359 ALASKA 2020 SECTION 633
633-1.01 DESCRIPTION . Furnish, install, maintain, and remove temporary silt fence as shown on
the Plans or as directed.
633-2.01 MATERIALS. Use materials that conform to the following:
Geotextile Subsection 729- 2.01 Silt Fence Subsection 729- 2.04 Posts Wood 1.5- inch x 1.5- inch x 36- inch min., steel, or approved synthetic material. Prefabricated Silt Fence Meet the Plans and Section 633 requirements. Attachment Devices Staples; wire; self -locking nylon, plastic, wire ties; or other approved means to attach fabric to posts. Support Mesh between Posts 14-gage welded wire fencing, metal chain- link fabric, or geosynthetic mesh with equivalent strength. Use maximum mesh spacing of 6 inches. Use height shown on the Plans, or specified in the Bid Schedule.
633-3.01 CONSTRUCTIO N REQUIREMENTS. Install silt fence according to Plans. Use
Trenchless Detai l when installing silt fence over permanently frozen ground. Drill holes for support posts, if required. When joining to another roll, place both end posts together and wrap them with silt fence by turning them one full rotation. Drive the wrapped posts .
633-3.02 MAINTENANCE . Maintain the integrity of the fence to contain sediment in runoff until
final stabilization.
633-3.03 REMOVAL. After disturbed area has been accepted as permanently stabilized or when
sediment protection is no longer needed, remov e silt fence.
633-4.01 METHOD OF M EASUREMENT. See Section 109. Measure silt fence by the length of
fence installed. No allowance will be made for overlap, whether at joints or patches.
633-5.01 BASIS OF PA YMENT. The contract price includes installation, m aintenance, removal
and disposal of the silt fence. Payment will be made under: PAY ITEM Item Number Item Description Unit 633.0001.____ Silt Fence LF 633.0002.____ Support Mesh Reinforced Silt Fence LF 360 ALASKA 2020 SECTION 634 GEO GRID FOR EMBANKMENT A ND ROADWAY STABILIZATION AND RE INFORCEM ENT
634-1.01 DESCRIPTION . Furnish and install ge ogrid material as show n on the Pla ns.
634-2.01 MATERIALS. Use materials that conform to the following:
Geog rid Subs ection 729-2.04
634-3.01 C Onstructio N Requirements.
1.Surface Preparation.
a.Soft Ground (C BR ≤3). Prep are surf ace by removal of stumps, brush, boulders, and sharp objects. Fill holes and ruts over 3 inches deep, with material shown on the Plans or as approved by the Engineer.
b.Firm Ground (C BR >3). Compa ct and finish s ubgrade or subb ase pri or to placement of the geog rid.
2.Geogrid Placement. Unroll geo grid di rectly onto t he prep ared ground surface in the direction of advancing construction, parallel to the centerline of the roadway or according to the Plans. Do not drag the geogrid across the subgrade. Install the geogrid in the longest continuous practical length, free from folds, creases or wrinkles. Hold the geogrid in place with pins, staples, sandbags or piles of granular material. Do not expose geogrids to sunlight for longer than 14 days after removal of protective covering.
a.Soft Groun d (CBR ≤3). Overlap geogrid panels a minimum of 24 inches at all joints with the upper geogrid in the dir ection that fill will be placed. Tie panel s togethe r securely with cable ti es or ho g rin gs at 20 foot intervals, or according to the manufacturer's recommendations.
b.Firm Ground (CBR >3). Overl ap geogrid pan els a minimum of 12 inches at all joints in the direction that fill will be pl aced. Tie panels toget her securely with cable t ies or hog rings at 20 foot intervals and hand- tension geogr id and stake to the groun d at the edge s, overlap s, and in the center of each roll, at 30 foot interval s or as shown on the Plans . Place the beginning of each new roll beneath the end of the previous roll to prevent the advancing fill from lifting the geogrid. Stagger end overlaps at least 10 feet from other end overlaps in adjacent rolls.
3.Placement of Cover Material. Do not operate equi pment directly on the unprotect ed geogrid. Spre ad fill material in the dir ection of the fabric overlap. Com pact using a smooth drum roll er. Do not allow construction eq uipment to make sud den stops, star ts, or tur ns on the cov er material.
a.Very Soft Ground (CBR < 1). End-dump material onto previously placed material and spread over the geogrid with a low gr ound pressure do zer to the dept h permitted. Maintain a minimum depth of 12 inches of cover material at all times between the geogrid and the wheels or tracks of the construction equipment unless otherwise shown on the Plans. Do not dump material directly onto the geogrid. To prevent a mud wave, end-dump fill along the edges of the geogrid to form toe berms or access roads that extend one to two panel widths ahead of the remainder of the embankment fill placement. After constructing the two berms, spread fill in the area between the toe berms by placing material parallel to the alignment and symmetrical from the toe berms inward toward the center to maintain a U -shaped leading edge (i.e., concave outward) to conta in the mud wave. Limit height of dumped piles above the geogrid to avoid local bearing failure. Traffic on the first lift should be parallel to the embankment alignment. Do not allow
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 387–387 of 584.