AD-AI04 667 ARMY ENGINEER DISTRICT ST LOUIS MO

F/ 13/13SEP 78NATIONAL DAM SAFETY PROGRAM. LAKE TURNER DAM IMO 30266), MISSIS-ETCU)

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4. TITLE (and Subtitle) S. TYPE OF REPORT 6 PERIOD COVEREDPhase I Dam Inspection ReportNational Dam Safety Program Final Report,Lake Turner Dam (MO 30266) 'I PERFORMING ORG. REPORT NUMBER

Dent County, Missouri7.- AUTHOR(q) S. CONTRACT OR GRANT NUMBER(&)

Corps of Engineers, St. Louis District

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AREA & WORK UNIT NUMBERSU.S. Army Engineer District, St.

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Dam Inventory and Inspection Section, LMSED-PD /210 Tucker Blvd., North, St. Louis, Mo. 63101

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U.S. Army Engineer District, St. Louis "/ . Septembur k78Dam Inventory and Inspection Section, LMSED-PD I IwUeWCr PAGES

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Dam Safety, Lake, Dam Inspection, Private Dams

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This report was prepared under the National Program of Inspection ofNon-Federal Dams. This report assesses the general condition of the dam withrespect to safety, based on available data and on visual inspection, todetermine if the dam poses hazards to human life or property.

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SPRING CREEK BASIN

TURNER LAKE DAMDENT COUNTY, MISSOURI

MISSOURI INVENTORY NO. 30266

PHASE I INSPECTION REPORTNATIONAL DAM SAFETY PROGRAM

PREPARED BY: ST. LOUIS DISTRICT CORPS OF ENGINEERSFOR: GOVERNOR OF MISSOURI

SEPTEMBER 1978 Accession For

NTIS GRA&I

DTIC TABUnannouncedJust ificat ion

ByDistribution/

Availability CodesAvail and/or

Dist Special

PHASE I REPORT

NATIONAL DAM SAFETY PROGRAM

Name of Dam Turner Lake DamState Located MissouriCounty Located DentStream Spring CreekDate of Inspection 5 September 1978

Turner Lake Dam No. Mo. 30266 was inspected using the"Recommended Guidelines for Safety Inspection of Dams." Theseguidelines were developed by the Chief of Engineers, U. S. Army,Washington, D. C., with the help of Federal and state agencies,professional engineering organizations, and private engineers. Theresulting guidelines are considered to represent a consensus of the

engineering profession.

Based on the criteria in the guidelines, the dam is in the highhazard potential classification, which means that loss of life andappreciable property loss could occur in the event of failure of thedam. Three houses and associated buildings, two improved roads andone railroad would be subjected to flooding with possible damageand/or destruction and possible loss of life. Turner Lake Dam is inthe small size classification since it is greater than 25 feet highbut less than 40 feet high and impounds less than 1000 acre-feet ofwater.

Our inspection and evaluation indicates that the spillway ofTurner Lake Dam does not meet the criteria set forth in theguidelines for a dam having the above size and hazard potential.The spillway of Turner Lake Dam wi'l pass a 1 percent chance flood(100-year flood) without overtopping the dam. Turner Lake Dam is asmall size dam with a spillway that will pass 20 percent of theProbable Maximum Flood without overtopping the dam. The guidelinesrequire that a dam of this size and hazard potential (high) passone-half of the Probable Maximum Flood to the Probable Maximum Floodwithout overtopping the dam. Since the spillway of Turner Lake Damis not capable of passing a minimum of one-half (50 percent) of thePMF without overtopping and causing failure, the spillway isconsidered seriously inadequate and the dam is accordinglyclassified as an unsafe, non-emergency structure. The 1 percentchance flood is defined as a flood that has a 1 percent chance ofbeing exceeded in any given year.

Other deficiencies visually observed by the inspection team

were the need to maintain a grass cover on the embankment by cuttingthe tall vegetation to prevent it from providing animal habitat andpossible burrowing by such animals; lack of erosion protection onthe dam and emergency spillway; erosion and undermining at the endof the 18 inch diameter discharge pipe. The lack of stability andseepage analyses on record is a deficiency that should be corrected.

It is recommended that the owner take action to correct orcontrol the deficiencies described.

ANDREW G. HEYDINGERSoils EngineerSt. Louis DistrictCorps of Engineers

CHIEN H. HSIEHHydraulic EngineerSt. Louis District

Corps of Engineers

SUBMITTED BY. 5j 8hi f, Engineering Division Date'

APPROVED BY: Lz d'2 4 ..

Colonel, CE, Distri ngineer 'bate

2

OVERVIEW OF LAKE, AND DAN

PHASE I INSPECTION REPORTNATIONAL DAM SAFETY PROGRAMTURNER LAKE DAM - ID NO. 30266

TABLE OF CONTENTS

Paragraph No. Title Pae No.

SECTION I - PROJECT INFORMATION

1.1 General i1.2 Description of Project 11.3 Pertinent Data 2

SECTION 2 - ENGINEERING DATA

2.1 Design 42.2 Construction 42.3 Operation 42.4 Evaluation 4

SECTION 3 - VISUAL INSPECTION

3.1 Findings 53.2 Evaluation 6

SECTION 4 - OPERATIONAL PROCEDURES

4.1 Procedures 74.2 Maintenance of Dam 74.3 Maintenance of Operating Facilities 74.4 Description of Any Warning System in Effect 7

4.5 Evaluation 7

SECTION 5 - HYDRAULIC/HYDROLOGIC

5.1 Evaluation of Features 8

SECTION 6 - STRUCTURAL STABILITY

6.1 Evaluation of Structural Stability 10

SECTION 7 - ASSESSMENT/REMEDIAL MEASURES

7.1 Dam Assessment 117.2 Remedial Measures 11

APPENDIX

A Hydrologic and Hydraulic Analysis Methodology

" .... .. .. . . . . . i + ' ' .. . . . . . ." . . . . . . ...- . .. ', , . . . . . . . .

LIST OF PLATES

Plate No.

I Vicinity Topography2 Plan3 Profile and Cross Section

LIST OF PHOTOGRAPHS

Photograph No. Title

I Turners Lake Dam - Crest of Dam2 Turners Lake Dam - Downstream Slope of Dam Toward Right

Abutment3 Turners Lake Dam - Downstream Slope of Dam Toward Left

Abutment4 Turner Lake Dam - Upstream Center Slope of Dam and Lake5 Turner Lake Dam - Downstream Center of Slope6 Turner Lake Dam - Spillway7 Turner Lake Dam - Spillway8 Turner Lake Dam - Overflow Intake9 Turner Lake Dam - Overflow Intake - Inside Pipe

10 Turner Lake Dam - Discharge Pipe - Downstream11 Turner Lake Dam - Seepage of Discharge Pipe above Outlet12 Turner Lake Dam - Upstream of Dam - Ziske Dam at Upper End

ii

PHASE I INSPECTION REPORTNATIONAL DAM SAFETY PROGRAM

TURNER LAKE DAM - ID NO. 30266

SECTION 1 - PROJECT INFORMATION

1.1 GENERAL

a. Authority. The National Dam Inspection Act, Public Law92-367, authorized the Secretary of the Army, through the Corps ofEngineers, to initiate a program of safety inspection of damsthroughout the United States. Pursuant to the above, the St. LouisDistrict, Corps of Engineers, District Engineer directed that asafety inspection of Turner Lake Dam be made.

b. Purpose of Inspection. The purpose of the inspection wasto make an assessment of the general condition of the dam withrespect to safety, based upon available data and visual inspection,

in order to determine if the dam poses hazards to human life orproperty.

c. Evaluation Criteria. Criteria used to evaluate the damwere furnished by the Department of the Army, Office of the Chief ofEngineers, in "Recommended Guidelines for Safety Inspection ofDams." These guidelines were developed with the help of severalFederal agencies and many state agencies, professional engineeringorganizations, and private engineers.

1.2 DESCRIPTION OF PROJECT

a. Description of Dam and Appurtenances.

(1) Turner Lake Dam is an earth fill dam.

(2) The outlet works consist of a 18 inch steel pipeconduit with 3 feet diameter drop inlet. The emergency spillway islocated on the right side of the dam and is grass covered.

b. Location: Section 17, Township 34 North, Range 6 West.

c. Size Classification: Small.

d. Hazard Classification: High

e. Ownership. Major and Mrs. Peter Turner, Salem,Missouri, 65560.

f. Purpose of Dam. Recreation lake.

g. Design and Construction History. The dam was constructedin 1972. Design guidiance was provided by the Soil Conservation

Service (SCS). No precorstruction design information or detailedconstruction data other than the information SCS has available areknown to exist. The SCS data are of advisory nature.

h. Normal Operating Procedure. No operating records exist.Outflow passes through an ungated steel pipe and emergency spillway.

1.3 PERTINENT DATA

a. Drainage Area.

(1) 58 Acres between Ziske Dam and Turner Dam.

(2) 433 Acress (Total drainage area including drainage area

above Ziske Dam.)

b. Discharge at Damsite.

(1) All discharge at Turner Lake Dam is through a conduit with

a 3 feet diameter drop inlet or over the emergency spillway.

(2) Emergency spillway capacity at maximum pool 740 c.f.s.

c. Elevation (Feet Above M.S.L.).

(1) Top of dam - 1150.0 +.

(2) Invert of steel pipe 1141.9 +.

(3) Crest of drop inlet 1145.9 +.

(4) Spillway crest 1147.5 +.

(5) Streambed at Centerline of Dam - 1120.0 + (Estimated).

(6) Maximum Tailwater - unknown.

d. Reservoir. Length of maximum pool - 1800 feet.

e. Storage.

(1) Normal - 154 acre-feet.

(2) Maximum - 221 acre-feet.

2

f. Reservoir Surface Area (Acres).

(1) Top of dam - 17.0.

(2) Drop inlet crest - 16.0.

g. Dam.

Type - earth fill.

Length - 600 feet.

Height - 32 + feet.

Top width - 16 feet.

Side Slope -

(a) Downstream: IV on 2H.

(b) Upstream: Unknown.

Zoning - unknown.

Impervious Core - unknown.

Cutoff - unknown.

h. Emergency Spillway.

(1) Type - Uncontrolled.

(2) Crest Elevation: 1147.50 + feet m.s.l.

3

SECTION 2 - ENGINEERING DATA

2.1 DESIGN.

No design drawings or data are known to exist exceptinformation at the Soil Conservation Service.

2.2 CONSTRUCTION. The dam was constructed in 1972. Assistance inthe design of the dam was obtained from the Soil ConservationService, U. S. Department of Agriculture, Salem, Missouri.

2.3 OPERATION.

No operating records exist.

2.4 EVALUATION.

a. Availability. There are no engineering data availableexcept information at Soil Conservation Service.

b. Adequacy. The field surveys and visual inspectionspresented herein are considered adequate to support the conclusionof this report. Seepage and stability analyses comparable to therequirements of the guidelines are not on record. This is adeficiency which should be rectified.

c. Validity. Information at Soil Conservation Service is ofgeneral and advisory nature.

4

SECTION 3 - VISUAL INSPECTION

3.1 FINDINGS

a. General. The owner did not accompany the inspectionteam. Turner Lake is the lower lake in the watershed. The upperlake, Ziske Lake, was inspected the same day (See report on ZiskeLake).

b. Project Geology. No rock outcrops are visible at thesite, however, the abutment soil contains residuum of the TowerOrdivician Roubidoux and Gasconade formations, indicating that thereservoir is underlain by Gasconade dolomite. The dam embankment isreportedly composed of soil excavated from the reservoir area.

Seepage was observed at the upper end of the lake in theabutment of Ziske Dam opposite the sillway. No other seeps orsprings were observed directly upstream or downstream of Turner Dam.

c. Dam. No detrimental settlement, cracking or sinkholeswere observed in or near the earth embankment.

An embankment cross-section near the maximum height forthe dam is shown on Plate 3. In a few areas, the embankment slopesare considerably steeper than the section shown. It is difficult todetermine the reason for the irregular slopes especially since therewas heavy vegetation on the slope but it appears that the slope hasexperienced some sliding. There is a slide scarp in the areaadjacent to the outlet pipe up from the toe of the dam where seepageis exiting from the embankment. The slides are not large but theydo pose a danger of progressive failure of the embankment. Noburrows were noted but some could be present and masked byvegetation.

The dam had tall grass and weeds growing on it. Itprovides animal habitat which increases the likelihood of animalburrows.

Based upon surface observations, the dam is composed ofclay and rock.

There is no riprap on the embankment.

Marshy areas with standing water and cattails wereobserved on the lower portion of the embankment from the dischargepipe to roughly the center of the dam and downstream of the toe fromroughly the center of the dam to near the left abutment. The

5

standing water indicates that a steady seepage condition exists.The seepage is greatest in the area immediately surrounding thedischarge pipe which indicates that the backfill around the pipe mayhave been placed improperly (see photograph 11). There is somescour and erosion at the outlet of the discharge pipe.

d. Appurtenant Structures. Appurtenant structures consist ofa spillway and an overflow intake structure and discharge pipe.

The spillway is approximately 16 feet wide. The spillwayextends from the dam embankment down past the toe of the dam. It iscomposed of embankment or foundation material.

The discharge pipe extends out unsupported from theembankment for a distance of approximately 10 feet. In addition tothe erosion that has taken place around the pipe, there is a largescour hole near the end of the pipe. The degree of erosion

associated with the discharge pipe indicates that there aresufficient velocities to endanger the embankement.

e. Reservoir Area. No pertinent problems were noted in thereservoir area.

f. Downstream Channels. There is a drainage channel

downstream of Turner Lake. It meanders through a large, broadfloodplain. Any excess logs or debris in the creek could causewater to overflow the creek in times of high flow, but this shouldnot significantly restrict flow from the spillway so as to cause

overtopping of the dam.

3.2 EVALUATION. Insufficient erosion protection on the upstreamface of the dam and in the spillway, the erosion of the soil fromaround the discharge pipe, seepage in the area of the dischargepipe, and the lack of scour protection and energy dissipator at thepipe outlet are all deficiencies which should be investigated andcorrected. The heavy vegetation on the embankment should be cut andmaintained to prevent it from providing an animal habitat andpossible burrowing by such animals. Also, the marshy areas withstanding water indicate the existence of a steady seepage conditionwhich could be contributing to the apparent instability of thedownstream embankment slope. The need for seepage-control measures

and remedial measures to provide adequate stability of thedownstream slope should be based upon an analysis of the stabilityand seepage conditions by a professional engineer experienced in thedesign and construction of dams.

6

SECTION 4 - OPERATIONAL PROCEDURES

4.1 PROCEDURES.

The spillway is uncontrolled; therefore, no regulatingprocedures exist for this structure.

4.2 MAINTENANCE OF DAM.

Little recent maintenance is apparent as evidenced by the

spillway areas.

4.3 MAINTENANCE OF OPERATING FACILITIES.

Not applicable.

4.4 DESCRIPTION OF ANY WARNING SYSTEM IN EFFECT.

The inspection team is not aware of any existing warning systemfor this dam.

4.5 EVALUATION.

Additional maintenance in the form of mowing of the slopes andcrown and erosion repairs at the discharge end of the outlet pipeneed to be made.

7

SECTION 5 - HYDRAULIC/HYDROLOGIC

5.1 EVALUATION OF FEATURES.

a. Design Data. Design data are not available.

b. Experience Data. All of the pertinent data furnished inthis report were obtained from U. S. Geological Survey 15 minutequadrangle sheets or from surveys made during the inspection.

c. Visual Observations.

(1) The lake is located immediately downstream of theZiske Dam.

(2) The level of the lake is controlled by a conduitspillway drop inlet which is located upstream of the dam near thecenter. The conduit spillway consists of an approximate 3 feetdiameter drop inlet and a 18 inch steel pipe through the dam at thebottom of the drop inlet the invert of the drop inlet and the 18inch pipe are at elevations 1145.9 and 1141.9 feet m.s.l.,respectively. (See Photos 8 and 9).

(3) Erosion and undermining at the end of the 18 inchpipe were observed.

(4) A grassy spillway located at the right side of thedam serves as an emergency spillway (See Plates 2 and 3 and Photos 6and 7). Any high and sustained flows through the emergency spillwaycould cause excessive erosions of the embankment. The excessiveerosions could threaten the safety of the dam.

(5) Drawdown facilities necessary to evacuate the lake

are not provided.

d. Overtopping Potential.

The drop inlet emergency spillway cannot pass one-half of theProbable Maximum '71ood (PMF) without overtopping the dam. TheProbable Maximum Flood is defined as the flood discharge that may beexpected from the most sever combination of critical meteorologicand hydraulic conditions that are reasonably possible in theregion. The spillway will pass 20 percent of the PMF or 1 percentchance flood (100-year flood) without overtopping with theassumption of no sudden collapse of Ziske Dam upstream (the spillwayof Ziske Dam will pass 15 percent of the PMF). A 1 percent flood isa flood that would have a 1 percent chance of being exceeded in any

given year. Routing the one-half PMF through the lake reveals thatthe dam would be overtopped for approximately 2.4 hours with amaximum 1.3 feet water and 2330 c.f.s. discharge over the low pointof the dam. The tsunami wave from a sudden collapse of the ZiskeDam upstream could threaten the safety of this dam.

I

i9

SECTION 6 - STRUCTURAL STABILITY

6.1 EVALUATION OF STRUCTURAL STABILITY.

a. Visual Observations. Visual observations of the dam,steel pipe conduit, drop inlet and spillwy are discussed andevaluated in Sections 3 and 5. The dam has no other appurtenantstructures.

b. Design and Construction Data. As discussed in Section 2.

Seepage and stability analyses comparable to the requirements of theguidelines are not on record. This is a deficiency which should berectified.

c. Operating Records. No appurtenant structures requiringoperation exist at this dam.

d. Post Construction Changes. No post-construction changes

are known or apparent except for possible repairs to past slides forwhich the only evidence is a varying downstream slope along thelength of the dam.

e. Seismic Stability. Turner Dam is in seismic zone 2, forwhich the recommended guidelines for inspection assign a "moderate"damage probability. Since neither original design analyses nor

strengths of embankment or foundation materials are available, an

accurate seismic analysis cannot be made.

10

SECTION 7 - ASSESSMENT/REMEDIAL MEASURES

7.1 DAM ASSESSMENT.

a. Safety. Several items are deficient which should becorrected. No erosion protection exists on the upstream slope ofthe dam. The discharge from the steel pipe conduit causes erosion.There is a slide scarp and seepage on the downstream slope. Thespillway is not sufficiently protected against erosion. Thespillway capacity of the dam is insufficient to pass 50 percent ofthe Probable Maximum Flood without overtopping the dam. Tallvegetation on the embankment could provide habitat for burrowinganimals.

b. Adequacy of Information. The statements andrecommendations in this report are based on visual observations andverbal discussions. Seepage and stability analyses comparable tothe requirements of the guidelines are not on record. This is adeficiency which should be rectified.

c. Urgency. We recommend the remedial measures listed inSection 7.2 be accomplished in the near future. The item listed inparagraph 7.2c should be pursued on a high priority basis.

d. Need for Phase II. No Phase II inspection is recommended.

7.2 REMEDIAL MEASURES.

The following remedial measures are recommended:

a. Fill any animal burrows found during clearing of brush.

b. Establish and maintain a grass cover on the embankment bycutting the tall vegetation to prevent it from providing animalhabitat and possible burrowing by such animals.

c. The spillway size and/or height of the dam should beincreased to pass at least 50 percent of the Probable Maximum Floodwithout overtopping the dam. Adequate erosion protection and/orenergy dissipator should be provided for the high flow over thespillway.

d. A stability and seepage analysis of the dam should beperformed by a professional engineer experienced in the design andconstruction of dams. The possible seepage around the outlet workspipe and the marshy area downstream of the dam should be evaluatedand considered in these analyses.

11

e. A detailed inspection of the dams and spillways should bemade every 2 to 5 years by a professional engineer experienced inthe design and construction of dams.

f. Erosion and undermining at the downstream end of thedischarge pipe should be repaired and protected with adequate riprapand/or energy dissipator.

12

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Pi1CTE 1 Crest of Damn

PHOTO 2 Downstream Slope of Damn TowardRight Abutment

PAHOTO 3 Downstream Slope of Darm TowardLeft Abutment

PHOTO 4 Upstream Center Slope of Darnand Lake

PHOTO 5 Downstream Center of Slope

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PHOTrO 6 Spillway

Pt!.ov V (vr f Ilow I n t A C,

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PHOTO 11 Seenage around Discharge

Pipe Above Outlet

PHOTO 12 Upstream of Damn Ziske Damnat Upper End

APPENDIX A

HYDROLOGIC AND HYDRAULIC ANALYSIS METHODOLOGY

HYDROLOGIC AND HYDRAULIC COMPUTATIONS

1. The hydrologic analysis used in development of the overtoppingpotential is based on applying a hypothetical storm to a unithydrograph to obtain the inflow hydrograph for a reservoir routing.The Probable Maximum Precipitation is derived and determined fromregional charts prepared by the National Weather Service in"Hydrometeorological Report No. 33." Reduction factors have notbeen applied. A 24-hour storm duration is assumed with the totalrainfall depth distributed over 6-hour periods in accordance withprocedures outlined in EM 1110-2-1411 (SPF Determination). Themaximum 6-hour rainfall period is then distributed to hourlyincrements by the same criteria. Within-the-hour distribution isbased upon NOAA Technical Memorandum NWS HYDRO-35. The non-peak6-hour rainfall periods are distributed uniformly. All distributedvalues are arranged in a critical sequence by the SPF criteria. Thefinal inflow hydrograph is produced by deduction of infiltrationlosses appropriate to the soil, land use, and antecedent moistureconditions.

2. The reservoir routing is accomplished by using Modified Pulsrouting techniques wherein the flood hydrograph is routed throughlake storage. Hydraulic capacities of the outlet works, spillway,and crest of dam are used as outlet controls in the routing.Storage in the pool area is defined by an elevation-storage capacitycurve. The hydraulic capacity of the outlet works, spillway, andtop of dam are defined by elevation-discharge curves.

3. Dam overtopping analysis has been conducted by hydrologicmethods for this dam and lake. This computation determines thepercentage of the PMF hydrograph that the reservoir can containwithout the dam being overtopped. An output summary in thehydrologic appendix displays this information as well as othercharacteristics of the simulated dam overtopping.

4. The above methodology has been accomplished for this reportusing the systemized computer program REC-l (Dam Safety Version),July 1978, prepared by the Hydrologic Engineering Center, U.S. ArmyCorps of Engineers, Davis, California. The numeric parametersestimated for this site are listed in the attached computerprintout. Definitions of these variables are contained in the"User's Manual" for the computer program.

5. Hydrologic and Hydraulic Data.

a. The capacity of the closed conduit spillway is controlledby the 18 inch pipe with inlet control.

b. Rating curves for emergency spillway and top of the dam aredertvel from the assumption of critical flows over the crest. Aloss of 0.5 velocity head is consided for spillway flow beforeovertopping.

c. The result of the overtopping analyses are obtained byrouting the PMF or percent PMF through the Ziske Lake and TurnerLake with the assumption of no failure of Ziske Dam upstream.

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