Embed Size (px)
Citation preview
AD-A1G4 648 ANDERSON ENGINEERING INC SPRINGFIELD NO F/0 13/13NATIOANAL DAM SAFETY PROGRAM. ARROWHEAD LAKES LOWER DAM (NO 302 ETC(U)
DEC 79 OACW43-79-C-070
UNCLASSIFIED NLI Emmmmmmmmmmmmmmmmmmmmmmmmmmmm
MISSSFPIASKASIAI-ST. L0UAS ME
AROWHMPLAOES LOWER DAM
~mv~ St, I INSPEI
NATIONAL DAM, SAFET PROGRAM
i a .
± 128 016
UNCLASSIFIEDSECURITY CLASSIFICATION OF THIS PAGE (When Date Entered)
PAGE READ INSTRUCTIONSREPORT DOCUMENTATION PBEFORE COMPLETING FORM
." REPORT NUMBER .GOVT ACC SSION No. 3. RECIPIENT'S CATALOG NUMBER
4 TTLErd ubttle S. TYPE OF REPORT & PERIOD COVEREDPhase IDam Inspection Report
National Dam Safety Program Final epwt,Arrowhead Lakes Lower Dam (MO 30267) 6. PZREPORT NUMBER
Dent County, Missouri ! ..
7. AUTHOR() S. CONTRACT OR GRANT NUMBER(s)
Anderson ~gneer~n.Ic
12iDACW43799. PERFORMI NIZATIONAME ANDMORESS 110. PROORAM ELEMENT.-ROJECT, TASK
AREA A WORK UNIT NUMBERSU.S. Army Engineer District, St. LouisDam Inventory and Inspection Section, LMSED-PD210 Tucker Blvd., North, St. Louis, Mo. 63101
ii. CONTROLLING OFFICE NAME AND ADDRESS BIM-_ 0 4" :1-
U.S. Army Engineer District, St. Louis DeceAA 79Dam Inventory and Inspection Section, LMSED-PD 13. NUMBER OF PAGES
210 Tucker Blvd., North,_I. Louis, Mo. 63101 Approximately 60,,. ITO .__ I_...... ?_ -' i IS. SECURITY CLASS. (of this report)/ T National Dam Safety Program. Arrowheai
Y Lakes Lower Dam (MO 3027) Mississippi- UNCLASSIFIEDKaskaskia-5t. Louis Basinr Dent County, IS. DECLASSIFICATION/DOWNGRADINGMissouri. Phase I Inspection Report. SCHEDULE
I-. DISTRIEL . . . ..
Approved for release; distribution unlimited.
17. DISTRIBUTION STATEMENT (of the abetract entered Ih Block 20, it diferlent hum Report)
I&. SUPPLEMENTARY NOTES
IS. KEY WORDS (Continue on reveree aide it neceasIn md identify by block number)
Dam Safety, Lake, Dam Inspection, Private Dams
26JAMTRACT? (Cbue m rever ebb N neaeey and Identify by block number)
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.
O W'~1473 EITION or OI ?Novs IOssOLr UNCLASSIFIED
SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered)
7DEPARTMENT OF THE ARMY~ST. LOUIS DISTRICT, CORPS OF ENGINEERS
210 NORTH 12TH STREET
ST. LOUIS, MISSOURI 63101
..*pf, egpua To
SUBJECT: Arrowhead Lakes Lower Dam Phase I Inspection Report
This report presents the results of field inspection and evaluation of
the Arrowhead Lakes Lower dam:1*
It was prepared under the National Program of Inspection of Non-FederalDams
This dam has been classified as unsafe, non-emergency by the St. LouisDistrict as a result of the application of the following criteria:
1) Spillway will not pass 50 percent of the ProbableMaximum Flood
2) Overtopping could result in dam failure3) Dam failure significantly increases the hazard to
loss of life downstream
SIGNED 28 MAR 1980SUBMITTED BY:
Chief, Engineering Division Date
BY: SIGNED 28MAR 1980Colonel, CE, District Engineer Date
Accession For
NTIS GRA&I
DTIC TABUnannounced 0Justifticatio
ByDistribution/
Availability .CodesAvail and/or
Dist Special
fl;
ARROWHEAD LAKES LOWER DAM
DENT COUNTY, MISSOURI
MISSOURI INVENTORY NO. 30267
PHASE I INSPECTION REPORTNATIONAL DAM SAFETY PROGRAM
Prepared By
Anderson Engineering, Inc. , Springfield, Missouri
Hanson Engineers, Inc. , Springfield, Illinois
Under Direction Of
St. Louis District, Corps of Engineers
For
Governor of Missouri
February 1980
PHASE I REPORTNATIONAL DAM SAFETY PROGRAM
Name of Dam: Arrowhead Lakes Lower DamState Located: MissouriCounty Located: DentStream: Unnamed Tributary of Meramec RiverDate of Inspection: August 15, 1979
* Arrowhead Lakes Lower Dam was inspected by an inter-disciplinary team of engineers from Anderson Engineering,Inc. of Springfield, Missouri and Hanson Engineers, Inc. ofSpringfield, Illinois. The purpose of the inspection was tomake an assessment of the general condition of the dam withrespect to safety, based upon available data and visualinspection, in order to determine if the dam poses hazardsto human life or property.
The guidelines used in the assessment were furnished bythe Department of the Army, Office of the Chief of Engineers,and they have been developed with the help of several Federaland State agencies, professional engineering organizations,and private engineers. Based on these guidelines, the St.Louis District, Corps of Engineers has determined that thisdam is in the hi h hazard potential classification, whichmeans that loss o life and appreciable property loss couldoccur if the dam fails. The estimated damage zone extendsapproximately 3 miles downstream of the dam. Locatedwithin this zone are a 29 acre lake (MO I.D. 30268) andthree dwellings. The dam is in the small size classifica-tion, since it is greater than 25 ft high but less than 40ft high, and the maximum storage capacity is greater than 50ac-ft but less than 1000 ac-ft.
Our inspection and evaluation indicates that the com-bined spillways do not meet the criteria set forth in theguidelines for a dam having the above size and hazardpotential. The combined spillways will pass 25 percent ofthe Probable Maximum Flood without overtopping. The Prob-able Maximum Flood is defined as the flood discharge thatmay be expected from the most severe combination of criticalmeteorologic and hydrologic conditions that are reasonablypossible in the region. The guidelines require that a damof small size with a high downstream hazard potential pass50 to 100 percent of the PMF. Considering the small size ofthe dam and the low storage capacity, S0 percent of the PMFhas been determined to be the appropriate spillway designflood. The 100-year frequency, flood will not overtop the
dam. The 100-year flood is one that has a 1 percent chanceof being equaled or exceeded in any given year.
Deficiencies visually observed by the inspection teamwere: (1) seepage area on downstream face between Stations3+10 and 3+40 about 10 ft below the crest; (2) apparentleakage of primary spillway pipe; (3) some brush and treegrowth on the lower half of the downstream embankment face;(4) lack of wave protection for the upstream face of thedam; and (5) minor erosion on the downstream face at thenorth abutment-dam contact. Another deficiency was the lackof seepage and stability analysis records.
It is recommended that the owners take the necessaryaction in the near future to correct the deficienciesreported herein. A detailed discussion of these deficien-cies is included in the following report.
Steve Brady, P.E. (AEIY>
Tom Beckley, P.IE. f.\:2!)
Ja Healy, P. (HEI)
rales, P.E. (HEI)
Dan Kerns.,/E.I-.T. (HEI)
AF
AERIAL VIEW OF LAKE AND DAM
PHASE I INSPECTION REPORTNATIONAL DAM SAFETY PROGRAM
ARROWHEAD LAKES LOWER DAM ID No. 30267
TABLE OF CONTENTS
Paragraph PageNo. Title No.
SECTION 1 PROJECT INFORMATION
1.1 General 11.2 Description of the Project 11.3 Pertinent Data 3
SECTION 2 ENGINEERING DATA
2.1 Design 72.2 Construction 82.3 Operation 82.4 Evaluation 9
SECTION 3 - VISUAL INSPECTION
3.1 Findings 103.2 Evaluation 11
SECTION 4 - OPERATIONAL PROCEDURES
4.1 Procedures 134.2 Maintenance of Dam 134.3 Maintenance of Operating Facilities 134.4 Description of Any Warning System in Effect 134.5 Evaluation 13
SECTION 5 - HYDRAULIC/HYDROLOGIC
5.1 Evaluation of Features 14
SECTION 6 - STRUCTURAL STABILITY
6.1 Evaluation of Structural Stability 16
SECTION 7 - ASSESSMENT/REMEDIAL MEASURES
7.1 Dam Assessment 177.2 Remedial Measures 18
APPENDICES
Sheet
APPENDIX A
Location Map IVicinity Map 2Plan, Profile and Section of Dam 3Plan Sketch of Dam 4
APPENDIX B
Geologic Regions of Missouri 1Thickness of Loessial Deposits 2
APPENDIX C
Overtopping Analysis - PMF 1-8
* APPENDIX D
Photographs of Dam and Lake 1-6
ii
SECTION 1 -PROJECT INFORMATION
1.1 GENERAL:
A. Authority:
The National Dam Inspection Act, Public Law 92-367,authorized the Secretary of the Army, through the Corps of
r Engineers, to initiate a program of safety inspection ofdams throughout the United States. Pursuant to the above,
a the St. Louis District, Corps of Engineers, District Engi-neer directed that a safety inspection be made of ArrowheadLakes Lower Dam in Dent County, Missouri.
lr,.B. Purpose of Inspection:
The purpose of the inspection was to make an assessmentof the general condition of the dam with respect to safety,based upon available data and a visual inspection in orderto determine if the dam poses hazards to human life or
property.KC. Evaluation Criteria:Criteria used to evaluate the dam were furnished by the
Department of the Army, Office of the Chief of Engineers,"Recommended Guidelines for Safety Inspection of Dams,Appendix D." These guidelines were developed with the helpof several federal agencies and many state agencies, pro-fessional engineering organizations, and private engineers.
1.2 DESCRIPTION OF PROJECT:
A. Description of Dam and Appurtenances:
Arrowhead Lakes Lower Dam is an earth fill structureapproximately 27 ft high and 375 ft long at the crest. Theappurtenant works consist of a 21 in. diameter corrugatedmetal primary spillway pipe with a 36 in. diameter riser,an earth swale emergency spillway and an 8 in. diametersteel drawdown pipe and gate valve. Sheet 3 of Appendix Ashows a plan, profile and typical section of the embankment.
B. Location:
The dam is located in the north central part of Dent
County, Missouri on a tributary of Meramec River. The dam
-( ---- -
and lake are within the Salem, Missouri 15 minute quadranglesheets (Section 5, T34N, R5W - latitude 370 41.9'; longi-tude 910 30.2'). Sheet 2 of Appendix A shows the generalvicinity.
C. Size Classification:
* - With an embankment height of 27 ft and a maximumstorage capacity of approximately 141 acre-ft, the dam is inthe small size category.
D. Hazard Classification:
The St. Louis District, Corps of Engineers has clas-.7 '~sified this dam as a high hazard dam. The estimated damage
zone extends approximately 3 miles downstream of the dam.Located within this zone are a 29 acre lake (MO I.D. 30268)and three dwellings.
E. Ownership:
* *, The dam is owned by Mr. Vance Harper. The owner'saddress is Sligo Star Route, Salem, Missouri 65560 (tele-phone: 314-729-4014).
F. Purpose of Dam:
The dam was constructed primarily for a lakeside residen-tial development, although some flood protection is alsoprovided.
G. Design and Construction History:
No design information is available. Mr. David Warner,the builder and original owner, indicated that the SoilConservation Service provided design and constructionassistance for the dam. However, the SCS office in Salem,Missouri did not have any records in their files. Mr. Warnerindicated that material for construction of the dam wasobtained from the north abutment area. Mr. Warner alsoreported that a key trench about 20 ft deep and 12 ft widewith 1.OH:l.OV side slopes was provided for the dam. Nointernal drainage or zoning was apparently provided in thedam. The present owner bought the dam in 1976. No problemsof seepage through the dam are reported to have occurred.The only reported post-construction change was the recentrepair of erosion at the emergency spillway inlet area.
-2-
H. Normal Operating Procedures:
The normal flows are discharged through uncontrolledspillways. An 8 in. diameter steel pipe can be used todewater the lake. Information from the owner indicates thatthe dam has never been overtopped. The emergency spillwayhas never been used, and the primary spillway has onlyoperated once or twice each year.
1.3 PERTINENT DATA:
Pertinent data about the dam, appurtenant works, andreservoir are presented in the following paragraphs. Sheet3 of Appendix A presents a plan, profile and typical sectionof the embankment.
A. Drainage Area:
The drainage area for this dam, as obtained from theU.S.G.S. quad sheet, is approximately 275 acres.
B. Discharge at Dam Site:
(1) All discharge at the dam site is through uncontrolledspillways.
(2) Estimated Total Spillway Capacity at Maximum Pool (lopof Dam - El. 1164.2): 826 cfs
(3) Estimated Capacity of Primary Spillway: 36 cfs
(4) Estimated Experienced Maximum Flood at Dam Site:34 cfs (Elev. 1161.3)
(5) Diversion Tunnel Low Pool Outlet at Pool Elevation:Not Applicable
(6) Diversion Tunnel Outlet at Pool Elevation: Not Appli-cable
(7) Gated Spillway Capacity at Pool Elevation: Not Appli-cable
(8) Gated Spillway Capacity at Maximum Pool Elevation: NotApplicable
3-
C. Elevations:
All elevations are consistent with an assumed mean sealevel elevation of 1159.2 for the crest of the primaryspillway riser pipe (estimated from quadrangle map).
(1) Top of Dam: 1164.2 (Low Point); 1164.9 (High Point)
(2) Principal Spillway Crest: 1159.2
(3) Emergency Spillway Crest: 1161.7
(4) Principal Outlet Pipe Invert: 1138.0
(5) Streambed at Centerline of Dam: 1137.7
(6) Pool on Date of Inspection: 1158.9
(7) Apparent High Water Mark: 1161.3
(8) Maximum Tailwater: Unknown
(9) Upstream Portal Invert Diversion Tunnel: Not Applicable
(10) Downstream Portal Invert Diversion Tunnel: Not Applicable
D. Reservoir Lengths:
(1) At Top of Dam: 1475 ft
(2) At Principal Spillway Crest: 1050 ft
(3) At Emergency Spillway Crest: 1250 ft
E. Storage Capacities:
(1) At Principal Spillway Crest: 79 ac-ft
(2) At Top of Dam: 141 ac-ft
(3) At Emergency Spillway Crest: 110 ac-ft
F. Reservoir Surface Areas:
(1) At Principal Spillway Crest: 11 ac.
(2) At Top of Dam: 14 ac.
(3) At Emergency Spillway Crest: 12.5 ac.
-4-
G. Dam:
(1) Type: Earth
(2) Length at Crest: 375 ft
(3) Height: 27 ft
(4) Top Width: 10 ft
(5) Side Slopes: Upstream Irregular; Downstream Irregular(see Sheet 3, Appendix A)
(6) Zoning: Apparently Homogeneous
-?,;(7) Impervious Core: None
(8) Cutoff: Key trench (12 ft wide, 20 ft deep -information
from Mr. Warner)
(9) Grout Curtain: Unknown
H. Diversion and Regulating Tunnel:
(1) Type: Not Applicable
(2) Length: Not Applicable
(3) Closure: Not Applicable
(4) Access: Not Applicable
(5) Regulating Facilities: Not Applicable
I. Spillway:
I.1 Principal Spillway:
(1) Location: South End of Dam (Station 0+70)
(2) Type: Drop Inlet Pipe
1.2 Emergency Spillway:
(1) Location: South Abutment
(2) Type: Earth Cut
J. Regulating Outlets:
The only regulating outlet for this dam is an 8 in.diameter steel pipe that can be used for the drawdown of thelake. The pipe passes through the embankment at Station1+20, and a gate valve is located at the downstream end ofthe pipe.
.6
''4
<.
-6-!
SECTION 2-ENGINEERING DATA
2.1 DESIGN:
Although Mr. Warner indicated that the Soil ConservationService provided design and construction assistance, nodesign computations or reports for Arrowhead Lakes Lower Damare available. No documentations of construction inspectionrecords have been obtained. To our knowledge, there are nodocumented maintenance data.
A. Surveys:
No information regarding pre-construction surveys wasable to be obtained. Sheet 3 of Appendix A presents a plan,profile and cross section of the dam from survey data ob-tained from the site inspection. The crest of the 36 in.diameter primary spillway riser pipe was used as a referencepoint to determine the other elevations. This referencepoint corresponds to an approximate M.S.L. elevation of
* . 1159.2 as derived from a U.S.G.S. quadrangle map and oursurvey notes.
B. Geology and Subsurface Materials:
The site is located in the central portion of theOzarks geologic region of Missouri. The Ozarks are char-acterized topographically by hills, plateaus and deep vallcv,-.The most common bedrock types are dolomite, sandstone andchert. The "Geologic Map of Missouri" indicates that thebedrock in the site area consists primarily of the Gasconadeformation of the Canadian Series in the Ordovician System.The Gasconade formation is predominantly a light brownish-gray, cherty dolomite. In the central Ozarks region, theaverage thickness of the Gasconade is 300 ft. Caves andsprings are common in this formation.
The publication "Caves of Missouri" indicates that nineknown caves exist in Dent County. Of the four caves within10 miles of the site, three are clustered about 4 milesnortheast of the site, and the fourth cave is about 4 milessoutheast of the site.
The "Geologic Map of Missouri" indicates a normal fault* passing about 11 miles northwest of the site in an east-west
direction. The Missouri Geological Survey has indicatedthat the faults in this area are generally considered to beinactive and have been for several hundred million years.
-7-
1 I
The soils in the area of the dam are of the Nixa-Clarksville-Lebanon-Hobson soil association. These soilshave developed from cherty dolomite, limestone and sand-stone. The thickness of loessial deposits in upland areasmay range from 2.5 ft to 5.0 ft. The published "Soil Surveyof Dent County"' indicates that the soils adjacent to thereservoir are the Coulstone and Clarksville cherty soils.These soils consist of a yellowish-red very cherty siltyclay loam.
C. Foundation and Embankment Design:
No foundation and embankment design information was
available. Seepage and stability analyses apparently werenot performed as required in the guidelines. There isapparently no particular zoning of the embankment, and nointernal drainage features are known to exist. No construc-tion inspection test results have been obtained.
D. Hydrology and Hydraulics:
No hydrologic or hydraulic design computations for thisdam were available. Based on a field check of spillwaydimensions and embankment elevations, and a check of thedrainage area on U.S.G.S. quad sheets, hydrologic analysesusing U.S. Army Corps of Engineers guidelines were performedand appear in Appendix C, Sheets 1 to 8.
E. Structure:
No design information for the primary spillway ordrawdown pipe was available.
2.2 CONSTRUCTION:
No construction inspection data were obtained.
2.3 OPERATION:
Normal flows are discharged through uncontrolled spill-ways. The only regulating facility associated with this damis the 8 in. diameter steel pipe used for the drawdown ofthe lake. The brush and small tree growth on the lower halfof the downstream face indicates that the dam has not beenrecently maintained.
-8
2.4 EVALUATION:
A. Availability:
No engineering data, seepage or stability analyses, orconstruction test data were available.
B. Adeiua!cy:
The engineering data available were inadequate to makea detailed assessment of the design, construction, andoperation of this structure. Seepage and stability analysescomparable to the requirements of the "Recommended Guide-lines for Safety Inspection of Dams" were not available,
e4 which is considered a deficiency. These seepage and sta-bility analyses should be performed for appropriate loadingconditions (including earthquake loads) and made a matter ofrecord.
C. Validity:
To our knowledge, no valid engineering data on the
design or construction of the embankment are available.
K9
SECTION 3 - VISUAL INSPECTION
3.1 FINDINGS:
A. General:
The field inspection was made on August 15, 1979. Theinspection team consisted of personnel from Anderson Engi-neering, Inc. of Springfield, Missouri and Hanson Engineers,Inc. of Springfield, Illinois. The team members were:
John Healy -Hanson Engineers, Inc. (Geotechnical Engineer)Steve Brady -Anderson Engineering, Inc. (Civil Engineer)Tom Beckley -Anderson Engineering, Inc. (Civil Engineer)Nelson Morales -HnoEgierInc. (Hydraulic Engineer)Dan Kerns - Hanson Engineers, Inc. (Geotechnical Engineer)
Photographs of the dam, appurtenant structures, and the* reservoir are presented in Appendix D.
B. Dam:
The dam appears to be generally in good condition.Minor erosion was observed on the downstream face at thenorth abutment-dam contact. No wave protection is providedfor the upstream face of the dam, although no erosion orsloughing was observed. A seepage area was observed on thedownstream face of the dam between Stations 3+10 and 3+40about 10 ft below the crest. This seepage area was softand wet, and no noticeable flow was observed. Some brushand small tree growth was noted on the lower half of thedownstream embankment face. The primary spillway pipe wasdischarging about .5 gallons of water per minute, despitethe reservoir being about .3 ft below the spillway crest.The primary spillway pipe appeared to be in good condition.However, the flow from the outlet would indicate that thepipe is leaking water. The owner indicated that the flowfrom the outlet stops when the reservoir level is a few feetbelow normal pool.
The horizontal and vertical alignments of the crestappeared good, and no surface cracking or unusual movementwas obvious. Shallow auger probes into the embankmentindicated the dam to consist of a brownish red silty claywith rock fragments. Information from Mr. Warner indicatesthat material for construction of the dam was obtained fromthe abutment areas.
- 10 -
C. Appurtenant Structures:
C.l Primary Spillway:
The area around the intake to the primary spillway wasclear. The trash rack appears to be in good condition. Aspreviously discussed, the primary spillway pipe apparentlyleaks. A small plunge pool has eroded at the primary spill-way outlet. The outlet channel is clear for about 200 ftbefore entering a wooded area.
C.2 Emergency Spillway:
The earth cut emergency spillway appears to be in goodcondition. The approach area to the emergency spillway wasclear. Some erosion was observed at the emergency spillwayentrance where drainage from the south abutment enters thelake. The owner has reported that this erosion area wasfilled with rock subsequent to our inspection. The emer-gency spillway outlet cascades down the south abutment andinto the valley. No erosion or debris was noted in thisarea.
C.3 Drawdown Pipe:
The 8 in. diameter steel drawdown pipe and valve appearedto be in good condition (see Photo 13). It is not knownwhether the valve is operated periodically.
D. Reservoir:
The watershed is generally wooded and grass-coveredwith no agricultural activity. The slopes adjacent to thereservoir are moderate, and no sloughing or serious erosionwas noted.
E. Downstream Channel:
The downstream channel is generally clear with someweed growth. The channel enters a wooded area about 200 ft
downstream of the embankment toe.3.2 EVALUATION:
Trees and brush on the dam constitute a potentialseepage hazard and encourage animal burrowing. The seepagefrom the embankment face may adversely affect the stabilityof the dam. The apparent leakage from the primary spillway
pipe could worsen and either lower the normal pool of thelake or-adversely affect the stability of the dam. Thesedeficiencies should be corrected under the direction of anengineer experienced in the design and construction of dams.
Because the lake drain valve is located on the down-stream side of the dam, the full head of water impounded bythe dam is acting entirely through the dam. The area aroundthe lake drain outlet s1'ould be periodically inspected forseepage which might indicate a leak or rupture of the drainpipe and could eventually initiate a piping failure through
* the embankment.
f - 12 -
f_7 7 T ____MfSECTION 4 - OPERATIONAL PROCEDURES
4.1 PROCEDURES:
Although there is a drawdown pipe under this dam, noregulating procedures are known to exist. The pool isnormally controlled by rainfall, runoff, evaporation, thecapacities of the uncontrolled spillways, and the seepagefrom the reservoir.
4.2 MAINTENANCE OF DAM:
ofThe presence of some small trees on the downstream face1 17 ofthe embankment indicates that the dam has not been main-
tained recently.k 4.3 MAINTENANCE OF OPERATING FACILITIES:
The drawdown pipe and valve appeared to be in goodcondition. No regular maintenance program for the dewater-ing facility is known to exist.
* 4.4 DESCRIPTION OF ANY WARNING SYSTEM IN EFFECT:
The inspection team is unaware of any existing warning* system for this dam.
4.5 EVALUATION:
* The brush and trees on the lower embankment face, theseepage area on the downstream face of the dam, apparentlyleakage of the primary spillway pipe, and minor erosion atthe north abutment-dam contact are serious deficiencieswhich should be corrected. However, to avoid creating anunsafe condition, these deficiencies should only be correctedunder the direction of an engineer experienced in the designand construction of dams.
- 13 -
SECTION S - HYDRAULIC/HYDROLOGIC
5.1 EVALUATION OF FEATURES:
A. & B. Design and Experience Data:
No hydrologic or hydraulic design computations for thisdam were available.
The hydraulic and hydrologic analyses were based on:(1) a field survey of spillway dimensions and embankmentelevations; and (2) an estimate of the pool and drainageareas from the U.S.G.S. quad sheet. The owner indicated
a.. that the dam has never overtopped, and the emergency spill-way has never operated. The primary spillway has operatedonly once or twice each year. Our hydrologic and hydraulicanalyses using U. S. Army Corps of Engineers guidelinesappear in Appendix C.
C. Visual Observations:
The approach channels to the spillways are clear.There is apparently a leak (.5 gpm) in the primary spillwaypipe. The outlet channel is fairly clear of brush anddebris. The emergency spillway is well separated from theembankment, and spillway releases would not be expected toendanger the dam.
D. Overtopping Potential:
Based on the hydrologic and hydraulic analysis pre-sented in Appendix C, the combined spillways will pass 25percent of the Probable Maximum Flood. The Probable Maximu'Flood is defined as the flood discharge that may be expectedfrom the most severe combination of critical meteorologicand hydrologic conditions that are reasonably possible inthe region. The recommended guidelines from the Departmentof the Army, Office of the Chief of Engineers, require thatthis structure (small size with high downstream hazardpotential) pass 50 percent to 100 percent of the PMF, with-out overtopping. Considering the small size of the dam andthe low storage capacity of the reservoir, 50 percent of thePMF has been determined to be the appropriate spillwaydesign flood. The structure will pass a 100-year frequencyflood without overtopping.
- 14 -
The routing of 50 percent of the PMF through the spill-ways and dam indicates that the dam will be overtopped by0.97 ft at elevation 1165.17. The duration of the over-topping will be 1.17 hours, and the maximum outflow will be2534 cfs. The maximum discharge capacity of the spillwaysis 826 cfs. Overtopping of an earthen embankment couldcause serious erosion and could possibly lead to failure ofthe structure.
I!
- 15-
SECTION 6 -STRUCTURAL STABILITY
6.1 EVALUATION OF STRUCTURAL STABILITY:
A. Visual Observations:
Observed features which could adversely affect thestructural stability of this dam are discussed in Sections
14 3.1B and 3.2.
aB. Design and Construction Data:
No design and construction data for the foundation andembankment were available. Seepage and stability analysescomparable to the requirements of the guidelines were notavailable, which constitutes a deficiency which should berectified.
C. Operating Records:
No operating records have been obtained.
D. Post-Construction Changes:
The only reported post-construction change was therepairing of minor erosion at the entrance to the emergencyspillway.
E. Seismic Stability:
The structure is located in seismic zone 1. An earth-quake of this magnitude would not generally be expected tocause severe structural damage to a well constructed earthdam of this size. However, it is recommended that theprescribed seismic loading for this zone be applied instability analyses performed for this dam.
- 16 -
SECTION 7 - ASSESSMENT/REMEDIAL MEASURES
7.1 DAM ASSESSMENT:
This Phase I inspection and evaluation should not beconsidered as being comprehensive since the scope of workcontracted for is far less detailed than would be requiredfor an in-depth evaluation of dams. Latent deficiencies,which might be detected by a totally comprehensive inves-tigation, could exist.
A. Safety:
The embankment is generally in good condition. Severalitems were noted during the visual inspection which shouldbe investigated further, corrected or controlled. Theseitems are: (1) seepage area on downstream face between
"* Stations 3+10 and 3+40 about 10 ft below the crest; (2)apparent leakage of primary spillway pipe; (3) some brushand tree growth on the lower half of the downstream embank-ment face; (4) lack of wave protection for the upstream faceof the dam; and (5) minor erosion on the downstream face atthe north abutment-dam contact.
Another deficiency was the lack of seepage and stabilityanalysis records.
The dam will be overtopped by flows in excess of 25percent of the Probable Maximum Flood. Overtopping of anearthen embankment could cause serious erosion and couldpossibly lead to failure of the structure.
B. Adequacy of Information:
The conclusions in this report were based on the per-formance history as related by others, and visual observa-tion of external conditions. The inspection team considersthat these data are sufficient to support the conclusionsherein. Seepage and stability analyses comparable to the"Recommended Guidelines for Safety Inspection of Dams" werenot available, which is considered a deficiency.
C. Urgency:
The remedial measures recommended in paragraph 7.2should be accomplished in the near future. If the defici-encies listed in paragraph A are not corrected, and if goodmaintenance is not provided, the embankment condition will
- 17 -
deteriorate and possibly could become serious in the future.The item recommended in paragraph 7.2A should be pursuedpromptly.
D. Necessity for Phase II:
Based on the result of the Phase I inspection, no PhaseII inspection is recommended.
E. Seismic Stability:
The structure is located in seismic zone 1. An earth-quake of this magnitude would not generally be expected tocause severe structural damage to a well constructed earthdam of this size. However, it is recommended that theprescribed seismic loading for this zone be applied in anystability analyses performed for this dam.
7.2 REMEDIAL MEASURES:
The following remedial measures and maintenance pro-cedures are recommended. All remedial measures should beperformed under the guidance of a professional engineerexperienced in the design and construction of dams.
A. Alternatives:
(1) Spillway size and/or height of dam should beincreased to pass 50 percent of the PMF. Ineither case, the spillway should be protected toprevent erosion.
B. O&M Procedures:
(1) Seepage and stability analyses comparable to theIrequirements of the recommended guidelines shouldbe performed by an engineer experienced in theconstruction of dams.
(2) The seepage area on the downstream face of the dambetween Stations 3+10 and 3+40 should be investigatedby an engineer experienced in the design andconstruction of dams. Remedial measures may berequired. As a minimum, this area should bedrained and monitored to determine if there is anyanreasbein caidtithe the water si atceinreaein uantidite and whtersi atce
- 18 -
-?-((3) The trees, brush and weeds should be removed from
the embankment face. The vegetative growth shouldbe cut on an annual basis.
(4) The leakage from the primary spillway pipe shouldbe investigated and corrected.
(5) Wave protection should be provided for the upstreamface of the dam.
(6) The minor erosion on the downstream embankmentface at the north abutment-dam contact should bemonitored and repaired if it becomes worse.
(7) A detailed inspection of the dam should be madeperiodically by an engineer experienced in thedesign and construction of dams.
- 19 -
A PPLENDIX A
Ki
Ii
KANSAS
Dom No. 50267
'*
SPRINGFIELD
LOCATION MAP
SHEET I OF APPENDIX A
i $¢ale -250000
"",,.. , -,'.;,..:.u t.8,
. - *o a m 3 0 6
.r : I,. . 741Z
35ke -Ap e di
o 0 o 0 0 00 0 0 0 0 0+. 4 +. +. 4+
SOT. OF PLUNGE WATPOOL *33.2 ELIE
WATER SURFACE l
IN V.
709~~~~RS OFSOEV 936
NOTEAD
As00
T L VA I N H W
TOP" OSP36LWAYPSERSTA *70 LEV:159. MS
1165.. - ___ ________ _______ __fill6
1160____ ___ ____ _______ ____ ___ ____1G6
3*, 2 0-
+ +IL!b
wl -1165WATER 9.47 1 1 160ELEV. 1158.9
_1155
PIPE
3 .2 9 - 1 1 5 0
- 1145
T IO N S S H O W N
\
IONS I I I I
40 20 0 20 40 60 80
SECTION A-A STA 1+00
SHEET 3 OF APPENDIX AANDERSON ENGINEERING, INC.
-1165 730 NORTH BENTON AVENUESPRINGFIELD, MISSOURI 65802
ARROWHEAD LAKES
MO. No. 30267
-160 PLAN It PROFILE
DENT COUNTY, MO.I L
4.00
..- TOE
S SEEPAGE
-AREA
3400
* 4 -N-
24-00- LAKE
DRAWDOWN VALVEPIPE
PRIMARY SPILLWAY PLUNGE 14.00
INTAKE -POOL
PLAN SK HARROWHEAD LAKES LOWER DAM
MO.1.D.302 67
PRINIL IuLL. PORA IL. SHEET 4 APPENDIX A
f
APPENDIX J.1,;
* A ~i
... . ...
. . .. .
tk0
4')~~~ 15 I
soe~ fJ OF) APPJU)I .
A( From "Soils of Missouri'
10-2-
*.5
Z.5~~~~~~ * H~ FAPNI
A PPENDIX C
From Salem 15' Quad From Stone Hil 15' Quad
Waeshee /Apni
HYDRAULIC AND HYDROLOGIC DATA
Design Data: No design data are available.
Experience Data: No records are available. The owner
indicated that the dam has never overtopped, and the emer-
gency spillway has never operated. The primary spillway has
operated only once or twice each year.
Visual Inspection: At the time of the inspection, the pool
level was approximately 0.26 ft below normal pool.*1-
Unit Hydrograph: Flood routings were performed to determine
the overtopping potential. The watershed area was obtained
by planimeter from the U.S.G.S., Salem, MO, 1.5 minute
quadrangle map and the reservoir surface area from the
U.S.G.S. Salem, Missouri 7.5 minute orthophotograph (advance
print). The storage volume was developed from these data.
A 5 minute interval unit hydrograph was developed for this
watershed, which resulted in a peak inflow of 749 c.f.s. and
a time to peak of 17 minutes. Application of the probable
maximum precipitation minus losses results in a flood hydro-
graph peak inflow of 5703 c.f.s. Rainfall distribution for
the 24 hour storm was according to EM 1110-2-1411.
The existence of two more dams upstream will reduce the
effect of the design flood by storing part of the flood and
by retarding the peak. To obtain a more realistic result of
the flood routing studies, the PMF was considered acting
simulataneously over the entire watershed area of the three
dams. First, the PMF was routed through the reservoir and
spillway of the 2nd upstream dam (see LAKE AND WATERSHED
Sheet 2 Appendix C
,4 1 - -Q - WFIA_'
MAP, sheet 1 Appendix C), then the outflow hydrograph from
this dam was combined with the inflow hydrograph of the Ist
upstream dam watershed and routed through the reservoir and
spillway of the 1st upstream dam; finally, the outflow
hydrograph from this dam combined with the inflow hydrograph
from the watershed of the dam under consideration was routed
through the reservoir and spillways of the last dam. The
flood routing studies were made using the HEC-l Dam Safetya!.Version Program. The computer input, output and hydrograph
for 50 percent of the PMF are presented on Sheets 6, 7 and 8
of Appendix C.
Sheet 3 Appendix C
.-
IOVERTOPPING ANALYSIS FOR ARROWHEAD LAKES LOWER DAM
INPUT PARAMETERS
1. Unit Hydrograph - SCS Dimensionless - Flood HydrographPackage (HEC-1); Dam Safety VersionWas Used.Hydraulic Inputs Are As Follows:
a. Twenty-four Hour Rainfall of 26.4 InchesFor 200 Square Miles - All Season Envelope
b. Drainage Area - 275_ Acres; - o.43 Sq. Miles
c. Travel Time of Runoff 0.39 Hrs.; Lag Time 0_24 Hrs.
d. Soil Conservation Service Soil Group C
e. Soil Conservation Service Runoff Curve No. 85 (AMC III)- MAIC II
f. Proportion of Drainage Basin Impervious 0.04
2. Spillways
a. Primary Spillway: 36 in. I.D. CMP Riser and 21 in.
I.D. CMP Outlet Pipe; Crest Elevation 1159.2
b. Emergency Spillway: Trapezoidal Cut
Length 25 Ft.; Side Slopes Va; C - Varies
c. Dam Overflow
Length 375 Ft.; Crest El. 1164.2 ; C = 3.0
3. Spillway and Dam Rating:
Curve Prepared by Hanson Engineers. Data ProvidedTo Computer on Y4 and YS Cards.Formula Used: Primary Spillway: Chart for CMP Flowing Full
Emergency Spillway: 2= A3
g T
Note: Time of Concentration From Equation Tc= ( )H
California Culvert Practice, California Highways andPublic Works, Sept. 1942.
Sheet 4 Appendix C
I
SUMMARY OF DAM SAFETY ANALYSIS
1. Unit Hydrograph
a. Peak - 749 c.f.s.
b. Time to Peak 17 Min.
2. Flood Routings Were Computed by the Modified Puls Method
a. Peak Inflow
50% PMF 2699 c.f.s.; 100% PMF 5703 c.f.s.
b. Peak Elevation
50% PMF 1165.17 100% PMF 1166.18
c. Portion of PMF That Will Reach Top of Dam
25 1; Top of Dam Elev. 1164.2Ft.
3. Computer Input and Output Data are shown on Sheets 5 and 6of this Appendix.
Sheets Appendix C
I I.-
o) co 4
9L.
C-CDC
do -
La 1- cn Il 1. I 0.I - -W z 10 ,- r C
qz5~~~~C tQ i C -
w 0i cc ccI-
A. 3.O a. .- o. qU)CIC2
ccv 0. r -. in--S
.0 La U
CD.l LA. CA. D.-La 1 0
= = p.. p-
cc c I- C. M w CD4 C'J o 9- CD 6.) w 0W C- d 0.- -
CD 6.) C. ..L" Z 6.m -0 6.) r-Z! 1
an m = .Ci = m
)1 lal co W - .0 O&J-C4C C DE n -a -a r 0.
CD CDI. C
acA me V-.- cc fi 30--
9-W La Z D c m 40 gg D.a D. c 4e - N C cm
1- on. U) La m Lai -j- aCaA m an
C. lop Pl. 0. 0. o. .
inaZ ZZ - - - -s *I
W-64 - W W4 CLP -1--q 'Ij ) 30 61 0 W 0WW A -MWWWWW- P-4S W ) 3-- *' 0 bWWM
I~ q -
£~~~ad coe-- Z fCO -1 Lii=
a-aww w.
-A 06~ X
-j - -
21 0. qrC > 0m4a.Nn S4w. m m. 0NI
-0 .4 - £3, CW
CD A- Waa- a-
o-0 -Co -0 -
C, -*1 2- -
ac f, CL m C4 4 - o M W
C3 t- = £
a- - am E0 a-at 3 De cc0. £34 % 4 o 4q I - %0C. -q C D
41F.O Co . 9. D. 4P 42, at *@ 0~ MI 3
-P M. F. INPU DATA-
She 6, Appendix-
"S C*% Co. .S ha *a (Am
,C ri l~ C14 G&- 40 W 3 C - co qr di.Nea42, - - ih W _
61 W; le 4c - -, A.- AX
2r -a - - -
*W P" - CM 91. 0.1 ine WI qr P* Co
ac I-0 inz " 0 N zI "0 65IPIzzrz "' gtC, I.- W =4- 0 - - a~
Li~~c C4 =ccM4~~~ z a: I-I 0;0-a 0
CD CD0 404d N. * . .0I. -4 -0 - - -0 CD
"cc - c 4c 5Ih =2 1 e* WS- -t WI acI saV CDW 44 i
cr C)flC 4 a Co M 0. N N .00 31- 3C
to a-A i I.- . -. - - -. fn h-i gSiC
*9 C ce I. o 10 'a ma hLaia a ma W-C*L W em 0. 0.4 0; *-4 r40 zc W;o NO .40 4D-j lOAM 3C La t- OW) aI bIO £4c .- P'W U;
*l Wm. C, -m -1 b* 3r*iI * 3 0 * C
Laid- we- -j W .0. l C iOa. A c W 9L L' A
LL P in 9- m r- W W -a -i -a =4~..-j ci 4f1 go . a1 A a Z a *a *a
*o 0-e 9- r% -W I"e -am N 4 c u
*w ac M-. -c Wm ' f* 431 C2- L..
*w 40- %a CoM Cb tr WCAC 0 - c i1-a 09 ac cs-IC LaM e O -ma *a ma4 m ma 4a m A
I CL5 0ai C41 C4 -W h 0~ 4 *~**
-"I. 4K a: -0
do Co, VO. Ccl go. -V r.. Cc 6.4 0a.C- io .463 -1. Im - 1. 0W1 a.l V) 0 e)-m 2o 1.La Me
Q.O -C .4 - - (N - 0D- -5
In wJ I
W CDC 1.La - -i I. -i" -; 0CD La W -C .c- 5 - - - -4C Wo - emmu
*c aCi CC b..an 0e . Zd .A CO
C. 0 AM co
O m
CC 29 v W o as %* C X
* an
. - 2z CDa
0. 'M gm 3r tA
CD LS D L
L 30. 0 C.0 0 0. 0 6
cm = mK
S, c .% t ac Ct IC *% = a a a 0. 42 0 CI m a0 *2 a0 40 .P .
u 1= 10 -49 R a o"4
42 C, 0C0
8a W- W- 40C . . C0 k. ,4.4' od o0-cc4 01 o
9- - - - - c4 a -n - -, - ta-40 C4 e-- VC $a 40 CIOe-4- W aa rv
14 q- 4- '-a-CCCD m. C L4
a a. ~ a. ~a ..4* CD C) C
0- 9 * 0C 40 .r -e av -m -- b-u~~ ene CoC o4 oC >I-WC >C Mr
W CDi 404 -) C >a m Li C-1 C-a. Z:j PSLC,;4 .C; In W
=I = a. Z n -
4c " a La2c. cc IaJ 0: C
A 4; c ci OP. Z L.3 CY
. L1 sn r3 W Cb0- R- M. W a0f V ,W
a gn CD en D
- C a aa o I- r.--0 ~ C aaa aa &4- I- -wo. ~;Z-ks -- a W a ai L-a aaa -- s - - -~ -. - -
3- . 3- 3- CD u >-WcI cc -ja -a .- 19 aa a : -M
CC4a C ; CI.
a- 4
t ~ a C> a->a =w a Cp a. 9- n S- C>J 4z C> C. =~ CP C> C> C -LD . 1.. C4 t.. "' WmCoC-C C o .I CD CC.. Ca>a~ @ CC . IC.- C> Co ) r. )-
2ine Cin C; C;U~ 3.Ci W C;~fl Cin *;C C C
*3 CD*a
I.* oZ D- S- a Ud )W t O Cb r..0.Lwo0 rw - C. C va M W- La inu~. al"f,41 le -A -A* nP.= 0- )- .C a . -C -. , aj I :C
=. . ".0 a3,.c A -L
W =
cc C; C;
P.-M. F. OUTPUT DATA
Sheet 7, Appendix C
I
jd
2800
2000 C
1600
1200o . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . .. . . . . ........... . .
§00 CDO0-
. .N . . . .. . .-. . .- .- -. . . .- . . .- - . . .- . . . .- - . .- . .-. .-
CD
5- ~ CD CCC* C C
5- 5- C C
5 CD
CCDca Co
C
-------------- ------ -- ------------- ---- --------
&" c CI m ip C -0 C, -0n CD a" C n . bC, -0V, - " " 0 T
INFLOW - OUTFLOW
HYDROGRAPH
. . .. . .... . . . . . . . . . .. . .. . . .. . . . . .. . . .. O 0 F.. m F 0.. a . .
So o o*o*o*oo. . . . . . .o . . . . . . . . . . . . .
MAX. INFLOW - 2699 C. F. S.
MAX. OUTFLOW - 2534 C. F. S.
. . .. .. .. . .. . . . . . . . S.. .. .. .. . .. ............................................... .S
.. INFLOW
moio
/---OUTFLOW
00
................. ..................................... . ............. .
C D
. i O i i i 0 O
.................. S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
oooD
OUFDLOW................ . . . . .
- CD
42 *- o 4 0 ) 0 C0' oc
. . .. . 000 .....
T12E (hrs.) Sheet 8, Appendi C
A , . '50
If
F.1 APPENDIX D
I
I.'
INDEX TO PHOTOGRAPHS
Photo No. Description
1 Aerial -Arrowhead Lakes (Lower Dam in Left Center
of Picture; Mo. I.D. 30268 in Background)
2 Overview of Dam, Looking Southwest
3 Downstream Face of Dam, Looking South
4 rs f aLokn ot
4 Crest of Dam, Looking South
6 Primary Spillway Inlet Structure
*7 Close-Up of Primary Spillway Inlet
8 Primary Spillway Outlet Pipe
9 Primary Spillway Outlet and Plunge Pool
10 Downstream Channel, Looking Downstream
11 Downstream Channel, Looking Upstream
12 Emergency Spillway, Looking Upstream
13 Drawdown Pipe Valve and Outlet
14 View of Lake and Watershed
15 Arrowhead Lakes Middle Dam, Looking North
16 Arrowhead Lakes Upper Dam, Looking Northeast
- Sheet 1, Appendix D
4#*00A'-' .. TOE
~ SEE AGE
3*00
LAKE
PIP I
PRIMAY SPLWAYPLUNE 2400
RAOODED VALVE
EMERGENC WOE
PLAN SKETCH ARROWHEAD LAKES LOWER DAM
MO. 1. D. 30287
WoomSmLD L.. PORIA ILL.. SHEET 2 APPENDIX D
Ilo
I-,t
Ioil
lit.
I
1014
i
