Design of the South Doña Ana Dam

Design of the South Doña Ana DamDesign of the South Doña Ana Dam

Project Members:Project Members:

Daneel NortierDaneel NortierDesh Raj SonyokDesh Raj Sonyok

Tran Tri DungTran Tri DungUmaima Al-AqtashUmaima Al-Aqtash

Civil Engineering DepartmentCivil Engineering DepartmentNew Mexico State UniversityNew Mexico State University

International Engineering Group (EIG)International Engineering Group (EIG)

What is GPRWhat is GPR??What is GPRWhat is GPR??ContentsContentsContentsContents

Background Background

Objectives Objectives

LocationLocation

Physiography and climatePhysiography and climate

MethodologyMethodology

Preliminary ResultsPreliminary Results

Discussion and ConclusionDiscussion and Conclusion

BackgroundBackgroundBackgroundBackground

Doña Ana county, southern New Mexico, 6.5mi North of Doña Ana county, southern New Mexico, 6.5mi North of Las CrucesLas Cruces

Originally installed in 1950’s (1600 ft)Originally installed in 1950’s (1600 ft)

The proposed South Doña Ana Dam for 100yr floodThe proposed South Doña Ana Dam for 100yr flood

Installation – almost unoccupiedInstallation – almost unoccupied

Readily developable (Flat): 60K (1960) – 175k (2000)Readily developable (Flat): 60K (1960) – 175k (2000)

7900Acres- (Private 54%,BLM 43%,State 4%)7900Acres- (Private 54%,BLM 43%,State 4%)

Unemployment: 6.4% (5.8%)Unemployment: 6.4% (5.8%)

Per Capita Income: $10,542 ($21,587)Per Capita Income: $10,542 ($21,587)

Below Poverty: 22.8% (12.4%)Below Poverty: 22.8% (12.4%)

ObjectivesObjectivesObjectivesObjectives

Propose 100 year return period structurePropose 100 year return period structure1)1) Elephant Butte Irrigation District (EBID)Elephant Butte Irrigation District (EBID)

2)2) Dona Ana County Office of the Flood Commissioner (DACFC)Dona Ana County Office of the Flood Commissioner (DACFC)

3)3) La Union Soil and Water Conservation Service (LUSWCD)La Union Soil and Water Conservation Service (LUSWCD)

4)4) USDA National Resource Conservation Service (NRCS)USDA National Resource Conservation Service (NRCS)

Effective DesignEffective Design1) Surface Hydrology1) Surface Hydrology

2) Storage and Drainage2) Storage and Drainage

3) Transmission3) Transmission

4) Stability and Settlement4) Stability and Settlement

Cost AnalysisCost Analysis $$$$$$$$

LocationLocationLocationLocation

City of Las Cruces, Dona Ana county, New MexicoCity of Las Cruces, Dona Ana county, New MexicoDam axis: lat. 32Dam axis: lat. 320023’28.25’’ and long. 10623’28.25’’ and long. 1060047’55.34’’ 47’55.34’’

Dam Axis

Highly populated

Physiography and ClimatePhysiography and ClimatePhysiography and ClimatePhysiography and Climate

TopographyTopography

Elevation: 4000 ft - 5833 ftElevation: 4000 ft - 5833 ft

Semi-desert climateSemi-desert climate

Rainfall: 9 inchRainfall: 9 inch

Snowfall: 3.2 inch annually Snowfall: 3.2 inch annually (peaks)(peaks)

MethodologyMethodologyMethodologyMethodology

Delineation of the Watershed Delineation of the Watershed

Use of AutoCAD 2007Use of AutoCAD 2007 Topographic maps from USGSTopographic maps from USGS

Soil CharacteristicsSoil Characteristics Soil survey of Dona Ana County area New Soil survey of Dona Ana County area New

Mexico (Bulloch and Neher, 1980)Mexico (Bulloch and Neher, 1980) Curve number of soils: Soil Conservation Curve number of soils: Soil Conservation

Service (SCS) methodService (SCS) method

Methodology Methodology …Continued…ContinuedMethodology Methodology …Continued…Continued

Hydrologic Analysis Hydrologic Analysis Determined 100 year rainfall from NOAA Determined 100 year rainfall from NOAA

database,(2007)database,(2007) UUsed HEC-HMS software to determine surface sed HEC-HMS software to determine surface

runoffrunoff Routing Analysis (Inflow-Outflow relationship)Routing Analysis (Inflow-Outflow relationship)

Maximum outflow and maximum storage Maximum outflow and maximum storage capacitycapacity

Design of trapezoidal channel for the outflowDesign of trapezoidal channel for the outflow

Hydraulic design: outlet pipe and trapezoidal channelHydraulic design: outlet pipe and trapezoidal channel Slope stability, settlement, and seepage analysisSlope stability, settlement, and seepage analysis Economic analysisEconomic analysis

Watershed CharacteristicsWatershed CharacteristicsWatershed CharacteristicsWatershed Characteristics

Total area: Total area:

17.27 km17.27 km22

1727.25 hectare1727.25 hectare

Stream gradients: Stream gradients:

0.018 – 0.1280.018 – 0.128

Watershed CharacteristicsWatershed CharacteristicsWatershed CharacteristicsWatershed Characteristics

16 sub-basins16 sub-basins

Soil Type and Curve NumberSoil Type and Curve NumberSoil Type and Curve NumberSoil Type and Curve Number

CN: 62 – 88CN: 62 – 88

)8.0(

)2.0( 2

SP

SPQ

+−=

101000 −=CN

S

HydrologyHydrologyHydrologyHydrology

HEC-HMS model of the watershedHEC-HMS model of the watershed

HydrologyHydrologyHydrologyHydrology

100 yrs flood: 3.6 100 yrs flood: 3.6 inin

HEC-HMS HEC-HMS Hydrograph:Hydrograph:

Peak flow: 918.36 cfs Peak flow: 918.36 cfs (after 13.5 hours)(after 13.5 hours)

HydraulicsHydraulicsHydraulicsHydraulics

Volume vs. Head Relationship : S=1.522*HVolume vs. Head Relationship : S=1.522*H2.0812.081

Max. Vol. without outflow: 376.79 acre-ft Max. Vol. without outflow: 376.79 acre-ft

Max. water depth without outflow: 14.5 ftMax. water depth without outflow: 14.5 ft

Inflow-outflow relationship:Inflow-outflow relationship:

Maximum storage: 263.98 acre-ftMaximum storage: 263.98 acre-ftMaximum outflow: 119.71cfs Maximum outflow: 119.71cfs Maximum head: 11.9 feet (after 23.5 hour)Maximum head: 11.9 feet (after 23.5 hour)

(I1+I2)/2 – (O1+O2)/2 = S2 – S1

Inflow-Outflow-StorageInflow-Outflow-StorageInflow-Outflow-StorageInflow-Outflow-Storage

Hydraulic DesignHydraulic DesignHydraulic DesignHydraulic Design

Concrete pipe length with square edge:Concrete pipe length with square edge:

Length = 140 ft Diameter = 3 ftLength = 140 ft Diameter = 3 ft

Trapezoidal concrete lined channel: Manning equationTrapezoidal concrete lined channel: Manning equation

B = 15 ft ; Minimal depth = 3.7 ft; B = 15 ft ; Minimal depth = 3.7 ft;

Side slope = 1V: 2H; Slope = .003Side slope = 1V: 2H; Slope = .003

For peak outflow:For peak outflow:

Froude number = 0.96 (subcritical condition)Froude number = 0.96 (subcritical condition)

Flow velocity = 5.58 ft/secFlow velocity = 5.58 ft/sec

V = k/n * (A/P)2/3 * S1/2

Height of embankment: Height of embankment:

Crest width: Crest width:

ftz

w 13105

=+=

boardfreewaterofdepthHeight +=

ftz 15=

ftw 15=

Cross-section A-A

Slope Stability AnalysisSlope Stability AnalysisSlope Stability AnalysisSlope Stability Analysis

Design of Embankment: Design of Embankment:


STABL computer program: STABL computer program:

2D limiting equilibrium methods2D limiting equilibrium methods

for the stability analysisfor the stability analysis

Bishop method:Bishop method:

Applicable to circular failure surfaceApplicable to circular failure surface

Janbu method Janbu method

A method of slices applicable to circular and noncircular A method of slices applicable to circular and noncircular failure surfacesfailure surfaces

Most critical surface and their corresponding Most critical surface and their corresponding factor of safetyfactor of safety

Design component

Soil type Wet unit wt (lb/ft3)

Sat. unit wt (lb/ft3)

Cohesive intercept (psf)

Friction angle (deg)

Foundation GC 116 135 1000 32

Core ML-Cl 110 120 700 20

Shell GM 108 127 800 33


Table: Seven cases of slope stability analysis

Table 2 Soil properties of dam

Case Description Operating condition

Safety Factor

I Wide core Normal 7.72

II Wide core Rapid drawdown 4.61

III Buttress 3:1 Rapid drawdown 4.49

IV Narrow core Rapid drawdown 4.88

V Buttress 3.5:1 Rapid drawdown 4.64

VI Buttress 4:1 Rapid drawdown 4.81

VII Downstream slope for case II Steady seepage 4.07


Case IV: Narrow core in rapid drawdown conditionCase IV: Narrow core in rapid drawdown condition

Crest width: 15 ftHeight: 15 ftWidth: 90 ft

Shell: Upstream slope: 3:1 Downstream slope: 2:1

Core: Upstream slope: 1: 1 Downstream slope: 1:1

Factor of safety = 4.88


Slope stability analysis of downstream slope for case IV:Slope stability analysis of downstream slope for case IV:

Factor of safety =4.069 with most critical failure surface from Janbu method


Details of the embankment design:Details of the embankment design:

Core:ML-CL Shell:

GCShell:GC

Seepage AnalysisSeepage AnalysisSeepage AnalysisSeepage Analysis

• Flow q=1.70 ft3/day/ft• Velocity = 2.43*10-6 ft/s

• Check for piping: i=.91 and icritical=1.04

i<icritical ; no piping will occur

Seepage AnalysisSeepage AnalysisSeepage AnalysisSeepage Analysis

Check for uplifting

umax = 916.56 lb/ft

Load (qb) due to the dam = 1113750 lb/ft

No uplift

Sources: J.W. Hawley, 1984Sources: J.W. Hawley, 1984 Sources: John Shomaker & Associates Inc.Sources: John Shomaker & Associates Inc.

Settlement: Geology and HydrogeologySettlement: Geology and HydrogeologySettlement: Geology and HydrogeologySettlement: Geology and Hydrogeology

Schmertmann method (1970): Schmertmann method (1970): - Define an average settlement (at the centerline) of dam under saturated / unsaturated soil condition

σ- settlement (mm)β - cone factor (3.5 for strip footing)qnet - net footing pressure in kPa (applied stress minus soil pressure above the base of footing)∆zi - thickness of the ith layer (m) (Ico)i –influence factor of the ith layerqc - cone resistance taken from quasi-static cone test data (Mpa)

SettlementSettlementSettlementSettlement

Timoshenko and Goodier method (1951):Timoshenko and Goodier method (1951):- Estimation of final elastic settlement at the center and corner of footing (with the sat/unsaturated soil in dam separately)- Can not consider saturation condition of the ground soil

Settlement time (consolidation): Settlement time (consolidation):

ρ - settlement (m)q - intensity of contact pressure in units of Es (MPa)B - least lateral dimension of footing in units of ρ (m)Iw – influence factor which depends on shape of footing and its rigidity Es, µ - elastic properties of soil

t - time (T)Tv - time factor Cv - coefficient of consolidation (L2/T)Hdr - drained length (L)



L/B > 10: Strip footing

Timoshenko-Goodier method: Inclination in the top of dam = 0.0002 mm

Consolidation time:Cv = 0.000101 cm2/secTime required for completion 93% of the maximum

settlement is to be 8927 years

MethodMethod UnsaturatedUnsaturated(mm)(mm)

SaturatedSaturated(mm)(mm)

Schmermann 32.2 39.9

Timoshenko-Goodier Center: 80.6 Center: 94.9

Corner: 41.8 Corner: 49.2


Estimation of settlement:

Embankment MaterialsEmbankment MaterialsEmbankment MaterialsEmbankment Materials

Shell: GC ~ TE Core: CL-ML ~ Bj Soil found within 10 miles

Soil Group Permeability USCS

Bj Very slow CL, ML, SM, SC

TE Moderate GM, GP, GC

Cost AnalysisCost AnalysisCost AnalysisCost Analysis

Dam Construction: Cost Rate Amount Cost

Earthwork $9.00 per yd3 670 $6,030.00

Fill - Impervious Material $7.50 per ton 83000 $622,500.00

Fill - Gravelly Sand $7.50 per ton 73140 $548,550.00

Pre-Cast 36" Concrete Pipe $36.00 per foot 140 $5,040.00

Concrete In Place $160.00 per yd3 130.5 $20,880.00

Trash Rack (assuming Square) $15.00 per ft3 64 $960.00

Reinforcing Steel $562.00 per short ton 1.5 $843.00

Roller $600.00 per day 90 $54,000.00

Scraper $1,000.00 per day 90 $90,000.00

Machine operation $25.00 per hr 1440 $36,000.00

Human Labor $12.00 per hr 1 Year $345,600.00

Erosion Control $20.00 per linear foot 2000 $40,000.00

Overhead Costs $15,000.00 1 $15,000.00

Total $1,785,403.00

ConclusionsConclusionsConclusionsConclusions

Average CN ranges from 62- 88 Average CN ranges from 62- 88

From HEC-HMS, peak flow was estimated as 918.36 cfs From HEC-HMS, peak flow was estimated as 918.36 cfs (after 13.5 hours) for 100 years storm(after 13.5 hours) for 100 years storm

Max. water depth without outflow is 14.5 ft and with Max. water depth without outflow is 14.5 ft and with outflow is 11.9 ftoutflow is 11.9 ft

Outlet pipe length is estimated as 140 ft and diameter is Outlet pipe length is estimated as 140 ft and diameter is 3 ft.3 ft.

Trapezoidal concrete lined channel parameter are Trapezoidal concrete lined channel parameter are estimated estimated

Dam geometry was calculated and evaluatedDam geometry was calculated and evaluated

Construction was found to be $1,785,403.00 Construction was found to be $1,785,403.00

The existing dam is found to be adequateThe existing dam is found to be adequate

Future worksFuture worksFuture worksFuture works

Monitoring system designMonitoring system design

Spillway designSpillway design

ReferencesReferencesReferencesReferences

Bulloch Jr., H.E. & R.E. Neher (1980). Soil Survey of Dona Ana County Area New Mexico. United States Department of Agriculture, Soil Conservation Service

City-data.com. Las Cruces: Geography and Climate. [Online] Available: http://www.city-data.com/us-cities/The-West/Las-Cruces-Geography-and-Climate.html (Visited on 4/7/2008)

USDA (1986). TR 55: Urban Hydrology for Small Watersheds. United States Department of Agriculture – Soil Conservation Service, pp. 2-1 and 2-8

http://www.city-data.com/us-cities/The-West/Las-Cruces-Geography-and-Climate.html

http://www.city-data.com/us-cities/The-West/Las-Cruces-Geography-and-Climate.html

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