§ 1176. Storm drainage materials and installation.

(a)

The table titled "Selection Guidelines for Storm Sewer Piping," sets out guidelines for the use of storm sewer pipes by pipe material and type of installation.

Selection Guidelines for Storm Sewer Piping

Type of Pipe Installation	Reinforced Concrete Pipe	Corrugated Steel AASHTO M-36		Corrugated Aluminum AASHTO M=196	Plastic AASHTO M 294	Reinforced Concrete Box Culvert
		Aluminized Type II CMP	Bituminous Coated CMP	Aluminum Alloy CMP	Corrugated High Density Polyethylene Smooth Lined	Per Georgia DOT Standards
Longitudinal (grade less than 10%)	Yes	Yes	Yes	Yes	See Note 1	n/a
Longitudinal (grade 10% or more)	No	Yes	Yes	Yes	See Note 1	n/a
Cross Drain, Local Street	Yes	Yes	Yes	Yes	No	n/a
Cross Drain, Collector or Arterial Street	Yes	No	No	No	No	n/a
Cross Drain, Flowing Stream	Yes	See Note 3	No	No	No	n/a
Cross Drain, 25-year Flow > 200 cfs Fill Depth > 18 feet	See Note 2	See Notes 2 and 3	No	See Note 2	No	Yes

 

Note 1: Corrugated high density polyethylene pipe, smooth lined type "S", can only be used for residential driveway applications and must be manufactured and installed in strict compliance with Georgia DOT Standard 1030-P. HDPE applications shall not exceed 36 inches in diameter.

Note 2: Reinforced concrete box culverts are required under excessive flow and/or fill depth conditions. Approved pipe materials may be utilized in some instances, based on the county engineer's assessment of existing conditions and future maintenance requirements.

Note 3: The addition of a type "A" full bituminous coating is required. (AASHTO M-190)

(b)

Only reinforced concrete pipe shall be used within street rights-of-way for arterial roads, and major and minor collectors. Concrete pipe shall not be used on grades exceeding ten percent. Metal pipe may be used within the rights-of-way of local streets and for driveway culverts. Metal pipe shall either be corrugated steel (AASHTO M-36) with aluminized type II or bituminous coating, or corrugated aluminum alloy pipe (AASHTO M-196).

(c)

Corrugated high density polyethylene pipe, smooth lined type "S", can only be used for residential driveway applications and shall not exceed 36 inches in diameter.

(d)

Pipe installation shall conform to Georgia Department of Transportation Standard Specifications for construction of roads and bridges. Before any traffic over a storm drain is allowed, the developer shall provide an adequate depth and width of compacted backfill to protect the structure from damage or displacement. The developer shall remove any debris or silt that constricts the flow through a pipe as often as necessary to maintain drainage. All pipe structures shall be cleaned before the work is accepted. Any damage or displacement that may occur due to traffic or erosion shall be repaired or corrected at the developer's expense.

(e)

Trench construction for storm drainage pipe shall be in accordance with State Highway Standard 1030D (or most current).

(f)

Backfilling of trenches shall be accomplished immediately after the pipe is laid. The fill around the pipe shall be placed in layers not to exceed six inches with each layer being thoroughly compacted. All material shall have an in place density of 98 percent modified proctor to a depth of six inches below the finished grade, and 95 percent modified proctor at depths greater than six inches below the finished grade. Compaction requirements shall be attained by the use of mechanical compaction methods. Each layer of backfill shall be placed loosely and thoroughly compacted in place.

(g)

All backfill shall be non-plastic in nature, free from roots, vegetative matter, waste, construction material or other objectionable material. Said material shall be capable of being compacted by mechanical means and shall have no tendency to flow or behave in a plastic manner under the tamping blows.

(h)

Material deemed by the county as unsuitable for backfill purposes shall be removed and replaced with selected backfill material.

(i)

Water shall not be permitted to rise in trenches that are not backfilled after the pipe has been placed.

(Ord. No. 17-003 , § 1, 10-2-2017)