Maui Snail Enclosures

I. Summary of Work:
Hawaiian terrestrial snails are quickly going extinct due to depredation by introduced predators
including rats, Jackson's chameleons, and the rosy wolf snail. Currently, the only reliable way to
protect populations in the field is to construct predator exclusion fences. This project includes
constructing small fence units at remote sites across the island of Maui.
Each fence unit will be between 200 - 500 feet in circumference and will be made entirely of
plastic lumber with HDPE geomembrane as the siding. The basic design of the fence includes a
solid wall with a hood to exclude rats. Three rosy wolf snail barriers will be attached to the
exterior of the wall consisting of two flared 15 degrees angled flanges and an array of copper bands, to
be electrified by DOFAW after completion of fence construction.
DOFAW will supply some of the material needed to complete fence units. The contractor will be
responsible for fence construction, transport of fence crew and equipment, the transport of
fencing materials from their current location to installation sites, and the provision of additional
materials needed to construct the fence as specified herein.
DOFAW requests bids for an indefinite quantity contract to construct fence units of three distinct
sizes, small (250 ft. in perimeter 50 ft.), medium (350 ft. in perimeter 50 ft.), and large (450
ft. in perimeter 50 ft). DOFAW will identify a proposed site, provide approximate perimeter size
estimates (small, medium, or large), delineate the proposed fenceline with flagging, and will take
the contractor to the site, prior to cutting a PO for a unit. Commented [SDR1]: Added language here regarding
three specific fence sizes. See what you think.
II. General Description of Project Sites:
All sites will be in remote areas in State Forest Reserves, State Natural Area Reserves, or
Private land zoned for conservation, on the island of Maui.
III. Access to Installation Sites:
Access to all project sites will be via helicopter. DOFAW will identify possible staging areas,
drop zones, and landing zones for each site prior to construction of a unit. Contractor is required
to conduct all proper due diligence to secure flights and land access.
The Contractor shall be responsible for transporting its work crew, equipment and materials to
the project sites. DOFAW will not provide any ground or helicopter transport.
IV. Equipment, Supplies, Transportation, and Labor:
All equipment, supplies, tools, transportation and labor will be provided by the Contractor, with
exception to any materials specified by DOFAW (see below, Section VI.).
The Contractor is advised that DOFAW shall not supply communications equipment or personal
protective equipment (PPE).
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The materials listed below in Section VI have already been purchased and are available for use.
The materials are currently located in a DOFAW base-yard and will be transported by the
Contractor to the build site(s). The Contractor may not use any DLNR base-yard as an office or
staging area; for storage of tools, supplies, equipment, or other materials; or for overnight
vehicle parking.
V. Site Preparation:
DOFAW has conducted surveys for rare/endangered plants and historic features. Any areas of
special concern will be conspicuously flagged, and will be identified during site visits, and must
not be disturbed or damaged.
The proposed fence lines will be marked and cleared of some trees and vegetation; however,
the lines will require additional vegetation clearing, and some groundwork to accommodate tree-
stumps and rocks. Removal of plants along the fence corridor should only include those plants
that may hinder fence construction. The Contractor may be asked to remove tree limbs that may
fall on the fence line even after the fence corridor has been brushed and the fence installed.
Note that it is not necessary to remove all vegetation.
Project sites are in forests that may have dense fern and shrub understory; brushing will be
required. Any clearing will be done by hand or with small power tools only. The Contractor may
clear a corridor no more than eight feet (8') ft. in width. Debris must be scattered away from the
fence so as not to impede foot traffic along the fence line or interfere with installation of fencing.
No standing trees greater than 4" DBH shall be cut without consultation with DOFAW project
coordinator.
The proposed fence lines will be marked with blue trail flagging. It is recognized that for
installation purposes the contractor may choose to shift the flagged alignment slightly (less than
10ft.). Any adjustments to the fence line will need approval from the project coordinator prior to
moving the line. Upon approval, the Contractor may re-align the fence to straighten alignments,
adjust corners, or to avoid certain trees and shrubs.
There are no known archaeological or historical sites within the fencing corridor(s) however, if
the Contractor finds bones or cultural artifacts at any time during site preparation or installation,
work must immediately cease and DOFAW must be notified immediately. All human litter and
waste must be removed from the site at all stages of fence construction.
VI. Fence Materials:
Materials provided by DOFAW:
1. Reinforced plastic lumber boards 2"x8"x16' (top board)
2. Reinforced plastic lumber boards 2"x6"x16' (barrier board)
3. Non-reinforced plastic lumber boards 2"x12"x16' (baseboard)
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4. Reinforced plastic lumber post 4"x4"x8' (post)
5. HDPE 7'x24' 100 mil rolls
7. Non-reinforced plastic lumber boards 2"x4"x10' (blocking)
8. Copper bands, (electrical barrier)
9. Stainless steel screws for copper band installation
10. Rat hood
11. Angle barrier
The contractor will receive an inventory of all materials supplied by DOFAW including where
they are stored. The Contractor will be responsible for supplying all materials needed to meet
the specifications of this project except for what is listed above.
Please note, it is crucial all materials must be free of any foreign organisms: arthropod pests
(ants, spiders etc.) and their egg clutches, mollusks (snails & slugs) and their egg clutches,
weeds, seeds, and dirt.
The following materials are not provided by DOFAW and must be provided by Contractor.
Materials include but are not limited to the following as specified herein:
1. Georunner system including all materials not specified above
2. Geotextile fabric
3. All materials to build the fence crossover and Covered Area (other than what is supplied
above)
4. All construction materials not listed including fasteners, nylon washers, washed gravel
and concrete, etc. All fasteners must be stainless steel or dipped galvanized. Zinc
plated fasteners will NOT be accepted.
All materials must be approved by the DOFAW project coordinator or their designated appointee
before installation.
VIII. Fence Construction
General
The proposed fences are designed to protect rare and endangered snails from introduced
predators, including the rosy wolf snail (Euglandina species), Jackson's Chameleons
(Trioceros jacksonii xantholophus), and three species of rats (Rattus rattus, Rattus
norvegicus, and Rattus exulans). Because these predators are small exclusion is difficult. It
is therefore imperative that there be no discrepancies in the fence or the predator barriers
that would allow for incursion.
Basic Fence description:
The backbone of the fence is a plastic lumber structure of 4"x4" reinforced plastic lumber
posts cemented into the ground with two 2"x6" and one 2"x12" reinforced plastic lumber
boards running parallel to the ground. Fixed on this backbone is HDPE sheeting. Mounted
on the sheeting are two types of exclusion barriers to the Rosy Wolf Snails: two angle
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barriers and an electric barrier. At the top of the HDPE wall is an 8" diameter rolled hood
that excludes rats. At the bottom edge of the fence the HDPE extends past the bottom edge
of the 2"x12" base board. Along the outside edge of the fence a Georunner erosion control
system installed to prevent erosion. See Figure 4. Each of these components is described
in depth in the sections below.
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Figure 4. Predator-proof fence detail.
Posts:
Posts are 8-foot-tall 4"x4" reinforced plastic lumber placed a maximum of 8' apart on center.
Posts must be a minimum of 60" above ground and 24" underground. They must be
trimmed to conform to rat hood height within 6". (Posts must not be more than 6" taller than
the wall.) All posts must be installed perpendicular to the ground to ensure conformity with
the HDPE sheeting. Post footings must be a minimum of 24" deep and 18" in diameter with
the post concreted in the center. There must be a minimum depth of 18" of concrete
securing the posts. There must be a minimum 6" soil layer between the concrete and
ground level. This allows for the installation of the 2"x12" baseboard.
2"x12" interior and 2"x6" exterior Baseboards:
A 2"x12" reinforced plastic lumber interior baseboard will be installed a minimum 5" below
ground level on the inside of the HDPE, parallel to the ground slope. The 2"x12" interior
baseboard will be secured to the posts with at least two 3/8"x6" galvanized (all fasteners
must be dipped galvanized and not zinc plated) carriage bolts per post and within 0.5"-1.5"
of the outside edge of the board. Bolts must be secured with nuts and washers on the
inside of the fence. The top of the concrete post footing must be at or within 2 inches of the
bottom of the board.
A 2"x6" reinforced exterior baseboard will be installed on the outside of the HDPE. This
exterior baseboard sandwiches the HDPE and excluder mesh to the interior baseboard and
ensures there are no gaps between the HDPE, excluder mesh, and the 2"x12" baseboard.
The 2"x6" must be fastened to the 2"x12" baseboard with 3/8"x4" galvanized carriage bolts
every 18". The top of the excluder mesh and the two baseboards must be parallel and even.
2"x6" Barrier Board:
A reinforced 2"x6" plastic lumber board will be installed a minimum of 20" from the top of the
2"x12" and 2"x6" baseboards (measured to the bottom of the barrier board). This board will
be used for mounting the lower angle barrier. It will parallel the ground slope and 2"x12"
baseboard. The 2"x6" will be secured to the posts with at least two 3/8"x6" galvanized
carriage bolts within 0.5"-1.5" of the outside edge of the board. Bolts must be secured with
nuts and washers on the inside of the fence.
2"x6" Top Board:
A reinforced 2"x6" plastic lumber board will be installed a minimum 39" from the top of the
top board to the top of the lower angle or 55" on center off the finished Georunner system.
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The top board should parallel the ground slope, 2"x12" baseboard, and the 2"x6" barrier
board. The 2"x6" will be secured to the posts with at least two 3/8"x6" galvanized carriage
bolts within 0.5"-1.5" of the outside edge of the board. Bolts must be secured with nuts and
washers on the inside of the fence.
Blocking:
Reinforced plastic lumber 2"x4" blocking will be installed on all posts between the baseboard
and barrier board (approximately 10") as well as the barrier board and top board
(approximately 33") to fill in the gap between the wall and post. The 2"x4" will be secured to
the posts with at least three 5" galvanized lag bolts within 5" of the center of the board. Lag
heads must be counter sunk, and not stand out beyond the edge of the post.
Hood:
A rolled or rounded hood a minimum of 8" in diameter will be installed at the top edge of the
fence a minimum of 42" from the top of the lower angle barrier. The hood can be
constructed of HDPE, PVC, or galvanized 18-gauge sheet metal and must be painted (dark
green or brown, non-glossy). Self-etching paint must be used if the hood is painted by the
contractor after it is zinc plated. The joints must be welded or glued such that there are no
irregularities that would allow for rats to gain a foothold. The hood must be fastened with
stainless steel fasteners (#10 screws with 0.5" OD washers) a maximum of 8" apart. The
hood must be secured between the inner side of the HDPE membrane and 2"x6" top board.
See Figure 5 for the proper order of installation.
Board joints:
All 2"x6" and 2"x12" boards must have flush butt joints within 1" of the post center. There
must be no gaps larger than 1/4" between board ends. Galvanized carriage bolts must be
within 0.5"-1.5" of the outside edges of the boards. All galvanized carriage bolts must be 3/8"
in diameter.
HDPE geomembrane and excluder mesh skirt:
The HDPE membrane must be flush with or extend above the top edge of the top board.
The HDPE membrane must be installed so that it sandwiches the base of the rat hood with
the top board, this is to divert rainwater away from the electric barrier that should be
installed just below. The HDPE should be screwed to the top board with #10 stainless steel
screws every 12". See Figure 5.
Moving down the wall, the 2" x 12" reinforced plastic lumber will be used to secure the lower
angle and HDPE to the 2"x 6" barrier board. The reinforced plastic lumber must be secured
every 12" with #8x1-5/8" star pan head stainless steel composite deck screws countersunk
0.25". All reinforced plastic lumber joins and corners must be flush and there must be no
gaps between the HDPE and wall. See Figure 5.
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The vertical membrane joins on posts must overlap for at least 4". All joins along posts must
be battened the full length between the hood and the lower angle, and the lower angle and
2"X6" baseboard. HDPE ends must be flush with the end of the battens. All joins must be
sealed with 100% silicone sealant prior to securing. Battens must either be plastic,
galvanized, or aluminum and must be beveled at the edges to prevent Jackson's
Chameleons from climbing. Battens must be pre-approved by project coordinator David
Sischo. All battens must be secured with #10 1" stainless steel screws. Fasteners must be
no greater than 4" apart along the posts and must be within 0.5"-1.5" from the edge of the
blocking board.
Along the 2"X12" baseboard the HDPE and excluder mesh will be sandwiched by the 2"X6"
baseboard. The excluder mesh must also run horizontal on the ground from the 2"x12" and
2"x6" baseboards for a minimum of 12" under the geotextile. At fence corners and excluder
mesh joins, excluder mesh patches may need to be added to ensure coverage between the
ends. All patches must overlap at least 6" and must be secured with stainless hog rings no
more than 2" apart.
The HDPE membrane should extend and be buried a minimum of 6" from the base of the
2"x12" baseboard into the ground. This is also to prevent rat incursions.
Excluder Mesh:
Excluder mesh will be installed along the outside edge of the fence to rodent incursions.
Process of installation is as follows. Soil within 48" of the fence must be cleared of all
vegetation, excavated approximately 3", leveled and compacted. The inside edge of the
Excluder Mesh is then installed vertically behind the 2"x6" exterior base board. The inside
edge must be level with the top edge of the exterior 2"x6" base board. The Excluder mesh
must extend down between the 2"x6" base board and the HDPE wall, transitioning from the
vertical to a horizontal orientation extending a minimum of 48" from wall edge. The mesh
must be secured by installing the Georunner Erosion Control System atop. The outside
edge must be a minimum of 48" from the baseboard.
Georunner Erosion Control System:
Georunner will be installed along the outside edge of the fence to prevent erosion. Process
of installation is as follows. Soil within 48" of the fence must be cleared of all vegetation,
excavated approximately 3", leveled and compacted. Heavy weight (Mirafi 180N,
Nonwoven) geotextile fabric is then installed from the 2"x12" baseboard to a minimum of 48"
from wall edge. The fabric must be secured with 18" geotextile pins with washers. Cut edges
must be folded under and pinned. Next, the Georunner is installed per manufacturing
instructions. The inside edge must be flush to the baseboard. The outside edge must be a
minimum of 48" from the baseboard (two 24" pavers). The pavers should be arranged in a
running, offset pattern so that the joins are not stacked.
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