DSHW-2024-004997

MEMORANDUM
Date: October 25,1999
To: Laundry Supply Company File
From: Rob Powers, Environmental Scientist RZZ
Subject: Monitoring Wells MW-6, MW-7 and MW-8
Three monitoring wells were installed on Monday October 18, 1999 north of the Laundry Supply
Companies property to continue the site investigation and PCE plume definition. Monitoring wells
MW-6, MW-7 and MW-8 where all drilled to a depth of 28 ft. with the screened intervals being
from 8 ft. to 28 ft. respectively. The wells where drilled by Earthprobe using the GEOPROBE
prepack screen monitoring well systern The hole diameters are 1.0 in. x 2.5 in. O.D. The attached
information was provided by GEOPROBE which describes in detail the installation of the
permanent monitoring wells.
Gropnosr@ L.0-rN. x 2.5-rN. OD PnrpACK ScnrnN MoNrroRrNG Wnr,r,
SrnxoARD Oprn luNG PnocEDURE
Technical Bulletin No. 99-2500
PREPARED: August, 1999
og
GEOPROBE 1.Gin. x 2.5-in. O.D. PREPACK SCREEN MONITORING WELL
1.0 OBJECTIV'I
The objective of this procedure is to install a perrnanent, small diameter groundwater monitoring well that can
be used to collect water quality samples, conduct hydrologic and pressure measurements, or perform any other
sampling event that does not require large amounts of water at any given time.
2.0 BACKGROUND
2.1 Definitions
Geoprobe@ Soil Probing Machine: A vehicle-mounted, hydraulically-powered machine that uses static
force and percussion to advance small diameter sampling tools into the subsurface for collecting soil
core, soil gas, or groundwater samples. The Geoprobe brand name refers to both machines and tools
manufactured by Geoprobe Systems, Salina, Kansas. Geoprobe tools are used to perform soil core and
soil gas sampling, groundwater sampling, soil conductivity and contaminant logging, grouting, materials
injection, and to install small diameter permanent monitoring wells or temporary piezometers.
1.0-in. x 2.5-in. OD Prepack Well Screen: This Geoprobe well screen is available in 5-foot (1,5 m)
sections with a 1.0-inch (25,5 mm) inside diameter (ID) and a 2.5-inch (63,5 mm) outside diameter (OD).
The inner component of the well screen consists of 1.0-inch Schedule 40 PVC with.0l0-inch (.25 mm)
slots. The outer component of the screen is stainless steel wire
mesh with a pore size of 0.01 I inches. These screens are
shipped without sand and are designed to be packed with 20-
40 grade silica sand before installation.
2.2 Discussion
This procedure describes the installation of a perrnanent moni-
toring well using [.O-inch x z.S-inch OD prepack well screens,
a Geoprobe percussion probing machine, and Geoprobe too[-
ing. Well installation begins by using a Geoprobe percussion
probing machine to advance 3 .Zl-inch OD probe rods to a pre-
determined depth. Next, the prepack well screen is assembled
and lowered through the 2.625-inch ID of the probe rods. The
process continues by installing a grout barrier, grouting the
well annulus while retrieving the probe rods, and installing a
surface cover. After installation, the well is developed and
water samples are collected. These wells may also be used to
conduct slug tests or as observation wells during pumping tests
to determine aquifer parameters.
As mentioned above, well installation begins by advancing
3.z5-inch OD probe rods to a predetermined depth with a
Geoprobe percussion probing machine. Once the rods are set
at depth, the prepack screen is lowered through the 2.625-inch
(38mm) ID of the probe rods on the leading end of a PVC riser
string (Fig. 2.1). After the prepack is lowered to depth, the
probe rods are retracted. As the rods are retracted above the
screen, either natural formation collapse or a fine-grade sand
Plastic Plug
(13227)
1.0-in. Sch 40 PVC
Riser Pipe
(12876)
1.0-in. Pipe x 2.5-in. OD
Prepack
(1 167e)
1.O-in. Pipe x 2.5 in. OD
Prepack
(1 167e)
PVC Bottom Plug
(1 2881 )
Expendable Point, 3.6-in. OD
(AT3215)
FIGURE 2.1
lnsertion of Prepack Screens
Standard Operating Procedure Page 3 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
t
,, u#,", above the prePacked screeninstalled by gravity through the rod and PVC pipe annulus, form
(Fig.2.2). This sand or natural formation banier prevents bentonite grout from penetrating into the
screened interval. Granular bentonite or bentonite slurry is then installed in the annulus to form a well
seal. A high-pressure grout pump (Geoprobe Model GSl000 or GS500) may be used to pump high-
solids bentonite slurry or neat cement grout to fill the well annulus as the probe rods are retracted (Fig.
2.3). The grout mixture must be pumped from the bottom up to accomplish a tight seal and to meet
regulatory requirements.
In certain formation conditions, the prepacked screens may bind inside the probe rods as the rods are
retracted. This is most common in sandy formations that produce conditions sometimes referred to as
Flush Mount
Well Cover Concrete Pad
Thickness: > 4.0 in.
J Plug
(Locking Plug)
PVC Pipe
2.0 in. Sch 40
24-in.length
PVC Riser
1.0-in. Sch 40
s-ft. lengths
(12876)
Plastic Plug
(13227)
High Solids Bentonite Slurry
or Neat Cement Grout
Bentonite Well Seal
Thickness: > 2 feet
Grout Barrier
(20140 Sand or Collapsed
Natural Formation)
Thickness: > 2 feet above top
of screens
1.0-in. Pipe x 2.5-in. OD
Prepack Well Screen
PVC Bottom Plug
(12881 )
Expendable Point, 3.6 in. OD
(AT321s)
FIGURE
lnstalled Geoprobe 1.0-in. x 2.5-in. OD
2.2
Prepack Screen Monitoring Well
Standard Operating Procedure Page 4 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
flowing or heaving sands. This bind-
ing can generally be overcome by
lowering extension rods down the
inside of the well riser and gently,
but firmly, tapping the extension
rods against the base of the well as
the rods are slowly retracted. If the
binding persists, clean tap water or
distilled water may be poured down
the annulus of the rods to increase
the hydraulic head inside the well.
This step, combined with the use of
extension rods, will free up the
prepacked screen and allow for
proper screen placement.
Once the well is set, conventional
flush-mounted or aboveground well
protection can be installed to prevent
tampering or damage to the well
head (Fig. 2.2). Prepack screen
monitoring wells can be sarnpled by
several available methods (peristal-
tic pump, mini-bailer, Geoprobe's
tubing check valve, etc.) to obtain
high integrity water quality samples.
These wells also provide accurate
water level measurements and can
be used as observation wells during
aquifer pump tests. Additionally,
commercially available interface
probes can be used to detect and
measure the thickness of free prod-
uct (LNAPL and DNAPL) inside the
wells.
When installed properly, these small diameter wells generally meet regulatory requirements for a perma-
nent monitoring well. While a detailed installation procedure is given in this document, it is by no means
totally inclusive. Always check local regulatory requirements and modiff the procedure accordingly.
Geoprobe Model GS1000
Grout Machine
Plastic Plug
(13227)
1) Fill Probe Rods with
grout from bottom up.
2) Continue operating Grout
Pump while retracting rods.
High Solids
Bentonite Slurry
or Neat Cement Grout
Side-Port Tremie Tube
(Flexible Tubing, 1 4299)
Bentonite Seal
FIGURE 2.3
Grouting Well Annulus with
Geoprobe Grout Machine
Standard Operating Procedure Page 5 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
3.0 REQUIRED EQUIPMENT
The following equipment is required to install a permanent monitoring well with the Geoprobe 1.0-in. x 2.5-in
OD Prepack Well Screens and probing system. Figure 3.1 identifies the major monitoring well components.
MONTTORINGWELL PARTS
Prepack Screen, 1.0-inch x 2.5-inch OD
PVC Riser, 1.0-inch Schedule 40 (S-foot lengths)
PVC Bottom Plug, 1.0-inch Schedule 40
Plastic Plug for 1.0-inch Schedule 40 PVC Riser
O-Rings for 1.0-inch PVC Riser (Pkg. of 25)
GEOPROBE TOOLS
Probe Rod, 3.25 x 48 or 60 inches
Probe Rod, 3.25 inches x I meter (optional)
O-Rings for 3.25-inch Probe Rods (Pkg. of 25)
Expendable Point Holder, 3.25 x 48 or 60 inches
Expendable Point Holder, 3.25 inches x I meter (optional)
Expendable Point Assembly, Steel, 3.6-inch OD
Drive Cap, 3.25-inch Probe Rods, GH40 or GH60 Hammer
Rod Grip Pull Handle, GH40 or GH60 Hammer
Extension Rod, 48 or 60 inch
Extension Rod, I -meter (optional)
Extension Rod Coupler
Extension Rod Handle
Extension Rod Quick Links (optional)
Screen Push Adapter
Grout Machine
Grout System Accessories
Water Level Indicator
Stainless Steel Mini-Bailer (optional)
Tubing Bottom Check Valve
Polyethylene Tubing, 3/8-inch OD (for purging, sampling, etc.)
Flexible Tubing (for tremie tube grouting)
ADDITIONAL TOOLS AND EQUIPMENT
Locking Pliers
Pipe Wrench
Volumetric Measuring Cup
PVC Cutting Pliers
Weighted Measuring Tape (optional)
Small Funnel or Flexible Container (for pouring sand)
Duct Tape Roll
Bucket or Tub (for dry material, water, and mixing)
PVC Pipe, 2-inch Schedule 40 (24-inch section)
J Plug (locking plug), 2-inch
Well Cover (aboveground or flush-mount)
Sand. 20-40 grade
Bentonite, Granular (8 mesh)
Bentonite, Powdered (200 mesh)
Portland Cement, Type I
Concrete Mix (premixed cement and aggregate)
Clean Water
QUANTITY
Variable
Variable
-l-
-l-
Variable
Variable
Variable
Variable
-l-
-l-
-l-
-l-
-l-
Variable
Variable
Variable
-l-
Variable
-l-
-l-
-l-
-l-
-l-
-l-
Variable
Variable
-2-
-2-
-l-
-l-
-t-
-1-
-l-
-l-
-l-
-t-
-l-
Variable
Variable
Variable
Variable
Variable
Variable
PART NUMBER
n679
t2876
1288t
t3227
13196
10594 or 9040
r3925
9960
10596 or 9796
13926
AT32l5
10605 or 9742
12235 or 9757
Nf 67l or 10073
AT675
AT68
AT69
AT694K
GWl535
GS500 or GS 1000
GS l0l0 or GS I 012
GW1200, GWl205, or GWl220
GW4t
GW42
TB25L
14299
FA2IO
AT95
AT9 I
Nt92
Standard Operating Procedure Page 6 OD Prepack Screen Monitoring Well
Ol
O-Ring
(131e6)
O-Ring
(131e6)
Prepack Screen
1.0 in. x 2.5-in. OD
S-foot lengths
(1 167e)
PVC Riser
1.0-in. Sch 40
S-foot lengths
(12876)
O-Ring
(131e6)
PVC Bottom Plug
(12881)
FIGURE 3.1
Geoprobe 1.O-in. x 2.5-in. OD Prepack Well Screen Parts
Standard Operating Procedure Page 7 1.0-in. x 2.5-in. oD Prepack Screen Monitoring well
{0 sd\-D r*rrtorroN rN 1.0 rN. x 2.s-rN. **rt* *ELL scREEN
by: fi rlx'irphlsical size, 1.0-in. x 2.5-in. OD Prepack Well Screens are shipped without sand. It is therefore
)t)sstu1tu install sand within the screen prior to use. A specific packing procedure must be followed in order
,. ,r,,,r..o, the sand from settling in the screen after well installation. This section describes the procedure for
ar*4tctly irstalling sand in a 1.0-in. x 2.5-in. OD Prepack Well Screen.
4J Rtquired Equipment
-i-
'''*
I Quart (l L, Container (1)
l)hillips-Head Screwdriver ( I )
2()-40 Mesh Sand (lgallon I 3.75 L)
f)ru'pack Screen Assembly, PA{ 11679 (1):
Red Plastic Plug, ( I )
Stainless Steel Screw, (2)
Gray PVC Cap, (1)
Sand Cylinder, (l)
l'rocedure
t , Ilnsure that the red plastic plug is pushed
into the top of the PVC riser and both
$crews are threaded into the gray bushing
(Fig. 4. I ).
?, Slide the clear sand cylinder over the
ricreen such that the leading end of the cyl-
inder is approximately 1.25 inches below
the top of the gray PVC bushing (Fig. 4. 1).
lpWrtant: Do not push the sand cylinder far-
tlwr onto the screen than indicated as this
',yill make it difficult to remove once the screen is packed with sand.
(',zrtialnz Use care when handling the prepacked screen with bare hands. Small wires protruding from
*e screen can easily puncture the skin.
l ?ra 3 quarts (3 L) of sand into the sand cylinder. This will fill the screen approximately 314 to 718
ltdL
/, '{'6e screen must now be tapped on the ground to settle (pack) the sand.
z Gtntly grasp the screen and raise it approximately 2 inches (5 cm) offthe ground.
,fi4rl,c?:.ot: Be careful when gripping the screen to squeeze it just hard enough to lift it from the ground.
'1-.rr: sr-reen may be damaged if too much pressure is applied before the screen is packed with sand.
< f.:lease the screen and allow it to fall back to the ground.
,4t@e Do not drop the screen more than 2 inches (5 cm) as this can damage the screen.
Sand Cylinder
(128e0)
Red Plastic Plug
(13227)
Stainless Steel Screw
(12347)
Gray PVC Bushing
FIGURE 4.1 .
Selected components of a 1.0-in . x 2.5-in. OD
Prepack Well Screen
Page B 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
c) Repeat Steps 4.2.4-4 and B for a total of l5 "drops".
5. Completely fill the screen with sand. Add enough sand to also fill the sand cylinder approximately
three/quarters full.
Note: The screen will hold approximately 4 quarts (3.75 L) of sand when all has settled after packing.
6. Lift and drop the screen an additional 60-80 times to finish packing the sand. Remember not to drop
the screen from a height of more than 2 inches (5 cm). After this step, the screen should feel very firm.
7. Remove the sand cylinder by rocking it from side-to-side while pulling upward. Let the excess sand
drain from the bottom of the cylinder. Brush any remaining sand from the top of the gray bushing.
8. Remove the stainless steel screws (Fig. .l) from the gray bushing using the phillips-head screw-
driver.
9. Place the gray PVC cap on top of the screen with the countersunk holes facing up as shown in Figure
4.2.
Important: Ensure that no sand is trapped between the cap and bushing as this may allow sand to leak
from the screen during handling.
10. Attach the PVC cap to the PVC bushing by installing the two stainless steel screws (Figs. 4.2).
Installation of sand in the prepack screen is now complete. Remember to remove the red plastic plug from the
top of the screen before attaching the first section of riser pipe. Do not throw away the plug as it may be used to
keep grout and other materials from entering the top of the riser during well installation.
Stainless Steel Screws
(12347)
PVC Cap
(1253e)Completed Prepack Screen
PVC Bushing
FIGURE 4.2.
The PVC cap is attached to the top of the screen with two stainless steel screws.
Standard Operating Procedure Page 9 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
rick *.f.;e Guide
Step 1 o.o
Stainless Steel
Sand Cylinder
Red Plastic Plug
1. Position sand Cylinder.
Step 2 ...
l. Fill screen with sand.
2.Tap screen on ground to pack sand.
3. Add more sand to completely fill screen.
Screen will hold about 4 quarts (3.75 L) of sand.
Step 3 ...
Y
Red Plastic Plug -/ \
PVC Cap
l. Remove sand cylinder.
2. Remove stainless steel screws.
3. Position PVC cap.
4. Replace and tighten stainless steel screws.
5. Remove red plastic plug.
Standard Operating Procedure Page 10 1.0-in. x 2.5-in. oD Prepack screen Monitoring Well
s.OWELL INSTALLATIT
Monitoring well installation can be broken into seven main steps:. Packing the 1.0-inch x 2.5-inch OD Well Screen with sand. Driving the probe rods to depth. Deploying the screen and riser pipes
. Installing a sand/grout barrier. lnstalling a bentonite seal above the screen. Grouting the well annulus. Installing surface protection
Size and material options have resulted in an extensive list of Geoprobe part numbers. To simplify the instruc-
tions presented in this document, part numbers are listed in the illustrations only. Refer to "Section 3.0: Re-
quired Equipment" for complete part descriptions.
5.1 Packing the 1.0-in. x 2.5-in OD Well Screen with Sand
The 1.O-inch x 2.5-inch OD Well Screen can be packed with
job site. However, to help make the well installation pro-
cess more efficient, Geoprobe Systems recommends pack-
ing all well screens with sand before mobiliztng to the job
site. Each box of 1.0-inch x z.5-inch OD Prepack Screens
comes with a complete set of sand filling instructions. In-
structions for filling the screens with sand are described in
Section 4.0.
5.2 Driving Probe Rods to Depth
Locate the Geoprobe probing machine over the proposed
monitoring well. Unfold the probe and place it in the
proper probing position as shown in the unit Owner's
Manual. Since access to the top of the probe rods is
required, it is important to allow room for derrick retrac-
tion when positioning the unit for probing.
Insert a 3.6-inch OD Expendable Point Assembly into
the unthreaded end of a 3.zl-inch Expendable Point
Holder. See Figure 5.1.
Place a3.25-inch Drive Cap over the threaded end of the
expendable point holder.
Place the expendable point holder under the probe ham-
mer in the driving position (refer to unit Owner's
Manua[). Drive the point holder into the ground, using
percussion if necessary. To install an accurately placed
monitoring well, it is important to drive the rod string as
straight as possible. If the point holder is not straight,
retract the assembly from the ground and start over with
Step l.
sand before arriving at the job site or at the
3.25-in. Drive Cap
(9742 or 10605)
3.25-in. Expendable
Point Holder
(13925, 10599,
e040)
Expendable Point,
3.6-in. OD
(AT3215)
FIGURE 5.1
Drive Crp, Expendable Point Holder
and Expendable Point Assembly
l.
2.
a5.
4.
Standard Operating Procedure Page 11 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
5. Remove the drive ."Ot the expendable point holder. Install rCir* on the point holder in the
groove located at the base of the male threads (Fig. 5.2).
IMPORTANT: O-rings must be used to seal the 3.25-inch Probe Rod joints.
NOTE: Make sure the O-ring groove and O-ring mating surface are clean. Any foreign material located
in these areas will prevent the O-ring from sealing properly.
6. Lubricate the O-ring and O-ring mating surface (Fig. 5.3) with a small amount of clean water. Apply
the water with either a moist cloth or a spray bottle.
7. Thread a 3.25-inch Probe Rod onto the expendable point.
8. Place the drive cap on the probe rod and advance the rod string.
O-ring
Mating
Sudace
O-Ring
(ee60)
FIGURE 5.3
Lubricating O-Ring and Mating Surface
9. Remove the drive cap. Again, install an O-ring in the probe rod's O-ring groove. Lubricate the O-ring
and the O-ring mating surface (Fig. 5.3). Add the next probe rod, replace the drive cap, and advance
the rod string.
10. Repeat Step 8 until the leading end of the rod string is 1.5 inches (3.8 cm) below the bottom of the
desired screen interval. The additional depth adjusts for the extra height created by the expendable
point and the PVC Bottom Plug. The top probe rod must also extend at least 15 inches (38 cm) above
the ground surface to allow room for the rod grip puller used later in this procedure. (An additional
rod may be added if necessary.) Move the probe foot back to provide access to the top of the rod
string.
5.3 Deploying the screen and riser pipe
l. With the probe rods driven to the proper depth, the next step is to deploy the screen and riser pipe.
Inspect the 1.0-in. x 2.5-in. OD Prepack Screen(s) to make sure that:
a) the plastic plug is removed.
b) the stainless steel screws are snug.(See Fig. 5.4)
FIGURE 5.2
Probe Rod O-Ring Groove
Standard Operating Procedure Page 12 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
I
Prastic Ptus n Stainless Steel
Screws
(12347)
(13227)
IMPORTANT!
Remove plastic
plug from well
screen before
installing.
FIGURE 5.4
lnspecting Prepack Screen
I
Have
assistant hold
on to top of
well screen or
first section of
riser.
Tape with left
hand using
open palm
Tap with right
hand using
open palm
FIGURE 5.6
lnserting Prepack into Rod String
I
O-Ring
(optional)
(131e6)
1 .0-in. x
2.5-in. OD
Well Screen
(1 167e)
O-Ring (optional)
(131e6)
PVC Bottom Plug
(12881 )
3.25-in. Probe Rod
(10594 or 9040)
FIGURE 5.5
lnserting Prepack Screen Assembly
into Rod String
2. Thread a PVC Bottom Plug into a 1.0-in. x 2.5-in. OD prepack screen. An O-ring may be used on the
plug if desired.
3. Insert the prepack screen assembly into the top of the probe rod string with the bottom plug facing
toward the bottom of the rods (Fig. 5.5). If the prepack does not slide easily into the rods, do not force
it. With the prepack's lower end in the probe rod, hit the screen simultaneously with both hands using
a clapping motion (Fig. 5.6). With this technique, the screen will drop by gravity into the probe rods.
Have an assistant hold onto the top portion of the screen to prevent the screen from unexpectedly
falling down hole.
Standard Operating Procedure Page 1 3 x 2.5-in. OD Prepack Screen Monitoring Well
Caution: Be careful *n.o "*tg" the screen. Sudden screen slippage .il,*n hands between the screen
and the probe rod. To prevent screen slippage, have an assistant hold onto the prepack during the
"kneading" operation.
4. Add additional five-foot prepacks to obtain the desired screened interval. O-rings can be installed
between the prepack sections if desired.
With the assistance of a second person, attach five-
foot sections of 1.0-inch Schedule 40 PVC Riser
to the top of the screen assembly. O-ringsare re-
quired at each riser joint to prevent groundwater,
located above the desired monitoring interval,
from seeping into the well. Continue to add riser
sections until the assembly reaches the bottorn of
the probe rods (Fig. 5.7). At least one foot (0.3
m) of riser should extend past the top probe rod.
Place the plastic plug into the top riser. Duct tape
may be used to help keep the plug in the riser.
It is now time to pull up the probe rods from around
the well screen and riser. Reposition the probe
unit so that the Rod Grip Puller can be attached to
the rod string.
Retract the rod string the total length of all the
screens plus an additional 3 feet (l m). While
pulling the rods, observe whether the top PVC
riser stays in place or moves up with the rods.
a) If the riser stays in place, stable formation con-
ditions are present. Continue retracting the rods
to the depth specified above. Go to Section 4.4.
b) If the riser moves up with the probe rods, have
a second person hold it in place while pulling up
the rods. An additional section of PVC riser may
be helpful. Once the probe rods have cleared the
lower section of screen, the screen and riser as-
sernbly should stop rising with the rods. Con-
tinue retracting to the depth specified above. Go
to Section 5.4.
c) If the risers continue to move up with the probe
rods and cannot be held in place by hand, sand
heave has most likely caused the screen to bind to
the inside of the rods. Extension rods are now
required. (Refer to Figure 5.8 for an illustration
of extension rod accessories.)
Plastic Plug
(13227)
1.0-in. Sch 40 PVC
Riser Pipe
(12876)
1.0-in. x 2.S-in. OD
Prepack Screen
(1 167e)
1 .O-in. x 2.5 in. OD
Prepack Screen
(1 167e)
PVC Bottom Plug
(12881 )
Expendable Point,
3.6-in. OD
(AT3215)
FIGURE 5.7
Prepack Assembly lnside Probe Rods
5.
6.
7.
Standard Operating Procedure Page 1 4 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
tt
Extension Rod, 1 meter (AT675), 48-inch (AT671), or 60-inch (10073)
:Fl-
\**tension Rod Coupler (AT68)
Extension Rod Quick Links (AT694K), includes (1) AT696 and (1) AT695
Extension Rod Jig - Top View
(Ar6eo)
Extension Rod Jig - Side View
(A16eo)
FIGURE 5.8
Geoprobe Extension Rods and Accessories
Extension Rod Handle
(Ar6e)
d) Place a Screen Push Adapter on the end of an Extension Rod. lnsert the adapter and extension rod
into the PVC riser and hold either by hand or with an Extension Rod Jig. Attach additional extension
rods with Extension Rod Couplers or Extension Rod Quick Links until the push adapter contacts the
bottom of the screens (Fig. 5.9). Place an Extension Rod Handle on the top extension rod after
leaving 3 to 4 feet (l to 1,2m) of extra height above the last probe rod.
e) Slowly retract the probe rods while another person pushes and taps on the screen bottom with the
extension rods (Fig. 5.9). To ensure proper placement of the screen interval and to prevent well
damage, be careful not to get ahead while pulling the probe rods. The risers should stay in place once
the probe rods are withdrawn past the screens. Retrieve the extension rods. Place the plug back into
the top riser and secure it with duct tape if necessary.
5.4 Installing grout barrier
The natural formation will sometimes collapse around the well screens and PVC riser as the probe rod
string is pulled back. This provides an effective barrier between the screens and grout material used to
seal the well annulus. If the formation does not collapse, a sand barrier must be installed from the
surface. This portion of the well installation procedure is important because an inadequate banier will
allow grout to reach the well screens. Grout contamination can produce non-representative samples and
retard groundwater flow into the wel[.
1. Using a Water Level
to the bottom of the
Standard Operating Procedure
Indicator or flat tape measure, determine the depth from the top of the PVC riser
riser and probe rod annulus. Two scenarios are possible:
Page 15 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
2.
a) Measured depth is 2 to 3 feet (0,6 to 0,9 m)
less than riser length: This indicates that unstable
conditions have resulted in formation collapse. A
nafural grout barrier was formed as material col-
lapsed around the PVC riser when the probe rods
were retracted. This commonly occurs in sandy
formations. No further action is required. Proceed
with Section 5.5 and perfiorm Step 2 (unstable for-
mation).
b) Measured depth is equal to or greater than
riser length: This indicates that stable conditions
are present. The probe hole has rernained open and
void space exists between the riser (and possibly
the screen) and formation material. Clean sand must
be placed downhole to provide a suitable grout bar-
rier. Continue with Step 2.
Begin slowly pouring 20140 grade sand down the
annulus between the PVC riser and probe rod string.
Reduce spillage by using a funnel or flexible con-
tainer as shown in Figure 5.10. Add approximately
1.3 gal. (5,0 L) for each S-foot (1,$2 m) screen sec-
tion, plus 0.9 gal. (3,4 L) for aZ-foot (0,6 m) layer
of sand above the screen section.
Measure the annulus depth after each 1,5 liters of
sand. The sand may not fall all the way past the
screen due to the tight annulus and possible water
intrusion. This is acceptable, however, since the
prepacked screens do not require the addition of
sand. The important thing is that a sand barrier is
provided above the screens.l-
Sand may also bridge within the annulus between
the risers and probe rods and consequently fail to
reach total depth (Fig. 5.10). This most likely oc-
curs when the sand contacts the water table during
deep well installations. Wet probe rods also con-
tribute to sand bridging. If the annulus is open,
skip to Section 5.5, Step l. If bridging is evident,
continue with Step 5.
I
Extension Rod Handle
(AT6e)
Extension Rod
(AT67 or 4T671)
Extension Rod
(AT67 or 4T671)
Screen Push Adapter
(GW1535)
FIGURE 5.9
Using Extension Rods to
Tap Out Wedged Screens
3.
4.
5. In case of a sand bridge above the screens (wet rods, high water table, etc.), insert clean extension rods
into the well annulus to break up the sand (Fig. 5.10). Simultaneously retracting the probe rods
usually helps. Check annulus depth again. If sand is no longer bridged, proceed to Section 5.5. If
bridging is stitl evident, continue with Step 6.
6. If the sand bridge cannot be broken up with extension rods, inject a small amount of clean water into
the annulus using a Geoprobe GS500 or GSl000 Grout Machine and 3/8-in. (9,5mm) OD polyethy-
Standard Operating Procedure Page 16 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
lene tubing. Simply insert the poly tub-
ing down the well annulus until the
sand bridge is contacted. Attach the
tubing to the grout machine and pump
up to one gallon of clean water while
moving the tubing up and down. The
jetting action of the water will loosen
and remove the sand bridge. Check
the annulus depth again. The distance
should be 2 to 3 feet (0,6 to 0,9 m)
less than the riser length. Proceed
with Section 5.5.
5.5 Bentonite Seal Above Screen
Bentonite is an expanding clay which
exhibits very low permeability. When
properly placed, bentonite prevents con-
taminants from moving into the well
screens from above the desired monitor-
ing interval. The seal is formed either
by pouring granular bentonite into the
annulus from the ground surface, or by
injecting a high-solids bentonite slurry
directly above the grout barrier. The use
of granular bentonite is limited to cases
in which the top of the screen ends above
the water table (no water is present in the
probe rods). Whichever method is used,
at least 2 feet (0,6 m) of bentonite must
be placed above the sand pack.
Stable Formation. Granular bento-
nite is recommended if the following
conditions are met:. Top of screen interval is above the
water table. Formation remained open when
probe rods were retracted
. Bridging was not encountered while
installirg sand for the grout barrier in
1.
Section 5.4
a) Withdraw the probe rod string another 3 to 4 feet (0,9 to I m) and ensure that the PVC riser does
not lift with the rods. It is important that the bottom of the rod string is above the proposed seal
interval. If positioned too low, dry bentonite will backup into the expendable point holder. Bridging
then results if moisture is present inside the probe rods.
b) Pour bentonite between the probe rods and PVC riser as was done with the sand in Section 5.4. To
properly hydrate the granular bentonite, it is necessary to periodically add water through a tremie tube
while installing the bentonite. To accomplish this, repeat adding six inches of granular bentonite
Plastic Plug
(13227)
Extension Rods
used to dislodge
sand bridge
Void space
resulting from
stable formation
(Must fill with
sand from
surface)
Probe Rod string
withdrawn 3-ft. above
screen
Sand placed above
screen to provide
grout barrier
FIGURE 5.10
lnstalling Grout Barrier from Ground Surface
with 2Ot4O Grade Sand
Standard Operating Procedure Page 17 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
followed by 1.0 *"fffr,S L) of water through a tremie t'oU" unti0-foot (0,6 m) bentonite layer is
created. Use the following procedure:
i. Pour 0.8 liters of granular bentonite into the annulus. This volume of bentonite will fill approxi-
mately 6 inches (15 cm) of annular space.
ii. Check for bridging inside the annulus. Measure the riser depth to the boftom of the annulus.
The depth should equal the riser length minus the 2-foot sand pack and the added bentonite. If the
measured depth is significantly less than expected, the bentonite has more than likely bridged
somewhere inside the rod string. A procedure similar to that identified for bridged sand (Section
5.4, Steps 5 and 6) may be used to dislodge the granular bentonite.
iii. Hydrate the bentonite by adding I gallon
Do not pour water directly into the annulus.
the rod string dry.
(3,8 L) of water to the annulus through a tremie tube.
A tremie tube will help prevent bridging by keeping
iv. Repeat this procedure an additional three times or until the 2-foot (0,6 m) thick bentonite layer
is completed.
2. Unstable formation. A grout machine is required to install the bentonite seal if the formation col-
lapsed when the rods were retracted or the sand bridged when installing the grout barrier. The grout
machine can pump a high-solids bentonite slurry under suffrcient pressure to displace collapsing soil.
Void spaces often develop when poured (gravity installed) granular bentonite is used under these
conditions, resulting in an inadequate annular seal. Wet rods will often lead to bridging problems as
well. Use the following procedure to install a bentonite seal with a grout pump.
a) Mix 1.5 gallons (5,7 L) of high-solids bentonite (20 to 25 percent by dry weight) and place in the
hopper of the grout machine.
b) Insert flexible tubing to the bottom of the annulus between the probe rods and well riser. Leaving
at least 25 feet (8 m) extending from the top of the rod string, connect the tubing to the grout machine.
This extra length will give needed slack for rod extraction (completed later in the procedure).
NOTE: The side-port tremie method is recommended to prevent intrusion of grout into the sand
barrier. To accomplish side-port discharge of grout, cut a notch approximately one-inch (25,4 mm) up
from the leading end of the tubing and then seal the leading end with a threaded plug of suitable size.
c) Reposition the probe unit and attach the 3.25-inch Rod Grip Puller.
d) Activate the pump and fill the tremie tube with bentonite. Begin slowly pulling the rod string
approximately 3 feet (1,0 m) while operating the pump (Fig. 5.ll). This will place bentonite in the
void left by the retracted rods before it is filled by the collapsing formation. Continue to watch that
the PVC riser does not come up with the rod string.
NOTE: When removing the retracted probe rod, slide the rod over the tremie tube and place it on the
ground next to the grout machine. This eliminates cutting and reattaching the tubing for each rod
removed from the string. Take care not to "kink" the tremie tube during this process as it will create
a weak spot which may cause the tubing to burst when pressure is applied.
e) Measure the annulus depth to ensure that at least 2 feet (0,6 m) of bentonite was delivered. Pump
additional bentonite slurry if needed.
Standard Operating Procedure Page 18 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
t
I
i
I,
i
5.6 Grouting the well annulus
The placement of grout material within
the remaining well annulus provides ad-
ditional protection from vertical contami-
nant migration. Most grout mixes are
composed of neat cement, high-solids
bentonite sluffy, or a combination of ce-
ment and bentonite. Such mixes must
be delivered with a high-pressure grout
pump. When stable formations exist, the
well may be sealed by pouring dry granu-
lar bentonite directly into the annulus
from the ground surface. Consult the
appropriate regulatory agency to deter-
mine approved grouting methods. This
section presents the procedure for grout-
ing the well annulus with the Geoprobe
Model GS500 or GS 1000 Grout Ma-
chine. Refer to Figure 5 .12 as needed.
[. Mix an appropriate amount of grout
material and place it in the hopper of
the grout machine.
NOTE: It is recommended that an addi-
tional 20 to 25 percent of the calculated
annulus volume be added to the total
grout volume. This additional amount
allows for grout that either remains in the
grout hose or moves into the formation
during pumping. Includit g the additional
20 percent, it will take approximately
0.54 gallons (2,0 L) of grout for each foot
of riser below ground surface.
2. Insert tremie tube into the well annu-
lus until the end of the flexible tubing
reaches the top of the bentonite seal. Ensure that at least 25 feet (8 m) of tubing extends from the top of
the rod string. This extra length allows rod retraction with the tubing attached to the pump.
3. Attach the tubing to the grout machine and begin pumping. If the bentonite seal was below the water
table (deep well installation), waterwill be displaced and flow from the probe rods as the annulus is filled
with grout. Continue operating the pump until undiluted grout flows from the top probe rod.
4. Reposition the probe unit and prepare to pull rods.
5. Begin pulling the probe rods while continuing to pump grout. Match the pulling speed to grout flow
so that the rods remain filled to the ground surface. This maintains hydraulic head within the probe rods
and ensures that the void left by the withdrawn rods is completely filled with grout.
Geoprobe Grout
Machine
(GS10o0) \
Plastic Plug f. \(13227)
Pumped
Bentonite slurry
fills void as rods
are slowly
withdrawn
High solids
Bentonite slurry
forms well seal
Tremie Tube
(Flexible Tubing,
142ee)
Grout Barrier
(20140 Grade Sand or
Natural Formation)
FIGURE 5.1 1
lnstalling Bentonite Seal with
Geoprobe GS1000 Grout Machine
Standard Operating Procedure Page 19 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
a
NOTE: Slide the probe rods over
the tremie tube and place neatly on
the ground next to the grout machine.
Be careful to not pinch or bind the
flexible tubing as this forms weak
spots which may burst when pressure
is applied.
NOTE: Try to avoid filling the up-
per l2 inches (305 mm) of well an-
nulus with grout when pulling the ex-
pendable point holder. This will
make for a cleaner well cap installa-
tion.
6. When all probe rods have been
retrieved and the well is adequately
grouted, unstring the tremie tube and
begin cleanup. It is important to
promptly clean the probe rods, grout
machire, and accessories. This is
especially true of cement mixes as
they quickly set up and are difficult
to remove once dried.
5.7 Surface CoverAMell Protection
A surface cover protects the PVC
well riser from damage and tamper-
ing. Although aboveground and
flush-mount well covers may be used,
most Geoprobe monitoring wells
have been installed with flush-mount
covers (F ig. 5 . I 3 ). Consult the
project planners and/or appropriate
regulators to determine the approved
Geoprobe Grout Machine
(GSl ooo)
Plastic Plug
(132271
1. Fill Probe Rods
with grout from
bottom up.
2. Continue
operating grout
machine while
withdrawing rods.
High solids
Bentonite slurry
forms well seal
Grout Barrier
Tremie Tube
(Flexible Tubing,
1 42ee)
Bentonite Seal
FIGURE 5.12
Grouting Well Annulus with
Geoprobe GS1000 Grout Machine
well cover configuration for your specific application.
l. In order to fit under a flush-mount cover, the top of the well riser must be below the ground surface.
Place the well cover over the riser and push it into the ground to mark the cover diameter. Remove the
cover and dig out approximately 6 inches (152 mm) of soil from within the cover mark.
2. Remove the plug from the 1.O-inch PVC riser. The top of the riser should be approximately 2 inches
(51 mm) above the bottom of the hole. If a joint is near this level, unthread the top riser. If a joint is not
positioned near the specified level, cut off the riser with PVC cutters. Cut at a slight angle to make it
easier to remove the plug. Place a plug (13227) in the well riser. Do not apply duct tape at this time.
NOTE: Do not cut offthe riser with a hacksaw as cuttings will fall down into the screens.
Standard Operating Procedure Page 20 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well
ao
Flush Mount
Well Cover Concrete Pad
Thickness: > 4.0 in.
J Plug
(Locking Plug)
PVC Pipe
2.0 in. Sch 40
24-in.length
PVC Riser
1.0-in. Sch 40
s-ft. lengths
(12876)-
Plastic Plug
(13227)
High Solids Bentonite Slurry
or Neat Cement Grout
Bentonite Well Seal
Thickness: > 2 teet
Grout Barrier
(20140 Sand or Collapsed
Natural Formation)
Thickness: > 2 feet above top
of screens
1.O-in. x 2.5-in. OD
Prepack Well Screen
PVC Bottom Plug
(12881)
Expendable Point, 3.6 in. OD
(AT3215)
FIGURE 5.13
Properly lnstalled Geoprobe 1.0 in. x 2.5 in. OD Prepack Screen Monitoring Well
3. Push aZ4-inch (610 mm) section of 2-inch PVC pipe over the well riser. Position the top of the 2-inch
pipe L5 to 2.0 inches (38 to 5l mm) above the top of the riser. This will provide adequate room to install
the locking cap on the 2-inch pipe and still allow removal of the riser cap.
4. Insert the locking cap into the 2-inch PVC pipe. Tighten the wing-bolt until the cap fits snugly.
5. Position the well cover so that it is centered over the PVC pipe. Push the cover into the ground using
the foot of the probe unit if needed. Provide at least 0.5 inches (13 mm) of space between the top of the
locking cap and bottom of the well cover lid. Do not push the cover so deep as to place the top of the lid
below the surrounding gfound surface.
Standard Operating Procedure Page 21 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
6.0 WELL DEVELOPMENT
"The development serves to remove the finer
grained material from the well screen and fil-
ter pack that may otherwise interfere with
water quality analyses, restore groundwater
properties disturbed during the installation
(probing) process, and to improve the hydrau-
lic characteristics of the filter pack and hydrau-
lic communication between the well and the
hydrologic unit adjacent to the well screen,"
(ASTM D s0e2).
The two most common methods of well de-
velopment are purging (bailing or pumping)
and mechanical surging.
6.1 Purging involves removing at least
three well volumes of water with either
a Tubing Bottom Check Valve (Fig.
6. I ), Stainless Steel Mini-Bailer. As-
sembly or Peristaltic Pump. Include the
entire 3.6-inch (91 mm) diameter of dis-
turbed soil at the screen interval when
calculating the well volume.
Mechanical Surging uses a surge
block which is attached to extension
rods and lowered inside the riser to the
screen interval. The extension rods and
surge block are moved up and down,
forcing water into and out of the screen.
Water and loosened sediments are then
6. Support the well .#0, installing a concrete pad accordi.* ,Q.o:"ct requirements. Pads are
commonly square-shaped with a thickness of 4 inches (102 mm) and sides measuring 24 inches (610
mm) or greater. Finish the pad so that the edges slope away from the center to prevent ponding of surface
water on the well cover.
7. Fill the inside of the well coverwith sand up to approximately 2 to 3 inches (51 to 76 mm) from the top
of the PVC pipe with locking cap.
Polyethylene Tubing
3/8-in. OD
(rB2sL)
1. Oscillate tubing up and
down to bring sample to the
sudace, or
2. lnsert Check Valve
(without check ball) to
sampling interval. Drop
check ball in tubing from
surface. Check valve is
sealed. Retrieve and collect
sample from poly tubing.
Check Ball
(GW421)
Tubing
Bottom
Check
Valve
(GW42)
Water Level
FIGURE 6.1
Sampling with Polyethylene Tubing and a
Tubing Bottom Check Valve
6.2
removed using one of three methods listed in 6. 1.
NOTE: Mechanical surging may damage the well screen and/or reduce groundwater flow across the filter pack
if performed incorrectly or under irnproper conditions. Refer to ASTM D 552l, "Standard Guide for
Development of Groundwater Monitoring Wells in Granular Aquifers" for a detailed discussion of me-
chanical surging.
Development should continue until consecutive samples yield representative water. "Representative water is
assumed to have been obtained when pH, temperature, and specific cohductivity readings stabilize and the water
is visually clear of suspended solids," (ASTM D 5092).
Standard Operating Procedure Page 22 1.O-in. x 2.5-in. OD Prepack Screen Monitoring Well
T.OSAMPLE COLLECT'O0
Groundwater samples are easily obtained with a tubing bottom check valve (with a 3/8-inch OD Polyethylene
tubing as shown in Figure 6.1), a stainless steel mini-bailer assembly, or a peristaltic pump. While the check
valve is the more economical sampling device, some field operators still prefer the traditional mini-bailer or
peristaltic pump.
NOTE: The up and down motion of the check valve may cause loss of volatile compounds from the sample. To
avoid volatiles loss, lower the check valve and tubing to the target monitoring zone without the check ball. Drop
the check ball to the bottom oftubing from the ground surface. This seals the check valve and captures the
sample inside the tubing without stripping away volatiles. To collect the sample, simply retrieve the tubing from
the well riser, remove the check valve, and place the groundwater in an approved container.
8.0 REFERENCES
American Society for Testing and Materials (ASTM), 1992. ASTM D 5092 Standard Practice for Design and
Installation of Ground Water Monitoring Wells in Aquifers: 1993 Annual Book of ASTM Standards, Vol. 0408.
Philadelphia, PA.
American Society for Testing and Materials (ASTM), 1995.
of Ground Water Monitoring Wells in Granular Aquifers:
Philadelphia, PA.
ASTM D 5 521 Standard Practice for Development
1996 Annual Book of ASTM Standards, Vol. 0409.
Geoprobe Systems, 1997. 1998-99 Tools and Equipment Catalog.
Geoprobe Systems, 1998. Geoprobe Prepacked Screen Monitoring Well, Technical Bulletin No. 96-2000, Au-
gust, 1998.
Equipment and tool specifications, including weights, dimensions,
materials, and operating specifications included in this brochure are
subject to change without notice. Where specifications are critical to
your application, please consult Geoprobe@ Systems.
COPYRIGHT@ 1999 by Kejr, lnc.
ALL RIGHTS RESERVED.
No part of this publication may be reproduced or transmitted in any
form or by any means, electronic or mechanical, including photocopy,
recording, or any information storage and retrieval system, without
permission in writing from Kejr, lnc.
Standard Operating Procedure Page 23 1.0-in. x 2.5-in. OD Prepack Screen Monitoring Well