Engineering Geology for Gas Pipelines in the Green River Area

Prepared By:John Blair

Sean DonahueCeleste Hoffman

Kimberly KlinkersMegan Slater

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

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

Geologic 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

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

concern.

RegionThe 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 -East

San 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 week

Inspections 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

Subsidence DamageSubsidence causes a

loss of support for the pipeline.

Damage may inhibit the functionality of the pipeline as a result of Structural damage.

Slope 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 causes

End ResultLoss of Foundation Support

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

Landslides Wildfires

Prevalent in the Green River Basin

De-vegetates the slope, which in turn reduces stability

EarthquakesSoil liquefaction due

to shaking of groundCohesion less soils are

prone to liquefaction as well as soils the are unconsolidated.

LandslidesHydrologic Events

Heavy precipitation

FloodingHuman caused

Clearing and grading before pipeline installation

Blasting when bedrock is present

Wyoming Climate5th driest state2nd highest stateMountains

Provide majority of surface water

Snow and runoffDeserts and plains

House groundwater

Aquifers recharged from surface water

Groundwater ResourcesUnconsolidated deposits

Alluvial depositsEolian sand/silt depositsGlacial depositsLacustrine deposits

Bedrock formationsSandstoneLimestone

Results in aquifer development“Water-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 formations

Springs naturally withdraw groundwater from saturated aquifers

Environmental ConstraintsWeather:Heavy rainfall and snowmelt paired with

limited drainage of the valley can cause flash flood conditions

Snowstorms 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 conditions

Destructive hailstorms occasionally pass over the valley

Environmental 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 mountainsides

Often valley temperatures are well below zero in the winter months

Environmental 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

Environmental ConstraintsImpacts ON the Environment:Pipe ruptures leak gas

If ruptures flare (left) they can cause a great deal of damage to the surroundings

This also produces a lot of air pollution from the smoke

This can be very dangerous to both humans and animals alike

The excavation required for drilling and laying pipelines is very disruptive to the environment Animal habitats can be damaged Construction pollutes area Soil and slope conditions are

changed

Referenceshttp://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/

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