16-25 covered by this provision, including, b ut not limited to, furnishing all materials, labor, 1
equipment and incidentals necessary to install the wattle barrier. 2 Matting for Erosion Control will be measured and paid for in accordance with Article 1631- 4. 3 Flocculant will be measured and paid for by the actual weight in pounds of flocculant applied 4 to the wattles. Such price and payment will be full compensation for all work covered by this 5 section, including, but not limited to, furnishing all materials, labor, equipment and 6 incidentals necessary to apply the Flocculant. 7 Silt Excavation will be measured and paid for in accordance with Article 1630- 3. 8 Payment will be made under: 9 Pay Item Pay Unit _____ Wattle Check Linear Foot _____ Wattle Barrier Linear Foot Flocculant Pound SECTION 1644 10 SKIMMER BASINS 11 1644 -1 DESCRIPTION 12 Provide a skimmer basin to remove sediment from construction site runoff at locations shown 13 in the erosion control plans. Work includes constructing sediment basin, installation of 14 temporary slope drain pipe and coir fiber baffles, furnishing, installation and cleanout of 15 skimmer, providing and placing stone pad on bottom of basin underneath skimmer device, 16 providing and pl acing a geotextile spillway liner, providing coir fiber mat stabilization for the 17 skimmer outlet, disposing of excess materials, removing temporary slope drain, coir fiber 18 baffles, geotextile liner and skimmer device, backfilling basin area with suitable m aterial and 19 providing proper drainage when basin area is abandoned. 20 1644 -2 MATERIALS 21 Refer to Division 10. 22 Item Section Anchors 1629-2 Coir Fiber Baffle 1640 Coir Fiber Mat 1060 -14 Fertilizer for Temporary Seeding 1060 -2 Geotextile for Soil Stabilization, Type 4 1056 Matting for Erosion Control 1060 -8 Seeding and Mulching 1060 -4 Seed for Temporary Seeding 1060 -4 Staples 1060 -8(D) Temporary Slope Drain 1622 -2 Provide appropriately sized and approved skimmer device. 23 Provide Schedule 40 PVC pipe with a length of 6 feet to attach to the skimmer and the 24 coupling connection to serve as the arm pipe. For skimmer sizes of 2.5 inches and smaller, 25 the arm pipe diameter shall be 1.5 inches. For skimmer sizes of 3 in ches and larger, refer to 26 manufacturer recommendation. 27 Provide 4 inch diameter Schedule 40 PVC pipe to attach to coupling connection of skimmer 28 to serve as the barrel pipe through the earthen dam. 29 The geotextile for the spillway liner shall meet Table 1644 -1 physical properties for low 30 permeability, woven polypropylene geotextiles: 31
16-26 Table 1644 -1
GEOTEXTILE PROPERTIES – SPILLWAY LINER Property Minimum Requirement Test Method Tensile Strength 315 lb s. ASTM D 4632 Tensile Elongation 15.0% (Maximum Requirement) ASTM D 4632 Trapezoidal Tear 120 lb s. ASTM D 4533 CBR Puncture 900 lb s. ASTM D 6241 UV Resistance 70.0% (% retained at 500 hr) ASTM D4355 Apparent Opening Size (AOS) 40 US Std. Sieve ASTM D4 751 Permittivity 0.05 sec -1 ASTM D 4491 Water Flow Rate 4 gal/min /sf ASTM D4 491 1644 -3 CONSTRUCTION METHODS 1
A.Skimmer Basin with Baffles and Lower Basin of Tiered Skimmer Basin with Baffles 2 Construct basin according to the plans with basin surface free of obstructions, debris, and 3 pockets of low -density material. Construct the coir fiber baffles in accordance with 4 Section 1640 and as directed by the Engineer. 5 Install skimmer device according to manufacturer recommendations. Install 4 inch 6 Schedule 40 PVC pipe into dam on the lower side of basin 1 feet from the bottom of the 7 basin and extend the pipe so the basin will drain. Attach a 6 f oot arm pipe to the coupling 8 connection and skimmer according to manufacturer recommendations. The coupling 9 shall be rig id and non- buoyant and not exceed 12 inches in length. Attach a retrieval 10 rope to the skimmer in a manner that will not interfere with the skimmer’s function, and 11 the other end to a wooden stake or metal post on the berm of the basin. Construct a stone 12 pad of Class B stone directly underneath the skimmer device at bottom of basin according 13 to the plans. 14 Line primary spillway with low permeability polypropylene geotextile unrolled in the 15 direction of flow and lay smoothly but loosely on soil surface without creases. Bury 16 edges of geotextile in a trench at least 5 inches deep and tamp firmly. If geotextile for the 17 primary spillway is not one continuous piece of material, make horizontal overlaps a 18 minimum of 18 inches with upstream geotextile overlapping the downstream geotextile. 19 Place staples along outer edges and throughout the geotextile a maximum of 3 feet. 20 horizontally and vertically. Geotextile shall be placed to the bottom and across the entire 21 width of the basin. Place sealant inside basin around barrel pipe on top of geotextile with 22 a minimum width of 6 inches. 23 At the skimmer outlet, install coir fiber matting in accordance with the plans and Section 24 1629. 25 All bare side slope sections of the skimmer basin shall be seeded with a temporary or 26 perm anent seed mix as directed and in accordance with Articles 1620 -3, 1620 -4, 1620 -5, 27 1660 -4, 1660- 5 and 1660 -7. Straw or excelsior matting shall be installed on all bare side 28 slope sections immediately upon the completion of seeding and in accordance with 29
Article 1631 — 3. 30
B.Upper Basin(s) of Tiered Skimmer Basin with Baffles 31 Construct upper basins according to the plans with basin surface free of obstructions, 32 debris, and pockets of low -density material. Construct the coir fiber baffles in 33 accordance with Sect ion 1640 and as directed by the Engineer. Multiple upper basins 34 may be required based on site conditions and as directed by the Engineer. 35 Install skimmer device according to manufacturer recommendations. Install 4 inch 36 Schedule 40 PVC pipe into dam on the lower side of basin 1 feet from the bottom of the 37 basin and extend the pipe to an energy dissipator pad on the bottom of the lower basin. 38
16-27 Attach a 6 feet arm pipe to the coupling connection and skimmer according to 1
manufacturer recommendations. The cou pling shall be rigid and non- buoyant and not 2 exceed 12 inches in length. Attach a retrieval rope to the skimmer in a manner that will 3 not interfere with the skimmer’s function, and the other end to a wooden stake or metal 4 post on the berm of the basin. C onstruct a stone pad of Class B stone directly underneath 5 the skimmer device at bottom of basin according to the plans. 6 Line primary spillway with low permeability polypropylene geotextile unrolled in the 7 direction of flow and lay smoothly but loosely on s oil surface without creases. Bury 8 edges of geotextile in a trench at least 5 inches deep and tamp firmly. If geotextile for the 9 primary spillway is not one continuous piece of material, make horizontal overlaps a 10 minimum of 18 inches with upstream geotextile overlapping the downstream geotextile. 11 Place staples along outer edges and throughout the geotextile a maximum of 3 feet 12 horizontally and vertically. Geotextile shall be placed to the bottom and across the entire 13 width of the basin. Place sealant i nside basin around barrel pipe on top of geotextile with 14 a minimum width of 6 inches. 15 All bare side slope sections of the skimmer basin shall be seeded with a temporary or 16 permanent seed mix as directed and in accordance with Articles 1620 -3, 1620 -4, 1620 -5, 17 1660 -4, 1660- 5 and 1660 -7. Straw or excelsior matting shall be installed on all bare side 18 slope sections immediately upon the completion of seeding and in accordance with 19
Article 1631 — 3. 20
1644 -4 MAINTENANCE AND REMOVAL 21 Place a marker in the basin indicating the 50% volume level. Clean out skimmer basin in 22 accordance with Section 1630. 23 Clean out skimmer device when it becomes clogged with sediment and/or debris and is unable 24 to float at the top of water in skimmer basin. Take appropriate measures to avoid ice 25 accumulation in the skimmer device. 26 Remove skimmer basins as the project nears completion or as directed by the Engineer. 27 Prepare a seed bed and seed and mulch the ar ea in accordance with Section 1660 after 28 removal of the skimmer basin. 29 1644 -5 MEASUREMENT AND PAYMENT 30 Silt Excavation will be measured and paid for in accordance with Article 1 630-4, as calculated 31 from the typical section throughout the length of the basin as shown on the plans. 32 Geotextile for Soil Stabilization will be measured and paid for in accordance with Article 270- 33
4.34 Low Permeability Geotextile will be measured and paid for as the actual number of square 35 yards measured along the surface of the spillway over which the geotextile is installed and 36 accepted. 37 Coir Fiber Baffles will be measured and paid for in accordance with Article 1640 -4. 38 __" Skimmer will be measured in uni ts of each. __" Skimmer will be measured and paid for 39 as the maximum number of each size skimmer acceptably installed and in use at any one time 40 during the life of the project. Barrel and arm pipe, cleanout, relocation and reinstallation of 41 __" Skimmer is considered incidental to the measurement of the quantity of __" Skimmer and 42 no separate payment will be made. No separate payment shall be made if __" Skimmer , barrel 43 and/or arm pipe(s) are damaged by ice accumulation. 44 Coir Fiber Mat will be measured and paid for in accordance with Article 1629 -4. 45 Temporary Slope Drain will be measured and paid for in accordance with Article 1622 -4. 46
Source: North Carolina Standard Specifications for Roads and Structures, 2024 Edition. Pages 775–777 of 857.