SEITec WaterSilo Series Technical Document

Installation Manual
and
Operating Guidelines
WaterSilo
Urban Stormwater Storage
SEITec, 25500 Hawthorne Blvd, Suite 1170, Torrance, CA 90505
www.SEITecinc.com

TABLE OF CONTENTS
1. INTRODUCTION ............................................................................................................................................. 1
1.1 What is WaterSilo............................................................................................................................ 1
2. HANDLING........................................................................................................................................................ 5
2.1 Safety.................................................................................................................................................... 5
2.2 Unloading............................................................................................................................................ 6
2.3 Positioning ......................................................................................................................................... 6
3. INSTALLATION............................................................................................................................................... 9
3.1 General................................................................................................................................................. 9
3.2 Excavation.......................................................................................................................................... 9
3.3 Tank Installation on Compacted Base...................................................................................10
3.4 Tank Installation on Concrete Base........................................................................................11
3.5 Tank Installation in Drilled Hole .............................................................................................12
3.6 Dry Well Installation ....................................................................................................................14
3.7 Backfilling.........................................................................................................................................17
3.8 Protection against Surface Loads............................................................................................18
4. PIPING & CONNECTION ............................................................................................................................20
5. OPTIONAL HYDROSTATIC TEST ...........................................................................................................20
6. OPERATING GUIDELINES.........................................................................................................................21

1
1. INTRODUCTION
1.1 What is WaterSilo
▪WaterSilo is a system of vertical, large-diameter, interconnected underground
vessels for stormwater storage (cistern), or detention-infiltration (drywell).
▪WaterSilos are vertically oriented and therefore have a small footprint that fits in the
public right of way, and is therefore a highly flexible stormwater management tool,
particularly for “Green Streets”.
▪Multiple WaterSilos can be installed under roads throughout an urban watershed to
capture runoff from various size basins.
▪WaterSilos incorporate either a dome top or an open top vertical Fiber Reinforced
Polymer (FRP) tank for storage, or an open top and bottom shell with a drywell at the
bottom for detention-infiltration.
▪Standard WaterSilo FRP tanks and shells are available in capacities of 750 to 30,000
gallons, with diameters of 6 to 12 feet, and heights of 6 to 40 feet. Please visit
www.watersilo.us for complete list of WaterSilo products.
▪Installation of WaterSilo tanks and shells plus companion drywells (for infiltration) is
best accomplished using the drilled hole excavation method described herein. Dome
top WaterSilo tanks may be installed by either open-dig or drilled hole excavation
methods.
▪The drilled hole installation method also has the advantage that it enables
installation of the connection piping by trenchless methods (microtunneling).
▪Figures 1.1 thru 1.6 show the various configurations and applications of WaterSilos.
Figure 1.1: Dome Top WaterSilo Cisterns –Shallow Piping
Vertical
Dome Top
FRP Tank
Concrete
Encasement
Inflow
Overflow
Reinforced
Concrete Slab

2
Figure 1.2: Dome Top WaterSilo Cisterns –Deep Piping
Figure 1.3: Open Top WaterSilo Cisterns –Shallow Piping
Vertical
Open Top
FRP Tank
Concrete
Encasement
Overflow
Inflow
Vertical
Dome Top
RFP Tank
Concrete
Encasement
Inflow
Overflow
Vault
Reinforced
Concrete Slab
Reinforced
Concrete Slab

3
Figure 1.4: Open Top WaterSilo Cisterns –Deep Piping
Figure 1.5: WaterSilo Detention-Infiltration Dry Wells –Shallow Piping
Vertical
Open Top
FRP Tank
Concrete
Encasement
Vertical FRP
Shell
Concrete
Encasement
Dry Well
Inflow
Overflow
Overflow
Inflow
Vault
Reinforced
Concrete Slab
Reinforced
Concrete Slab
Grating

4
Figure 1.6: WaterSilo Detention-Infiltration Dry Wells –Deep Piping
Vertical FRP
Shell
Concrete
Encasement
Dry Well
Inflow
Overflow
Vault
Reinforced
Concrete Slab
Grating

5
2. HANDLING
2.1 Safety
The following definitions will serve as a guide when reading this manual:
\
▪It is the responsibility of the owner, installer, and operator to follow all requirements
contained in this manual and to comply with all federal, state, and local safety
regulations that may apply to WaterSilo tank installation and operations.
▪No instructions or procedures presented in this document should be interpreted to
put as risk any person’s health or safety, or to harm any property of theenvironment.
Follow OSHA regulations for excavations. Collapse of excavation walls could result in death or
serious injury.
▪Contractor shall follow all Occupational Safety and Health Administration (OSHA)
requirements for excavations, particularly “Standard, Part 1926, Subpart P”.
▪It is important to follow the procedures and instructions in this document to safely
and properly install a SEITEC WaterSilo tank or shell. Failure to follow these
instructions will void the obligations under the limited warranty and may cause
failure, serious personal injury or property damage. A copy of the relevant limited
warranty is found in the printed material that accompanies each tank and shell.
▪Comply with all applicable federal, state and local construction, health, safety and
environmental codes, and industry standard practices and OSHA regulations.
▪Federal, state and local codes and regulations always take precedence over SEITec
requirements. SEITEC must authorize –in writing and prior to WaterSilo tank or shell
installation –any variation to, or deviation from, these instructions.
▪All correspondence regarding variations must be retained for any warranty claims.
▪If you have questions or encounter situations not covered in these instructions,
contact SEITEC at [phone].
CAUTION
A caution without the safety alert symbol indicates a potentially hazardous
situation, which if not avoided may result in property damage.
WARNING
Indicates a potentially hazardous situation, which if not avoided could result in
death or serious injury.
WARNING
CAUTION
Indicates a potentially hazardous situation, which if not avoided may result in minor
or moderate injury.

6
2.2 Unloading
▪Although SEITEC WaterSilo tanks and shells are rugged, the owner and/or the owner’s
representative must take care so that the WaterSilo tank or shell is not dropped or
damaged during delivery, unloading and handling on the jobsite.
▪Before unloading the tank or shell from the truck, the owner and/or the owner’s
representative must make sure that all tools or other items that may damage the
WaterSilo tank or shell during unloading are removed from the trailer bed.
▪When unloading the WaterSilo tank or shell from the trailer bed, the owner and/or
the owner’s representative must make sure that the WaterSilo tank or shell is secured
in such a way that it does not roll off.
Do not allow driver to release straps securing the WaterSilo tank or shell to the truck until
lifting equipment (such as a crane) is secured to the WaterSilo tank’s lifting lug(s). Failure to
do so could result in death or serious injury.
Always lock the WaterSilo tank or shell. The WaterSilo tank or shell is heavy and has a large
surface area. The WaterSilo tank or shell will roll on sloped surfaces and could be blown about
by the wind. Movement of the WaterSilo tank or shell could result in death or serious injury.
▪Before the WaterSilo tank or shell is unloaded or relocated on the jobsite, the owner
and/or the owner’s representative must complete the following steps:
oVisually inspect the entire exterior surface of the tank or shell to make sure
that no shipping or handling damage has occurred. Look particularly for holes,
cracks or deep scrapes. If damage is detected, do not attempt repairs. Contact
SEITECimmediately.
oSign the shipping papers accepting the tank or shell asdelivered.
oBe sure that all equipment used to lift the WaterSilo tank or shell is rated to
handle the load.
oSelect a solid, level area to place the tank, and clear that area of all rocks, trash
and debris.
2.3 Positioning
▪Two cranes are needed at the jobsite to lift the WaterSilo tank or shell off the trailer
and turn it right side up.
▪There are either two lifting lugs at the top and two at the bottom, or three lifting lugs
at the top and one at the bottom.
▪With tanks or shells having two lifting lugs at the top and two at the bottom:
oThe lifting lugs at the top and bottom are aligned in straight lines.
oTank or shell is shipped with the aligned top and bottom lifting lugs on the
WARNING
WARNING

7
sides.
oThe two lifting lugs at the top are rigged to one crane via a spreader bar, and
the two lifting lugs at the bottom are rigged directly to the second crane (see
figure 2.1 A).
▪With tanks or shells having three lifting lugs at the top and one at the bottom:
oThe lifting lugs at the top are 120-degree apart and the one at the bottom
aligns with one of the three at the top.
oThe tank or shell is shipped with the aligned top and bottom lifting lugs on top
i.e. at 12:00 O’clock, leaving the other two lifting lugs at the top on either side
at 4:00 and 8:00 O’clock.
oThe three lifting lugs at the top are rigged to one crane, and the one at the
bottom is rigged to the second crane.
oTwo separate straps of equal lengths of at least twice the tank or shell
diameter are rigged to the lifting lugs at the top; one strap is fastened to lifting
lugs at 4:00 and 12:00 O’clock, and the other strap is fastened to lifting lugs at
8:00 and 12:00 O’clock.
oBoth straps at the top pass through a single shackle that is hoisted to the crane
and lifts them simultaneously. The straps are free to slide in the shackle to
maintain uniform tension during the lifting process.
oNo spreader bar is required.
▪The WaterSilo tank or shell is lifted initially by both cranes. Once lifted off the truck,
the lifting lugs at the top are raised while the one(s) at the bottom slowly eased down
and lowered to arrive at an upright tank.
▪Figures 2.1 shows the above steps (for a tank with two lifting lugs at the top and two
lifting lugs at the bottom).
▪Do not wrap chain or cable around the WaterSilo tank or shell.
▪Use guide ropes to guide the WaterSilo tank or shell when needed.
▪Do not roll the WaterSilo tank or shell to move it.
▪A single crane may be used to offload or move the tank or shell, if there is no
intent to turn it right side up. Is this case, the tank or shell shall be moved by
rigging all four lifting lugs to the crane. For such lifting, the angle between any of
the lifting straps and the vertical shall not exceed 30 degrees. When a situation
arises that the angle will be greater than 30 degrees, the length of the straps shall
be increased to reduce the angle to less than 30 degrees.
▪Whenever a WaterSilo tank or shell is temporarily placed aboveground at the site,
the tank or shell shall be properly secured in place to prevent rolling. Tie the
WaterSilo tank or shell down as it may topple if high winds arepresent or expected.
▪Whenever a WaterSilo tank or shell is temporarily placed above ground in a situation
in which there could be freezing temperatures, always take extra care so that water
does not accumulate in a way that could result in damage to the WaterSilo tank or
shell, or any internalcomponents.

8
Figure 2.1: Lifting a WaterSilo Tank with two cranes to rotate it upright
A. Lift the Tank with two cranes
hoisting all four lifting lugs
D. Slowly lower and place the upright
tank in position
B. Continue lifting the front while
slowly releasing the bottom
C. Continue releasing the bottom
till the tank is upright

9
3. INSTALLATION
3.1 General
Follow OSHA regulations for tank excavations. Collapse of excavation walls could result in death or
serious injury.
▪The installing contractor must take all precautions necessary to protect employees
working in or near a tank excavation. These precautions should include but are not
limited to the following.
▪Locate and protect any utility installations near the excavation before opening the
excavation.
▪Secure the walls of the excavation.
▪Protect employees from hazards associated with water accumulation in the
excavation.
▪Erect barricades, etc. to prevent unauthorized vehicle or pedestrian traffic.
▪Inspect a minimum of once a day, the excavation and surrounding area.
▪For additional information on excavation, trenching and shoring safety practice,
consult OSHA’s Standard, Part 1926, Subpart P (Excavations), 650-652; and “Fall
Protection Rules and Regulations.”
3.2 Excavation
Improper placement of the excavation may result in damage to the tank and/or property damage.
▪Excavations for tank installation may be by either open-dig or the drilled hole
method. WaterSilo shells may only be installed by the drilled hole method.
▪SEITEC recommends that the tank or shell owner seek the advice of a foundation
professional engineer to determine the preferred method and location of the
excavation, particularly near any existingstructures.
▪The tank or shell owner and/or the owner’s technical representative is responsible
for determining the proper method and location of excavation.
▪When selecting a WaterSilo location, care must be taken to avoid undermining the
foundations of existing structures or new buildings to be constructed.
▪Ensure that downward forces from loads carried by the foundations and supports of
nearby structures (constructed before or after tank or shell installation) are not
transmitted to theWaterSilo tank or shell.
▪Figure 3.1 shows the minimum limit of excavation recommended near footings.
WARNING
Notice

10
Figure 3.1: Excavation limit in proximity of footings
3.3 Tank Installation on Compacted Base
▪WaterSilo tank installation on compacted base is only permitted with open-dig
excavations where groundwater level is always below the WaterSilo tank bottom at
all times during the facility life.
▪A minimum of 6 inches of compacted base shall be provided and compacted to a
minimum of 85% Standard Proctor Density (SPD, See Figure 3.2).
▪Actual compaction achieved shall be field verified by a third-party testing lab, to
fulfill the requirements of the limited warranty.
▪The burial depth of tank dome below finished grade shall not exceed 7 ft.
Figure 3.2: WaterSilo tank installation in open-dig excavation on compacted base
Min. 12”
Min. 12”
Excavation Limit
6” Minimum Base
Compacted to 85%
SPD
Native Soil
WaterSilo Tank

11
3.4 Tank Installation on Concrete Base
▪Where groundwater level may rise above the WaterSilo tank bottom during the
project life, then a WaterSilo tank in open-dig excavation shall be installed on a
concrete base.
▪Excavation shall be dewatered to below the native soil level.
▪A minimum of 6 inches of crushed stone or pea gravel leveling course shall be
provided below the concrete base (see Figure 3.3).
▪The concrete base shall have minimum 12 inches of thickness over the crushed
stone, 2500 psi minimum compressive strength, and extend minimum 16 inches
outside from body of the WaterSilo tank.
▪The WaterSilo tank bottom shall be embedded minimum 2 inches inside the
concrete base.
▪There shall be sufficient quantity of 12-inch thick concrete encasement above the
concrete base to resist buoyancy.
▪There shall be water in the WaterSilo tank during concrete encasement with the
water level inside the tank approximately 12 inches above the level of concrete
encasement outside until concrete sets.
▪With dome top tanks, the burial depth of tank dome below finished grade shall not
exceed 7 ft.
Figure 3.3: WaterSilo tank installation in open-dig excavation on concrete base
Crushed stone
or pea gravel
Native Soil
12”
Min.
12” Min.
2” Min.
Concrete encasement in
sufficient quantity to
resist buoyancy
WaterSilo Tank
4” Min.
6” Min.

12
3.5 Tank Installation in Drilled Hole
▪Drilled hole is the preferred installation method for WaterSilo tanks where soil
conditions allow.
▪The completed drilled hole shall have a minimum clear diameter of 24 inches larger
than the WaterSilo tank diameter to leave a minimum gap of 12 inches between the
WaterSilo tank body and the drilled hole wall (see Figure 3.4-A).
▪With backfilled dome top tanks, the drilled hole depth shall be limited such that the
backfill depth over tank dome does not exceed 7 ft (see Figures 3.4-A and 3.4-D).
See Section 3.8 for further details.
▪The drilling contractor is responsible for ensuring adequate stability and uniformity
of the drilled hole wall that is free of caving. Contractor shall use appropriate
shoring or drilling fluid as necessary to ensure adequate stability of the drilled hole.
▪The bottom of the drilled hole shall be filled with approved concrete to a minimum
depth of 24 inches above the bottom of drilled hole. The concrete shall fill any pilot
hole extending below the bottom of the drilled whole that might be present as part
of the drilling operation (see Figures 3.4-A and 3.4-B).
▪The WaterSilo tank shall be centered in the drilled hole and gradually lowered down
until it rests on top of the wet concrete at the bottom. Water shall then be used
inside the WaterSilo tank as ballast to sink the tank down into the wet concrete by at
least 6 inches, but no more than 12 inches such that there is 12”-18” concrete below
the WaterSilo tank base (see Figure 3.4-C).
▪With the WaterSilo tank positioned, contractor shall allow a minimum of 6 hours for
the bottom concrete to set before starting the concrete encasement.
▪Concrete encasement shall proceed in 12-inch lifts and shall commence by first
pouring water into the WaterSilo tank to increase its internal water level by 12
inches. This will be followed by pouring concrete in the annular space between the
drilled hole and the tank to realize a 12-inch lift. The cycle of adding water followed
by pouring concrete shall be repeated until encasement concrete reaches the top of
the tank body at transition to the dome (see Figure 3.4-D).
▪Encasement concrete mix design shall have a target consistency of 7 to 9 inches
slump, minimum compressive strength of 2500 psi, and be approved by Engineer for
local conditions
▪With open-top WaterSilo tanks, the concrete encasement shall reach the rim of the
tank.
▪The purpose of the water inside the tank during encasement is to provide ballast
against any buoyancy created by the wet concrete. The water also serves to roughly
equalize the internal and external pressures and serve as a sink for the heat from
concrete hydration.
▪Once the pouring of the encasement concrete has been completed, contractor shall
allow a minimum of 6 hours for the encasement concrete to set before starting the
backfilling.
▪Contractor shall allow a minimum of 24 hours after completion of concrete
encasement before pumping the water out of the WaterSilo tank.

13
A. Drilled Hole Complete B. Bottom Concrete Poured
C. WaterSilo Tank Positioned D. Concrete Encasement Complete
Figure 3.4: WaterSilo tank installation in drilled hole
Drilled Hole,
Min. Diameter,
D + 24”
Tank Diam., D
Grade Level
12”
Min.
Native Soil
Shoring
(if necessary)
Pilot Hole
(if present)
24”Min.
Lifting
Lug
Rope
12” – 18”
WaterSilo Tank
Backfill
Depth, 7 ft
Max.
Drilled Hole,
Depth
Approved
Concrete
Approved
Concrete

14
3.6 Dry Well Installation
▪WaterSilo dry wells are comprised of a vertical FRP shell, which is an open top and
bottom WaterSilo tank, with a drywell at the bottom.
▪Installation of WaterSilo shells in open-dig excavations in not allowed. WaterSilo
shells shall only be installed in drilled holes.
▪The shell is installed first, and is followed by installation of the dry well.
▪For installing the shell, the drilled hole shall have a minimum clear diameter of 24
inches larger than the shell diameter to leave a minimum gap of 12 inches between
the shell body and the drilled hole wall (see Figure 3.5-A).
▪The drilling contractor is responsible for ensuring adequate stability and uniformity
of the drilled hole wall that is free of any caving. Contractor shall use appropriate
shoring or drilling fluid as necessary to ensure adequate stability of the drilled hole.
▪The shell shall be centered in the drilled hole and gradually lowered down until it
rests on the bottom of the drilled hole (see Figure 3.5-B).
▪With the shell positioned, contractor shall encase the shell by pouring concrete in
the annulus until encasement concrete reaches the shell rim (see Figure 3.5-C).
▪Having completed the pouring of the encasement concrete, contractor shall allow a
minimum of 6 hours for the concrete to set before starting to drill the dry well at the
bottom.
▪Before drilling the hole for the dry well, contractor shall ensure that the interior
surface of the encased shell is protected with an impact resistant sleeve inside that
shields the shell from contact with the drilling equipment (see Figure 3.5-D). One
possibility for the sleeve is a hexagonal or octagonal lumber frame with plywood on
the inside.
▪With the protective shield in place, the contractor may start drilling the dry well at
the bottom of the installed shell.
▪The diameter of the drilled hole for the dry well shall be at least 24 inches smaller
than the inside diameter of the shell leaving a 12” wide circular bench at the bottom
of the shell on top of the dry well (see Figure 3.5-E).
▪Having completed the drilling of the hole for dry well, the contractor shall then
complete the construction of the dry well per the Engineer.
▪Options for the drywell include dumped crushed stone with geotextile lining (see
Figure 3.5-F), perforated concrete pipe filled with dumped stone, or any other
owner/engineer approved detail.

15
A. Drilled Hole Complete B. Shell Positioned in Place
C. Concrete Encasement Complete D. Protective Sleeve Inserted
Figure 3.5: WaterSilo shell and drywell installation --- Continued on Page 16
Shell Drilled Hole,
Min. Diameter:
D + 24”
Shell Diam., D
Grade Level
12”
Min.
Native Soil
Shoring
(if necessary)
Pilot Hole
(if present)
Lifting
Lug
WaterSilo Shell
Temporary
Sleeve to
Protect
Inner
Surface of
WaterSilo
Shell during
Drywell
Auger
Drilling
Approved
Concrete

16
E. Drywell Drilled Hole Complete F. Installation Complete
Figure 3.5: WaterSilo shell and drywell installation --- Continued from Page 15
Drywell Drilled
Hole,
Max. Diameter:
D - 24”
6” Min.
Geotextile
Crushed
Stone
12” Min.

17
3.7 Backfilling
▪Backfilling is the process of placing and compacting select backfill material around
and above the installed tank up to the grade level.
▪Drilled hole installed tanks require backfilling only for the space directly above the
concrete encasement and the tank dome.
▪Open-excavation installed tanks require backfilling all around and above the tank.
▪Backfill material shall be either dumped rounded stone or compacted soil as
specified herein.
▪Rounded stone particle sizes shall be between 1/8 inch and 3/4 inch and conform to
ASTM C-33, paragraph 9.1, sizes 6, 67 or 7 as specified in Table 3.1.
TABLE 3.1 –Rounded stone backfill particle size distribution
Material passing through each laboratory sieve given as percentage of total weight.
Grade
Number
6
100%
90-100%
20-55%
0-15%
0-5%
-
67
100%
90-100%
-
20-55%
0-10%
0-5%
7
-
100%
90-100%
40-70%
0-15%
0-5%
Sieve Size
1 inch
25.0 mm
3/4 inch
19.0 mm
1/2 inch
12.5 mm
3/8 inch
9.5 mm
0.187 inch
4.75 mm
No. 4
0.094 inch
2.36 mm
No. 8
Note: Standard sizes per ASTM D-448, ASTM C-33 AND AASHTO M43.
▪Compacted soil backfill shall conform to specification in Table 3.2. Actual compaction
levels achieved shall be independently tested and documented.
TABLE 3.2 –Compaction requirements for bedding, backfill, and surface course materials.
Material
Material Description
Compaction
Effort
Compaction
Definition
Proctor
Density
Relative
Density
Round Stone,
Crushed
Stone,
See Tables 3.1
Dumped
No compaction
effort (self-
compacting)
At least
85%
At least
40%
GW, GP, SW,
SP
Coarse grained soils with
less than 12% fines
Slight
Some compaction
effort required.
At least
85%
At least
40%
CL, ML, ML-
CL
Fine grained material with
liquid limit < 50, medium
to no plasticity, more
than 25% coarse-grained
Moderate
Additional
compaction effort
required.
85% - 95%
40% - 70%
GM, GP, SW,
SP
Coarse-grained soils with
fines
Moderate
Additional
compaction effort
required.
85% - 95%
40% - 70%
Note: Material symbols are according to Unified Soil Classification System (USCS)
▪Soft limestone, sandstone, seashells or shale shall not be used as backfill because they

18
may break down overtime.
▪Contractor may use approved geotextile fabric to separate the backfill material from
native soils, where necessary.
▪All backfilling shall proceed in 12-inch lifts and shall extend up to the top per details
provided in Section 3.8.
▪Backfilling for tanks installed in open-dig excavations shall commence by first pouring
water into the WaterSilo tank to increase its internal water level by 12 inches,
followed by backfilling to realize a 12-inch lift, and repeating. The cycle of adding
water followed by backfilling shall be repeated until backfilling is complete.
3.8 Protection against Surface Loads
▪The WaterSilo tank fiberglass dome top can support the dead weight of maximum 7.0
feet of backfill to grade.
▪For occasional foot-traffic live loads such in unpaved areas, lawns, or greens, no
additional surface protection is required and the WaterSilo tank may be completed
per the detail provided in Figure 3.6.
Figure 3.6: Backfill detail for occasional foot-traffic live loads
▪For frequent foot-traffic live loads, such as under paved footpaths in public areas,
with occasional light vehicles such as golf carts and similar, a 6-in thick engineered
reinforced concrete slab on the surface directly over the compacted fill, per the
detail provided in Figure 3.7, is required.
Occasional Foot-Traffic
Max.
7.0’