an aem survey over owens valley, california...22 march 2016 1 an aem survey over owens valley,...

22 March 2016 1

An AEM Survey Over Owens Valley, CaliforniaTed Asch1 (CA PGp #1038), Jared Abraham1, James Cannia1, Clint Carney2, Andrew Genco3,

Rachel Woolf3, Kristen Pierce3All formerly XRI Geophysics, currently:1. Aqua Geo Frameworks, LLC2. Wyoming Department of Environmental Quality3. XRI Blue

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Presentation Outline

• Investigation Objectives

• AEM Data Acquisition

• Processing

• Inversion

• Interpretation

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In 1982 William L. Kahrl

The 1986 Marc Reisner

1974 Roman Polanski

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Astronaut photograph ISS006‐E‐24783 was taken February 6, 2003, with an Electronic Still Camera equipped with 180 mm lens and is provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=11270

Starting in 1913, the river and streams that fed Owens Lake were diverted by Los Angeles Department of Water and Power (LADWP) into the Los Angeles Aqueduct.

In 2004, the California Department of Fish and Wildlife (CDFW) acquired a 218‐acre (88 ha) parcel at the foot of Owens Lake. Designated the Cartago Wildlife Area in 2007, it is one of the few remaining spring and wetland areas on the shore of Owens Lake.

As part of an air quality mitigation settlement 2014, LADWP is currently shallow flooding 27 square miles 69.9 km2 of the salt pan to try and help minimize alkali dust. There is also about 3.5 square miles 9.1 km2 of managed vegetation being used as a dust control measure.

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Project Objectives

Client – Los Angeles Department of Water and Power

Objective ‐ Investigate areas east and west of I‐395 in Owens Valley and northern Owens Lake area

1. Owens Lake ‐ Identify water resources for dust mitigation

2. Alabama Hills & west of I‐395

a) Delineate water resources for input to LADWP canal

b) Delineate bedrock elevation for groundwater model

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Project Schedule

1. July 25‐26, 2015 – 652.2 line‐km surveyed over 2 days, approximately 325 line‐km per day acquired by Native American Helicopters (NAH)

2. August, 2015 – Processing, Laterally Constrained Inversion, and multiple Spatially Constrained Inversions by XRI Geophysics under subcontract to NAH

3. August 25, 2015 – Preliminary results presented to LADWP

4. September, 2015 – Analysis performed on AEM Inversion results and delineation of water resources and bedrock surfaces west of I‐395 and northern Owens Lake.

5. September 30, 2015 – Final report delivered by XRI to NAH per contract schedule

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AEM Data Acquisition

SkyTEM 508

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AEM Data Processing

Low‐Moment

High‐Moment

Coupled

De‐Coupled

Power Line Noise Intensity Map

Coupled

De‐Coupled

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Red – CutBlue ‐ Kept

AEM Data Processing

Map of “Cut” and Retained Data Used in the Inversions

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Example of Inversion

Aarhus Workbench Inversions Used 30‐Layer Model:• First Layer – 5 m (16 ft)• 2nd to Last Layer – 41 m (133 ft)• Last Layer ‐ Halfspace

Inversion:• ‘Spatially Constrained’ – Along the Current Flight Line

and on Neighboring Flight Lines, Spatially to a Set Distance

• The area was broken into two parts, one for the high conductive lake and one for the resistive valley sides

• Data residual mean 0.6 to 0.7

AEM Numerical Inversion

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AEM Flight Lines & Topography

AEM Flight Lines & Faults & Topography

AEM Flight Lines & Geology

Topographic & Geologic Images used in AEM Interpretation

Geology Maps Source USGS

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Faults & LineamentsIdentified

Color Scale: 1 – 400 ohm‐m

Color Scale: 1 – 100 ohm‐m

From MWH

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Known Faults

Unknown Faults

Paleo‐Channels


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Interpreted Geologic Structures:• Faults – Known, Unknown• Paleochannels


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Seismic Horizon 1 Aquifer Delineation, Northern Owens Lake

Near‐Surface Seismic Reflection Lines

Intersected by AEM

Seismic “Soundings”

Water Resources –East of I‐395

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KMZ of Horizon 1 Aquifer Delineation, Northern Owens Lake


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West of I‐395 & the Alabama Hills

Map from MWH

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From USGS Report Hollet et al., 1991


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Digitization of the Aquifer Top, Bottom, & Thickness

and Bedrock Top

Top

Bottom

Bedrock

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and Bedrock Top

Top

Bottom

Bedrock

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and Bedrock Top

Top

BottomBedrock

New Bedrock Interpretation

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and Bedrock Top

Top

BottomBedrock

New Bedrock Interpretation

After the additions of new wells in the area the bedrock was revised

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KMZ of the Aquifer Top, Bottom, Thickness


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KMZ of the Bedrock Surface


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The Source of the Northwest Seep

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‐31 m‐70 m

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‐103 m

‐218 m

‐238 m

‐2.5 m

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Summary

1. 652.2 line‐km surveyed over 2 days.

2. Near‐surface geology including known and unknown faults identified along with paleochannels.

3. Aquifer No. 1 (top, bottom, and thickness) identified by near‐surface seismic further delineated by AEM across northern Owens Lake.

4. Interpreted aquifer top, bottom, and thickness west and southwest of I‐395 and the Alabama Hills.

5. Source paths of seeps/springs on west side of Owens Lake delineated.

6. Deliverables included the report, raw data, processed data, and Google Earth kmz’s.

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Acknowledgements

Saeed Jorat, LADWPVictor Harris, MWH Americas, Inc.B.J. Crocker, NAHAlan Stack, NAHKeven Pete, NAHFlemming Effersø, SkyTEMBill Brown, SkyTEM

XRI Geophysics:Ted Asch, AGFJim Cannia, AGFClint Carney, WY DEQAndrew Genco, XRI BlueRachel Woolf, XRI BlueKristen Peirce, XRI BlueTodd Meglich, PRSM Geophysical Consulting

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Questions? Comments?

an aem survey over owens valley, california...22 march 2016 1 an aem survey over owens valley,...

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