vertical assessment wells_deviation from work plan

TECHNICAL MEMORANDUM
Date: 9/13/2017 File: 1026.102
To: John Toepfer
Cc: Ryan Czop, Danny McCormick, Kathy Webb
From: Todd Plating
Subject: Asheville Steam Electric Plant — Deviations from work plan for vertical
delineation well installation
Additional evaluation of the horizontal and vertical extent of impacted groundwater at
the Asheville Steam Electric Plant (Site) was requested by the NCDEQ Asheville
Regional Office (ARO) via email on May 11, 2017 (Campbell to Toepfer). A subsequent
meeting was held on June 30, 2017 to discuss this request and other aspects of the
ongoing assessment. Provided herein is a formal request for deviations from the
Revised Groundwater Assessment Work Plan for the Asheville Steam Electric Plant
submitted in December 2014. The following exceptions to the workplan may be deemed
necessary to complete the installation and subsequent evaluation to be included in the
Comprehensive Site Assessment:
0 Air rotary drilling and Optical Televiewer (OTV) logging for deep bedrock well
drilling and well installation.
0 Installation of nested wells (multiple wells within a single boring).
01 Use of Baroid Aquaguard grout (as determined necessary during field operations).
DRILLING METHOD
The use of air rotary drilling in combination with borehole geohpysics in lieu of
standard coring methods will allow more efficient well installation and provide high
resolution data regarding borehole characteristics. Following completion of the
borehole to pre -determined and agreed upon depths, a series of borehole geophysical
logs, including OTV, will be conducted within the deepest bedrock well at each
location.
Borehole geophysical logs will be conducted at water producing open -hole bedrock
well locations to determine appropriate discrete screen intervals within the fractured
bedrock flow system. Logs may include fluid temperature/resistivity/3-arm
caliper/SPR, optical and/or acoustic televiewer, and heat pulse flowmeter under
P: \ Duke Energy Progress.1026 \ 102. Asheville Ash Basin GW Assessment Plan \ Vertical assessment wells \ vertical
assessment wells deviation from work plan.docx

Deviations from work plan for vertical delineation well installation September 13, 2017
Asheville Steam Electric Plant Page 2 of 2
ambient and pumping conditions. A report documenting findings of the geophysical
survey may include logs, interpretations and results. Using optical televiewer data, the
dip, azimuth and aperture for each detected fracture could be calculated, and the results
could be presented in tadpole and stereographic plots. Geophysical logs and well
construction details could be used to further characterize the nature and extent of
groundwater flow in deep bedrock within a CSA or subsequent report.
MONITORING WELL INSTALLATION
In order to effectively and efficiently evaluate the potentially stratified nature of
contaminant occurrence at the Site, an alternative well construction technique is
proposed for consideration. Standard single well construction is proposed for locations
where a single water -bearing zone is encountered, while nested wells (rather than a
well cluster) would be appropriate should numerous viable water -bearing zones be
identified within bedrock. For example, up to four 2-inch PVC monitoring wells can be
installed within a single 10 inch boring. The use of nested wells allows measurement of
discrete hydraulic head potentials and water chemistry from individual fracture sets
through the use of multiple bentonite seals and well screens within a single borehole.
The typical schematic below provides a conceptual layout of the system. Please note,
surficial and transition wells are not proposed to be considered in well nests for this
project.
BAROID AQUAGUARDO
AQUAGUARDO is a single -sack grout containing granular Wyoming sodium bentonite
blended with inorganic additives. The grout is designed for sealing the annular space
around monitor or water well casing. The reported pH of typical Aquaguard slurry
(8%) is 8.0 standard units. Therefore this material may be determined preferable to
reduce potential influence of grout placement in the vicinity of the well installation.
Product information from the manufacturer has been included as an attachment.
ATTACHMENTS:
FIGURE 1 - TYPICAL NESTED WELL DETAIL
BAROID AQUAGUARD SPECIFICATIONS
P: \ Duke Energy Progress.1026 \ 102. Asheville Ash Basin GW Assessment Plan \ Vertical assessment wells \ vertical
assessment wells deviation from work plan.docx

MW-xxxD (TRANSITION WELL) MW-xxxBR (FIRST BEDROCK FRACTURE WATER WELL)
MW-xxxS (SURFICIAL WELL) r/ MW xxxBRL (SECOND BEDROCK FRACTURE WATER WE
1 1. .
WITHIN ONE
5%
BENTONITE SEAL
(THICKNESS VARIES)
BENTONITE SEAL
(THICKNESS VARI
BENTONITE SEAL
(THICKNESS VARIES)
FIRST WATER BEARI
SECOND WATER BEARING FRACTURE
IN COMPETENT BEDROCK
NOT TO SCALE FIGURE 1
148 RIVER STREET, SUITE 220 MULTI -LEVEL WELL SCHEMATIC
GREENVILLE, SOUTH CAROLINA 29601 ASHEVILLE PLANT
PHONE [phone]
www.synterracorp.com DUKE ENERGY PROGRESS
.WnTerra DRAWN BY: JOHN CHASTAIN DATE 09/15/2016 ARDEN NORTH CAROLINA
PROJECT MANAGER: TODD PLATING 7
LAYOUT: FIG 3 (WELL SCHEMATIC)
09/16/2016 2:11 PM P \nuke Fncrov Prnrtracc 1-\l m Ac ,,illa Ach Racin ( A...cc ant Plan\2T FRR\nwn\nF ARHNII I F FRR MW CnHFMATIP.H.,

AQUAGUARD°
Description
AQUAGUARD° is a single -sack grout containing granular Wyoming sodium bentonite
blended with inorganic additives. The grout is designed for sealing the annular space around
monitor or water well casing.
Applications/
The use of AQUAGUARD grouting material assists or promotes the following:
Functions
• Grout plastic and steel casings in monitor or water wells
• Seal downhole instruments in test and observation holes
• Seal cathodic protection installations
AQUAGUARD grouting material is not recommended for use as a cement additive.
Advantages
Does not contain any polymers
• Easy, one -sack, dust -free mixing
• Develops a 30% solids slurry weighing 10.1 lb/gal (1.21 g/cm3) with a hydrostatic
gradient of 0.525 psi/ft (11.88 kPa/meter)
• Low -permeability, flexible seal helps prevent commingling of aquifers and entry of
surface contaminants
• No heat of hydration, no damage to plastic casing due to temperature elevations
• NSF/ANSI Standard 60 certified
Typical Properties
Appearance Tan to gray granules
• Specific gravity 2.5
• Slurry pH (8%) 8.0
• Electrical Resistivity, ohms -meter 0.5
• Yield Volume gal/sack (liters/sack) 16.3 (61.7)
• Permeability (30% solids grout) 3.0 x 10-8 cm/sec (in fresh water)
Recommended
Do not over mix and do not use a centrifugal pump
Treatment
1. Add one 50-lb (22.7 kg) sack of AQUAGUARD grouting material into 14 gallons (53
liters) of circulating fresh water over a 20 to 30 second interval. The resulting slurry
contains 30% active solids and has a slurry density of 10.1 lb/gal, or 1.21 g/cm3.
2. Immediately tremie the grout into place after addition of AQUAGUARD grouting material.
Note: The slurry should contain suspended, unyielded bentonite granules which are allowed to
hydrate and swell in situ.
© Copyright 2010 Halliburton
Rev. 0112011 - IDP 029
AQUAGUARD is a registered trademark of Halliburton
Because the conditions of use of this product are beyond the seller's control, the product is sold without warranty either express or implied and upon condition that
purchaser make its own test to determine the suitability for purchaser's application. Purchaser assumes all risk of use and handling of this product. This product will be
replaced if defective in manufacture or packaging or if damaged. Except for such replacement, seller is not liable for any damages caused by this product or its use.
The statements and recommendations made herein are believed to be accurate. No guarantee of their accuracy is made, however.

Additional The grouting material and method selected will depend upon the specific subsurface
Information environment including all prevailing geological and hydrological factors and any existing
regulatory requirements. The grouting process may not be complete until the grout is
static at the desired level.
• The use of bentonite may not be appropriate in environments where the formation water
chemistry has a total hardness of 500 parts per million or greater and/or a chloride
content of 1500 parts per million or greater.
If questions arise regarding subsurface environments it is always best to consult your
local Baroid IDP representative to determine if the Baroid product of choice is
appropriate for the given conditions.
Packaging AQUAGUARD° is packaged in 50-lb (22.7 kg) multiwall paper bags containing 0.7 ft3 (0.02 m).
Availability AQUAGUARD can be purchased through any Baroid Industrial Drilling Products Retailer. To
locate the Baroid IDP retailer nearest you contact the Customer Service Department in
Houston or your area IDP Sales Representative.
Baroid Industrial Drilling Products
Product Service Line, Halliburton
3000 N. Sam Houston Pkwy E.
Houston, TX 77032
Customer Service [phone] Toll Free [phone]
Technical Service [phone] Toll Free [phone]