Re: Revised Work Plan for Soil Gas Sampling Downgradient ...

GHD

655 Montgomery Street Suite 1010 San Francisco California 94111 USA T 415 283 4970 F 415 283 4980 W www.ghd.com

17 October 2019 Reference No. 1133607001.21

Ms. Maile Gee, P.G.

Engineering Geologist

Santa Ana Regional Water Quality Control Board

3737 Main Street, Suite 500

Riverside, California 92501 Re: Revised Work Plan for Soil Gas Sampling Downgradient of the Former Los Amigos Dry

Cleaners, 1312 West Edinger Avenue, Santa Ana, California, SCP No. SL0605987803

Dear Ms. Gee:

On behalf of Daytom Enterprises, Inc. (Daytom), GHD Inc. (GHD) has prepared this revised work plan for

the proposed soil gas sampling downgradient of the Daytom property referred to as the Former Los

Amigos Dry Cleaners, located at 1312 West Edinger Avenue, Santa Ana, California (the Site). The

original work plan titled Work Plan for Soil Gas Sampling Downgradient of the Former Los Amigos Dry

Cleaners, 1312 West Edinger Avenue, Santa Ana, California, SCP No. SL0605987803, was submitted to

the Santa Ana Regional Water Quality Control Board (Regional Board) on 10 June 2019. The Regional

Board provided comments to the original work plan in its letter dated 18 September 2019 titled: Comments

on Groundwater Monitoring Plan for Downgradient Monitored Natural Attenuation at Former Los Amigos

Dry Cleaners; 1321 West Edinger Avenue, Santa Ana, California (Global ID # SL0605987803; PCA #

2080064). This revised work plan incorporates the comments provided by the Regional Board in its

referenced letter.

The Site is located in a shopping center at the southwest corner of West Edinger Avenue and South

Bristol Street in Santa Ana, Orange County, California. The location of the Site is shown on Figures 1 and

2, and an aerial photograph illustrating the location of the Site and the surrounding area is provided on

Figure 3.

The objective of the soil gas sampling is to evaluate the potential presence of Volatile Organic

Compounds (VOCs) in soil gas downgradient of the Site. At the request of the Regional Board in an email

to GHD transmitted on 23 January 2018, GHD prepared and submitted a groundwater monitoring plan for

downgradient monitored natural attenuation (MNA) entitled Groundwater Monitoring Plan for

Downgradient Monitored Natural Attenuation (Groundwater Monitoring Plan), dated 9 February 2018. The

Groundwater Monitoring Plan included an outline of the MNA evaluation process and a contingency plan.

As presented in the Regional Board’s letter dated 24 April 2018, entitled Comments on Groundwater

Monitoring Plan for Downgradient Monitored Natural Attenuation at Former Los Amigos Dry Cleaners;

1312 West Edinger Avenue, Santa Ana, California (Global ID # SL0605987803; PCA # 2080064), in

addition to the request for two (2) additional wells to be added to the quarterly sampling program and

additional analytes to be included in the quarterly analysis for each groundwater monitoring well sampled,

the Regional Board also stated: “Contingency 1 of the Contingency Plan must also include collection and

evaluation of soil vapor data in addition to groundwater data”. The soil gas data proposed in this work

http://www.ghd.com/

Revised Downgradient SG Sampling Work Plan.docx 2

plan is intended to be used in a Human Health Risk Assessment (HHRA) as part of the MNA evaluation.

Below is a scope of work for performing the soil gas investigation.

GHD proposes to install temporary soil gas sampling probes at the eleven (11) locations shown on

Figure 4. At each location, sampling will be performed at 5 feet below ground surface (bgs) and, as

requested by the Regional Board, within approximately 5 feet above first encountered groundwater.

Based on information gathered from previous investigations in the immediate vicinity of the proposed soil

gas sampling probes, the total depth of the deeper probes will vary from approximately 13 to 17.5 feet

bgs. Soil gas sample locations SG-1-MNA through SG-3-MNA, located in the cul-de-sac of South Poplar

Street, soil gas sample locations SG-4-MNA through SG-7-MNA, located along South Pacific Avenue, soil

gas sample locations SG-8-MNA through SG-11-MNA, located along South Spruce Street, were selected

based on the location of VOCs in groundwater. The distribution of VOCs in groundwater downgradient of

the Site is shown on Figure 5.

1. Preliminary Activities

1.1 Permitting

Prior to soil gas sampling activities, GHD will obtain the required street work permit from the City of Santa

Ana Public Works Agency for the installation and sampling of the temporary soil gas sample probes.

1.2 Underground Service Alert Notification

GHD will notify Underground Service Alert of Southern California (DigAlert) a minimum of 72 hours prior to

the planned soil gas sampling activities so that utilities in the investigation area can be identified and

marked by the respective utility companies.

1.3 Independent Utility Clearance Survey – Inside the Tenant Space

In addition to the DigAlert notification, GHD will conduct a utility survey using a private utility locator prior

to installing the soil gas probes. In the event that underground utilities are identified in the location of the

soil gas probes, soil gas probe locations will be relocated accordingly.

1.4 Health and Safety Plan

Work at the Site as described in this scope of work will be conducted under a GHD Health and Safety

Plan.

2. Soil Gas Probe Installation

Soil gas probes will be installed in accordance with the guidelines for temporary soil gas sampling probes

presented in the Advisory – Active Soil Gas Investigations, developed by the California Environmental

Protection Agency (CalEPA), dated July 2015 (CalEPA 2015 Guidance).


At each location, a hole through the asphalt pavement will be drilled using an approximately 3-inch

diameter drill core, and 2.3-inch outside diameter drive rods will then be progressively advanced using a

direct-push rig to a depth between 13 to 17.5 feet bgs creating a boring for the installation of the soil gas

probe at each of the two depths. The total boring depth at each location will be approximately 4.5 feet

above the uppermost water-bearing zone (i.e., the top of the Upper Sand Unit observed during prior

subsurface investigations) so that the probe tip of the deeper probes will centered at approximately 5 feet

above the uppermost water-bearing zone. To complete the installation, the drive rods will be removed

and 6 inches of sand will be emplaced at the bottom of the borehole. Clean, dedicated nylon tubing with

an attached new, 1-inch long probe tip (either a ceramic airstone filter or a polyethylene vapor implant) will

be placed into the boring with the other end of the tubing extending to the surface and completed with a

shut-off valve. Sand will then be emplaced in the boring to 6 inches above the probe tip, creating a one-

foot long zone of sand pack extending from the bottom of the boring to approximately 6 inches above the

probe tip. A minimum of 6 inches of dry granular bentonite will be placed above the sand pack. The

remainder of the borehole to 5.5 feet bgs, will be grouted using bentonite hydrated with potable water.

The bentonite will be hydrated within a container at the surface and slowly poured into the borehole.

After the deeper of the two probes has been installed, the second probe will be installed in the same

borehole. To complete the installation of the second probe, 6 inches of sand will be emplaced on top of

the bentonite that was used to seal the deeper probe. Clean, dedicated nylon tubing with an attached

new, 1-inch long probe tip (either a ceramic airstone filter of a polyethylene vapor implant) will be inserted,

such that the center of the probe tip is at an approximate depth of 5 feet bgs. The other end of the tubing

will be extended to the surface and completed with a shut-off valve. Sand will then be emplaced in the

boring to 6 inches of above probe tip, creating a one-foot long zone of sand pack from approximately 5.5

to 4.5 feet bgs, with the probe tip centered at approximately 5 feet bgs. A minimum of 6 inches of dry

granular bentonite will be placed above the sand pack. The remainder of the borehole to the surface will

be grouted using bentonite hydrated with potable water. The bentonite will be hydrated within a container

at the surface and slowly poured into the borehole.

3. Soil Gas Sampling

The CalEPA 2015 Guidance recommends that at least two (2) hours of time should elapse following

installation of a soil gas probe using direct push methods to allow the construction material to cure and to

allow for the subsurface to equilibrate before sample collection. To comply with the above guideline, a

minimum of two (2) hours will be allotted to allow each probe to equilibrate before the soil gas samples are

collected.

Soil gas purging and sampling will be performed through the probe tip and nylon tubing installed at each

location at both depths. At the surface, the tubing will be connected to a sampling manifold using

stainless steel fittings. The sampling manifold consists of a stainless steel tube with a pressure gauge, a

vacuum gauge, and connections for a sample canister and a purge pump. The sampling train at each


location will be contained within a shroud containing Helium used for leak testing (see Section 5.0 for

details).

3.1 Shut-In Test

After the sampling manifold is properly connected and all fittings are tightened, a shut-in test will be

performed prior to purging / sampling activities. The shut-in test is performed to demonstrate that all

fittings have been attached properly and are airtight. This shut-in test will be conducted by applying

vacuum to the tubing and fittings equivalent to approximately 100 inches of water column (W.C.) while the

main valve attached to the nylon tubing exiting the ground surface and the valve to the Summa canister

are in the closed position. The manifold vacuum will be observed for a minimum of 1 minute. If vacuum

loss is not observed, the fittings will be considered air tight and purging and sampling will immediately

commence. In the event that a vacuum loss is observed, the vacuum will be released, all fittings re-

attached or tightened and the shut-in test performed again. This process will be repeated until all

connections are considered airtight.

3.2 Purging

After the shut-in test is complete, purging will be conducted. A purge volume at each location will be

calculated based on the length and diameter of the nylon tubing, and the height and thickness of the filter

pack and non-hydrated bentonite with assumed porosities of 40 and 50 percent, respectively. During

purging, the flow rate will not exceed 200 milliliters per minute (ml/min) nor will the vacuum exceed 100

inches W.C. in order to minimize partitioning of vapors from pore water to soil gas. After purging is

completed and the leak test procedures indicate the integrity of the soil gas probe and manifold, the

sample will be collected.

3.3 Sampling

Soil gas samples will be collected using pre-cleaned, evacuated, 400-milliliter Summa canisters. During

sampling, the flow rate will be regulated so that the flow rate does not exceed 150 ml/min and the vacuum

does not exceed 100 inches W.C.

Once the samples are collected, the Summa canisters will be appropriately packed for transport to the

laboratory for analysis. Chain of custody (COC) records will be completed for the soil gas probe samples

and will accompany the samples until received by the laboratory.

3.4 Clay Formation and Soil Gas Probes Contingency

Based on previously performed cone-penetrometer testing in this area, GHD anticipates that air flow at

depths greater than 4-5 feet may be inadequate for sample collection due to the presence of an

impermeable clay formation that extends from approximately 4-5 feet bgs to first encountered

groundwater (approximately 18 to 20 feet bgs). In the event that some probes cannot be successfully

sampled due to lack of air flow, GHD may adjust the depth of the shallow probes to obtain adequate air


flow and/or make a judgment in the field whether to install deeper probes in impermeable clay. GHD will

attempt at least three deeper probes to determine whether adequate air flow can be obtained.

3.5 Sample Identification Protocol

Once collected, each sample container will be labeled with waterproof ink with the following information, at

a minimum:

Sample identification: i.e., SG-1-MNA-14’, SG-1-MNA-5’, SG-2-MNA-14’, SG-2-MNA-5’, etc.

Project name

Date of sample collection

Time of sample collection

Volume purged prior to sampling

Analyses requested

Sampler’s initials

4. Analytical Methods

The soil gas samples will be analyzed using United States Environmental Protection Agency (USEPA)

Method TO-15 (limited suite) by an offsite (fixed) laboratory certified through the National Environmental

Laboratory Accreditation Program (NELAP). A standard 10-day turnaround time will be requested.

Proper Chain of Custody documentation will be prepared for samples collected and transported to the

stationary laboratory.

The USEPA Method TO-15 analysis will include the dry cleaning compound tetrachloroethene (PCE) and

the related compounds trichloroethene (TCE), the dichloroethene (DCE) isomers cis-1,2-DCE, trans-1,2-

DCE and 1,1-DCE, and vinyl chloride.

5. Quality Assurance / Quality Control

Quality Assurance / Quality Control (QA / QC) will be completed in accordance with the QA / QC

procedures recommended in the CalEPA 2015 Guidance, outlined below:

Leak Check: Helium will be used as a leak check compound at each sample collection point to

evaluate for ambient air leakage through the manifold or the seal of the temporary soil gas probe

during sample collection. Prior to sample collection at each location, approximately 300 milliliters of

soil gas will be purged from the installed probe to fill a Tedlar bag. The helium content in the purged

soil gas contained in the Tedlar bag will be monitored using an onsite mobile helium detector.

Sampling will proceed if helium is not detected, or is detected at a concentration of 5 percent or less.

If the helium is detected at a concentration of greater than 5 percent, the sampling fittings and the


annular seal of the temporary soil gas probe will be checked and corrected and the helium content of

the purged soil gas rechecked after additional purging. This process will continue as necessary until

the helium content of the purged soil gas is 5 percent or less. In the event that the leak cannot be

corrected, the temporary soil gas probe will be abandoned and a new temporary soil gas probe will be

installed nearby.

Duplicate: One (1) duplicate sample will be collected during this sampling event. The sample will be

identified with the sample location followed by “Dup”. The duplicate will be collected in the same

manner as the primary sample and will be analyzed by the stationary laboratory.

Laboratory QA / QC: Standard laboratory QA / QC will be conducted by the subcontracted NELAP-

certified lab.

6. Decommissioning of Temporary Soil Gas Sampling Probes

Upon completion of sampling activities, the soil gas probes will be decommissioned by manually removing

the probe tip and tubing from both depths. The borehole will be filled with a bentonite slurry and a

concrete patch material to restore the upper 6 inches of the surface pavement.

7. Sample Frequency

The soil gas probe installation and sampling described in Sections 2 through 6 above will be performed

twice: first during a cold weather month (i.e., fall or winter) and again in a warm weather month (i.e., spring

or summer). At the time of this work plan, it is anticipated that the first sample event will occur in

November or December 2019 and the second sample event will occur in May or June 2020.

8. Reporting

Upon completion of this work and receipt of laboratory analytical results after each sample event, GHD will

prepare a brief letter report summarizing the sampling procedures and results. The letter report shall

include tables and figures to present the analytical results. The soil gas data will also be used in updating

the HHRA if needed, which will be submitted under separate cover.

9. Schedule

The installation and sampling of the proposed temporary soil gas probes in the residential streets

southwest of the Site will be scheduled upon receipt of approval of this work plan from the Regional

Board.


If you should have any questions or would like to discuss this submittal in greater detail, please contact

me.

Sincerely,

GHD

Mark S. Dockum, PG, CEG – Principal

1 415 296 2040 (direct dial)

Attachments: Figure 1 - Site Location Map Figure 2 - Site Vicinity Topographic Map Figure 3 - Aerial View of Former Los Amigos Dry Cleaners Figure 4 - Proposed Soil Gas Sampling Locations Figure 5 - Distribution of VOC Concentrations in Groundwater

cc: Ms. Patricia A. MacLaughlin, Daytom Enterprises, Inc. (with enclosure) Mr. R. Morgan Gilhuly, Esq. - Barg Coffin Lewis & Trapp, LLP (with enclosure)

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NOT TO SCALE

655 Montgomery Street Suite 1010 San Francisco California 94111 USA T 1 415 283 4970 F 1 415 283 4980 W www.ghd.com

GHD STANDARD A3 SHEET CAD File No.: GHD_G_0043 Updated: 08-07-03 Version: 1.1GHD STANDARD A3 SHEET CAD File No.: GHD_G_0043 Updated: 08-07-03 Version: 1.1

Plot Date: Cad File No:6 June 2019 - 8:35 AM N:\US\San Francisco\Projects\11336 Daytom Enterprises, Inc\11336-07-001 Los Amigos\Work in Progress\Remediation System\2019 Soil Gas Inv for MNA\SG Sampling Workplan\Figures\CAD\Figure 01 - Site Location Map_Los Amigos.dwg

Figure

Date

Revision

Job Number

Daytom Enterprises, Inc.

Former Los Amigos Dry Cleaners

1312 West Edinger Avenue, Santa Ana, CA

1133607001

Downgradient Soil Gas Sampling Work Plan - 2019

Site Location Map

1

Jun 2019

SITE

NORTH


Plot Date: Cad File No:6 June 2019 - 8:32 AM N:\US\San Francisco\Projects\11336 Daytom Enterprises, Inc\11336-07-001 Los Amigos\Work in Progress\Remediation System\2019 Soil Gas Inv for MNA\SG Sampling Workplan\Figures\CAD\Figure 02 - Site Topo Map_Los Amigos.dwg

Figure

Date

Revision

Job Number




1133607001


Site Vicinity Topographic Map

2

Jun 2019

Source: United States Geological Survey (USGS) Topographic Map, 1965

FORMER LOS AMIGOS

DRY CLEANERS

SO

UT

H P

OP

LA

R S

TR

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T

SO

UT

H P

AC

IF

IC

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WEST OCCIDENTAL STREET

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PR

UC

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TR

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PARE DE SUFRIR

IGLESIA UNIVERSAL CHURCH

SO

UT

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RIV

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WEST POMONA STREET

MARKETRETAIL

STORES

AUTO

PARTS

STORE

FITNESS

CENTER

NORTH


Plot Date: Cad File No:10 June 2019 - 9:38 AM N:\US\San Francisco\Projects\11336 Daytom Enterprises, Inc\11336-07-001 Los Amigos\Work in Progress\Remediation System\2019 Soil Gas Inv for MNA\SG Sampling Workplan\Figures\CAD\Figure 03 - AerialView_Los Amigos.dwg

Figure

Date

Revision

Job Number




1133607001


Aerial View of


3

August 2019

BOUNDARIES OF FORMER LOS

AMIGOS DRY CLEANERS

LEGEND

Source: Google Earth, ©2018 Google

MW-7

MW-8

MW-5

MW-1B

MW-1

MW-14

MW-13

MW-10

MW-6

MW-11

MW-12

MW-9

MW-4

MW-16

MW-19

MW-18

MW-17

MW-20

MW-21

MW-15

MW-23

MW-22

MW-24

SG-1-MNA

SG-2-MNA

SG-3-MNA

SG-5-MNA

SG-4-MNA

SG-6-MNA

SG-7-MNA

SG-8-MNA

SG-9-MNA

SG-10-MNA

SG-11-MNA

NORTH


Plot Date: Cad File No:5 June 2019 - 11:54 AM N:\US\San Francisco\Projects\11336 Daytom Enterprises, Inc\11336-07-001 Los Amigos\Work in Progress\Remediation System\2019 Soil Gas Inv for MNA\SG Sampling Workplan\Figures\CAD\Figure 04 - Prop Soil Gas Sampling.dwg

Figure

Date

Revision

Job Number




1133607001


4

Jun 2019

NOTES

Proposed Soil Gas Sampling Locations

MNA NETWORK GROUNDWATER MONITORING WELL

(UPPER SAND UNIT)


(LOWER SAND UNIT)

BOUNDARIES OF FORMER LOS AMIGOS DRY CLEANERS

TENANT SPACE

LEGEND

MW-16

MW-14

GROUNDWATER MONITORING WELL

(UPPER SAND UNIT)

GROUNDWATER MONITORING WELL (LOWER SAND UNIT

OR SECOND ENCOUNTERED WATER-BEARING ZONE)

MW-1

MW-6

PROPOSED TEMPORARY SOIL GAS SAMPLING LOCATION

SG-1-MNA

MW-7

MW-8

MW-5

MW-1B

MW-1

MW-14

MW-13

MW-10

MW-6

MW-11

MW-12

MW-9

MW-4

MW-16

MW-19

MW-18

MW-17

MW-20

MW-21

MW-15

MW-23

MW-22

MW-24

SAMPLE

EVENT

PCE TCE Total DCE VC

1Q2018 <1.0 <1.2 1.1 <2.0

2Q2018 <1.0 <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 4.7 0.85J

4Q2018 <1.0 <1.2 5.3 0.94J

SAMPLE

EVENT


1Q2018 <1.0 <1.2 <1.0 <2.0

2Q2018 0.52J <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 <1.0 <2.0

4Q2018 <1.0 <1.2 <1.0 <2.0

SAMPLE

EVENT


1Q2018 <1.0 <1.2 <1.0 <2.0

2Q2018 <1.0 <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 <1.0 <2.0

4Q2018 <1.0 <1.2 <1.0 <2.0

SAMPLE

EVENT


1Q2018 <1.0 <1.2 <1.0 <2.0

2Q2018 0.41J <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 <1.0 <2.0

4Q2018 <1.0 <1.2 <1.0 <2.0

SAMPLE

EVENT


1Q2018 <1.0 <1.2 <1.0 <2.0

2Q2018 0.56J <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 <1.0 <2.0

4Q2018 <1.0 <1.2 <1.0 <2.0

SAMPLE

EVENT


1Q2018 <1.0 <1.2 <1.0 <2.0

2Q2018 2.4 <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 <1.0 <2.0

4Q2018 <1.0 <1.2 <1.0 <2.0

SAMPLE

EVENT


1Q2018 <1.0 <1.2 <1.0 <2.0

2Q2018 1.5 <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 <1.0 <2.0

4Q2018 <1.0 <1.2 <1.0 <2.0

SAMPLE

EVENT


1Q2018 <1.0 <1.2 <1.0 <2.0

2Q2018 0.81J <1.2 <1.0 <2.0

3Q2018 <1.0 <1.2 <1.0 <2.0

4Q2018 <1.0 <1.2 <1.0 <2.0

SAMPLE

EVENT


1Q2018 470 40 31 12J

2Q2018 480 42 28 18J

3Q2018 390 35 23 14

4Q2018 280 31 18 14

SAMPLE

EVENT


1Q2018 19 2.1 <1.0 2.5

2Q2018 45 5.4 2.6 6.7

3Q2018 23 3.0 1.2 4.7

4Q201827 5.0 2.2 5.4

SAMPLE

EVENT


1Q2018 640 8.0J 26 <20

2Q2018 740 12 32 <20

3Q2018 460 8.0 27 <10

4Q2018 570 9.2J 27 <20

SAMPLE

EVENT


1Q2018 41 0.84J 1.8 <2.0

2Q2018 40 0.91J 1.8 <2.0

3Q2018 110 2.8 2.0 <2.0

4Q2018 45 1.1J 1.5 <2.0

SAMPLE

EVENT


1Q2018 83 1.7 9.2 <2.0

2Q2018 110 2.4 13 <4.0

3Q2018 130 3.2 13 <2.0

4Q2018 140 3.1 11 <2.0

NORTH


Plot Date: Cad File No:7 June 2019 - 7:50 AM N:\US\San Francisco\Projects\11336 Daytom Enterprises, Inc\11336-07-001 Los Amigos\Work in Progress\Remediation System\2019 Soil Gas Inv for MNA\SG Sampling Workplan\Figures\CAD\Figure 05 - Distrib VOC GW.dwg

Figure

Date

Revision

Job Number




1133607001


5

Jun 2019

NOTES

Distribution of VOC Concentrations

in Groundwater


(UPPER SAND UNIT)


(LOWER SAND UNIT)

BOUNDARIES OF FORMER LOS AMIGOS DRY CLEANERS

TENANT SPACE

LEGEND

MW-16

MW-14

· Samples analyzed by USEPA Method 82608

· VOC = Volatile Organic Compounds

· PCE = Tetrachloroethene

· TCE = Trichloroethene

· Total DCE = Total Dichloroethene (The sum of CIS-1, 2-DCE, trans-1,2-DCE and 1,1-DCE)

· VC = Vinyl Chloride

· µg/L = micrograms per liter

· J = Result is less than the laboratory reporting limit but greater than or equal to the method detection limit; the

reported concentration is an approximate value

· <Symbol notes analyte was not detected at or above the specified laboratory reporting limit

· Detections at or above the laboratory method reporting limit are shown in boldface type

GROUNDWATER MONITORING WELL

(UPPER SAND UNIT)

GROUNDWATER MONITORING WELL (LOWER SAND UNIT

OR SECOND ENCOUNTERED WATER-BEARING ZONE)

MW-1

MW-6

SAMPLE

EVENT

PCE

(µg/L)

TCE

(µg/L)

Total DCE

(µg/L)

VC

(µg/L)

1Q2018 <1.0 <1.2 <1.0 <2.0

VOC analytical results from GHD's DowngradientMonitored Natural Attenuation Annual Report - 2018,dated 14 February

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