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AECOM 4051 Ogletown RoaNewark DE, 19713 USA aecom.com

Project name: Montague Site

Project ref: Chemours: 507756 AECOM: 60494178

From: George E. Gre

Date: June 23, 2017

uality (MDEQin the area of

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Figure 3 displays boring logs from monitoring well PCL-05-078 and the two 2015 CPTs (CPT01 and CPT02c on the lithologic logs). These are displayed side-by-side in Figure 3 and are approximately to scale. Their layout is adjusted to approximate actual ground surface elevation. As shown near the right-hand edge of the figure, the following well screen intervals are proposed for PCL-007:

• PCL-007-060 is near the top of the water table.

• PCL-007-085 is a mid-depth well. Samples from similar depths at 2015PC-CPT-01 had detectable (but estimated) concentrations of benzene and toluene.

• PCL-007-105 is projected to be the base of the aquifer and would correspond to roughly the same interval screened by well PCL-005-078. Ground surface at PCL-005-078 is lower; hence, the difference in depth to the base of the aquifer. The base of the aquifer is underlain by a dark gray, plastic clay believed to be lacustrine in origin.

Well Construction Monitoring wells will be installed using a rotosonic rig as this drilling method has been successful at the site. An 8-inch borehole will be drilled using a full-sized truck rig. During the first well installation, the boring will be lithologically described and drilled to the gray clay. This clay is encountered typically at about 130 to 145 feet below ground surface. The rig will core at least 5 feet into this unit (there have been locations where thinner clay layers have had sand beneath them. This will confirm that the well will screen the base of the sand-gravel aquifer).

Tentatively, the deepest well will be identified as PCL-007-140. The proposed screen intervals will be adjusted where field observations indicate conditions different from those based on the CPT data. The intent is to screen across the three most likely flow intervals. The remaining two wells will be installed within 10 feet of the first well and will not require lithologic logging.

All three monitoring wells will be constructed of 2-inch diameter, schedule 40 polyvinyl chloride (PVC) with 10-foot well screens (0.01-inch slot). A filter pack of 20/40 mesh silica sand will be placed around the well screen and extend 2 feet above the top of screen. A minimum 2-foot thick annular seal of bentonite chips or pellets will be placed on the sand pack and allowed to hydrate per manufacturers recommendations before the remaining annual space is filled with cement-bentonite grout to near surface. Wells will be completed with 3-foot-square concrete surface pads and a lockable steel surface casing. The space between the PVC casing and the steel casing will be filled with gravel to near the top of casing and a weep hole will be drilled near the base of the casing to allow condensation to escape. The outside of the steel casing will be painted yellow to reduce corrosion and improve its visibility.

Development After installation, the wells points will be developed by the drilling contractor to remove sediment that may have entered the screen during installation. Well sampling will be performed after the wells have had a period to equilibrate with the aquifer.

Surveying Top of casing and ground surface elevations will be surveyed for the new monitoring wells. Coordinates will be surveyed in Michigan State Plane, South system. These measurements will be used with depth to water measurements to provide hydrogeologic information to determine if Pierson Creek is intercepting groundwater flow and preventing underflow.

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George E. GrSenior GeoloAECOM Corp

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AECOMSabre Building, Suite 300

4051 Ogletown RoadNewark, DE 19713

SITE MAPProposed Groundwater Monitoring

Well Cluster PCL-007 West of Pierson CreekChemours Montague Facility

Montague, MichiganTASK NUMBER:

DESIGNED BY:

DRAWN BY:

DATA QUALITY CHECK BY:GEG

CAD

PJC18984840.201010

PROJECT NUMBER:

DATE:

FIGURE NUMBER:

60426164

1

®0 1,200 2,400600

Feet

MAP FORMATTED FOR "B" (11" X 17") SIZE SHEET. TEXT SCALE NOT VALID FOR DIFFERENT PAGE SIZE.

1 inch = 1,200 feet

Illinois Ohio

Wisconsin

Indiana

MichiganSite

Location

2005 NAIP Aerial Source: Credit to Remote Sensing& GIS Research and Outreach Services (RS&GIS),USDA-FSA Aerial Photography Field Office

Area Map

C:\D

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ject\6

0426

164_

Prop

GW_M

WPC

L007

_Jun

2017

\Fig1

_Site

Map.m

xdLegend

Pierson Creek - Main ChannelPierson Creek - TributaryChemours Property Line (from ChemoursReal Estate)Road CenterlineFormer Manufacturing AreaWaste Management Unit (WMU) orArea of Concern (AOC)

6/14/2017

PiersonCreek

SadonyBayou

MirrorLake

PiersonCreek

Landfill

LakeMichigan

White Lake

PROPOSED LOCATIO N O FPCL-007

Proposed Groundwater MonitoringWell Cluster PCL-007 West of Pierson Creek

Chemours Montague FacilityMontague, Michigan

TAS K NUMB ER:

DESIG NED BY:

DRAW N B Y:

DATA QU ALIT Y CHECK B Y:GEG

CAD

PJC18984840.201010

PRO JECT NUM BER:

DATE :

FIG URE NUM BER:

60426164

2

2005 Aerial C redit: Remote Sensing & GIS Researchand O utreach Services (RS&GIS), USDA-FSA AerialPhotography Field Office

MAP F O RMATT ED FO R "B" (11 " X 17 ") SIZ E SHEE T. TEX T SCALE NO T VA LID F O R D IF FE RENT PA G E SIZE .

C:\D

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\_GIS

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4261

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LegendPCL-007 ClusterCPT Boring

!A Monitoring Well LocationPierson Creek - Main ChannelPierson Creek - TributaryChemours Property Line (from ChemoursReal Estate)Road CenterlinePierson Creek Landfill Boundary

®0 150 30075

Feet1 inch = 150 feet

ChemoursProperty

Boundary

Map E xten t

AECO MSabre Building, Su ite 300

4051 Ogletow n RoadNewark, DE 19713

6/14/2017

!A!A

!A !A

!A

!A

!A

!A

!A !A

!A

!APCL-5S PCL-5D

PIERSONCREEK

LANDFILL

PCL-6-77

PCL-3-17

PCL-1-67

PCL-2-70

MW-209-67

MW-250-54

PCL-4-17MW-207-55

MW-208-83MW-208-20

2015PC-CPT-02(Incomplete CPT - Installing PCL-007)

2015PC-CPT-01(Completed CPT)

Old Channel Trl

Wilkes Rd

Pierson Creek - Main

Tributary 1

Tributary 4

Tributary 3

Tributary 6

Tributary 5

Tributary 3 - Fork

Tributary 2

---

0' 500' 1000'

NOTES:Each log presented at same vertical scale (ground surface to -120').Approximate vertical difference between PCL-005-078 and 2015 CPTs = ~30 feet.

PCL-005-0452015PC-CPT-01 sample results:J-value of benzene and toluenedetected in 76' and 81.8' samples.All other depths ND for VOCs.