Appendix H. DRAINAGE SYSTEM
DRAINAGE SYSTEM
1)
An adequate drainage system, including necessary closed drainage systems, pipes, culverts, intersectional drains, drop inlets, bridges, etc., shall be provided for the proper drainage of all surface water.
2)
The design of the system shall be in accordance with the best modern engineering practices to adequately carry the expected runoff.
3)
All culverts positioned within the drainage system shall be constructed of concrete or metal in accordance with Louisiana Department of Transportation and Development (DOTD) Engineering Directives and Standards Manual (EDSM) Nos. II.2.1.1; II.2.1.6 and II.2.1.13, dated July 20, 1992 as amended and within standards acceptable to the town.
4)
All subsurface drainage pipe shall be reinforced concrete pipe.
5)
Grading and drainage plans prepared by a registered professional engineer shall be submitted for approval by town engineer. These plans shall meet the requirements included in Appendix I of this code.
6)
Reinforced concrete pipe and appurtenances may be used in accordance with the following requirements:
ASTM Specification C14, Specification for Concrete Sewer, Storm Drain and Culvert Pipe
Minimum culvert size 15" Minimum cover 2'6" Minimum grade 1/16 "/foot ASTM Specification C76, Specification for Reinforced Concrete Culvert, Storm Drain and Sewer Pipe; ASTM Specification C506, Specification for Reinforced Concrete Arch Culvert, Storm Drain and Sewer Pipe; ASTM Specification C507, Specification for Reinforced Concrete Elliptical Culvert, Storm Drain and Sewer Pipe; ASTM Specification C655, Specification for Reinforced Concrete D-Load Culvert, Storm Drain and Sewer Pipe;
In addition, pipe permitted for pressure sewers will be permitted for gravity sewers.
7)
Joints in concrete pipe used for gravity sewers must be packed and sealed with a cement mortar, a preformed mastic gasket, or a trowel applied mastic compound in a procedure acceptable to the town. In addition, any joining sealing method acceptable for pressure sewers may be used for gravity sewer.
8)
Pressure sewers:
a)
Concrete pipe conforming to ASTM Specification C361, Reinforced Concrete Low-Head Pressure Pipe, may be used for pressure sewers with maximum heads as indicated in the specification.
b)
Joints in concrete pipe used for pressure sewers will conform to ASTM Specification C443, Joints for Circular Concrete Sewer and Culvert Pipe, with Rubber Gaskets.
9)
Pipe shall be laid true to the lines and grade shown on the plans. Bell and spigot pipe shall be laid with bell ends upgrade. Tongue and groove pipe shall be laid with outer tip or groove end upgrade.
10)
In jointing bell and spigot pipe, a gasket of jute of suitable thickness to properly align the pipes shall be placed around the pipe and rammed solidly home with a suitable caulking tool. The jointing compound, heated to the proper temperature, shall be poured completely around the joint. The pouring ladle shall be large enough to pour the entire joint without refilling.
11)
In jointing concrete tongue and groove pipe the manufacturer's recommendations shall be followed exactly. In general, the GS-702 compound shall be applied as follows:
a)
Apply one brush coat of GS-702 primer to the surfaces to be jointed on the tongue and groove at least 24 hours prior to laying pipe.
b)
Set pipe in trench and trowel a one-half inch thick layer of compound on the groove end covering about two-thirds of the joint surface around the outerpipe circumference.
c)
Shove home the tongue end of the pipe and smooth off excess compound which may have squeezed out of the joint.
12)
The inside of all pipes shall be cleared of debris as the work progresses, and all joints shall be wiped clean inside.
13)
Pipe used for drainage shall be at least 15 inches in diameter.
14)
The minimum culvert size to be used for drainage shall be 15 inches.
15)
Metal arch pipe shall be corrugated, asbestos-bond, and asphalt-coated. All pipe shall conform in all respects to the requirements of the ASSHO Standard Specifications for corrugated metal culvert pipe, Designation M36, latest revision. The following gauge sizes are required:
Size
(in inches)Gauge Size
(in inches)Gauge 18 × 11 16 43 × 27 12 22 × 13 16 50 × 31 12 25 × 16 16 58 × 36 12 29 × 18 14 65 × 40 12 36 × 22 14 72 × 44 10 Pipe shall be galvanized on both sides by the hot dip process with not less than two ounces of zinc per square foot. During the galvanizing process, a layer of asbestos felt shall be pressed into the molten zinc and impregnated with a special saturant and seal coat. In addition, the pipe shall be completely and uniformly coated inside and outside with 0.03 inches of asphaltic hot-poured compound.
16)
Whenever any stream or improved surface drainage course is located in an area that is being subdivided, the subdivider shall dedicate an adequate right-of-way along each side of the stream for the purpose of widening, deepening, sloping, improving, or protecting the stream or for drainage maintenance. For all drainage courses having a bottom width or normal water surface of five feet or more, the subdivider shall dedicate a right-of-way having a width of five feet for every one foot of bottom width. For example, a 25-foot right-of-way shall be dedicated for all drainage courses having a bottom width of five feet. All surface drainage courses shall have sufficient right-of-way width for at least 1:1 side slope, or side slopes having at least one foot of horizontal distance for each one foot vertical drop. (Drainage right-of-way shall not be considered a part of street right-of-way.)
17)
Lots created along a drainage channel shall not encroach upon the drainage easement or servitude right-of-way and all such easements or servitudes shall be excluded from the lot area.
18)
Site grading and fill operations must not interfere with natural watercourses.
19)
No individual, firm or corporation shall deepen, widen, fill or reroute, or change the location of any existing ditch, stream or drainage canal or reclaim, fill, dredge or otherwise change the natural condition.
20)
The minimum finished flood elevation required in areas subject to periodic inundation shall be indicated on the plans.
TRENCHING & BACKFILLING
1)
All excavations shall be carried down to the depths required for the satisfactory installation of lines and other appurtenances shown on the drawings.
2)
Excavations shall be open cuts with vertical sides. The sides of trenches shall be sloped only when necessary.
3)
The standard width of storm sewer trenches shall be such as to leave on each side of the pipe a clearance of one foot between the greatest external diameter of the barrel of the pipe and the sides of the trench or of the timber used for shoring same.
4)
The contractor shall pump or otherwise remove any water which may accumulate or be found in trenches or other excavations and keep them free from water while foundation work, masonry work, or pipe laying is in progress.
5)
Disposition of water from trenches and excavations shall be made in such a manner as to avoid injury to public health.
6)
All material excavated shall be placed so as to minimize interferences with public travel and to permit proper access for prosecution and inspection of the work.
7)
At street crossings the trenches shall be bridged in a proper and secure manner so as to prevent any serious interruption of travel upon the roadway or sidewalk.
8)
The contractor shall furnish, put into place and maintain such sheeting, bracing, etc., as may be required to prevent failure or caving of the excavation.
9)
Sheeting which extends below 18 inches above the top of the pipe shall be left in place.
10)
Sheeting may be cut off at or above 18 inches above the top of the pipe and must be cut off at or below two feet below the finished grade.
11)
Pipe shall be installed in surface-dry trenches. Sump pumping (in impervious or slightly pervious soils) and well points (in pervious soils) will be used as necessary to achieve and maintain the surface-dry condition. When joint materials or support materials require "curing," no water will be permitted in the trench until these materials have set.
12)
All pipe, culverts, or other structures shall be adequately supported. Full responsibility for the security of such structures and of all excavations shall be with the contractor.
13)
When a firm foundation is not encountered at the established grade, due to soft, spongy or other unstable soil, and when other special construction methods such as "special foundation" are not called for on the plans or in the special provisions, all such unstable soil under the pipe shall be removed and replaced with a foundation fill consisting of sand, shell, gravel or other suitable material.
14)
Bedding will conform to Class C, "shaped bottom" as shown on Page 212, ASCE Manual No. 37, 1969. Where the soil appears different from the typical soil of the project, especially if it appears inadequate for support, the unsuitable material will be removed and replaced with a clean well-compacted granular material and the bedding will conform to Class C, "granular bedding" as shown in the same manual on the same page.
15)
The use of fine materials for fill around pipe makes it necessary to use tight caulked joints in drain lines. Regardless of class, size, length or type, pipe furnished must have ends that will permit tight and proper jointing.
16)
All lines shall be laid to lines and grades shown on plans. Bell and spigot pipe shall be installed with bell upgrade. Before being set in place, each length of pipe shall be thoroughly cleaned, free of earth, or foreign material.
17)
Each pipe shall be laid to form a close joint with the adjoining pipe sections having a continuous invert to the established line and grade. When pipes are laid between manholes or other structures, a complete circle of light shall be visible from the pipe ends.
18)
Raising the pipe to grade by ramming or tamping of earth and bedding material will not be permitted. Upon proper bedding of the pipe, the opening under its bell shall be properly filled in a manner such as not to disturb its position or joint. At points where work is temporarily suspended all open ends of pipe shall be securely sealed to prevent entrance of water, earth or other substances.
19)
Jacked or bored installations are permissible.
20)
Backfilling of all excavations, pipe trenches, and culvert pipe under pavement shall be made of river sand, or other approved materials. Backfill shall be placed in layers not exceeding six inches in thickness for the full depth of excavation. Each layer shall be carefully and solidly tamped with suitable tools in a manner not to injure or disturb the pipe line or structure. Backfill of all excavations shall be thoroughly compacted. No base or surfacing materials shall be placed over soft trenches or other excavated areas until fully compacted.
21)
No backfilling shall be done until the completed work has been inspected and approved by the town. Backfilling around masonry structures shall not be started until cement has become sufficiently hardened to prevent injury to the structure.
22)
When the trench is backfilled with soil from the original excavation, the soil must be hand-placed and compacted to 90 percent of maximum standard Proctor density to a level 12 inches above the pipe. Special care must be taken to ensure placement and compaction between the pipe haunches and around the sides of the pipe. Soil will be placed in lifts not more than six inches thick before compaction.
23)
All material used for backfill will be free of roots, timber, trash, or other deleterious material. Excess soil will be mounded as necessary to prevent a depression from forming due to subsequent consolidation.
24)
Ditches shall be constructed to grade and cross-section shown on the plans. Excavated materials or spoil shall be removed from the site and shall not be deposited on adjacent lands.
25)
All surfaces damaged will be restored to a condition equivalent to that existing before the work began.
MANHOLES & CATCH BASINS
1)
Manholes and catch basins shall be constructed at locations shown on the plans. An approved cast iron frame and cover shall be provided and installed with the top of the cover flush with the finished grade or at another elevation specified on the plans.
2)
Manholes for sewers less than 24 inches in diameter will have concrete interior bottoms and will be watertight for the full height. In general, all lines joining the manhole will enter at the bottom. Bottoms will have U-shaped channels of width and depth at least equal to the incoming lines leading to outgoing lines. Where a change in direction occurs, the lines should be brought in off-center as necessary to provide the largest possible radius to the curved channel, which is done by placing the ends of the outer channel side on opposite ends of a manhole diameter. The remaining area of the bottom will be shaped as a flat bench having a slope of one-half inch per foot towards a channel.
3)
Where pipe entry at the general elevation of the bottom cannot be achieved, the following requirements apply:
a)
If the pipe invert is less than 24 inches above the outfall invert, no drop inlet is required, but a channel in the manhole bottom is required. The channel will have dimensions as though the pipe entered at the bottom.
b)
If the pipe invert is more than 24 inches above the outfall invert, a drop inlet is required.
4)
Steps will be installed in manholes.
5)
Manholes shall not be more than 400 feet apart.
6)
Manholes and catch basins shall be constructed of brick masonry on concrete foundations and fitted with cast iron castings as shown on the drawings.
7)
Brick for manholes and catch basins shall be burned clay brick conforming to ASTM specifications C32-58, Grade NA.
8)
Castings for manholes and catch basins frames and covers shall be tough grey iron free from all injurious defects and of such quality that a blow from a hammer on a square edge of a casting will produce an indentation without flaking the metal. When castings are broken, faces shall show a fine grain fracture. All castings shall be made accurately to the dimensions shown on the plan.
9)
Concrete used in manholes and catch basins shall have a minimum 28-day crushing strength of 2,500 PSI.
10)
Mortar used in the construction of manholes and catch basins shall consist of an approved manufactured mason's mix with specified sand, conforming to ASTM Specification C270, or shall consist of a uniform mixture composed of one part Portland cement, 2½ parts of an approved sand, to which shall be added hydrated lime in an amount not exceeding ten percent of the volume of the cement.
11)
Bricks must be laid in full, close-shoved joints or mortar at least one-fourth inch thick at the narrowest end and not more than one-half inch thick at the widest end. Vertical joints shall be broken at each course. No spalls or bats will be allowed, except for shaping around openings and connections. In the event any brick is moved or a joint is broken during the brick laying, the brick shall be taken up, the mortar thoroughly cleaned from the brick, the bed, and the joints, and the brick relaid in fresh mortar. Bricks colder than 45 degrees Fahrenheit will not be used. Manholes must be at least eight inches thick above eight feet from the surface, and 12 inches thick below eight feet from the surface.
12)
Inside and outside surfaces of sewer manholes shall be plastered with a layer of mortar not less than one-half inch thick. The completed brick masonry shall be protected and kept moist for at least 48 hours from completion. In freezing weather the masonry shall be maintained above 45 degrees Fahrenheit for the same period.
13)
Precast concrete manholes and catch basins conforming to ASTM Specification C478 are allowed.
14)
Preformed manholes and catch basins of fiberglass or other suitable materials cannot be used without approval of the town engineer.
15)
Adjustment of existing manholes. Existing storm and sewer manholes as shown on the drawings shall be adjusted to proper grade as established by the town. This will also include manholes that may not be shown on the drawings but that may be found during construction. Materials and workmanship shall be the same as specified for new manholes except that on sanitary sewer manholes mortar shall be plastered inside and out to a thickness of one-half inch. Extreme care must be taken to prevent the entrance of debris into the existing lines.