HARGIS + ASSOCIATES, INC. HYDROGEOLOGY ENGINEERING La Jolla Gateway 9171 Towne Centre Drive, Suite 375 San Diego, CA 92122 Phone: 858.455.6500 Fax: 858.455.6533

Other Offices: Folsom, CA Mesa, AZ Tucson, AZ

February 5, 2018

VIA EMAIL Mr. David P. Bolin, CHG Principal Hydrogeologist ORANGE COUNTY WATER DISTRICT 18700 Ward Street Fountain Valley, CA 92708 Re: South Basin Groundwater Protection Project, Additional Groundwater Assessment Field Sampling Plan Addendum 1 Dear Mr. Bolin: Hargis + Associates, Inc. (H+A), on behalf of the Orange County Water District (OCWD), prepared the Additional Groundwater Assessment Field Sampling Plan and Quality Assurance Project Plan Addendum (FSP) as part of the South Basin Groundwater Protection Project (SBGPP) (H+A, 2017a). The FSP described additional assessment activities to be conducted in support of the Remedial Investigation and Feasibility Study that is being conducted in the cities of Santa Ana, Irvine, and Tustin, California (the Study Area). Specifically, the FSP described additional groundwater assessment activities that are and will be conducted to further characterize the hydrogeology and extent of contamination in areas of the SBGPP that have been identified as having key data gaps; and provide data to support the development of appropriate remedial actions. H+A prepared an analysis of data gaps that described the process of identifying the key data gaps and a summary of the results of the analysis (H+A, 2017b). The analysis of data gaps identified seven areas where additional monitor well clusters were recommended. Installation, sampling, and aquifer testing at six of the proposed monitor well clusters commenced in mid-2017 and is on-going (SAM-7 thru SAM-11; SAM-13) (Figure 1). Construction of one of the seven monitor well clusters was deferred (SAM-12) and the recommended activities to complete the data gaps analysis at this location were revised in October 2017 (H+A, 2017c). The revised proposed activities include installation, sampling, and testing of two new deeper monitor wells; and sampling and testing of the closest accessible existing Former Service Chemical Facility shallow monitor well (MW-42B or MW-43B). With the exception of SAM-12, the new monitor well clusters being installed and sampled as part of the FSP are located within2 and near the downgradient portions of the SBGPP (H+A, 2017a). More than 500 monitoring wells have been installed as part of contaminant investigation programs at “source sites” located within and near the SBGPP source areas. In general, samples collected from the “source site” monitor wells are shallow (up to 70 feet below land surface) and analyzed for a limited suite of analytes. The wells installed as part of the FSP are being sampled and analyzed for Contaminants of Concern (COC) and an expanded suite of analytes to evaluate potential remedial technologies in the Feasibility Study (Table 1). In order to characterize the groundwater quality in the areas downgradient of relatively high COC concentrations it is recommended that groundwater samples be collected and analyzed for the expanded suite of analytes from select existing accessible “source site” shallow monitor wells that are not on source properties (Figure 1; Table 2). The recommended locations include:

HARGIS + ASSOCIATES, INC.

Mr. David P. Bolin, CHG February 5, 2018 Page 2

Holchem/Former Service Chemical monitor well MW-42B or MW-43B in the vicinity of SAM-12 as

previously proposed in the vicinity of SAM-12 (H+A, 2017c);

GE Plastics monitor wells MW-8A and MW-8B;

Bell Industries monitor wells OW-1A and OW-1B. It is anticipated that the groundwater samples could be collected by OCWD during an upcoming monitoring event conducted by the respective potentially responsible party in the next several months. In the case where an upcoming event is not planned in this time frame or the respective party does not want to provide samples to OCWD, then OCWD would collect the samples using methods outlined in the FSP. If you have any questions or require additional discussion, please contact us. Sincerely, HARGIS + ASSOCIATES, INC.

Christopher G.A. Ross, PG 4594, CHG 221 Kevin L. Coons, PE Principal Hydrogeologist Senior Engineer CGAR/KLC/jak

HARGIS + ASSOCIATES, INC.

Mr. David P. Bolin, CHG February 5, 2018 Page 3

Enclosures Figure 1. Groundwater Sampling Locations Table 1. Handling Protocol for Initial Groundwater Samples Table 2. Proposed Existing Monitor Well Sampling Locations and Recent Contaminants of

Concern in Groundwater cc w/encl: Mr. Roy L. Herndon, RG CHG, District Hydrogeologist, Orange County Water District Mr. William Hunt, Executive Director Operations, Orange County Water District

REFERENCES CITED

Hargis + Associates, Inc., 2017a. South Basin Groundwater Protection Project, Additional Groundwater Assessment Field Sampling Plan and Quality Assurance Project Plan Addendum, Version 2.0. Orange County Water District, Orange County, California. May 9, 2017.

_____, 2017b. Letter to David P. Bolin of Orange County Water District Re: Summary of Data Gaps

Evaluation and Basis of Proposed Additional Groundwater Assessment Well Locations. June 12, 2017.

_____, 2017c. Letter to David P. Bolin of Orange County Water District Re: South Basin Groundwater

Protection Project Remedial Investigation, Data Gaps, Groundwater Assessment Well Location SAM-12. October 31, 2017.

1170_A01_01_FSPAddm1.docx

SAM-127-MW-8B7-MW-8A

5-MW-43B5-MW-42B

13-OW-1B13-OW-1A

SAM-9

SAM-8

SAM-7 SAM-13SAM-ll

SAM-lO

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E EDINGER AV

MAIN ST

ALTON PKWY

E WARNER AVS BRI

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JAMBOREE RD

S MAIN

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W WARNER AV

W EDINGER AV

MACARTHUR BLVD

W MACARTHUR BLVD

NEWP

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VON KARMAN AV

HARVARD AV

WALNUT AV

SUNFLOWER AV

S STA

NDAR

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W DYER RD

WARNER AV

PAULARINO AV

W SEGERSTROM AV

VALENCIA AV

EXPLANATIONProposed Existing Groundwater Sampling Location Proposed OCWD Monitor Well ClusterOCWD Monitor Well Cluster installed in 2017

5405

133

241

261

731

22

55

57

39

73

241

57

0 2,000 4,0001,000Feet

FIGURE 1

Groundwater Sampling Locations

ORANGE COUNTY WATER DISTRICTSOUTH BASIN GROUNDWATER PROTECTION PROJECT

FOUNTAIN VALLEY, CALIFORNIA

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TABLE 1

HANDLING PROTOCOL FOR INITIAL GROUNDWATER SAMPLES

ANALYTEANALYTICAL

METHOD

OCWD LABORATORY ANALYTICAL

METHOD SAMPLE CONTAINER OTHER REQUIREMENTS

PRESERVATION

METHOD* MAXIMUM HOLDING TIME GROUPING

FIELD PARAMETERS

pH SM 4500 H+B -- Field

TEMPERATURE SM 2550 B -- Field

TOTAL RESIDUAL CHLORINE SM 4500 Cl -- Field

DISSOLVED OXYGEN SM 4500 O -- Field

ORGANIC COMPOUNDS

VOLATILE ORGANIC COMPOUNDS + OXYGENATES 8260B 524.23 X 40 ml VOA VIAL, TEFLON

LINED SEPTUMVIALS FILLED COMPLETELY,

NO HEAD SPACE HCl, COOL TO 4oC 14 DAYS COC

2-CHLOROETHYL VINYL ETHER, ACROLEIN & ACRYLONITRILE

8260B --3 X 40 ml VOA VIAL, TEFLON

LINED SEPTUMVIALS FILLED COMPLETELY,

NO HEAD SPACE COOL TO 4oC 3 DAYS Expanded

1,4-DIOXANE 8270C OR 1625 524.2 Modified2 X 1 LITER AMBER GLASS

BOTTLEBOTTLE FILLED TO NECK COOL TO 4oC

7 DAYS EXTRACTION / 40 DAYS AFTER EXTRACTION COC

SEMI-VOLATILE ORGANICS 8270C 525.22 X 1 LITER AMBER GLASS

BOTTLEBOTTLE FILLED TO NECK COOL TO 4oC

7 DAYS EXTRACTION / 40 DAYS AFTER EXTRACTION Expanded

N-NITROSO-DIMETHYLAMINE (NDMA) 521OCWD NDMA Test

Method2 X 1 LITER AMBER GLASS

BOTTLEBOTTLE FILLED TO NECK Na2S2O3, COOL TO <10oC

7 DAYS EXTRACTION / 40 DAYS AFTER EXTRACTION COC

ORGANOCHLORINE PESTICIDES 8081A 525.22 X 1 LITER AMBER GLASS

BOTTLEBOTTLE FILLED TO NECK COOL TO 4oC

7 DAYS EXTRACTION / 40 DAYS AFTER EXTRACTION Expanded

ocwd 8082 --2 X 1 LITER AMBER GLASS

BOTTLEBOTTLE FILLED TO NECK COOL TO 4oC

1 YEAR EXTRACTION /1 YEAR AFTER EXTRACTION Expanded

TOTAL ORGANIC CARBON SM 5310B SM 5310B1 X 40 ml VOA VIAL, TEFLON

LINED SEPTUMVIALS FILLED COMPLETELY,

NO HEAD SPACEH2SO4, COOL TO 4oC 28 DAYS Expanded

--2 X 1 LITER AMBER GLASS

BOTTLEBOTTLE FILLED TO NECK COOL TO 4oC

7 DAYS EXTRACTION / 40 DAYS AFTER EXTRACTION

Expanded

--3 X 40 ml VOA VIAL, TEFLON

LINED SEPTUMVIALS FILLED COMPLETELY,

NO HEAD SPACE HCl, COOL TO 4oC 14 DAYS Expanded

GENERAL INORGANIC PARAMETERS

TOTAL ALKALINITY SM 2320 B SM 2320 B 14 DAYS Expanded

BICARBONATE/ALKALINITY SM 2320 B SM 2320 B 14 DAYS Expanded

TDS SM 2450 C SM 2450 C 7 DAYS Expanded

TSS SM 2450 D SM 2450 E 7 DAYS Expanded

ELECTRICAL CONDUCTANCE SM 2510 B SM 2510 B 28 DAYS Expanded

INORGANIC ANIONS (CHLORIDE NITRATE, NITRITE, SULFATE)

300.0 300.0 48 HOURS Expanded

HEXAVALENT CHROMIUM 218.6 218.7 24 HOURS COC

METHYLENE BLUE ACTIVATED SUBSTANCES SM 5540C SM 5540C 48 HOURS Expanded

AMMONIA350.3 / SM 4500-NH3

350.3 / SM 4500-NH3

Required for total inorganic nitrogen

Expanded

TOTAL PHOSPHORUS 365.3 365.1, 4500-PF Expanded

TOTAL PHENOLS 420.1 -- 1 LITER AMBER GLASS H2SO4, COOL TO 4oC Expanded

SULFIDE (TOTAL) SM 4500-S2 SM 4500-S2-D 500 ml PLASTIC BOTTLE1 ml ZINC ACETATE AND

NaOH, COOL TO 4oC7 DAYS Expanded

PERCHLORATE 314.0 332.0 1 X 1 LITER HDPE COOL TO 4oC 28 DAYS COC

OIL & GREASE 1664A --2 X 1 LITER AMBER GLASS

BOTTLEREQUEST HEM AND SGT HCl, COOL TO 4oC 28 DAYS Expanded

CYANIDESM 4500

CN / 335.4SM 4500

CN / 335.41 X 1 LITER HDPE NaOH, COOL TO 4oC 14 DAYS Expanded

TOTAL PETROLEUM HYDROCARBONS

1 X 1 LITER HDPE NA

1 LITER PLASTIC BOTTLE H2SO4, COOL TO 4oC

15 MINUTES

8015B

2 X 1 LITER HDPE BOTTLE FILLED TO NECKUNPRESERVED, COOL

TO 4oC

28 DAYS

1170_H01_2018-1_FSPadd1_Tbl_1 Page 1 of 3

TABLE 1

HANDLING PROTOCOL FOR INITIAL GROUNDWATER SAMPLES

ANALYTEANALYTICAL

METHOD

OCWD LABORATORY ANALYTICAL

METHOD SAMPLE CONTAINER OTHER REQUIREMENTS

PRESERVATION

METHOD* MAXIMUM HOLDING TIME GROUPING

METALS

TOTAL & TOTAL RECOVERABLE METALS

TOTAL ARSENIC 7060 200.8 Expanded

TOTAL ANTIMONY 6010B 200.8 Expanded

TOTAL BERYLLIUM 6010B 200.8 Expanded

TOTAL RECOVERABLE SELENIUM 7740 200.8 Expanded

TOTAL RECOVERABLE CADMIUM 6010B 200.8 Expanded

TOTAL RECOVERABLE CHROMIUM 6010B 200.7 Expanded

TOTAL RECOVERABLE COPPER 6010B 200.8 Expanded

TOTAL RECOVERABLE LEAD 6010B 200.8 Expanded

TOTAL RECOVERABLE NICKEL 6010B 200.8 Expanded

TOTAL RECOVERABLE SILVER 6010B 200.8 Expanded

TOTAL RECOVERABLE THALLIUM 6010B 200.8 Expanded

TOTAL RECOVERABLE ZINC 6010B 200.8 Expanded

TOTAL CALCIUM 6010B 200.7 Expanded

TOTAL MAGNESIUM 6010B 200.8 Expanded

TOTAL MERCURY 7470 200.8 28 DAYS Expanded

HARDNESS SM 2340C CALC Expanded

TRIVALENT CHROMIUM CALC -- Expanded

DISSOLVED METALS

DISSOLVED COPPER 6010B EPA 200.8 Expanded

DISSOLVED LEAD 6010B EPA 200.8 Expanded

DISSOLVED ZINC 6010B EPA 200.8 Expanded

DISSOLVED MANGANESE 6010B EPA 200.7 Expanded

DIOXINS & FURANS 1613B --2 X 1 LITER AMBER GLASS

BOTTLEBOTTLE FILLED TO NECK COOL TO 4oC

1 YEAR EXTRACTION40 DAYS AFTER

EXTRACTIONExpanded

COLIFORMS

TOTAL & E. COLI SM 9223 9221 100 ml HDPE STERILEMust use sterile bottle provided

by labNa2S2O3, COOL TO <10oC 8 HOURS Expanded

ASBESTOS 100 -- 1 X 1 LITER HDPE COOL TO 4oC 48 HOURS Expanded

180 DAYS

180 DAYS1 X 1 LITER HDPE BOTTLE FILLED TO NECK HNO3, COOL TO 4oC

1 X 1 LITER HDPE BOTTLE FILLED TO NECKFIELD FILTERED, HNO3,

COOL TO 4oC

1170_H01_2018-1_FSPadd1_Tbl_1 Page 2 of 3

TABLE 1

HANDLING PROTOCOL FOR INITIAL GROUNDWATER SAMPLES

ANALYTEANALYTICAL

METHOD

OCWD LABORATORY ANALYTICAL

METHOD SAMPLE CONTAINER OTHER REQUIREMENTS

PRESERVATION

METHOD* MAXIMUM HOLDING TIME GROUPING

DISSOLVED OXYGEN FIELD METER -- Field

OXIDATION-REDUCTION POTENTIAL FIELD METER -- Field

pH FIELD METER -- Field

ELECTRICAL CONDUCTIVITY FIELD METER -- Field

TEMPERATURE FIELD METER -- Field

TURBIDITY FIELD METER -- Field

DISSOLVED GASES (METHANE/ETHENE/ETHANE) RSK1753 X 40 ml VOA VIAL, TEFLON

LINED SEPTUM COOL TO 4oC 7 DAYS Expanded

DISSOLVED IRON EPA 200.7 250 ML PLASTIC BOTTLEFIELD FILTERED, HNO3,

COOL TO 4oC180 DAYS Expanded

FOOTNOTES

( * ) = Additional preservative may be required if residual chlorine is contained in water, contact laboratory with questions.

(<) = Less than oC = degrees Celsius

H2SO4 = Sulfuric Acid

NA = Not applicableCOC = Compounds of concern

HCI = Hydrochloric Acid

NA

ADDITIONAL MONITORED NATURAL ATTENUATION PARAMETERS

FLOW CELL OR TRANSFER BOTTLE

NA

VOA = Volatile Organic Analysis

HEM = N-Hexane Extractable Material

ml = Millileter

OCWD = Orange County Water District

HNO3 = Nitric Acid

SGT = Silica Gel Treated

TDS = Total Dissolved Solids

TSS = Total Suspended (non-filterable) Solids

Lab = Laboratory

PCBs = Polychlorinated biphenyls

HPDP = High Density Polyethylene

HNO3 = Nitric Acid

Na2S2O3 = Sodium thiosulfate

NaOH = Sodium Hydroxide

1170_H01_2018-1_FSPadd1_Tbl_1 Page 3 of 3

Well ID FacilityRecent Sample

Date

Screen Interval

(feet below land surface)

1,1-Dichloroethene (1,1-DCE) 1,4-Dioxane Tetrachloroethene (PCE)

Trichloroethene (TCE) Perchlorate

OW-1A Bell Industries 3/10/2017 30 - 40 430 17 < 1.3 45 NA

OW-1B Bell Industries 3/10/2017 46 - 56 55 7.2 < 0.5 3.7 NA

MW-42B*Holchem/Former Service Chemical

7/10/2017 51 - 71 190 230 120 2,500 NA

MW-43B*Holchem/Former Service Chemical

7/13/2017 42 - 62 530 320 180 3,400 NA

MW-8A GE Plastics 2/22/2017 15 - 25 NA NA NA NA 66

MW-8B GE Plastics 10/19/2016 39 - 49 NA NA NA NA 3.2

* Either MW-42B or MW-43B will be sampled based on accessibilityNA = Analyte not analyzed

TABLE 2

PROPOSED EXISTING MONITOR WELL SAMPLING LOCATIONS AND RECENT CONTAMINANTS OF CONCERN IN GROUNDWATER

micrograms per liter

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