READ AND REMOVE THIS PAGE BEFORE PLACING
THE SPECIFICATION SECTION IN THE CONTRACT

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DIVISION 2:  SITE CONSTRUCTION

SECTION 02373 ‑ GABIONS

Use:	Construction of gabion structures.

NOTES TO SPECIFIER:

	A.	Options within paragraphs are identified by enclosure in brackets; blank spaces enclosed by brackets [_____] provide for information to be inserted, as appropriate, to individual projects.

	B.	TO AVOID CONFLICTING REQUIREMENTS AND COSTLY MISTAKES, the specifier must edit (delete, substitute or add to the text).  The remaining paragraphs must be renumbered.

	C.	DELETE FOR FINAL COPY: Notes to the Specifier, located between lines of asterisks; all [brackets], underlining, boldface, and italics, within the paragraphs; and this page.  (Open Reveal Codes [alt F3] to do this accurately.)

	D.	To Edit “(Footer B)”: (Corel 8).  ENTIRE FOOTER SHOULD BE BOLDED.  Click in the footer and delete the “Project Name (ftr B)” text and replace it with the Name of the Project (upper and lower case).  Replace date with current MM/YY (WITHOUT BRACKETS).

	E.	The Guide Specifications are intended to be continuously reviewed and revised.  User’s technical comments are appreciated.  Also, other related or similar specification that are written “from scratch” that could benefit others, or other questions can be sent to NSTC A/E Group, ST 110, or call (303) 987-6868.

DRAWING DATA REQUIRED:

REVISIONS OF THIS SECTION:
CSI format, editorial changes:  12/01
Metric:  
Technical Update:  10/96

SECTION 02373

GABIONS

PART 1:  GENERAL

1.1	SUMMARY

A.	Section Includes:  [Furnishing and installing] [Installing with Government‑furnished property] [Installing with Contractor‑furnished and Government‑furnished property] [gabion] [revet mattress] structures [including filter cloth].

1.2	SUBMITTALS

A.	General:  Submittals shall be according to [Section 01009 - General Information Requirements.]  [Section 01330 - Submittal Procedures.]  [Section 01331 - Certificates.]

B.	Certificates of Conformance:  Submit [____] copies of written certification from the gabion manufacturer [and from the geotextile manufacturer] that the requirements of ASTM A 641 and this specification section have been met.

C.	Shop Drawings:  Submit [____] copies of shop [and erection] drawings for the gabions to be used on this project.  [A bill of materials shall be furnished with the shop drawings.]  Include a schedule showing the location of [_________________________________.]  Drawings shall be [same] [larger] scale as the full-size Contract Drawings.

D.	Test Data:  Submit [____] copies of test data for the geotextile to be used on this project.  [Testing shall have been performed be according to ASTM D 4759 by an independent testing laboratory within [____ years] [____ months] of submitting the report for approval.]

1.3	DELIVERY, STORAGE, AND HANDLING

A.	Handling
1.	Gabion Baskets:  Follow the manufacturer's instructions for handling premanufactured gabion cages.
2.	Geotextile:  Keep the geotextile wrapped, dry, and protected from direct sunlight during shipping and storage.  Each roll shall be labeled according to ASTM D 4873.

PART 2:  PRODUCTS

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GABIONS ARE CURRENTLY AVAILABLE FROM TWO KNOWN SOURCES:  MACCAFERRI GABIONS WEST COAST INC., 3650 SEAPORT BLVD., W. SACRAMENTO, CA  95691; TELEPHONE (916) 371-5805 AND TERRA AQUA, INC., P.O. BOX 7546, RENO, NV, TELEPHONE (702) 329‑6262.
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2.1	MATERIALS

A.	Gabion Baskets:  ASTM A 641, galvanized steel wire.  The baskets shall be fabricated at the jobsite.  Gabions shall be fabricated so that the sides, ends, lids, and diaphragms can be assembled into rectangular baskets of the sizes specified and as shown on the drawings.  Minimum wire diameters are 3.03.0 mm (11-gauge) for mesh wire; 3.8 mm (9-gauge)  for selvedge or perimeter wire.  Zinc galvanized coating shall be a minimum of 270 g/m2 (0.80 oz/ft2), and the mesh pattern shall be hexagonal in shape and uniform in size not exceeding 80 mm x 100 mm (3‑1/2 x 4‑1/2 inches).  They shall consist of a uniform wire mesh woven in a triple twist pattern, fabricated as to be non‑ravelling.  Gabions shall be supplied in various lengths and heights.  The lengths shall be multiples (2, 3, 4) of the horizontal width.  The horizontal width shall be not less than 900 mm (36 inches).  Gabion dimensions are subject to a tolerance limit of + 5% of the stated sizes.

B.	Revet Mattress:  ASTM A 641, uniform hexagonal wire mesh woven in a triple twist pattern with openings 60 mm x 80 mm (2‑1/2 x 3‑1/2 inches), fabricated as to be non‑ravelling.  The perimeter edges of the mesh shall be woven around a reinforced wire to prevent slippage, and the edges of the mesh shall be securely selvedged.  Covers shall be reinforced by the heavier wire.  Minimum wire diameters are 2.2 mm (13-1/2-gauge) for mesh wire; 2.7 mm (12-gauge) for selvedges and corner wire; 3.0 mm (11-gauge) for selvedge rod wire.  Zinc galvanized coating shall be a minimum of 220 g/m2 (0.70 oz/ft2)for 2.2 mm (13-1/2 gauge) wire, 240 g/m2 for 2.7 mm (12-gauge) and 3.0 mm (11-gauge) wire.  

C.	Tie and Lacing Wire: 2.2 mm (13-1/2-gauge), with a minimum zinc coating of 220 g/m2 (0.65 oz/ft2).

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USE OF HOOKING RINGS IS A DESIGN DECISION.  IF NOT ALLOWED ON THE JOB, DELETE PARAGRAPH BELOW, AND LATER REFERENCE TO HOOKING RINGS IN PART 3.
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D.	Hooking Rings (Hog Rings): 3.0 mm (11-gauge), stainless steel or galvanized (minimum weight of zinc coating shall be 240 g/m2 (0.80 oz/ft2).

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PROVIDE REQUIREMENT FOR APPARENT OPENING SIZE (AOS) DEPENDING UPON SOIL CONDITIONS ON THE JOB.  THE REQUIREMENTS MAY RANGE FROM U.S. SIEVE NO. 70 (0.18 MM) TO U.S. SIEVE NO. 30 (0.6 MM).  PROVIDE REQUIREMENT FOR PERMITIVITY DEPENDING ON SOIL CONDITION AND APPLICATION.  PERMITIVITY OF 0.5 IS CONSERVATIVE FOR MOST GABION APPLICATIONS.
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E.	Geotextile:  A pervious sheet of nonwoven or woven polypropylene monofilament yarns with an average thickness not less than 16 mils. The geotextile shall be calendared so that the filaments retain their relative position with respect to each other.  Sheets sewn together shall be sewn with polypropylene thread.  Field fabric sections or sheets shall be 12‑ft minimum width.  Fabric shall be free of tears or defects.  The geotextile shall meet the requirements listed in the following table:

        Test        	   Standard			Minimum Requirement
Grab Strength, Breaking Load, and Elongation	ASTM D 4632	[400] N (190 lb) weakest direction; [15]% elongation	
Seam Strength	ASTM D 4632	[355] N ((80] lb)	
Bursting Strength	ASTM D 3786	[1000] kPa ([145] psi)	
Trapezoid Tear 	ASTM D 4533	[130] N ([30] lb)	
Puncture Strength	ASTM D 4833	[175] N ([40] lb)	
Apparent Opening	ASTM D 4751	[212 Fm-600 Fm] (U.S. Sieve No. [30/70])	
Permittivity	ASTM D 4491	[0.5] sec-1	

Note:  Effects of alkalies, acids, and temperature to be less than 10% decrease in strength of breaking load and elongation tests.

F.	Geotextile Staples:  Shall be run through grommets in the fabric or through washers with 40 mm (1-1/2 inches) outside diameter.  The securing staples shall be 4.7 mm (3/16-inch) diameter (min.) steel, 550 mm (22 inches) (min.) in length.  One end shall be pointed and other end shall have a head that is larger than the grommet or inside diameter of the washer and will securely hold the fabric in place.  Diametrically opposed "ears" or similar deformations shall be stamped along the length of the shaft that will provide pull-out resistance.

An alternate style for soft ground shall consist of a 30-inch length of 9-ga galvanized wire bent in a "U" shape (3 inches wide), that shall be pushed into the ground through the filter cloth.  Where this staple cannot be pushed into the ground it full length, the staple and washer assembly described above shall be used.

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STRENGTH REQUIREMENTS ARE FOR A "PROTECTED" APPLICATION, SUCH AS A PREPARED BASE AND CAREFULLY PLACED GABION COVER.  REQUIREMENTS SHOULD BE INCREASED FOR AN "UNPROTECTED" APPLICATION, SUCH AS RIPRAP WITHOUT A FILTER LAYER OR WITH AN UNPREPARED BASE.

CHANGE ROCK FILLER GRADATION REQUIREMENTS TO MEET LOCAL SITUATION AS REQUIRED.
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G.	Rock Filler:  Rock approved by the Contracting Officer, available [from commercial sources] [onsite].  Rock shall be 250 mm (10 inches) or smaller in its largest dimension, and shall conform to the following gradation requirements:

	     Gradation mm (inches), least dimension)          Percentage Volume

	           100    (4)		  						0 ‑ 5%
	           100-125(4 ‑ 5)	 						40 ‑ 80%
	           125-175(5 ‑ 7)	 						10 ‑ 50%
	           175-250(7 ‑ 10)	  						0 ‑ 10%

1.	Physical Characteristics:  Stone shall be hard, durable, and resistant to weathering and to water action.  Neither breadth nor thickness of a single stone should be less than one‑third its length.  Stone shall be free from overburden, spoil, shale, and organic material.
2.	Minimum Density: AASHTO T 185, 2480 kg/m3 (155 pcf); minimum loose weight 1440 kg/m3 (90 pcf). 
3.	Resistance to Disintegration
a.	Sulfate Soundness Test:  Stones shall have a loss not exceeding 10% with the sulfate test after 5 cycles as determined by AASHTO T 104
b.	Freezing and Thawing Test:  AASHTO T 103; the stone shall not have a loss exceeding 10% after 12 cycles of freezing and thawing.

PART 3:  EXECUTION

3.1  PREPARATION

A.	Clearing:  [Section 02231 ‑ Clearing and Grubbing.]  [Clearing and grubbing is not required.]

B.	Excavation and Backfill:  [Perform excavation to the lines and grades shown on the drawings, unless staked otherwise.  Excavation and backfill work shall not be done in frozen materials.  Sources of suitable backfill material shall be obtained at the site as approved by the Contracting Officer.  The material shall be free of stones larger than 40 mm (1‑1/2 inches) in diameter, sticks, and other deleterious material; and shall be the best clay‑bearing material available.  Backfill shall not be placed against completed gabion structures until approval is received from the Contracting Officer.]  [Section 02315 - Excavation and Fill.]  [Section 02322 - Excavation and Fill for Structures.]

3.2  INSTALLATION

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DELETE LAST SENTENCE IF HOOKING (HOG) RINGS WILL NOT BE ALLOWED ON THE JOB.
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A.	Assembly:  Bind together unbound vertical edges with a continuous piece of connecting wire laced around the vertical edges (lacing shall include the heavy perimeter wires), as shown on the drawings.  Anchor lacing and lace adjacent gabions along the perimeter of contact surfaces as shown on the drawings.  [Hooking (hog) rings may be used at 100 mm (4-inch) spacing when approved by the Contracting Officer.]  [However, there use is restricted to basket assembly only.]

B.	Gabions  
1.	Tiers:  Set tiers of assembled gabion units at locations and to lines and grades shown on the drawings unless staked otherwise.  Each tier shall be set in place, laced, filled with rock filler, and approved by the Contracting Officer before lids are laced down and successive tiers are placed.  
2.	Diaphragms:  Where the length of the gabion exceeds its horizontal width, the gabion shall be equally divided by diaphragms, of the same mesh and gauge as the body of the gabions, into cells the length of which does not exceed the horizontal width.  Diaphragms shall be tied on the vertical sides.  Use lacing wire to join adjacent baskets together.
3.	Interconnections:  Interconnect gabions and check alignment carefully before placing rock filler.  
4.	Tie Wires:  Vertical gabion cells that will remain exposed after completion of backfilling operations shall be furnished with internal tie wires perpendicular to the exposed faces, as shown on the drawings.  Partially fill the gabion basket to the level where the tie wires shall be installed, install the tie wires equally spaced according to basket dimensions, and carefully continue filling to avoid dislodging, breaking, or bending the tie wires.  
5.	Basket Completion:  When filling is complete, bend lids over to close the basket, and secure lid firmly by lacing shut with connecting wires.  The completed gabion or revet mattress structure shall be within ± 75 (3 inches) of the top elevations shown on the drawings.  The surface alignment, including bulges, shall not vary more than 75 mm (3 inches).

C.	Geotextile  
1.	Placement:  The geotextile shall be placed so as to form a filter membrane between soil and gabion or revet mattress interfaces or as shown on the drawings.  The surface shall be prepared to a smooth condition free of obstructions, depressions, and debris.  The cloth shall not be laid in a stretched condition, but shall be laid loosely with the long dimension perpendicular to the channel centerline.  The panels shall be overlapped a minimum of 300 mm (12 inches) with securing pins inserted through both layers at not greater than 2000 mm (6‑feet) intervals along a line through the approximate midpoint of the overlap.  The cloth shall be placed so that the upstream panel will overlap the downstream panel. 
2.	Securing Staples:  Shall be placed along a line approximately 50 mm (2 inches) in from the edge of the outer limits of the completed filter cloth area at intervals not greater than 2000 mm (6 feet) unless otherwise shown on the drawings.  Additional staples shall be installed as necessary to prevent slippage of the filter cloth, regardless of location.  Each securing staple shall be inserted through the cloth until the washer or grommet bears against the cloth and secures it firmly to the foundation.  Overlaps on vertical faces shall be staggered a minimum distance of 1500 mm (5 feet) between adjacent sheets or sections.  The alternate style "U‑shaped" staple shall not be used where it cannot be pushed into the ground its full length. 

D.	Rock Filler Placement:  Do not begin placing of rock filler until installation of the gabion baskets has been inspected and approved by the Contracting Officer.  Fill gabion baskets with the specified rock material; place rock filler carefully to avoid dislodging internal tie wires, creating voids, or causing bulging or crushing of the basket fabric.  Rock shall not be dropped from a height greater than 600 mm (2 feet).

PART 4:  MEASUREMENT AND PAYMENT

4.1  METHOD OF MEASUREMENT

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WHEN A "LUMP SUM" CONTRACT IS USED, DELETE THE TITLE PART 4:  MEASUREMENT AND PAYMENT, AND BOTH ARTICLES FROM THIS SECTION.  MEASUREMENT AND PAYMENT WILL BE ADDRESSED IN PART 4 OF SECTION 01009 - GENERAL INFORMATION AND REQUIREMENTS OR SECTION 01010 -SUMMARY OF WORK.

WHEN NOT A "LUMP SUM" CONTRACT, SELECT APPLICABLE PHRASES; USE THE "NO MEASUREMENT" PHRASE WHEN NONE OF THE PAY ITEMS IN THIS SECTION ARE INCLUDED IN THE BID SCHEDULE.
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A.	Units:  The assembly and installation of [gabions] [revet mattresses] will [not be measured for payment.]  [be measured and paid for] [on a lump sum basis.] [by the cubic [meter] [yard].]  [Clearing, grubbing, excavation, backfill, and installation of filter cloth required to place gabion structures is considered incidental to the work of this section, and will not be measured and paid for separately.]  [Filter cloth will be measured and paid for [by the square [meter] [foot] [by the cubic [meter] [foot] installed.]  [Clearing and grubbing required for placement of gabions will be measured and paid for under Section 02231 ‑ Clearing and Grubbing.]  [Excavation and backfill work required for placement of gabions will be measured and paid for under Section 02315 - Excavation and Fill.]  [Excavation and backfill work required for placement of gabions will be measured and paid for under Section 02322 ‑ Excavation and Fill for Structures.]
4.2  BASIS OF PAYMENT

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WHEN NOT A "LUMP SUM" CONTRACT AND PAYMENT IS TO BE MADE UNDER THIS SECTION, SELECT APPLICABLE PAY ITEMS.  DO NOT CHANGE PAY ITEM NUMBER.  WHEN MORE THAN ONE DIAMETER OR GAUGE IS SPECIFIED FOR ANY PAY ITEM, LETTER SUFFIXES WILL BE ADDED AFTER THE PARENTHESIS OF THE ITEM NUMBER.  WHEN GOVERNMENT-FURNISHED PROPERTY IS SPECIFIED FOR PAY ITEMS, THE LETTER SUFFIX GF WILL BE ADDED AFTER THE PARENTHESIS OF THE ITEM NUMBER.
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A.	Payment:  [No direct payment for the work described under this section will be made.  Consideration for this item shall be included in the bid price for other items of the Contract.]  [Prices and payment will be full compensation for the work described in this section.  Payment will be made under:]

Pay Item                                   				Pay Unit
02373(01) Gabions	Lump Sum
02373(02) Gabions	Each
02373(02) Gabions 	Cubic Meter
02373(03) Gabions	Cubic Yard
02373(10) Revet Mattresses	Lump Sum
02373(11) Revet Mattresses	Each
02373(12) Revet Mattresses	Cubic Meter
02373(12) Revet Mattress	Cubic Yard
02373(20) Filter Cloth	Lump Sum
02373(21) Filter Cloth	Square Meter
02373(21) Filter Cloth	Square Foot

END OF SECTION

DATA WORKSHEET
for
SECTION 02373 ‑ GABIONS

Gabion dimensions:

		Standard Gabion Table

  Letter Code	  Length	  Width	  Height	
  A	2 m (6 ft)	1 m (3 ft)	1 m (3 ft)	
  B	3 m (9 ft)	1 m (3 ft)	1 m (3 ft)	
  C	4 m (12 ft)	1 m (3 ft)	1 m (3 ft)	
  D	2 m (6 ft)	1 m (3 ft)	0.5 m (1 ft 6 in)	
  E	3 m (9 ft)	1 m (3 ft)	0.5 m (1 ft 6 in)	
  F	4 m (12 ft)	1 m (3 ft)	0.5 m (1 ft 6 in)	
  G	2 m (6 ft)	1 m (3 ft)	0.3 m (1 ft)	
  H	3 m (9 ft)	1 m (3 ft)	0.3 m (1 ft)	
  I	4 m (12 ft)	1 m (3 ft)	0.3 m (1 ft)	

The metric series gabions converted to English units will not be the rounded English units as shown above for the U.S. series.

Filter cloth size:

Selected backfill:

Riprap:

Revet mattress dimensions:

Note: When several gabion projects are included, the tabular format may be more appropriate.  (11/05/96)