SW

N

Prepared in cooperation with

California Division of M

ines and Geology

6 0 06 0 0

5 5 05 5 0

5 0 05 0 0

4 5 04 5 0

4 0 04 0 0

3 5 03 5 0

3 0 03 0 0

2 5 02 5 0

2 0 02 0 0

1 5 01 5 0

1 0 01 0 01 5 0

1 5 02 0 02 0 0

2 5 02 5 0

1 0 01 0 0

50

50

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6 0 0

5 5 0

5 0 0

4 5 0

4 0 03 5 0

3 0 0

2 5 0

50

00

2 0 0

1 5 0

1 0 01 5 02 0 0

2 5 0

1 0 0

00

5 0

QTc QTc

QTc

QTc

QTc

Tuss

Tuss

Tmd

Tmd

Tmd

Tsm

Qal/Qof Qal/Qof Qal/Qof

Qal/Qof

Qal/Qof

QTc

Qal/Qof

Qt

Qal/Qof Qal/Qof

Tsm

Tsm

QTc - CoarseKqm

-800

-600

-400

-200

0

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-800

-600

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-200

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Tuss

Tmd

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-600

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-200

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Qal/Qof

Geologic Map and Cross-Sectionsfrom El Toro to Salinas Valley

X1

X1

X2 X3

X1

X2 X3

Z

X1

X2

X2

X3

X3 Y

Z

Y

Z

Y

P:\GIS\ElToro\AI\CrossSectionA.ai

June 2010

2,500 0 2,500 Feet

1 0 1 Mile

El Toro Groundwater StudyMonterey County, CA

Cross-Sections Have 2X Vertical Exaggeration

Inset Scale

Well from MCWRA database (see Table 1 for well ID)

Well from Yates et al 2005

Estimated Groundwater Elevation ContourBased on Jan 2001 data and contour map(Geosyntec, 2007), MCWRA database, and Yates et. al (2005).

NOTES:Geology adapted from Clark et al. 2000, Rosenberg, L.I. 2001,Yates et al. 2005, Kennedy Jenks, 2004Well locations are approximate.

LEGEND

Well AWell A

Well BWell B

Well CWell C

1

3 4

5

78 9

1010

62

Well A

Well B

Well C

Proposed Harper Canyon ProjectP e aP ia n n i n g

E l T o r oP l a n n i n g A r e a

1

3 4

5

78 9

10

62 T rro CCC kkkk

RRiv

San

Bena

ncio

Cre

ek

Har

per C

reek

El Toro Creek

Watson Creek

Salin

as R

iver

Highway 68

Well IDs for Supplemental Wells

1) 16S/02E-03A012) 16S/02E-02D053) 16S/02E-02D014) 15S/02E-25C015) 15S/03E-18M02

6) 15S/03E-18F017) 15S/03E-18C028) 15S/03E-18B019) 15S/03E-08T5010) 15S/03E-17M01

Salinas RiverEl Toro Creek

Salinas River

Highway 68 Reliz - Las Palmas Fault

Harper FaultReliz - Las Palmas Fault

³5 0

475 14th Street, Suite 400 Oakland, California 94612 

PH 510.836.3034 www.geosyntec.com 

 

Accompanying Documentation Geologic Map and Cross-Sections from El Toro to Salinas Valley

The geologic map and cross-sections are presented as a supplement to the El Toro Groundwater Study (Geosyntec, 2007). The geologic interpretations are based on the USGS Geologic Map of the Spreckels 7.5-minute Quadrangle (Clark et al. 2000), and additional compilations of geology and hydrostratigraphy of the vicinity (e.g. Rosenberg, 2001; CH2M Hill, 2004; Yates et al., 2005; Kennedy Jenks, 2004). A stratigraphic column of geologic units in the El Toro Area is attached. A detailed explanation of units depicted on the geologic map is included on Figure 2-3 of the El Toro Groundwater Study (Geosyntec, 2007). Additional geologic cross-sections within the El Toro Area are provided as Figures 2-4 through 2-8 in the 2007 Report. The U.S. Geologic Survey (USGS) geologic map of the Spreckels quad is also available on a USGS web site: http://pubs.usgs.gov/mf/2001/2349/. Based on available information, the Plio-Pleistocene Continental Deposits (QTc) are contiguous between the El Toro area and the Salinas Valley. The QTc deposits comprise the majority of the Primary Aquifer in the El Toro Planning Area, and are commonly called the Paso Robles, but portions may also include the Aromas sands. Granitic rocks uplifted along the Harper Fault likely limit hydraulic connection to the northeast from the San Benancio subarea of the El Toro Planning Area to the Salinas Valley. However, the continuous presence of the Paso Robles Formation beneath the El Toro Creek, the Hwy 68 corridor, and Fort Ord military reserve to the northwest provides hydraulic connection between the El Toro Planning Area and the Salinas Valley. Groundwater level data indicate that hydraulic gradient under the El Toro Creek Valley and the Hwy 68 corridor is generally northeastward toward the Salinas Valley. Groundwater contours shown on the geologic map are based on the January 2001 contour map and data provided in the El Toro Groundwater Study (Figure 4-5, Geosyntec, 2007) and supplemental well and water level data from additional wells for a similar time period provided by the Monterey County Water Resources Agency (MCWRA). As reported previously (e.g. Staal Gardner & Dunne, 1991; Fugro, 1996; Geosyntec, 2007), planning boundaries based on local topographic watersheds are not relevant to the groundwater aquifers, which are the sole source of water supply in the El Toro Planning Area.

El Toro – Salinas Valley Geology    page 2 of 3 

References

Anderson-Nichols & Co, 1981, Final report, El Toro Area Groundwater Study, prepared

for Monterey County Flood Control and Water Conservation District, 112, p. CH2M Hill, 2004, Hydrogeologic Assessment of the Seaside Groundwater Basin, Draft

Report, prepared for Somach, Simons and Dunn, and Cal Am Water, January 2004. Clark et al., 2000, Geologic map of the Spreckels 7.5 minute quadrangle, Monterey,

California, USGS MF-2349. Feeney, Martin, and L. Rosenberg. 2002. Deep Aquifer Investigation—Hydrogeologic

Data Inventory, Review, Interpretation and Implications. Technical Memorandum—Technical Review Draft. Prepared for WRIME, Inc. September 2002.

Fugro West, Inc., 1996, Additional Hydrologic Update, El Toro Area, Monterey County,

California, prepared for Monterey County Water Resources Agency, 28 p. Harding ESE. 2001a. Final Report: Hydrogeologic Investigation of the Salinas Valley

Basin in the Vicinity of Fort Ord and Marina, Salinas Valley, California. Prepared for Monterey County Water Resources Agency. Prepared by Taraszki, M. and D.J. Craig. April 2001.

Kennedy/Jenks Consultants, 2004, Hydrostratigraphic Analysis of the Northern Salinas

Valley, prepared for MCWRA, 14 May 2004. Logan, John. 1982. Hydrogeology of the Seaside Area. Prepared for Monterey Peninsula

Water Management District. June 1982. Rosenberg, L.I. 2001. Geologic Resources and Constraints, Monterey County,

California: A Technical Report for the Monterey County 21st Century General Plan Update Program. Unpublished Report to Monterey County Environmental Resource Policy Department, 167 pp., 10 sheets, scale 1:250,000, one CD-ROM.

Schmidt and Associates, 2001, Letter regarding groundwater conditions to

Monterey County Environmental Health Division, May 31, 2001.

Staal, Gardner & Dunne, Inc., 1991, Hydrogeologic Update, El Toro Area, Monterey County, California, prepared for Monterey County Water Resources Agency, 53 p.

Thorup, Richard R., 1971a, Groundwater report for Toro Water Committee, unpublished

report to Monterey County Board of Supervisors. _____, 1974, Groundwater survey of Laguna Seca Ranch, Salinas-Monterey Highway 68,

Monterey County, California, unpublished report.

El Toro – Salinas Valley Geology    page 3 of 3 

_____, 1977, Final report, groundwater study of Highway 68, unpublished report to

Laguna Seca Ranch and Standex International, 57 p. 7 appendices, 7 sheets. USGS, 2002. Geohydrology of a Deep-Aquifer System Monitoring-Well Site at Marina,

Monterey County, California. Prepared in cooperation with the Monterey County Water Resources Agency. Water-Resources Investigations Report 02-4003. Prepared by Hanson, R.T., R.R. Everett, M.W. Newhouse, S.M. Crawford, M.I. Pimentel, and G.A. Smith.

Yates, Eugene B., Feeney, Martin B., Rosenberg, Lewis I., 2002, Laguna Seca

Subarea Phase III Hydrogeologic Update, prepared for Monterey Peninsula Water Management District, November 2002.

Yates, Feeney & Rosenberg, 2005, Seaside Groundwater Basin: Update on water resource conditions, prepared for Monterey Peninsula Water Management District, April 2005.

Stratigraphic ColumnEl Toro Groundwater Study

Monterey County, CA

Adapted from Clark et al. (2000)

P:\GIS\ElToro\AI\StratigraphicColumn.ai

June 2010

PERIOD ORSYSTEM

QU

AR

TER

NA

RY

HO

LOC

ENE

PLEI

STO

OC

ENE

PLIO

CEN

EM

IOCE

NETER

TIA

RYC

RET

AC

EOU

SPR

EC

RET

AC

EOU

S

GEOLOGICSYMBOL

MAPUNIT

DESCRIPTIONOF MAP UNITS THICKNESS (FT)

Granitic - Plutonic RocksKgd, Kqm, Khqd

Metamorphic Quartzofeldespathic Rocksms

Landslide Deposits

Alluvial Deposits, FloodPlain Deposits

Qls

Qal, QyfQc, Qof

0-120

Continental Deposits(Aromas / Paso Robles)

Qtc 0-1,000

Santa MargaritaSandstone

Tsm 0-450

Monterey Formation(Shale)

Tmd, Tm 0-2,300

Unnamed Sandstone(Basal Sands)

Tus 0-150

Unnamed Sandstone(Undifferentiated)

Tuss 0-1,500

Schistmsc 0-4,560

El ToroPrimaryAquiferSystem

Tuss

Tuss