard and size classification of the dam. The recom-mended spillway design flood for a dam of this size and hazard classi-fication is in the range of 1/2 PMF to PMF.

No definitive criteria exists to assist the evaluating engineerin selecting a SDF within the given range. The current practiceadopted by the Baltimore District Corpsof Engineers relates theselection of a Spillway Design Flood to the size and storage potentialof the dam.

The Baltimore District Corpsof Engineers has determined that theSDF be selected at the lesser value (1/2 PMF) of the 1/2 PMF to PMFrange for high hazard dams which barely meet the minimum storage orheight criteria (size classification), and which are located in ruralareas.

Since the Derry Rod and Gun Club Dam just meets the minimum sizecriteria; and since the dam is located in a rural area suggesting onlyappreciable economic loss; compliance with current practice of theBaltimore District Corpsof Engineers leads to the selection of the 1/2PMF as the Spillway Design Flood (SDF).

Based on the following definition provided by the Corps ofEngineers, the spillway is rated as inadequate as a result of ourhydrologic analysis.

Inadequate - All high hazard dams which do not pass theSpillway Design Flood (1/2 PMF), and where the downstream routingof the flood wave does not significantly increase the downstreamhazard potential from that which existed just prior ta failureof the dam.

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The spillway and - Aervoir are capable of controlling .pproxiza-191 of the PI( % .hout overtopping the t--Bb-hnfrnt.

5.4 Summary of Damn rach Analysis. As the subject dam cannot atis-factorily pass 50% of the PF (based on our analysis), it -,ss necessaryto perform t&e dam breach anaa.ysis and downasreau routing of theflood wave. This analysis -etermined the degree of increased floodingdue to dee failure. A po0l elevation of 1927.7 (0.6 foot of over-topping) was considered sufficient to cause failure of the dam due toovertopping.

The flood wave was routed through the Kennametal Reservoirlocated approximately I mile downstream of the Derry Rod and Gun ClubDam, and was assumed to cause failure of the Keneamental Dan. Theflood wave from the Derry Rod and Gun Club Dam and Kennametal Danwas routed downstream. The failure criteria associated with theKannametal Dam was consistent with information supplied as part of the

Phase I report foý the Kennametal Dam.

"!he results of the dam breach analysis indicate that thedowratreas potential for loss of life and property is not signifi-cawcly iucreased by dam failure. Therefore, the qpillway is rated asAlidequate, but not seriously inadequate. Details of the downstreamro ting of the flood wave are included in Appendix D.

11

F SUNCTION 6STRUCTURAL ¶SThflLixf

6.1 Evaluation of Structural Stability.

a. Visual Observations. No major visible deficiencies wercobserved on the embankment which could be considered as having animmediate effect on the stability of the structure. No major erosionareas were observed on the .-rest or downstream slope of the dam. Hoseepage was observed during the inspection, although a wet area wasobserved on the downstream A~ope of the dam. No visible flow wasdischarging from the wet aret, during either the March 26, 1981 or Aay12, 1981 inspections.

Surface runoff was observed from the right abutment of thestructure. The source of flow was determined to be groundwater fromthe right abutment. Flow from the area discharges through an erosionchannel near the right downstream toe of the dam. The flow ultimatelyjoins discharges from the principal spillway discharge pipe. It wasnoted during the inspict ion that the surface runoff should be divertedaway from the toe of the dam.

b. Design and Construction Data. No information regarding ttmwdesign and construcdon of the dam were available. It was reportedthat the dam was constructed by the Graver Construction Company ofLigonier, Pennsylvania. No stability analyses have been conducted.

c. Operating Records. No operating records exist for the dam.

d. Post Construction Cl- igest. No post construction changes areknown to have occurred at the structure.

e. Evaluation. No obvious deficiencies were observed during theinspection which were considered as having an immediate effect uponthe static stability of the structure. Therefore. the dam is assumedto be safe for static loading conditions.

f. Seismic Stability. The dam is located in seismic zone 1. Noseismic stability analyses have been performed. Normally, it can beconsidered that if a dam in this zone is stable under static loadingconditions, it can be assumed safe for any expected earthquakeloading. The dam is assumed safe for expected earthquake loading.

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SECTION 7ASSESSMENT AND RECOMMENDATIONS/RJRMEDIAL MEASURES

7,1 Dam Assessment.

a. Safe . The dam appears to be in fair condition and poorlymaintained. The condition of the spillway discharge, and reservoirdrainline is questionable. The exposed p~rtion of the pipe at theoutlet was visibly deteriorated.

No major erosion areas were observed on the crest or downstreamslope of the dam. A wet area was observed on the downstream slope andextended for almost the entire length of the downstream slope betweenthe spillway discharge pipe and the left abutment. The effect of thewet area on the stability of the structure is unknown. No flow wasobserved discharging from the area. The wet area should be monitor4i.If the wet area increases in size or flow begins to discharge on thearea, an analysis of the affects of the wet area on the stability ofthe dam should le completed.

Erosion existr along the toe of the dam near the .right abutmentcontact. Erosion is due to groundwater and surface runoff. Therunoff has the potential to erode the area adjacent to the toe of nedam.

The drainline pipe for the reservoir and principal spillway( discharge line is in a deteriorating condition. Discharges from thepipe were observed along the entire length of the exposed portion ofthe pil e. The condition of the line through the embankment isqueRticnable. The condition of the pipe through the embankment shouldbe ascertained. Deteriorated portionb %f the pipe through the embank-ment should be repaired or replaced. The existence of cutoff collarson the pipe is unkanown.

The Derry Rod and Gun Club Dam is a high hazard-smalL size dam.

The recommended Spillway Lesign Flood (SDF) f~r a dam of this size andclassificacior 16 in the range of 1/2 PMF to PMF, Since the Derry Rodand run Club Dam just meets the minimum r:ze criteria and since thedam is lc'.ed in a rural area eggesting only appreciable economicloss, compliance with current practice of the Baltimore District Corpsof Engineers leads to the selection of the 1/2 PMF as the SpillwayDesign Flood (SDF).

The visual observatiors, review of available data, hydraulic andhydrologic calculations, and past operational operational performanceindicate that the Derry Rod and Gun Club Dam is capable of controllingapproximately 19% of the PMF. The spillway is termed inadeouate, but notseriousiy inadequate.

b. Adegacy of Information. Sufficient information is availableto complete a Phase I report.

13

I

_____J

c. UrgencZ. The recomndations suggested below should beimplemented lmediatwly.

d. Necessity for Further Investigation. In order to accomplishsome of the rocoumendations/remedial measures outlined below, furtherinvestigations will be required.

7.2 Recommandations/lemedial Measures.

1. A detailed hydrologic and hydraulic analysis should be con-ducted by a registered professional engineer knowledegable in damdesign and construction to increase the spillway capacity.

2. The wet area on the downstream slope of the dam should bemonitored. If the mt area increases in size or flow is observed fromthe wet area an analysis should be made as to the effect of theseepage on the stability of the embankment. Seepage monitoring shouldbe conducted at the direction of a registered professional engineerknowledgeable in dam design and analysis.

3. It should be ascertained whether the drainline valve rp,,ortedon the upstream end of the drainline is capable of operation. If itis determined whether the valve is operable, it should be operatedand lubricated on a regular basis. If it is determined that the valveis not operable, it should be made operable or some other methoddevised to drain the reservoir.

4. The condition of the pipe through the embankment should bedetermined. Deteriorated portions of the pipe through the embankmentshould be repaired or replaced. Erosion control measures should beimplemented at the outlet of the pipe to prevent erosion at theoutlet.

5. Groundwater and surface runoff near the right abutment shouldbe diverted away from the toe of the dam.

6. The top of dam should be filled to an elevation consistentwith the top of slope at the emergency spillway as a temporary ineasureuntil the owner determines what permanent modifications will be made.

7. A regularly scheduled operation and maintenance plan shouldbe prepared and implemented to insure the continued safe operation ofthe structure. The operation and maintenance plan should include theregular operation and lubrication of the drainline valve.

8. A warning system should be developed to warn the downstreamresidents of imminent failure of the dam.

9. A safety inspection program should be implemented withinspections at regular intervals by qualified personnel.

14

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

APPEN4DIX ACHECKLIST, VISUAL INSPECTION, PHASE I

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DERRY ROD AND GUN CLUB DAM

PA 518

Sheet I

Front

1. Upper left - View of upstream slope, crest, and rightabutment.

2. Upper right - View of downstream slope. View towards leftabutment.

3. Lower left - Principal spillway intake.4. Lower right - Emergency spillway approach, and control.

section. View towards the reservoir.

Sheet 1

3ack o ie

5. Upper left. - Spillway discharge line. Note deterioration

6. Upper right - Downstream exposure.

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APPENDIX DHYDROLOGY AND HYDRAULICS

APPENDIX DHYDRLOGY AND HYDRAULICS

MethonojW. The dan overtopping and breach analyses wereacc~Apj.ished using the systemized ccmputer program HEC-1 (Dan SafetyInvestigation), September, 1978, prepared by the HydrologicEngineuring Center, U.S. Army Corps of Engin~eers, Davis, California.A brief description of the methodology used in the analysis is pres-sented below.

1. Precipitation. The Probable Maximum Preci2itation (PMP) isderived and determined from regional charts prepared from past rain-fall records including "Hydrometeorological Report No. 33" prepared bythe U.S. Weather Bureau.

The index rainfall may be reduced from 10% to 202 depending onwatershed size by utilization of what is termed the HOP Brook adjust-ment factor. Distribution of the total rainfall is made by the com-puter program using distribution methods developed by the Corps.

2. Inflow Hydrograph. The hydrologic analysis used in develop-ment of the overtopping potential is based on applying a hypotheticaA.storm to a unit hydrograph to obtain the inflow hydrograph for reser-voir routing.

The unit hydrograph is developed using the Snyder uathod. This methodrequires calculation of several key parameters. The following listgives these parameters their definition and how they were obtained forthese analysis.

Parameter Definition Where Obtained

Ct Coefficient representing Fron Corps ofvariations of watershed Engineers*

L Length of main stream From U.S.G.S.channel miles 7.5 minute

topgraphic

Lca Length on main stream From U.S.G.S.to centroid of watersaed 7.5 minute

topographic

Cp Peaking coefficient From Corps ofEngineers*

A Watershed size From U.S.G.S.7.5 minutetopog• apnic

*Developed by the Corps of Engineers on a regional basis for

Pennsylvania.

D-1

3. Routina Reservoir routing is accomplished by usiing ModifiedPlus routing techniques iwere the flood hydrograph is routed throughreservoir storage. Hydraulic capacities of the cutlet works,spillways and the crest of the dam are used as outlet controls in therouting.

The hydraulic capacity of the outlet works can either be calculatedand input, or sufficient dimensions input, a-d the program will calcu-late an elevation discharge relationship.

Storage in the pool area is defined by an area - elevation rela-tionship from which the computer calculates storage. Surface areasare either planimstered from available mapping or U.S.G.S. 7.5 minuteseries topographic saps or taken from reasonably accurate design data.

4. Dam Overtopping. Using given percentages of the PMF, the com-

puter program will calculate the percentage of the PMF, which can becontrolled by the reservoir and spillway without the dam overtopping.

5. Dam Breach and Downstream Routing. The computer program isequipped to determine the increase in downstream flooding due tofailure of the dam caused by overtopping. This is accomplished byrouting both the pre-failure peak flow and the peak flow through thebreach (calculated by the computer with given input assumptions) at agiven point in time and determining the water depth in the downstreamchannel. Cbannel cross-sections taken from U.S.G.S. 7.5 minutetopographic maps were used in the downstream flood wave routing. Proand post failure water depths are calculated at locations where cross-sections are input.

D

I•--2

HYDROLOGY AND HYDRAULICS ANALYSISDATA BASE

NAME OF DAM: Derry Rod and Gun Club Dam

PROBABLE M&XIMMU PRECIPITATION (PKP) " 24.0 inches

STATION 1 2 3

Derry Rod and

Station Description Gun Club Dam

Drainage Area(square miles) 0.40

Cumulative Drainage Area(square miles) 0.40

Adjustment of PMF forDrainage Area (M)(M) (Zone 7)

6 hours 102

12 hours 120

24 hours 130

48 hours 140

72 hours N/A

Snyder HydrographParameters

Zone (2) 24Cp T)0.45

Ct (3) 1.6L (miles) (4,)) 0.95Lca (miles) (4) 0.2tp " Ct(LxLca) 0.3 hrs. 0.97

Spillway DataCrest Length (ft) 28 (bottom width)

Freeboard (ft) 2.1

Discharge Coefficient C'-O.95

Exponent N/A

(1)H7ydrometeorological Report 33 (Figure 1), U.S. Weather Bureau

and U.S. Army Corps of Engineers, 1956.(2)Hydrological zone defined by Corps of Engineers, Baltimore

District, for determining Snyder's coefficients (Cp and Ct).( 3 )Snyder' s Coefficients.( 4 )L-Length of longest water course from outlet to basin divide.

Lca-Length of water course from outlet to point opposite the

centroid of drainage area.

D-3

CHRCK. LISTUTVM.OLOGIC ANlD JYDRAULIC

INIEmmING DATA

DRAINAGE ARA CHARACTUSTICS: 0.40 sq.mi. [opon fields. moderate slopes]

SLEIV TON TOP NORMAL POOL (STORAGE CAPACITT): 1925 [41 ac-ft]

ELEVATION TOP FLOOD CONTROL POOL (STORAGE CAPACITY): 1927.10 f54 at-ft]

ELEVATION MAX32M DESIGN POOL: Unknown

EEVATION TOP DAM: 1227.1 rlnw AP._l

SPILLYA! CREST:

a. Elevation 1 , .b. Type ,44 ^ ,pc. Width . ,j4A _

d. Lengthe. Location Spillover TLft -_"_-f. Number and Type of Gates . . ..

OUTLET WORKS:

a. Type 12" diameter bituminous coated corrugated metal pipe

b. Location Maximum sectiona. Entrance, inverts -d. Exir invcrts faiie LiZ iameter bituminous coateda . E me r g e nc y d r a w d o w m f a c i l it ie s c o r g td-t l F pS~corrugated meta pipe

RYDROMIEOROLOGICAL GAUGES:

a. Type Noneb. Location --c. Records None

MAXIIM NON-DAMAGING DISCHARGE Unknown

NOTE: All elevations are referenced to M.S.L.

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A APPENDIX EDRAWINGS

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APPENDIX FGEOLOGY

I!

I.

General Geology

The Derry Rod and Gun Club Dan is located in the PittsburghPlateaus Section one half mile from Chestnut Ridge, which acts as thedivision between this section and the Allegheny Mountsin Section ofthe Appalachian Plateau Province. The surface is conposed nf sore orless elevnted plateaus, broken by a few ridges where broad folds iAveaffectad the strata. The rocks are deforiwd by veveral sub-parallel

secondary folds which are superimposed upon a broad, flat canoe-&s.apadtrough of first magnitude. The axes of these folds trend northeast,plunging gently southward. The dam lies on the common limb of theChestnut Ridge Anticline ar:1 the TAtrobe Syncline to the west. Thestrata beneath and outcropping near the dam strike about N43E and dipabout ." to the northwest. No major faulting is evident in the vicin-ity of the Derry Rod and Gun Club Dam.

The bedrock underlying the dam consists of shales, sandstones andclays with several workable coal beds. These belong to the AlleghenyFormation of Pennsylvanian Age #Aich extends from the Upper Freeportcoal bed at the top to the Brookville-Clarion coal seam at the bottom.

The dam is located in the Main Bituminous Coal Field, of whichthe Allegheny Formation is characteristic due to the seven coal bedsit carries. From the uppermost member to the lowest, these coal seamsare: the Upper Freeport; Lower Freeport; Upper, Middle, and LowerKittanaing; Clarion; and Brookville. The rocks which crop out nearthe dam are located stratigraphically at the Kittanning coal horizon.Of the Kittannu.ng group of coal beds the lower is the most important

due to its good quality and fairly consistent thickness, between 3 and4 feet. The Clarion and Brookville coals are generally too thin to beof commercial impoctance. Data obtained prior to 1974 indicates nomining of any of these coal seams to have taken place in the vicinityof the Derry Rod and Gun Club Dam.

F-1

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F-2OGI MAPu OFTEAEIRUDMRURT A