§ 50-75. Minimum requirements for erosion and sedimentation control using best management practices.

(a)

General provisions. Excessive soil erosion and resulting sedimentation can take place during land disturbing activities if requirements of this section and the NPDES general permit are not met. Therefore, plans for those land disturbing activities which are not excluded by this article shall contain provisions for application of soil erosion and sedimentation control measures and practices. The provisions shall be incorporated into the erosion and sedimentation control plans. Soil erosion and sedimentation control measures and practices shall conform to the minimum requirements of this section. The application of measures and practices shall apply to all features of the site, including street and utility installations, drainage facilities and other temporary and permanent improvements. Measures shall be installed to prevent or control erosion and sedimentation pollution during all stages of any land disturbing activity and the NPDES general permit. Land disturbing activities that are exempted from obtaining a permit and preparing a plan (as listed in section 50-74) shall institute minimum soil erosion and sedimentation control measures.

With respect to development on properties with stream buffers (refer to subsections 50-75(b)15. and 16., below) any permit applications shall be required to include the following information:

(1)

A site plan showing:

a.

The location of all streams on the property;

b.

Limits of required stream buffers and setbacks on the property;

c.

Buffer zone topography with contour lines at no greater than five-foot contour intervals;

d.

Delineation of forested and open areas in the buffer zone; and,

e.

Detailed plans of all proposed land development in the buffer and of all proposed impervious cover within the setback;

(2)

A description of all proposed land development within the buffer and setback; and

(3)

Any other documentation that the Cobb County Community Development Agency may reasonably deem necessary for review of the application and to insure that the buffer zone ordinance is addressed in the approval process.

(b)

Minimum requirements/BMPs.

(1)

Best management practices as set forth in this article shall be required for all land disturbing activities. Proper design, installation and maintenance of best management practices shall constitute a complete defense to any action by the director or to any other allegation of noncompliance with subsection (b)(2) of this section or any substantially similar terms contained in a permit for the discharge of stormwater issued pursuant to O.C.G.A. § 12-5-30(f), the Georgia Water Quality Control Act. As used in this subsection, the terms "proper design" and "properly designed" mean designed in accordance with the hydraulic design specifications contained in the "Manual for Erosion and Sediment Control in Georgia" specified in O.C.G.A. § 12-7-6(b).

(2)

A discharge of stormwater runoff from disturbed areas where best management practices have not been properly designed, installed and maintained shall constitute a separate violation of any land disturbing permit issued by a local issuing authority or of any state general permit issued by the division pursuant to O.C.G.A. § 12-5-30(f), the Georgia Water Quality Control Act, for each day on which such discharge results in the turbidity of receiving waters being increased by more than 25 nephelometric turbidity units for waters supporting warm water fisheries or by more than ten nephelometric turbidity units for waters classified as trout waters. The turbidity of the receiving waters shall be measured in accordance with guidelines to be issued by the director. This paragraph shall not apply to any land disturbance associated with the construction of single family homes which are not part of a larger common plan of development or sale unless the planned disturbance for such construction is equal to or greater than five acres.

(3)

Failure to properly design, install or maintain best management practices shall constitute a violation of any land disturbing permit issued by a local issuing authority or of any state general permit issued by the division pursuant to O.C.G.A. § 12-5-30(f), the Georgia Water Quality Control Act, for each day on which such failure occurs.

(4)

The director of EPD may require, in accordance with regulations adopted by the board, reasonable and prudent monitoring of the turbidity level of receiving waters into which discharges from land disturbing activities occur to verify that the minimum requirements in subsection (b)(2) are being met.

(c)

General design principles. The application of this section gives due consideration to the differences regarding requirements for development of commercial properties as opposed to those requirements for residential properties. The permittee and exempt persons who are required to comply with this article shall be required to provide protections at least as stringent as the state general permit and follow as a minimum best management practices, including sound conservation and engineering practices to prevent and minimize erosion and resulting sedimentation which are consistent with and no less stringent than, those practices contained in the Manual for Erosion and Sediment Control in Georgia published by the Georgia Soil and Water Conservation Commission as of January 1 of the year in which the land disturbing activity was permitted, as well as the following:

(1)

Stripping of vegetation, regrading and other development activities shall be conducted in a manner so as to minimize erosion.

(2)

Cut-fill operations must be kept to a minimum.

(3)

Development plans must conform to topography and soil type so as to create the lowest practical erosion potential.

(4)

Whenever feasible, natural vegetation shall be retained, protected and supplemented.

(5)

The disturbed area and the duration of exposure to erosive elements shall be kept to a practicable minimum. Development/construction shall be so scheduled and performed to allow for the required installation of temporary silt fence, construction of sediment basins, and other type best management practices prior to grading operations. Grading operations and best management practices must follow immediately thereafter.

(6)

Disturbed soil shall be stabilized as quickly as practicable, according to criteria set forth in the county development standards and specifications.

(7)

Temporary vegetation or mulching shall be employed to protect exposed critical areas during development.

(8)

Permanent vegetation and structural erosion control practices shall be installed as soon as practicable, according to criteria set forth in the county development standards and specifications.

(9)

To the extent necessary, sediment in runoff water must be trapped by the use of debris basins, sediment basins, silt traps or similar measures until the disturbed area is stabilized. As used in this subsection, a disturbed area is stabilized when it is brought to a condition of continuous compliance with the requirements of O.C.G.A. § 12-7-1 et seq.

(10)

Adequate provisions must be provided to minimize damage from surface water to the cut face of excavations or the sloping surface of fills.

(11)

Cuts and fills may not adversely impact adjoining property.

(12)

Fills shall not encroach upon natural watercourses or constructed channels in a manner so as to adversely affect other property owners and in accordance with chapter 58 of this code.

(13)

Grading equipment must cross flowing streams by means of bridges or culverts, except when such methods are not feasible.

(14)

Land disturbing activity plans for erosion and sedimentation control shall include provisions for treatment or control of any source of sediments and adequate sedimentation control facilities to retain sediments on-site or preclude sedimentation of adjacent waters beyond the levels specified in this article.

(15)

Land disturbing activities in unincorporated Cobb County shall not be conducted within:

a.

Twenty-five feet of the banks of any state waters not defined on the current county stream buffer map, and as measured from the point where vegetation has been wrested by normal stream flow or wave action, except where the director determines to allow a variance that is at least as protective of natural resources and the environment, where otherwise allowed by the director pursuant to O.C.G.A. § 12-2-8, or where a drainage structure or a roadway drainage structure must be constructed, provided that adequate erosion control measures are incorporated in the project plans and specifications and are implemented. Ephemeral streams do not require any type of undisturbed buffer.

b.

Fifty feet of the banks of any stream in the county, as defined on the current county stream buffer map, and as measured from the point where vegetation has been wrested by normal stream flow or wave action where total watershed area (on site and off site area) intercepted is less than or equal to five square miles; except where the director determines to allow a variance that is at least as protective of natural resources and the environment. For the purposes of this section, at least as protective shall mean that there is no net decrease in the square footage of the county-mandated 50-foot buffer. Any request to allow a variance that would result in a net decrease in the square footage of the county-mandated 50-foot buffer must be approved by the Cobb County Board of Zoning Appeals in accordance with sections 134-34 and 134-94. An additional impervious setback shall be maintained for 25 feet, measured horizontally, beyond the undisturbed natural vegetative buffers, in which all impervious cover shall be prohibited. Grading, filling and earthmoving shall be minimized within the setback. Ephemeral streams do not require any type of undisturbed buffer.

c.

Seventy-five feet of the banks of any stream in the county, as defined on the current county stream buffer map, and as measured from the point where vegetation has been wrested by normal stream flow or wave action where total watershed area (on site and off site area) intercepted is equal to five square miles and less than or equal to ten square miles; except where the director determines to allow a variance that is at least as protective of natural resources and the environment. For the purposes of this section, at least as protective shall mean that there is no net decrease in the square footage of the county-mandated 75-foot buffer. Any request to allow a variance that would result in a net decrease in the square footage of the county-mandated 75-foot buffer must be approved by the Cobb County Board of Zoning Appeals in accordance with sections 134-34 and 134-94. Ephemeral streams do not require any type of undisturbed buffer.

d.

One hundred feet of the banks of any stream in the county, as defined on the current county stream buffer map, and as measured from the point where vegetation has been wrested by normal stream flow or wave action where total watershed area (on site and off site area) intercepted is greater than ten square miles; except where the director determines to allow a variance that is at least as protective of natural resources and the environment. For the purposes of this section, at least as protective shall mean that there is no net decrease in the square footage of the county-mandated 100-foot buffer. Any request to allow a variance that would result in a net decrease in the square footage of the county-mandated 100-foot buffer must be approved by the Cobb County Board of Zoning Appeals in accordance with sections 134-34 and 134-94. Ephemeral streams do not require any type of undisturbed buffer.

e.

Two hundred feet of the banks of Nickajack Creek, as defined on the current county stream buffer map, and as measured from the point where vegetation has been wrested by normal stream flow or wave action, from Church Road downstream to its confluence with Mill Creek No. 2 (Cross-Section AA according to effective Cobb County Flood Insurance Study dated August 18, 1992) and from Buckner Road downstream to its confluence with the Chattahoochee River except where the director determines to allow a variance that is at least as protective of natural resources and the environment. For the purposes of this section, at least as protective shall mean that there is no net decrease in the square footage of the county-mandated 200-foot buffer. Any request to allow a variance that would result in a net decrease in the square footage of the county-mandated 200-foot buffer must be approved by the Cobb County Board of Zoning Appeals in accordance with sections 134-34 and 134-94. Ephemeral streams do not require any type of undisturbed buffer.

f.

Per DNR Rule 391-3-16.01:

1.

For perennial streams tributary to Lake Allatoona and within a 7-mile radius of the Lake Allatoona reservoir boundary:

•

A buffer shall be maintained for a distance of 100 feet on both sides of the stream as measured from the stream banks.

•

No impervious surface shall be constructed within a 150-foot setback area on both sides of the stream as measured from the stream banks.

•

Septic tanks and septic tank drain fields are prohibited in the setback area of 2, above.

2.

For perennial streams tributary to the Chattahoochee River (including the Chattahoochee River upstream of the water supply intake at Johnson Ferry Road, or tributaries which enter the Chattahoochee River upstream of the water supply intake at Johnson Ferry Road) and which are within a seven-mile radius of the water supply intake at Johnson Ferry Road:

•

A buffer shall be maintained for a distance of 100 feet on both sides of the stream as measured from the stream banks.

•

No impervious surface shall be constructed within a 150-foot setback area on both sides of the stream as measured from the stream banks.

•

Septic tanks and septic tank drain fields are prohibited in the setback area of 2, above.

g.

Once established, a permanent natural undisturbed buffer, shall be recorded on all plats and revisions and/or property deeds which encumbers this property as undisturbed buffer area to all future property owners. Said buffer will also contain a restrictive covenant in favor of the county for conservation uses. The buffer shall be subject to exceptions set forth below and the county retains the right on a per case basis to grant variances.

h.

Exceptions to these buffers are as follows:

1.

Where a sewerline easement exists or must be constructed to serve the general public (this exception is not applicable to the state-mandated 25-foot buffer).

2.

Where the 100-year floodplain constricts within the buffer and "buffer averaging" is permitted such that the net buffer area is not reduced or the average buffer width conforms to the widths as outlined above (this exception is not applicable to the state-mandated 25-foot buffer).

3.

Where a roadway crossing occurs and the buffer must be constricted to allow construction of a bridge or a culvert. The state-mandated 25-foot buffer will apply in these areas for a distance of 50 feet upstream and downstream of the face of the bridge or culvert headwall.

4.

Where the director of the county community development agency, or his assign(s) determine to allow a variance to the requirements greater than the state-mandated 25-foot buffer that is at least protective of natural resources and the environment, or where otherwise allowed pursuant to O.C.G.A. § 12-2-8. For the purposes of this section, at least as protective shall mean that there is no net decrease in the square footage of the required buffer that is greater than the state-mandated 25-foot buffer. Any request to allow a variance that would result in a net decrease in the square footage of the required buffer that is greater than the state-mandated 25-foot buffer must be approved by the Cobb County Board of Zoning Appeals in accordance with sections 134-34 and 134-94.

5.

Where a drainage structure or a roadway drainage structure must be constructed, provided that adequate erosion control measures are incorporated in the project plans and specification and are implemented; provided that buffers established pursuant to part 6 of article 5 of chapter 5 of the Metropolitan River Protection Act (O.C.G.A. § 12-5-440 et seq.) shall remain in force.

6.

The state-mandated 25-foot buffer shall not apply to the following land disturbing activities, provided that they occur at an angle, as measured from the point of crossing, within 25 degrees of perpendicular to the stream; cause a width of disturbance of not more than 50 feet within the buffer; and adequate erosion control measures are incorporated into the project plans and specifications and are implemented:

(i)

Stream crossings for water lines; or

(ii)

Stream crossings for sewer lines.

i.

The developer or property owner shall maintain ownership of the buffer areas. In instances of conflict between the buffers mandated by the Metropolitan River Protection Act and the buffers required by this article, the wider of the two required buffers shall apply.

j.

The donation (or dedication) of land for stream buffers, outside any floodplain area, may be compensated for by allocating the density of the donated (or dedicated) land to the owner's remaining property, if so requested by the owner. The owner shall make the request to the director of the community development agency and the request shall be processed in accordance with section 134-35.

(16)

Unless a larger buffer is specified on the current county stream buffer map, there is established a 50-foot buffer as measured horizontally from the point where vegetation has been wrested by normal stream flow or wave action, along the banks of any state waters classified as "trout streams" pursuant to article 2 of chapter 5 of title 12, the "Georgia Water Quality Control Act," except where a roadway drainage structure must be constructed; provided, however, that small springs and streams classified as trout streams which discharge an average annual flow of 25 gallons per minute or less shall have a 25-foot buffer or they may be piped, at the discretion of the landowner, pursuant to the terms of a rule providing for a general variance promulgated by the board of natural resources, so long as any such pipe stops short of the downstream landowner's property and the landowner complies with the buffer requirement for any adjacent trout streams. The director of EPD may grant a variance from such buffer to allow land disturbing activity, provided that adequate erosion control measures are incorporated in the project plans and specifications and are implemented. No land disturbing activities shall be conducted within a buffer described in paragraph (15) or (16) and a buffer shall remain in its natural, undisturbed, state of vegetation until all land disturbing activities on the construction site are completed. Once the final stabilization of the site is achieved, a buffer may be thinned or trimmed of vegetation beyond the first 50 feet as long as a protective vegetative cover remains to protect water quality and aquatic habitat and a natural canopy is left in sufficient quantity to keep shade on the stream bed; provided, however, that any person constructing a single family residence, when such residence is constructed by or under contract with the owner for his or her own occupancy, may thin or trim vegetation in a buffer beyond the first 50 feet at any time as long as protective vegetative cover remains to protect water quality and aquatic habitat and a natural canopy is left in sufficient quantity to keep shade on the stream bed; trimming and thinning of vegetation within the first 50 feet of a stream buffer is allowed with the approval of the director or the director's designee; this 50-foot buffer shall not apply to the following land disturbing activities, provided that they occur at an angle, as measured from the point of crossing, within 25 degrees of perpendicular to the stream; cause a width of disturbance of not more than 50 feet within the buffer; and adequate erosion control measures are incorporated into the project plans and specifications and are implemented:

a.

Stream crossings for water lines; or

b.

Stream crossings for sewer lines.

(17)

When a pond, either new or existing, is incorporated into a development, the developer shall note on his plans if the pond is to be used for sediment control and/or retention during construction. If the pond is to be used for sediment control, the developer or current title holder will be required to dredge, clean and grass the pond upon completion of construction of the project and prior to acceptance by the county. Further, sediment control devices shall be required to protect downstream property during construction.

(18)

Lakes, either new or existing, incorporated into a development shall not be used for sediment control and will be classified and used as adjacent property; hence, and therefore, siltation thereof will be treated as a violation of this article.

(19)

Hazardous conditions at sediment basins and floodwater retention structures shall be fenced and posted to avoid danger to life or property.

(20)

All erosion and sedimentation control measures, whether temporary or permanent, shall be maintained by the permittee or exempt person until the areas affected by such measures are permanently stabilized.

(Ord. of 3-27-90; Code 1977, § 3-6-110; Ord. of 11-14-95; Ord. of 7-27-99 (eff. 10-1-99); Ord. of 1-25-00; Ord. of 1-23-01; Ord. of 7-10-01; Ord. of 4-13-04; Ord. of 2-27-07; Amd. of 2-23-10; Ord. of 7-24-12)

State law reference

Minimum standards, O.C.G.A. § 12-7-17.