§ 5-299. Seawalls and bulkheads.

(a)

All seawalls, bulkheads, and retaining walls constructed or altered, projected or prolonged, on or adjacent to waters subject to tidal action shall be concrete or aluminum construction in compliance with the following standards:

(1)

Concrete seawalls.

a.

All seawalls, retaining walls, and bulkheads may be of concrete using the tongue and groove, or other approved method of sheet pile type construction, with poured in place concrete cap and tie-back anchors. The reinforced concrete shall have a minimum test strength of three thousand five hundred (3,500) psi at twenty-eight (28) days.

b.

The concrete piling sheet shall have a minimum thickness of and contain vertical steel reinforcement. Each slab shall have two (2) No. 4 steel hairpins extending into the cap a minimum of three (3) inches.

c.

The poured-in-place cap shall not be less than nine and one-half (9½) inches in thickness nor less than sixteen (16) inches in width.

d.

The cap shall contain continuous horizontal steel reinforcement equivalent in cross-sectional area to four (4) No. 4 deformed reinforcing bars. All splices shall be lapped not less than forty (40) bar diameters; provided however, that the steel shall not be continuous through expansion joints. Expansion joints shall normally be provided every forty (40) feet.

e.

All tie-back rods shall be steel and have a cross-sectional area equal to, or greater than, a No. 9 reinforcing bar. All such rods shall be spaced not more than ten (10) feet on center and shall be encased in concrete with a minimum coverage of three (3) inches. The length of all tie rods shall be equal to or greater than two (2) times the height of the seawall slab projecting above the ground line. In no case shall the tie rods be of shorter length than sixteen (16) feet (unless a continuous deadman, with prints sealed by an engineer certified in the State of Florida, is approved by the building director and the city manager, only in the case of extreme hardship on the property owner).

f.

Tie-back anchors shall be poured-in-place concrete containing not less than seven and five tenths (7.5) cubic feet of concrete, and have not less than seven and five tenths (7.5) square feet of vertical surface, perpendicular to the alignment of the tie rod. Each anchor shall contain horizontal steel reinforcement equivalent in cross-sectional area to four (4) No. 4 deformed reinforcing bars and be provided with No. 2 steel stirrups, twelve (12) inches on center.

g.

The penetration of each seawall slab into firm ground shall be equal to or greater than one-half the total length of the slab. In no case shall the seawall slab be of shorter length than ten (10) feet.

(2)

Aluminum seawalls.

a.

Aluminum seawalls shall not have an exposed height of more than five (5) feet.

b.

Sheet piles [shall be] fabricated from aluminum alloy 5052-H141, conforming to ASTM designation B209 alloy 5052 for chemical composition; also having a minimum thickness of 0.125 inch and minimum tensile strength of 35.500 psi. Corrugations shall have nominal 9 inch pitch and nominal 2.5 inch depth. The penetration into firm ground shall be equal to 0.67 times the height of the wall above the ground line, or 0.4 times the total length of the sheet, whichever is greater. In no case shall the total sheet be less than 8 feet in length. Where sheet lengths required are more than 8.5 feet, and when soil conditions, surcharges and other factors exceed the scope of these standard specifications, a special design shall be submitted, signed and sealed by a Florida registered engineer.

c.

Cap and joint extrusion [shall be] fabricated from aluminum alloy 6063-T6, conforming to ASTM designation B221 alloy 6063 for chemical composition; also having a minimum thickness of 0.15 inch and a minimum tensile strength of 30,000 psi. The cap shall be a minimum of 6 inches wide and 5.75 inches deep.

d.

Anchor rods and deadman anchor plates [shall be] fabricated from aluminum alloy 6061-T6, conforming to ASTM designation B221 alloy 6061 for chemical composition; also having a minimum thickness of anchor plates 0.10 inch and minimum tensile strength of 38,000 psi. The anchor plates shall be not less than 1.5 by 2.5 feet, equipped with a 3 inch by 2.25 inch backing channel 0.25 inches thick and 1.5 feet long. Anchor plates shall be placed with the top at least two (2) feet below the elevation of the wall cap. The anchor rods shall be not less than 0.75 inch in diameter and equipped with a rod sleeve, nut and curved washer where it passes through the cap. Anchor rods shall be installed continuously along the wall at a maximum spacing of 6.5 feet. The normal length shall be 12 feet. One tieback system shall be constructed 6.5 feet on center. All tie rods shall be pretensioned after placement of backfill around anchor plates, but before final backfill of sheeting. Such pre-tensioning shall not tend to move the sheets or anchors. Tie rods shall be placed in the coping so that the anchor pull brings the coping in direct contact with a bay side corrugation of the wall sheeting.

e.

Surcharge from fill behind the wall shall be controlled by limiting the slope to a maximum of ten (10) degrees, and prohibiting objects other than landscaping to be located closer than five (5) feet from the wall cap. The minimum standards described above assume sandy soil with an angle of repose of thirty (30) degrees for soil against the wall. They also assume that the environment is not highly alkaline or acidic. If conditions require a design in excess of limitations specified in this subsection, the wall shall be of concrete construction in accordance with subsection [5-299(a)(1)].

f.

If the aluminum material is brought in contact with mortar or concrete, a coating of clear methacrylate lacquer shall be applied to an aluminum contact surface to prevent corrosion. There shall be no dissimilar metals or metal systems bonded to the wall.

(Ord. No. 86-7, § 1(5-299), 4-8-86)