Sec. 110-56. Storm drainage system standards.
Plans and specifications for proposed storm drainage systems shall be equal to the following minimum standards.
(1) Pipe:
a. Reinforced concrete pipe shall conform to AASHTO M 170 for circular pipe and to AASHTO M 206 FOR ARCH-SHAPED PIPE. Class III shall be the minimum class of pipe used. The joint seal shall be cement mortar, three parts sand and one part cement, or cold-applied preformed plastic gaskets conforming to AASHTO M 198, type B.
b. All pipes for driveways shall be reinforced concrete pipe.
c. Corrugated steel pipe shall conform to AASHTO M 36, AASHTO M 190 for coated pipe and to AASHTO M 218 for sheets-to-form pipe. As an alternate to bituminous-coated pipe, pre-coated pipe meeting the requirements of AASHTO M 245 and M 246, for type B, may be substituted.
d. The manufacturing and furnishing of corrugated aluminum pipe shall conform to the requirements of AASHTO M 196 and to AASHTO M 197 for sheets-to-form pipe.
e. Other pipe materials will be accepted with the approval of the planning and community development director or his/her designated representative.
f. Flared end sections may be used when approved by the planning and community development director or his/her designated representative and shall be of the same material as the pipe for a given installation, except bituminous coating will not be required for metal ends when specified for the pipe. The steel sheets shall have a thickness of 0.064 inch or more.
g. The reinforced concrete flared end sections for circular and arch concrete pipe shall meet the applicable requirements for class II or higher class of pipe.
h. Corrugated metal pipe shall be capable of withstanding a H-20 load.
i. Coupling bands for corrugated metal pipe shall be the same metal as used in the pipe and shall be a single or couple piece with bolts and angles.
(2) Excavation, trench preparation and installation:
a. Where the pipe is laid below ground line, the trench shall be excavated to the required depth and width to allow sufficient room for tamping of backfill. See City of Springdale, Arkansas Standard Details for Street and Drainage Construction. The bottom of the trench shall be shaped to conform to the bottom of the pipe with recesses excavated to receive the bells where bell-and-spigot pipe are used. Where pipe is not laid in a trench, a uniform firm bed shall be made as specified above.
b. When rock is encountered in the trench, it shall be removed to a minimum depth of six inches below the pipe, and the excess depth shall be filled with a suitable material as defined in section 110-54 and compacted.
c. All unsuitable material, including soft and yielding material, shall be removed and replaced with suitable material and compacted to ensure a firm support.
d. The pipe shall not be laid in water or in unsuitable weather or trench conditions, unless approved by the planning and community development director or his/her designated representative.
e. After each joint of pipe has been graded, aligned and placed in final position, the bedding material shall be deposited and compacted under and around each side of the pipe and back of the bell, or the end thereof, to firmly hold and maintain the pipe in proper position and alignment during subsequent pipe joining, embedment and backfilling operations.
f. No debris creating a clogging action shall be allowed to remain in the storm drainage system.
g. All storm drainage pipe under any street improvement shall be backfilled with class seven base material approved by the planning and community development director or his/her designated representative and compacted before the base course and curb and gutter are constructed. The backfilled base material shall be brought up evenly on each side of the pipe to avoid displacement. Special care shall be taken to compact the material under the haunches of the pipe. The base material shall be compacted with mechanical equipment to at least 95 percent of the maximum density as determined by AASHTO T 180.
h. When culvert pipe is to be relayed, the construction procedures shall be in accordance with the AHTD standard specification requirements for relaying culvert pipe.
i When structural plate pipe and arches are used, the materials and construction procedures shall be in accordance with the AHTD standard specification requirements for structural plate pipe and arches.
(3) Headwalls, drop inlets and junction boxes:
a. All drainage structures shall be constructed of concrete.
b. All concrete shall have a minimum 28-day compressive strength of 3,000 psi when tested in accordance with AASHTO T 23. The concrete shall contain an air-entraining agent, which produces five percent plus or minus two percent air entrainment in the concrete.
c. The minimum thickness of concrete walls, floors, and tops shall be six inches.
d. Concrete drainage structures shall be constructed in accordance with City of Springdale Arkansas Standard Details for Street and Drainage Construction.
e. Walls shall be constructed to form a tight joint with the floor and around the inlet and outlet pipes. The pipes shall be flush with the inside surface of the wall.
f. A drop inlet shall be located at the lowest point of all sag vertical curves.
g. Drop inlets are not allowed in intersection curb radii unless approved by the planning and community development director or his/her designated representative.
(4) Rings, covers, grates and frames:
a. Iron castings shall conform to ASTM A 48 class 30A for gray iron castings.
b. The combined weight of the ring and lid shall be a minimum of 300 pounds.
(5) Pipe underdrain:
a. Pipe underdrains shall be installed in any area where subsurface water is encountered and other areas as determined by the planning and community development director or his/her designated representative.
b. The underdrain shall be located just behind the curb.
c. Outlets shall be provided on at least 300-foot intervals, or as approved by the planning and community development director or his/her designated representative. To the extent possible, the under drain pipe should be connected with a drop inlet of the storm drainage system.
d. The under drain material and construction procedures shall be in accordance with the AHTD standard specifications for pipe under drain, with the following exceptions:
1. Corrugated polyethylene tubing and acrylonitrilebutadine-styrene pipe shall be used in the construction of pipe under drains, or other materials as approved by the planning and community development director or his/her representative.
2. Granular filter material shall meet the requirements of subsection 802.02(f) of the AHTD standard specifications for coarse aggregate for class A concrete.
3. A non-woven geotextile fabric having the following properties shall be used as a liner for the pipe under drain: