Bed Installation

- Carefully
lay out the system components and define setbacks from wells, property
boundaries and land forms such as streams and drainage ways in
accordance with state and local regulations.
- Prepare
the site according to, and following all state and local regulations.
Do not install a system on frozen ground, saturated ground, or wet
soils that are smeared during excavation. Keep heavy machinery off
clayey soils used for the GSF system as well as down-slope from the
system where soil structure is critical for absorption and drainage of
the treated effluent.
- Plan
the diversion of upslope stormwater. Set soil grades at 3% minimum to
ensure that stormwater drainage is diverted away from the GSF system
area once the system is complete.
- Excavate
the bed. Scarify the receiving layer to maximize the interface between
the native soil and the ASTM C33 specified sand layer.
- Remove all organic soil and roots at disposal and fill extension areas.
- Minimize walking in the trench or bed prior to placement of the ASTM C33 specified sand to avoid soil compaction.
- Based
on the GSF approval in your state, place the proper amount of a
specified ASTM C33 sand with less than 10% passing a #100 sieve and
less than 5% passing a #200 sieve and with a Coefficient of
Permeability greater than 5 feet per day on the bottom of the excavated
bed.
- A hand tamper is
sufficient to stabilize the sand below the GSF modules. Set the
elevation of the top of the ASTM C33 specified sand and check to make
sure it is level using a 2” x 4” board and a carpenter’s level, or a
laser level before placing the GSF modules.
- Avoiding
footprints, place GSF modules with PAINTED STRIPE FACING UP, end to end
on the ASTM C33 specified sand layer in the bottom of the bed. The
distance between module rows is 12” minimum and can vary based on the
Eljen approval from the state or local issuing authority. CAUTION:
Spacer cores can have sharp edges.
- Provide distribution box(s) or drop-boxes depending if the site is level or sloped.
- Use
4” SDR 35 non-perforated pipe from the distribution box to the
perforated pipe that is installed above the GSF modules. Note:
perforated pipe is only used above the modules.
- Center
4” SDR 35 perforated distribution pipe lengthwise over modules with
orifices at 5:00 and 7:00. In level systems, connect distribution lines
using non-perforated pipe at the distal (far) end of the system, and at
the mid-point of the system in systems that are over 40’ in length.
- Secure
the distribution pipe to GSF modules using one Eljen wire clamp per
module. Push clamp ends straight down into up-facing core, through the
fabric, and into the underlying ASTM C33 specified sand layer.
- Spread
Eljen cover fabric lengthwise over the pipe and drape over the sides of
the GSF module rows. Secure the fabric by placing several shovels of
specified sand on top of the modules, between and along the sides of
the modules. Avoid blocking holes in perforated pipe by placing the
cover fabric over the pipe prior to placing fill over the modules.
- Based
on the GSF approval in your state, place the proper amount of the
specified ASTM C33 sand between module rows (12” minimum), and along
the sides and ends of modules in the bed.
- Complete
backfill using excess ASTM C33 sand on top of the modules then loam to
12" minimum over the entire GSF system. Backfill should be clean,
porous and devoid of large rocks. Backfill exceeding 18” requires
venting at the distal (far) end of the bed. Do not use wheeled
equipment over system. A light track machine may be used with caution,
avoiding crushing or shifting of pipe assembly. Backfill in direction
of perforated pipe.
- Final
grading of the site shall be in accordance with state and local
regulations. Set grade of system and upslope area to divert stormwater
runoff. Finish grade over the GSF system shall be at a 3% minimum to
prevent surface ponding. Backfill material surface shall be stabilized
by seeding or sodding to establish a good vegetative cover to prevent
erosion.