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Hwy 58

Desert View Dairy

Approximate limit of saturated alluvium

Upper Aquifer

Bedrockexposed at

ground surface

26-65ND/ND

26-66ND/1.5

MW-23C20.5/20.7

MW-31CND/ND

MW-55C0.47/ND

MW-68CND/ND

MW-90CND/ND

MW-91CND/ND

23-130.66/1.2

23-153.6/3.8

23-193.0/3.2

23-242.7/2.1

23-250.77/1.4

23-260.51/ND

23-301.9/3.2

23-320.76/1.7

24-022.9/2.9

24-083.3/3.2

24-101.7/2.5

25-073.6/3.4

25-103.3/3.3

25-141.7/1.5

26-493.5/3.4

27-032.2/2.4

27-082.7J/1.7J

27-212.3/1.927-36

2.2/1.927-382.9J/1.6J

27-390.88/1.3

27-402.1/1.9

27-461.3/2.1

34-010.32/ND

34-34ND/ND

36-241.9/1.8

BGS-462.0/1.8

#

BGS-491.4/1.7

CA-MW-204D62.4/62.1

CA-MW-312D23.4/21.5

CA-MW-31354.7/49.3

CA-MW-315D75.8/72.8

CA MW 317S

CA-MW-405D72.7/71.6 CA-MW-411S

51.5/47.7

CA-MW-412D56.6/47.1

CA-MW-501S40.6/44.4

CA-MW-506D52.5/56.7

CA-MW-508S15.3/13.1

CA-MW-510S10.3/8.8

DW-014.3/3.8

DW-020.31/ND

DW-031.5J/1.0J

MW-06134/115

MW-1330.8/30.3

MW-14A57.6/52

MW-21BND/ND

MW-21B15.1/5.6

MW-23B42.4/41.2MW-28A

3.0/3.8MW-28B48.9/46.3

MW-2911.8/12.3 MW-30B1

4.5/6.8MW-30B26.6/6.7

MW-3115.5/15.9

MW-32B13.5/3.6MW-32B2

ND/ND

MW-32S2.1/2.5

MW-38A64.5/58.1

MW-41S10.3/10.1

MW-42B130.7/30.6

MW-42B243/43.4

MW-4312.8/12.7

MW-44A1.9/2.1

MW-44B3.3/4.3

MW-45A40.3/39MW-45B2.0/2.1

MW-477.0/6.4

MW-49A4.9/4.2

MW-49S3.4/3.8

MW-50A4.6/3.8MW-50B

2.6/2.8

MW-50S13.5/13.5

MW-541.6/2.0

MW-55AND/ND

MW-55BND/ND

MW-55S2.4/3.4

MW-566.4/6.3

MW-572.9/2.6

MW-58

MW-592.1/1.8

MW-611.4/1.5

MW-62A19.7/17.1MW-62BND/ND

MW-630.73/1.6

MW-64A0.71/ND

MW-66A2.6/2.7

MW-68D5.0/5.7

MW-68S0.35/2.2

MW-69D1.7/2.7

MW-69SND/2.9J

MW-70D4.6/4.8

MW-70S1.6/3.0 MW-71D

2.6/2.6

MW-71S2.4/2.4

MW-72DND/1.0

MW-72S7.2/6.3

MW-75D1.4/1.6

MW-76D0.92/1.1

MW-76S3.7/3.5

MW-79DND/ND

MW-79S5.5/5.5

MW-80D1.0/1.5

MW-80SND/ND

MW-81S0.84/ND

MW-82S1.4/2.1

MW-83D2/2.3

MW-83S1.8/2.4

MW-84DND/ND

MW-84S1.9/3.4

MW-85D0.29/ND

MW-85S0.54/1.4

MW-86D1.2/1.4

MW-86S5.3/5.7

MW-87D1.5/1.6

MW-87S2.1/2.3

MW-88DND/ND

MW-88S5.5/5.2

MW-89D0.74/1.2

MW-89S2.6/3.0

SC MW 06S

SC-MW-07D0.98/ND

SC-MW-07S1.0/1.3

SC-MW-08D1.6/2.1

SC-MW-08S1.4/2.2

SC-MW-09S15.6/11.2

SC-MW-10S1.9/2.3

0.45/3.6*

EX-0416.1/17.1

EX-051.1/3.8

EX-090.52/1.2

EX-100.82/1.1

EX-1546.6/42.6

EX-1641.3/38.2

EX-2043.5/41

EX-0113.7/14.7

EX-0210.0/10.3

EX-0322.3/24.2

EX-17ND/ND

EX-2142.9/38.1

EX-2245.4/39.5

EX-235.7/5.3

EX-242.5/2.1

IN-01NS

IN-02NS

IN-03NS

IN-04NS

IN-05NS

24-093.2/3.2

25-162.3/2.7

25-173.2/2.7

Acacia St

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Manacor Rd

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Alcudia Rd

Serra

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Approximate 50 µg/L outlineof Cr(VI) or Cr(T)concentrations in Upper Aquifer, October-November 2010

Approximate 10 µg/L outline of Cr(VI) or Cr(T) concentrations in Upper

23-22NS

Hinkley School

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PG&E Compressor Station

Freshwater Supply WellPGE-140.44/ND

SC-MW-16C1.2/ND

02-02A0.33/ND

02-05ND/ND

35-04ND/ND

CA-MW-317S8.7/8.2

MW-0326.6/22.9

MW-0441.2/39.5

MW-050.73/ND

MW-11B1660/1560

MW-1632.7/31.3

MW-17113/110

MW-201650/1500

MW-400.27/ND

MW-460.66/ND

MW-67A1.4/1.4

MW-73D0.85/1.1

MW-73S0.79/ND

MW-74D2.3/2.3

MW-77D1.3/1.7

MW-77S1.0/1.3

MW-78D1.8/1.9

MW-78S0.77/ND

PT2-MW-10555/506

SA-MW-16S401/338

SA-MW-17S221/177

SA-SM-01S1120/1030

SA-SM-02S2230/2040

SC-MW-01D1.1/1.3

SC-MW-01S0.54/ND

SC-MW-02D228/226

SC-MW-02S0.63/ND

SC-MW-03D411/371

SC-MW-03S6.9/6.7

SC-MW-04D9.5/9.1

SC-MW-04S0.7/ND

SC-MW-05D1.4/1.5

SC-MW-05S0.93/ND

SC-MW-06D1.3/1.5

SC-MW-06S0.91/ND

SC-MW-11DND/ND

SC-MW-11S0.38/ND

SC-MW-12S17.1/16.7

SC-MW-13S25.2/21.2

SC-MW-14D1.0/ND

SC-MW-14S1.3/1.1

SC-MW-15D1.6/1.5

SC-MW-15S1.4/1.3

SC-MW-16D1.0/1.5

SC-MW-16S0.84/1.8SC-MW-21S

334/292SC-MW-26D

1540/1480

SC-MW-38D177/157

SC-MW-38S7.9/6.0

X-1162.8/60.2

MW-36NS

MW-74SNS

X-16185/171

( ) ( ) ppAquifer, October-November 2010

Approximate outlne of Cr(VI) or Cr(T) in Upper Aquifer exceeding backgroundvalues of 3.1 and 3.2 µg/L, respectively, October-November 2010

\\ZINFANDEL\PROJ\PACIFICGASELECTRICCO\HINKLEYREMEDIATIONPROJECT\GIS\MXDS\MP_MONITORINGPROGRAM\2010\MP_CRT_DISTRIBUTION_2010OCTNOV_REV03.MXD GMOON 2/10/2011 13:41:14

FIGURE 4HEXAVALENT AND TOTAL CHROMIUM CONCENTRATIONSOCTOBER-NOVEMBER 2010AND INTERPRETED MAXIMUM PLUMEOUTLINE IN UPPER AQUIFER

SITE-WIDE GROUNDWATER MONITORING PROGRAMPACIFIC GAS & ELECTRIC CO. COMPRESSOR STATIONHINKLEY, CALIFORNIA

Notes:1. Chromium results are shown for all site-wide Groundwater Monitoring Program wells sampled in the October-November 2010 sampling event. In addition, October-November results for selected In-situ Reactive Zone (IRZ) monitoring wells are shown for plume mapping. See Appendix E for the chromium results for all IRZ monitoring wells sampled in October-November 2010.

2. The concentration contours are based on chromium results from the groundwater monitoring wells. Results for long-screen (>25 feet) supply or extraction wells, shown in italics, and lower aquifer wells (gray shade labels) were not used for contouring.

3. Concentration contours represent the maximum extent of either Cr(VI) or Cr(T) at any depth within the Upper Aquifer based on monitoring well data. Some chromium results for wells within the 50, 10, and 3.1/3.2 chromium contours are less than those concentrations.

4. The 3.1/3.2 ug/L Cr(VI)/Cr(T) plume outline shown in the northeast, Summerset Road area, is inferred based on available data from all monitoring wells sampled in this area in August and October-November 2010 sampling events. As required by the Water Board, PG&E is installing additional monitoring wells to improve delineation of the chromium plume boundaries in this area.

±0 500 1,000 1,500

Feet

LEGEND

. Groundwater Monitoring Well> Domestic Supply Well<

Agricultural Supply Well+ Other Supply Well/ Active Groundwater Extraction Well)Ñ Inactive Extraction or Multi-Use Well

A Freshwater Injection Well

PG&E Property

( < 3.1 μg/L or ND! 3.1 - 10 μg/L! 10 - 50 μg/L

! 50 - 100 μg/L! 100 - 1,000 μg/L! > 1,000 μg/L

Groundwater Cr(VI) Concentrations in Monitoring Wells

REVISED 2/10/2011

Cr(VI) = Hexavalent ChromiumCr(T) = Total Dissolved ChromiumND = Not Detected; NS = Not SampledJ = Analyte was present in the sample but the laboratory reported concentration is qualified as estimated by data validation because one or more quality control criteria were not met

MW-611.99/2.04

Well IDCr(VI)/Cr(T) concentrations in micrograms per liter (µg/L); maximum of primary and duplicate samples

* = The Cr(T) result initially reported for well MW-58 during fourth quarter 2010 (shown on this figure) was rejected due to data quality issues related to the laboratory analysis, and is not representative of Cr(T) concentrations in the aquifer at this location. The same sample was re-analyzed for Cr(T) and the second result was 1.3 μg/L.