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GEOLOGIC ASSESSMENT OF THE 183 NORTH MOBILITY PROJECT, TRAVIS AND WILLIAMSON COUNTIES, TEXAS
Prepared for
CP&Y 13809 Research Blvd., No. 300 Austin, Texas 78750 Attn: Mr. Andy Atlas, Vice President (512) 241-2210
on behalf of
CENTRAL TEXAS REGIONAL MOBILITY AUTHORITY 3300 N IH-35, Suite 300 Austin, Texas 78705 Attn: Mr. Sean Beal, P.E., Engineering Manager (512) 996-9778
Prepared by
SWCA ENVIRONMENTAL CONSULTANTS 4407 Monterey Oaks Boulevard Building 1, Suite 110 Austin, Texas 78749 Texas Board of Professional Geoscientists Firm Registration No. 50159 www.swca.com
SWCA Project Number 25572-AUS
July 2, 2015 Revised September 2, 2015
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TABLE OF CONTENTS
INTRODUCTION ...... 2 METHODOLOGY ...... 2 RESULTS ...... 2 Site Overview...... 2 Geology ...... 4 Soils...... 4 Site Hydrogeologic Assessment ...... 4 REFERENCES ...... 10
LIST OF FIGURES
Figure 1. Project Area Location Map...... 3 Figure 2. Stratigraphic Column within Project Area...... 5 Figure 3a. Soil Units Map of the Northern Section of the Project Area...... 6 Figure 3b. Soil Units Map of the Central Section of the Project Area...... 7 Figure 3c. Soil Units Map of the Southern Section of the Project Area...... 8
APPENDICES
Appendix A: TCEQ Forms Appendix B: Site Geologic Map
SWCA Project Number 25572-AUS 1
INTRODUCTION
This narrative Geologic Assessment accompanies the Texas Commission on Environmental Quality (TCEQ) Geologic Assessment form TCEQ-0585 (Appendix A) completed for the 183 North Mobility Project (Project). This study was prepared for CP&Y and the Central Texas Regional Mobility Authority (CTRMA).
Proposed Project activities involve a total of approximately 724.6 acres; 714.2 acres of existing right-of-way (ROW), 8.0 acres of proposed ROW, and 2.4 acres of existing easements, as shown in Figure 1 (Project Area).
METHODOLOGY
Registered professional geologists with SWCA Environmental Consultants (SWCA) conducted a field survey of the Project Area for a Geologic Assessment from September 2013 to February 2014, and on 10 October 2014 and 19 March 2015. The pedestrian survey was completed by walking parallel transects spaced approximately 50 feet apart as directed by the TCEQ in the Instructions to Geologists for Geologic Assessments on the Edwards Aquifer Recharge/Transition Zones (Rev. 10-01-04). Closer spacing was used where vegetation inhibited clear observation. All potential karst features, including depressions, holes, and animal burrows, were carefully examined for evidence of subsurface extent. A number of techniques were used for this effort, including probing with a digging implement to determine the thickness and consistency of fill material and feeling for the presence of air flow, which may indicate the presence of a sub-surface void space. Other techniques included making observations of any notable characteristics of the feature site such as the presence of various types of vegetation or a semi-circular burrow mound produced by the activities of small mammals.
RESULTS
Site Overview
Approximately 75 percent of the Project Area is located within the Edwards Aquifer Recharge Zone. A small portion of the Project Area is located within the Edwards Aquifer Transition Zone where U.S. Highway 183 (US 183) extends east of the intersection with MoPac. Topographically, the portion of the Project Area associated with US 183 occurs atop the Edwards Plateau within an area locally known as the Jollyville Plateau area at elevations ranging between 975 and 900 feet above mean sea level. The southern end of the Project Area associated with the MoPac segment exits the plateau and occurs at lower elevations between 800 and 650 feet above mean sea level. Vegetation on the Project Area consists mostly of mowed and maintained assorted grasses within the ROW.
SWCA Project Number 25572-AUS 2
Figure 1. Project Area Location Map.
SWCA Project Number 25572-AUS 3
Geology
The Edwards Formation is exposed at the surface within the US 183 segment of the Project Area. At the US 183 and MoPac interchange, the Project Area enters the Balcones Fault Zone (a series of geologic faults associated with the western edge of the Edwards Plateau) and eventually crosses off of the Edwards Plateau. The outcropping geologic formations for the MoPac segment of the Project Area is a mix of Edwards Formation, Walnut Formation, Austin Chalk, Buda Limestone, Eagle Ford Group, and Tributary Terrace deposits. A Stratigraphic Column is presented as Figure 2. A Site Geologic Map is presented in Appendix B.
Recharge into the Edwards Aquifer primarily occurs in areas where the Edwards Group is exposed at the surface. Most recharge is from direct infiltration via precipitation and streamflow loss. Recharge occurs predominantly along secondary porosity features such as faults, fractures, and karst features (caves, solution cavities, sinkholes, etc.). Karst features are commonly formed along joints, fractures, and bedding plane surfaces in the Edwards Group.
Soils
Soils in the Project Area consist of nine different series of soils. Austin, Brackett, San Saba, Speck, Tarrant, Volente, and Whitewright series soils are within the hydrologic soil group “C” classification. Type “C” soils have a slow infiltration rate when thoroughly wetted. Crawford, Eckrant, Fairlie, and Georgetown series soils are within the hydrologic soil group “D” classification. Type “D” soils have a very slow infiltration rate when thoroughly wetted. Soil units are displayed on Figures 3a, 3b, and 3c.
Site Hydrogeologic Assessment
The likelihood of recharge from the Project Area contributing to the main body of the aquifer is thought to be low to moderate. No point source karst features were identified on site and impervious cover and fill material cover much of the site. Multiple faults cross the project site, primarily within the Transition Zone.
SWCA Project Number 25572-AUS 4
Navarro and Taylor Groups, undivided; 600 feet thick
Austin Group; 325-420 feet thick Upper Confining Units Eagle Ford Group; 25-65 feet thick
Upper Cretaceous Buda Limestone; 40-50 feet thick
Del Rio Clay; 40-70 feet thick
Georgetown Formation; 30-80 feet thick
Edwards Limestone; Up to 200 feet thick
Edwards Aquifer Edwards Comanche Peak Formation; 80 feet thick
Lower Confining Walnut Formation; Up to 120 feet thick
Lower Cretaceous Lower Units
Upper member of Glen Rose Limestone; 500 feet thick
Note: The shaded areas represent the lithology that outcrops on the Project Area.
Figure 2. Stratigraphic Column within Project Area.
SWCA Project Number 25572-AUS 5
Figure 3a. Soil Units Map of the Northern Section of the Project Area.
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Figure 3b. Soil Units Map of the Central Section of the Project Area.
SWCA Project Number 25572-AUS 7
Figure 3c. Soil Units Map of the Southern Section of the Project Area.
SWCA Project Number 25572-AUS 8
Feature Descriptions Feature locations are displayed on the Site Geologic Map (Appendix B) and are described on the Geologic Assessment Table (Appendix A).
F-1 Fault. The feature consists of an inferred fault trending approximately N25˚E as mapped by Garner and Young (1976). No evidence of this fault was observed in the field. The probability of rapid infiltration along this fault within the project is considered low due to the extent of existing impervious cover and graded developments.
F-2 Cave. The feature consists of a cave, referred to as Jug Cave, which was sealed during the construction of US 183 and has been covered by construction-related soils and fill. It is considered destroyed by the USFWS (Berkhouse 2005).
F-3 Fault. The feature consists of a fault trending approximately N15˚E as mapped by Garner and Young (1976). No evidence of this fault was observed in the field. The probability of rapid infiltration along this fault within the Project Area is considered low due to the extent of existing impervious cover and graded developments.
F-4 This feature was omitted from this report because it lies outside the proposed ROW.
F-5 Fault. The feature was omitted from this report because it lies outside the area regulated by TCEQ. The feature consists of a fault trending approximately N20˚E as mapped by Garner and Young (1976). No evidence of this fault was observed in the field. The probability of rapid infiltration along this fault within the Project Area is considered low due to the extent of existing impervious cover and graded developments.
F-6 Fault. The feature was omitted from this report because it lies outside the area regulated by TCEQ. The feature consists of a fault trending approximately N40˚E as mapped by Garner and Young (1976). No evidence of this fault was observed in the field. The probability of rapid infiltration along this fault within the Project Area is considered low due to the extent of existing impervious cover and graded developments.
F-7 Sanitary Sewer Line. The feature consists of a network of City of Austin sanitary sewer lines. Approximately 25 sanitary sewer lines occur within the project area. The sewer lines occur primarily beneath impervious cover and areas overlain by fill material and landscaped areas. Therefore, the probability of rapid infiltration is considered low.
SWCA Project Number 25572-AUS 9
REFERENCES
Berkhouse, C. 2005. Summary of Information for Assessing the Status of the Tooth Cave Ground Beetle (Rhadine persephone). Prepared by HNTB for USFWS Region 2, Austin Ecological Services Field Office. 75pp.
Garner, L.E. and K.P. Young. 1976. Environmental Geology of the Austin Area: An Aid to Urban Planning. Report of Investigations RI-86, USGS.
SWCA Project Number 25572-AUS 10
APPENDIX A
TCEQ FORMS
APPENDIX B
SITE GEOLOGIC MAP
1 8 3 A
lvd e B lin ke La
Ked
Edwards Aquifer Recharge Zone
U S 1 8 3 N o r t h
S H
4 5
F-1 (Fault)
F2 - Jug Cave
20 FM 6
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Site Geologic Map Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Fault (Approximate) Page 1 of 17 Geologic Feature Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community Ked
F-7 (MB)
620 FM Edwards Aquifer Recharge Zone
ek Lake Cre
ake L C re L ek ak P e C k r w ee y k y ek Pk w Lake Cre
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Site Geologic Map Drainage Page 2 of 17 Fault (Approximate) Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community 620 FM
ek Lake Cre
F-7 (MB)
Ked
U S
1 8 3
N o r t h Edwards S H Aquifer 4 Recharge Zone 5
Lake Creek Pkwy
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Site Geologic Map Drainage Page 3 of 17 Fault (Approximate) Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community F-7 (MB)
Ked
U Edwards S
1 Aquifer 8 3 Recharge Zone N
o
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d ill R n M erso And
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Site Geologic Map Drainage Page 4 of 17 Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community d ill R n M erso And
Edwards Aquifer Recharge Zone
US 1 83 No rth
Ked
F-7 (MB)
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone F-7 (MB)
Kcp
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kcp - Cedar Park Limestone Site Geologic Map Existing Easement Ked - Edwards Limestone Drainage Edwards Aquifer Recharge Zone (TCEQ Regulatory) Page 5 of 17 Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community F-7 (MB)
Edwards Aquifer Recharge Zone
F-7 (MB)
Ked
U S 18 3 No rth
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
d gs R prin Kcp od S ewo Spic
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kcp - Cedar Park Limestone Site Geologic Map Existing Easement Ked - Edwards Limestone Drainage Edwards Aquifer Recharge Zone (TCEQ Regulatory) Page 6 of 17 Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community k n Cree Ratta
Edwards Aquifer Recharge Zone
Ked
Dr Neil Mc
U S 1 83 No rth
d gs R prin od S ewo Spic F-7 (MB)
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Site Geologic Map Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Drainage Page 7 of 17 Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community r eil D Mc N
Edwards Aquifer Recharge Zone
Ked
U S 1 83 No rth
F-7 (MB)
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Site Geologic Map Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Sewer Lines Page¯ 8 of 17 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community Edwards Aquifer Recharge Zone
U S 1 83 No rth
F-7 (MB)
Ked
Outside TCEQ Regulatory Boundary of the d Edwards Aquifer Recharge Zone l R va Du
F-7 (MB)
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Site Geologic Map Sewer Lines Page¯ 9 of 17 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community F-7 (MB)
F-7 (MB) D uv Ked al Rd
Edwards Aquifer Recharge Zone
U
S
1
8
3
N
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Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kcp - Cedar Park Limestone Existing Easement Ked - Edwards Limestone Site Geologic Map Drainage Edwards Aquifer Recharge Zone (TCEQ Regulatory) Page 10 of 17 Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community F-7 (MB)
Ked
Edwards Aquifer Recharge Zone
h
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Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Existing Easement Edwards Aquifer Recharge Zone (TCEQ Regulatory) Site Geologic Map Sewer Lines Page¯ 11 of 17 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community Edwards Aquifer Recharge Zone
Hwy Texas Ked tal Of Capi
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1 8 3
N o r t h
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
M o P a c
S ho al Cr eek
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Ked - Edwards Limestone Existing Easement Qtt - Tributary Terrace Site Geologic Map Drainage Edwards Aquifer Recharge Zone (TCEQ Regulatory) Page 12 of 17 Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community Sh oal Cr eek
Edwards Aquifer Recharge Zone Edwards Aquifer Transition Zone
F3 (Fault)
F4 (CD) Qtt
U S 183 No rth
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
F7 (MB) Ked
Kau
F-7 (MB)
c a P o M
F3 (Fault)
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
Kef
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kau - Austin Chalk Existing Easement Ked - Edwards Limestone Site Geologic Map Drainage Kef - Eagle Ford Group Page 13 of 17 Fault (Normal) Qtt - Tributary Terrace Sewer Lines Edwards Aquifer Recharge Zone (TCEQ Regulatory) ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community F3 (Fault)
F4 (CD)
Edwards Aquifer Transition Zone
F7 (MB)
U S 1 83 N or th
M oP ac
k e e Kau r C l a o h S
Outside TCEQ Regulatory Boundary of the Edwards Aquifer Recharge Zone
Kef
Qtt
d
R
t
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B
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kau - Austin Chalk Existing Easement Kef - Eagle Ford Group Site Geologic Map Drainage Qtt - Tributary Terrace Page 14 of 17 Fault (Normal) Edwards Aquifer Recharge Zone (TCEQ Regulatory) Fault (Approximate) Sewer Lines ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community S Outside tec k A TCEQ Regulatory ve Boundary of the Edwards Aquifer Recharge Zone
Ked
Kau
Kef
c a P o
M
F3 (Fault)
S p ic ew o od S pr in gs R d
F7 (MB)
k e e r C l a o h S
Qtt
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Kef
F3 (Fault) Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kau - Austin Chalk Existing Easement Ked - Edwards Limestone Site Geologic Map Drainage Kef - Eagle Ford Group Page 15 of 17 Fault (Normal) Qtt - Tributary Terrace Sewer Lines Edwards Aquifer Recharge Zone (TCEQ Regulatory) ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community F3 (Fault)
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Outside TCEQ Regulatory c Boundary of the a P o Edwards Aquifer M Qtt Recharge Zone
Far We F7 (MB) st B lvd
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Kwa
Kau
Kau Kau
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Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kau - Austin Chalk Existing Easement Ked - Edwards Limestone Site Geologic Map Drainage Kef - Eagle Ford Group Page 16 of 17 Fault (Normal) Kwa - Walnut Formation, undivided Sewer Lines Qtt - Tributary Terrace Edwards Aquifer Recharge Zone (TCEQ Regulatory) ¯ 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community Kwa Ked
Kwa
Kgr
k ree Dry C
Ked Ked
Outside TCEQ Regulatory c a Boundary of the P Kau o Edwards Aquifer M Recharge Zone
F5 (Fault)
Kef
Kwa
Kbu
F6 (Fault)
F7 (MB) k e re C l Kbu a o h S
Kdr Kef
RM 2222
Existing ROW Garner and Young (1976) 183 NORTH MOBILITY PROJECT Proposed ROW Kau - Austin Chalk Existing Easement Kbu - Buda Limestone Site Geologic Map Drainage Kdr - Del Rio Clay Page 17 of 17 Fault (Normal) Ked - Edwards Limestone Sewer Lines Kef - Eagle Ford Group Kgr - Glen Rose Formation Kwa - Walnut Formation, undivided ¯ Edwards Aquifer Recharge Zone (TCEQ Regulatory) 0 100 200 300 400 Service Layer Credits: UTBEG Geologic Map of the Austin Texas Area Source: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, Feet USGS, AEX, Getmapping, Aerogrid, IGN, IGP, swisstopo, and the GIS User Community