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Engineering Geology for Gas Pipelines in the Green River AreaPrepared By:John BlairSean DonahueCeleste HoffmanKimberly KlinkersMegan Slater

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Green River Basin Location

Green River Basin Stratigraphic Correlation Chart showing Study Map Units

Sample of Existing Pipelines and Proposed Pipelines

Gas Fields in the Green River Basin

6Pipeline Installation ProcessClearing and gradingStringing pipes along right of wayExcavating/trenchingPipe bending, welding, and coatingLower Pipe into trenchBack fillRestoration

7Geologic HazardsGeologic Hazards are natural physical conditions that exist and if they were to become active could damage structures as well as injure people. These hazards include.Fault CrossingsSubsidenceSlope stabilityHydrogeologyEnvironmental Constraints

8What is the importance?Safety of the general public.Pipelines stay safe and operational.Pipeline failure is a serious environmental concern.

9RegionThe area is composed of several faults. Most of the Mountain Ranges were formed in the Eocene EraGreen River Basin is surrounded on all sides by mountains.Wind River Mountains-NorthFront Range, Park Range and Sawatch Range of Rockies -EastSan Juan Volcanic Field-SouthWasatch Mountains-West

Pipelines and Fault CrossingsDue to the numerous active faults and numerous pipelines, several of these intersect.This provides potential breaking of pipelines due to movement of faults

Construction of PipelinesTo protect from this, all pipelines are built of steel and treated with a protective coating. The pipeline is carefully inspected to make sure it meets all safety requirements. In fault zones pipes are padded with fill material to dampen vibrations and minimize damage.

Safety ConsiderationsIf there is a break in the line, a high-tech computer monitoring system can detect a loss in pressure due to a leak and shut off all access to the length of pipe where a leak is detected. This system is monitored 24 hours a day 7 days a weekInspections occur in the pipelines through camera inspections

SubsidenceSubsidence is the downward motion of the earths surface relative to a datum. Causes of subsidence:Mining induced from caving in of excavated material Dissolution of LimestoneExtraction of Natural GasGroundwater changes

Mine subsidence is movement of the ground surface due to collapse of underground mines. Surface subsidence may be sinkholes or troughs.Sinkhole subsidence occur from the collapse of the mine roof into a mine opening, leaving a pit or sinkhole in the grounds surface.Subsidence troughs occur over active or abandoned mines. They may be similar in appearance to sinkholes but are due to failure of mine pillars.

14Subsidence DamageSubsidence causes a loss of support for the pipeline.Damage may inhibit the functionality of the pipeline as a result of Structural damage.

Damages to structures are generally classified as cosmetic, functional, or structural. Cosmetic damage refers to slight problems where only the physical appearance of the structure is affected, such as cracking in plaster or drywall. Functional damage refers to situations where the structures use has been impacted, such as jammed doors or windows. More significant damages that impact structural integrity are classified as structural damage. This would include situations where entire foundations require replacement due to severe cracking of supporting walls and footings.15Slope Stability Issues-LandslidesLandslides according the USGS are the upward and downward movement of earth materials on a slope.Causes of Landslide include: Steep SlopesWildfiresEarthquakesHydrological EventsHuman causesEnd ResultLoss of Foundation Support

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Landslides-Steep SlopesSteep slopes constrain where a pipeline line can be placed cost effectively.Slopes greater than 30 degrees are highly susceptible to failure. Erosion becomes a significant issue

18Landslides WildfiresPrevalent in the Green River BasinDe-vegetates the slope, which in turn reduces stabilityEarthquakesSoil liquefaction due to shaking of groundCohesion less soils are prone to liquefaction as well as soils the are unconsolidated.

19LandslidesHydrologic EventsHeavy precipitationFloodingHuman causedClearing and grading before pipeline installationBlasting when bedrock is present

20Wyoming Climate5th driest state2nd highest stateMountainsProvide majority of surface waterSnow and runoffDeserts and plainsHouse groundwaterAquifers recharged from surface water

Groundwater ResourcesUnconsolidated depositsAlluvial depositsEolian sand/silt depositsGlacial depositsLacustrine depositsBedrock formationsSandstoneLimestoneResults in aquifer developmentWater-saturated portion of an unconsolidated deposit or geologic bedrock formation which may yield usable quantities and qualities of groundwater through springs and/or wells

Groundwater ResourcesWater wells withdraw groundwater from aquifers toMonitor water levels and water qualityDischarge through alluvial deposits and bedrock formationsSprings naturally withdraw groundwater from saturated aquifers

Environmental ConstraintsWeather:Heavy rainfall and snowmelt paired with limited drainage of the valley can cause flash flood conditionsSnowstorms are frequent from November through MayWind frequently follows snowfall Wind can cause extreme cases of drift High winds and the low temperature of the valley can cause blizzard or near blizzard conditionsDestructive hailstorms occasionally pass over the valley

25Environmental ConstraintsTemperature Concerns:Winters are Long and ColdLow overnight temperatures due to cold air collection in the valley can cause freezing issuesValley temperatures can be considerably lower than surrounding mountainsidesOften valley temperatures are well below zero in the winter months

26Environmental ConstraintsImpacts of the Environment:Snow, rain and hail all have an effect on slope stability in the valley regionHigh wind storms and hail storms can damage above ground pipingLow temperatures can cause freezing of the groundwater causing additional stresses on buried pipes

27Environmental Constraints

Impacts ON the Environment:Pipe ruptures leak gasIf ruptures flare (left) they can cause a great deal of damage to the surroundingsThis also produces a lot of air pollution from the smokeThis can be very dangerous to both humans and animals alikeThe excavation required for drilling and laying pipelines is very disruptive to the environmentAnimal habitats can be damagedConstruction pollutes areaSoil and slope conditions are changed

28Referenceshttp://www.dom.com/about/gas-transmission/covepoint/expansion/construction.jsphttp://www.wsgs.uwyo.edu/surficial/http://3dparks.wr.usgs.gov/landslide/types.htmhttp://www.esa.int/esaCP/SEMX4QVLWFE_index_1.htmlhttp://www.fieldmuseum.org/expeditions/lance/map.htmlhttp://skytruth.mediatools.org/gallery/270http://www.wrds.uwyo.edu/sco/climate/wyoclimate.htmlhttp://www.wsgs.uwyo.edu/hydrology/http://www.canadiandiscovery.com/PDF/Green-River-Basin.pdfhttp://waterplan.state.wy.us/plan/green/techmemos/gwdeterm.htmlhttp://en.wikipedia.org/wiki/Green_River_Formation http://www.geology.wisc.edu/~unstable/Sedimentary/Green_River_Basin.jpg