| |
AUTOMATIC LEVEL CONTROL
SRT (Self-Regulating Tidegate)
- For tidal wetlands preservation & restoration
- Restores tidal flushing of marshes without flooding
of upland property behind dikes and levees
- Restoration of estuarine plants, fish, shellfish,
waterfowl & wildlife
- Reduces mosquito breeding through natural control
- Helps eliminate marsh fires (both peat nad phragmites
or tall reed grass)
- Reduces sheet flooding of the marsh
- Deepening of downstream channels resulting in improved
navigation
- Proven by 20 years experience
The SRT is usually attached to an end wall or cross-culvert
on the tidal side of a causeway or dike. The buoyant SRT is hinged on
the top of the culvert so that it floats on the surface of the water until
it is closed by counterfloats extending above and behind the hinge point.
The position of the counterfloats on the arms is adjusted to meet the
required gate closure water levels on a site-specific basis. Once the
predetermined high water level is achieved, the SRT automatically closes
and stays closed during the flood event, thereby protecting the flood
prone area. Once the tide recedes on the outside of the dike the hydraulic
head reverses in the culvert and the SRT automatically reopens thereby
allowing any water to flow out of the flood protection drainage system.
The SRT stays open, floating on the rising and falling tide as the water
flows in and out, until such time as the elevation of the tide water reaches
the user set gate closure level. Depending on the float settings, the
SRT could close with every daily tide or it could just rise and fall with
the tide for months or even years closing only during hurricane flood
events. It all depends on the goals of the water management agency which
adjusts the float settings. The SRT always allows upland stormwater runoff
and creek water to discharge when the tide is low. The conventional one-way
gate closes when the tide rises, thereby preventing saltwater from returning
to the diked watercourse or wetland. In contrast, the SRT can be adjusted
to allow tide water to flow into the culvert thereby feeding the channel
or marsh behind the dike. Because the SRT is located on the outfall or
tidal side of the dike's culvert, its float system responds to any tidal
threat by closing the gate to incoming water when the tide reaches the
design high water level. Sensing the storm tide water elevation, the SRT
closes "early" thereby preserving a relatively large volume
of potential water storage capacity behind the dike should it be needed
for detention of upland runoff associated with the coastal storm. In this
way the SRT simultaneously maintains flood protection to the upland area
while allowing tidal flushing of the low-lying wetlands. Restored tidal
flushing of the wetlands will help restore the estuarine ecosystem; eliminate
marsh fires (both dry peat fires, phragmites or tall reed grass fires),
greatly reduce mosquito breeding, reduce sheet-flooding of the marsh;
and restore upland drainage through re-scoured marsh channels. Because
of the increased tidal prism to the restored wetland, deepening of the
downstream channel and improved navigation will result as well.
Part 1 General
1.1 References The publications listed below form a part of this specification
to the extent referenced. Publications are referred to in the text by
their basic designation only.
American Society for Testing and Materials (ASTM)
ASTM A 276 (1995) Standard Specification for Stainless Steel Bars and
Shapes ASTM B 209 (1993) Standard Specification for Aluminum and Aluminum-Alloy
Sheet and Plate ASTM B 221 Standard Specification for Aluminum and Aluminum-Alloy
Extruded Bars, Rod, Wires, Shapes and Tubes ASTM B 308 Standard Specifications
for Aluminum-Alloy 6061-T6 Standard Structural Shapes ASTM F 593 (1995)
Standard Specification for Stainless Steel Bolts, Hexcap Screws, and Studs
ASTM F 594 (1991) Standard Specification for Stainless Steel Nuts
Part 2 Products
2.1 Self-Regulating Tide Gates Patented self-regulating tide gates shall
be manufactured by Waterman Industries, Inc., Exeter, California, telephone
number 209-562-4000, and no other will be acceptable.
2.1.1. General
Self-regulating tide gates shall be as manufactured
by Waterman Industries, Inc., Exeter, California [(559) 562-4000]. The
intent of the self-regulating tide gate is to allow tidal flushing of
the salt marsh during normal tidal cycles, while providing flood protection
for upland areas. Traditional flapper-style tide gates, electrically operated
sluice gates or other electrically powered devices will not be accepted.
Each self-regulating tide gate shall be installed such that the tide gate
flap floats on the surface of the rising and falling tidal water, allowing
flow through the existing culverts during normal tidal cycles. Each tide
gate shall be constructed such that the tide gate flap automatically closes
at the pre-designated high water elevation. The tide gate shall be provided
with an appropriately sized vacuum relief vent and bypass doors to relieve
air and water trapped behind the gate when the main tide gate flap closes.
During storm tide, the tide gate shall remain in the closed position after
automatically closing on the high set point until the tide recedes, at
which point the tide gate shall automatically reopen to allow free passage
of water into and out of the salt marsh area. Each gate shall be designed
with adjustable floats and float support arms to allow field adjustment
of the high water closing elevation through the maximum feasible range.
Each self-regulating tide gate shall be fabricated such that one person
can adjust the closing elevation using readily available hand tools. They
shall be designed such that one person can convert the operation mode
of the gate to that of a standard flap-type gate. The Contractor shall
provide shop drawings of the self-regulating tide gates for review and
approval prior to fabrication of the tide gates. Copies of manufacturer’s
recommended installation practices, gate adjustment procedures, and maintenance
instructions shall also be furnished with the shop drawings.
2.1.2. Materials and Finish
The Contractor shall furnish and install Waterman self-regulating
tide gates of the size indicated on the plans, at the locations indicated
on the plans. If provided, the body of the self-regulating tide gate shall
be fabricated from tubular segment(s) of aluminum conforming to ASTM B
209 alloy 6061-T6, of rectangular cross-section, with external reinforcement
of like material as required to provide structural rigidity. The bottom
interior segment of the tubular body shall be reinforced with an aluminum
wear plate conforming to ASTM B 209 alloy 6061-T6, formed to match the
bottom of the tubular body. The wear plate shall be permanently attached
to the interior main body of the tide gate structure. The rear body of
the tide gate shall comprise a mounting flange, with factory drilled bolt
holes. The tide gate shall be provided with a neoprene or urethane rubber
gasket with factory drilled holes corresponding to the rear mounting flange.
The main flap cover of the tide gate shall be fabricated of fiberglass
with a frame fabricated of aluminum channels conforming to ASTM B 209
alloy 6061-T6. The tide gate shall be provided with a reinforced neoprene
molded door gasket. The lateral bypass doors shall be hinged to open outward
from the body of the tide gate, and shall be fabricated of aluminum conforming
to ASTM B 209 alloy 6061-T6. Floats shall be fabricated of fiberglass,
except the high-water closure floats which shall consist of a polyurethane
foam ball float (foam density to be determined by manufacturer, sufficient
to ensure proper operation of the tide gate closure mechanism) enclosed
in linear low-density polyethylene or polyvinyl chloride outer casing.
The vacuum relief vent shall be fabricated from a segment of high density
polyethylene tubing of circular cross-section, or aluminum conforming
to ASTM B-209 alloy 6061-T6, and shall be securely bolted to the main
body of the tide gate structure. The tide gates shall be provided with
stainless steel mounting bolts conforming to ASTM F 503 AISI 304 and shall
be provided with a non-conductive (nylon) sleeve to prevent potential
electrical continuity. Miscellaneous hardware shall conform to ASTM F593
AISI 304 SS, ASTM F-594 AISI 304 SS, or other approved materials suitable
for use in salt water. All dissimilar metals shall be electrically isolated
from one another with non-conductive washers, gaskets, spacers, or other
suitable means to prevent the occurrence of galvanic action. Metallic
portions of the self-regulating tide gate which may be subject to corrosion
shall have a factory applied coating of primer and anti-fouling paint
which is compatible with the tide gate materials of construction. Other
components and hardware materials not specifically designated above shall
be suitable for use in salt water.
Part 3 Execution
3.1 Self-Regulating Tide Gate Installation The self-regulating tide gates
shall be securely mounted as indicated on the drawings, utilizing the
mounting flange, flange gasket and mounting hardware provided by the tide
gate manufacturer. The self-regulating tide gates shall be installed such
that the invert of the self-regulating tide gate body corresponds to the
invert shown on the plans. The self-regulating tide gates shall be installed
in strict accordance with the manufacturer’s specifications. The
Contractor shall ensure that the self-regulating tide gates are installed
plumb and level within the tolerances specified by the manufacturer, to
ensure proper operation of the tide gates. The Contractor shall take special
care to ensure that dissimilar metals of the tide gate, the mounting hardware
and the concrete reinforcing rods are isolated from one another using
non-conductive sleeves, washers, gaskets, spacers, or other devices as
prescribed by the manufacturer. The Contractor shall provide an authorized
representative of the manufacturer on-site to adjust and fine-tune operation
of the self-regulating tide gates. The manufacturer’s representative
shall observe and adjust the tide gate through several tidal cycles (no
less that three cycles, unless otherwise directed by the Engineer) to
ensure proper operation of the self-regulating tide gate. The tide gate
manufacturer’s representative shall certify that the final gate installation
is correct and in accordance with the manufacturer’s requirements.
|
