HomeMy WebLinkAboutSTORMWATER MANAGEMENT PLAN
Augusta Richmond GA
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STORMW ATER MANAGEMENT PLAN
TECHNICAL MANUAL
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Development Document #6
Augusta-Richmond County Commission
June 1999
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STORMW ATER MANAGEMENT PLAN
TECHNICAL MANUAL
TABLE OF CONTENTS
Pal!e
General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Part I:
Hydrology/Hydraulics
Section I
Section II
Section III
Section IV
Section V
Section VI
Section VII
Section VIII
Part II:
Determination of Storm Runoff. . .. . .. . .. . .. ...... . .. . .. ... . .. . .. . .. ......3
Storm Drains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 5
Open Channels........................................................... .... 6
Culverts. . .. . .. . .. . .. . .. . .. ...... .......... ..... . .. . .. . ... .. . .. . .. . ...... ...... 8
Detention. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . .. . ...... .. . .. ... . .. . .. .... .......9
Outfall. . . . . . . . . . . . . . '. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 12
Special Basin Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 13
Detention and Sediment Basin Construction. . .. . .. . ... .. . .. . ......... 13
Environmental Requirements
Section I
Section II
Section III
Part III:
Wetlands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . : . . . . . , . . . . . . . . . . . . . . . . . .. 15
Water Quality. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 15
Local Regulations........................................................... 16
Materials of Construction
Section I
Section II
Section III
Section IV
Section V
Part IV:
Update
Storm Drains. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 17
Culverts....................................................................... 18
Soil and Rock Structures.................................................. .18
Grassing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 19
Fencing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .., .19
References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . '.' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... . ... 20
Appendix. ...... . .. . .. . ..... . .. . .. . .. . ......... .. ... . .. . .. . .. . .. . .. ...... . .. . ..... . .. . ... .. . .. . .. . .. . ....21
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General
In order to comply with the Stormwater Management Policy adopted by Augusta-
Richmond County Commission, the following ,technical manual has been compiled to provide
engineers, developers, land planners, and others information necessary to construct public/private
facilities in Augusta. The goal of the stormwater management policy is as follows:
To develop a stormwater management system that is a feasible, constructable
system designed to collect, convey and release stormwater in a manner that
protects public safety, minimizes damage to all impacted properties, protects
water quality, and is maintainable in perpetuity.
The contents of the technical manual have been developed to establish minimum
requirements for the design and construction of individual and collective stormwater
management systems in Augusta. Furthermore, sound engineering practices and judgement
should be applied in the planning and design of all facilities proposed to comply with the
stormwater management policy for Augusta-Richmond County Commission. Constructed
facilities designed and based on criteria in excess of the minimum established requirements as
stated in this technical manual may be necessary in order to effectively control and manage
stormwater runoff for newly constructed facilities. Augusta-Richmond County Commission
does not assume to provide complete and comprehensive technical review of construction plans
and reports submitted for the construction of new facilities but rather provides a general review
of information and documentation submitted through the Public Works Engineering Department
to generally insure that appropriate documentation of design calculations have been submitted in
accordance with the minimum technical criteria stated herein. To this end, the engineer,
developer, and land planner shall be responsible for the intent of the stormwater management
policy based on actual field conditions and construction techniques.
In the event that exceptions to the minimum requirements should be proposed by the
developer, the engineer and designer shall meet with the City Engineer to discuss proposed
exceptions to minimum requirements. .
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PART I HYDROLOGY/HYDRAULICS
Section I Determination of Storm Runoff
1.01 General:
Determination of storm water runoff is a complex issue involving existing drainage basin
characteristics, future drainage basin characteristics, the relationship of the proposed
development to the drainage basin and the characteristics of downstream properties and receiving
waters. The most obvious and accurate method of determining runoff for a particular basin area
would be to utilize historical data of measured runoff values. However, except in certain,
limited, instances, this information is not available. Therefore, establishing runoff data for a
particular drainage basin requires the utilization of rainfall - runoff relationships through various
hydrology models.
1.02
In order to effectively establish rainfall - runoff relationships, basic data concerning the
basin and site must be collected and provided in the hydrologylhydraulics report:
Delineation of the drainage basin of which the site is a part. The drainage basin
shall be provided at an appropriate scale that can be utilized in the overall
hydrologylhydraulics report evaluation. USGS quadrangle maps of the drainage
basin area shall be used as a minimum standard map.
A topography map of the site proposed for development shall be provided with 2
foot contour intervals accurate to 1/2 the contour interval. The site topography
map shall be provided with sufficient data to determine site characteristics prior to
development and following construction of proposed improvements. The site
topography map shall be provided' at a scale commensurate with construction
drawings.
Drainage features, natural or man-made, designed to receive discharge from
proposed site improvements shall be identified on the drainage basin map and the
site topography map. Sufficient data regarding the drainage features shall be
provided to accurately characterize the feature including but not limited to depth,
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width, side slopes, surface materials, etc.
Soil characteristics of the proposed developed area as well as immediate
downstream receiving areas shall be provided.
1.03
Each project designed in Augusta shall comply with the following criteria and guidelines.
Construction plans and details are required for review by the City Engineer. A hydrology and
hydraulics report of the project and associated basin, as outlined herein, shall be prepared and
submitted to the City Engineer for review.
Numerous rainfall - runoff computation methods are available. It is essential that a
computation methodology consistent with both site and drainage basin characteristics be selected
to design the storm drainage and flood control system. The rational method may be used to
determine the flows for sites located in contributing drainage basins less than 100 acres. For
drainage basin areas 100 acres or greater, Natural Resources Conservation Service TR-20 and
TR-55, or the US Army Corps of Engineers HEC-1 method should be used.
Documentation of runoff generated by the selected methodology shall include data for the
2, 5, 25, 50, and 100 year return frequency storms. Runoff data shall be calculated for the
drainage basin and site both prior to development and after development. For contributing
drainage basins 100 acres or greater, the Natural Resources Conservation Service Type II storm
for a 24 hour period is required as a minimum.
All rainfall - runoff computations require physical site characteristics expressed in
numerical designation. Runoff coefficients utilized for the Rational Method shall be in
accordance with the table provided in the Appendix of this manual. Runoff curve numbers as
established in the Natural Resources Conservation Service manual for hydraulic computations
shall be utilized in SCS computation methods.
The Hydrology/Hydraulic Report of the drainage basin area and site shall include input
data, method of analysis, runoff generation, and routing calculations for on-site and off-site
subbasin areas.
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Section II Storm Drains
2.01 General:
The purpose of this section is to consider the hydraulic aspects of storm drains and their
appurtenances in a storm drainage system. Hydraulically, storm drainage systems consist of
conduits (open or enclosed) in which unsteady and non-uniform flow exists. The design storm
shall be 25-year return frequency storm with evaluation ofthe overall storm drainage system in
the event of 1 OO-year return frequency storm.
2.02 Guidelines:
General rules in minimum design criteria required for public storm drain systems are as
follows:
a. Minimum acceptable pipe size shall be 18 inch diameter.
b. Do not discharge the contents of a larger pipe into a smaller one even though the
capacity of the smaller pipe may be greater due to a steeper slope.
c. Provide routing calculations for storm drainage system including off-site flows for
the 25-year return frequency storm. Hydraulic grade lines for systems should not
exceed ground surface elevation at inlets for design storm.
d. S'torm drain should be designed to allow velocities of flow sufficient to prevent
deposition of solid materials.
e. For inlet and outlet pipe conditions, headwall shall be constructed in accordance
with GA Department of Transportation Standards. All headwalls shall be GA
Department of Transportation Construction Standard 1125. Safety end-sections
may be utilized for longitudinal pipe located within the right-of-way and F.E.S.
for storm drainage pipe located outside right-of-way.
f. Documented appropriate coefficients of roughness for pipe material shall be used
in Mannings equation.
2.03 Inlets:
Inlets shall be constructed as part of the storm drainage system to intercept surface water
and convey the water to the storm drainage system. The following guidelines shall be used in
design of inlets located in streets:
a. Inlets shall be located within the proposed street system based on the drainage
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area and the overall storm drainage system design.
b. Inlets shall be spaced and sized based on drainage area contributions and by-pass
quantities.
c. All inlets shall be constructed in accordance with the Georgia Department of
Transportation Standards for Construction.
d. Recessed inlets shall not decrease the width of the sidewalk.
e. Design and location of inlets shall take into consideration pedestrian and bicycle
traffic. In particular, grate inlets shall be designed to assure safe passage of
bicycles.
f. The use of slotted drains in public systems shall not be acceptable unless no other
alternatives are available.
g. Storm drainage system plans shall depict the location of all inlets and other storm
drainage system structures including, but not limited to manholes, mains, laterals,
ditches, culverts, etc.
h. For each inlet, data shall be submitted indicating the drainage area to the inlet,
inlet time of concentration, design rainfall frequency, and peak: flow.
1. Catch basins shall not be located with radii at street intersections. If stormwater
collection is necessary along radius, use Georgia Department of Transportation
1019-A, Type "E". Use multiple grates if volume warrants.
Section III. Open Channels
3.01 General:
Open channels may be designed and constructed as an integral part of the storm drainage
system. The benefits of open channel drainage systems related to cost, capacity, or potential
storage should be carefully considered in comparison to disadvantages such as easement and
right-of-way needs and maintenance cost. Open channels may be classified as natural or man-
made. The function and characteristics of these channels may be altered by the addition or
construction of channel linings. Three (3) main classifications of channel linings are recognized:
vegetative, flexible, and rigid. '
3.02 Desi2n Guidelines:
The minimum requirements for the design of open channels shall be based on the
following criteria:
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a. Open channels shall be designed to accommodate the 25-year design frequency
storm as a minimum. Should open channels be located in areas where rainfalls
exceeding the 25-year return frequency storm would cause excessive damage to
surrounding properties, additional capacity may be required.
b. Maximum permissible velocity for gi-ass lined channels is six (6) feet per second
for the design storm. Flow velocities shall not exceed six (6) feet per second at
transition locations where storm water flow exits onto grass lining. Exceptions
may be processed when an approved modeling method such as HEC-15 shows
that the channel is stable under the proposed conditions.
c. Roughness coefficients for the design of open channel drainage systems shall be
based on the Natural Resources Conservation Service manual or by the design
method.
d. The minimum slope for grass lined channels shall be one (1 %) percent.
e. Generally in public systems side slopes for grass lined channels shall be three (3)
horizontal to one (1) vertical or flatter with the exception of roadside ditches
(roadway design standards). Changes in direction of channels shall be
accomplished using simple horizontal curves. The centerline curvature shall have
a minimum radius of twice the top width of the design of flow.
f. Concrete lined channels shall be designed to avoid hydraulic jumps. Ifhydraulic
jumps are unavoidable, sufficient freeboard shall be provided. The channel shall
be constructed of reinforced concrete.
g. Appropriate energy dissipation devices shall be constructed in channels to control
flow velocities.
h. Channel drop structures may be required to reduce channel velocities and reduce
upstream and downstream channel slopes. Design of channel drop structures shall
be accomplished to contain design flow in channel, maintain allowable velocities
and minimize maintenance cost.
3.03 Erosion Control:
Appropriate erosion control methods shall be employed to insure functional operation of
the open channel and minimize maintenance cost. The "Manual for Erosion and Sediment
Control for Georgia" shall be used for appropriate erosion control methods.
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Non-structural erosion control measures are encouraged where feasible. Other structural
erosion control measures may include rip-rap, gabions, or other constructed facilities. The
designer shall provide adequate calculations to the City Engineer for review of such facilities to
determine required velocity control and appropriate soil and erosion control measures
Section IV CUL VERTS
4.01 General:
The traditional use of culverts is to convey storm flow through or under an existing
structure or facility without causing excessive backwater build-up or overtopping the structure
while minimizing excessive downstream velocities. Culvert sections will include upstream
approaches, headwalls, culvert piping, outletheadwalls, and downstream energy
dissipation/velocity control structures. Unless required by the Augusta-Richmond County Public
Works Engineering Department, culverts shall be designed for a 25-year return frequency storm
with back water elevations not exceeding a height six (6) inches below the shoulder of the
roadway.
4.02 Desi~n Guidelines:
a. Inlet and outlet headwalls shall be Georgia Department of Transportation
Construction Standard 1125. Outlet headwalls shall include the energy
dissipation structures.
b. Additional energy dissipation devices/structures may be required at outlets to
control velocity.
c. Selection of culvert size shall be based on hydraulic calculations for inlet control
and outlet control conditions.
d. For culverts draining greater than four (4) acres of runoff, hydraulic design
calculations shall be submitted.
e. In outlet control conditions, the determination of tail water depth shall be included
in the design.
f. The drainage basin and peak flow for culvert design shall be provided.
g. A minimum velocity of2.5 feet per second is required for culverts flowing
partially full to minimize sedimentation build-up.
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Section V DETENTION
5.01 General:
This Stormwater Management Program has been developed to control increased runoff
generated by development of property in the urban, suburban, and rural areas of the county.
General impacts ofland development include: increased rates and volumes of runoff, increased
channel erosion and degradation, increased sedimentation, greater levels of pollution, and lower
base flows during non-storm conditions. Augusta requires the design and construction of
stormwater management facilities such as detention, retention, infiltration, and sedimentation
ponds to address and mitigate the results of urbanization.
In general, stormwater management facilities shall be designed to provide for temporary
storage of stormwater runoff. The volume of stormwater runoff collected and stored will then be
released at a controlled rate not to exceed the pre-developed peak runoff rate of the site for the
equivalent storm. Augusta encourages the use of best management practices in the design and
construction of stormwater managelpent facilities, including storage facilities, to minimize the
transportation of pollutants, provide for effective erosion control, and minimize the transport of
sediment.
5.02 Detention Guidelines:
Stormwater runoff storage facilities shall be designed in accordance with the following
minimum criteria; depending on project location, basin characteristics, and evaluation ofproject
impacts by the City Engineer, additional requirements or support documentation may be
necessary.
a. Storage facilities shall be located to collect all runoff from proposed developed
areas; justifiable exceptions to allow portions of a development to bypass
detention may be made by the City Engineer.
b. Storage facilities shall not be located within the 100-year flood plain in
accordance with the flood plain managemen.t policy of the current Augusta-
Richmond County Commission Flood Plain ordinance.
c. Storage facilities shall be designed to provide adequate volume to detain the
runoff difference between the pre-developed and post-developed site area for the
design storm.
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d. Stormwater runoff data shall include tabular hydro graphs of pre-developed and
post-developed runoffs for the 2,5,25,50, and lOa-year storms.
e. Outlet structures shall be designed to control the release of stored stormwater
runoff not to exceed the pre-development runoff rate for the corresponding storm,
based on the 2,5,25, and 50-year return frequency storms.
f. Detailed construction information including plan and cross-section(s) views shall
be provided on the outlet structure, including type of structure, type of release
control, ie weir and orifice control, etc.
g. Stage-discharge rating data shall be presented in tabular form with all discharge
components, including orifice, weir and outlet conduit flows and velocities clearly
indicated.
h. The bottom area of the storage facility should be sloped towards the outlet to
prevent standing water conditions, other methods acceptable to the City Engineer
may be used.
1. Sedimentation control measures shall be installed within the storage facility to
prevent transport of settlement into the outlet structure and downstream receiving
waters.
J: For each storm event, a hydro graph routing methodology shall be used to indicate
staged-storage-discharge relationships. Routing hydro graphs will not be required
for storage facilities designed on sites smaller than five (5) acres.
k. The design of storage facilities that require storage volumes in excess of 100 acre
feet or earthen embankments in excess of 25 feet shall be prepared in accordance
with the Georgia Safe Dams Act and submitted to the Georgia Department of
Natural Resources Safe Dams Division for review.
1. Slopes of earthen embankments shall be constructed with two (2) horizontal to
one (l) vertical dimensions or flatter. Details of embankment construction,
including geometry, materials of construction, compaction characteristics, etc.
shall be provided. .
m. For embankments in excess of 15 feet in height, design and construction data
relating to embankment stability, foundation preparation, and resistance to erosion
shall be provided.
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n. Outlet structures shall be designed to provide release of low flow volume and
prevent standing water within the detention pond.
o. An emergency overflow shall be provided for all storage facilities, capable of
passing the lOa-year return frequency storm unless the lOa-year storm is
accommodated through the principle spillway/outlet.
p. Grassing schedule for earthen embankment and exposed soils from construction
activities shall be provided.
q. Trash racks and safety grates will be required for all outlet structures and outlet
pipes greater than or equal to 18 inches.
r. A six (6) foot chain link fence with three (3) strands of barbed wire and 14 foot
access gate shall be installed around public detention ponds. Hold Harmless
Agreements may be executed by the developer for private systems (see
Appendix).
s. Sheet flow over side banks of the detention pond is discouraged; off-site flow
shall be routed to the common locations and conveyed into the stormwater storage
facility utilizing structural practices to minimize erosion.
t. For facilities to be dedicated to Augusta-Richmond County Commission, O-ring
RCP shall be required for the entire length of pipes penetrating the embankment
or dam; justifiable exceptions may be accepted by the City Engineer.
5.03 Exemptions:
Exemption to stormwater runoff storage requirements may be made on a case-by-case
basis within the urban areas of Augusta. In order to apply for an exemption to stated stormwater
requirements, the following criteria must be met:
a. The site must be located within the urban district, or
b. Proposed changes to the site or proposed development activities produce no
change in runoff, or
c. The site is less than one (1) acre in size and the proposed development does not
produce stormwater runoff greater than 1 cfs in excess of pre-developed
conditions on a 50-year return frequency storm.
Page 11
Section VI OUTFALL-RUNOFF RELEASE
6.01 General:
The outfall of stormwater runoff storage facilities directly impacts down stream
properties and receiving waters. The location of the outfall structure is therefore crucial in the
design of an overall stormwater management system. In general, the outfall from a storage
facility should be located to access the nearest natural drainage feature or stormwater conveyance
system with adequate capacity to convey released flow from the storage facility. Overflow or
emergency spillways designed to .accommodate a 100 year return frequency storm mayor may
not be located near the principal outlet structure depending on capacities and the impact of
down stream properties.
6.02 Desien Guidelines:
The following information shall be provided for evaluation of the stormwater release
locations:
a. Indicate and label the drainage feature located immediately downstream of the
outlet structure.
b. Indicate the nearest receiving creek, stream or tributary as delineated by FEMA or
USGS quadrangle maps and distance to such feature.
c. Indicate outlet location and discharge flows on plans.
d. Provide energy dissipation structures to control outlet velocities for erosion
control, if necessary.
Section VII SPECIAL BASIN RESTRICTIONS
7.01 General:
Urban development has significantly impacted certain creek drainage basins resulting in
serious damage to property and the d(sruption of infrastructures services to commercial and
residential areas within the basin during significant rainfall events. Consequently, these basins
have been identified as requiring special consideration in design of residential and commercial
developments. The drainage basins identified as requiring additional design consideration are as
follows:
a. Rae's Creek Basin
b. Rocky Creek Basin
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c. Rock Creek Basin
Within these basins, the following restrictions, shall apply:
For site developments less than ten acres, no fill or detention facilities shall be
placed in the flood plain based on a 100 year return frequency storm as
established by FEMA
Stormwater management facilities are required for all developments
The release of stormwater runoff from storage facilities shall be limited to 90% of
the pre-developed rates
Section VIII DETENTION AND SEDMIMENT BASIN CONSTRUCTION
8.01 General:
Sedimentation control basins and detention ponds and other stormwater management
facilities are required for all grading activities, roadway construction, and site development to
minimize damage and protect Georgia's lands and water resources. Where practical or at the
direction of the City Engineer, such structures shall be constructed immediately following initial
clearing and grubbing activities. In all cases, structures are considered to be a part of the soil
erosion and sedimentation control practices for the site and shall be installed as soon as practicaL
Failure to install these structures in a practical sequence or in such cases where failure to install
these structures allows mitigation of sediment erosion or other damage to adjacent land or water
resources will constitute a violation of the Soil Erosion and Sedimentation Control Plan and
associated ordinance.
Page 13
PART II ENVIRONMENTAL REQUIREMENTS
General:
All stormwater management plans are required to comply with local, state and federal
regulations including environmentally sensitive land areas, "wetlands", stormwater run-off
quality, and specific National Pollution Discharge Elimination System, "NPDES" programs.
Depending on location and impact on downstream waters from proposed developments, other
state and federal regulations may require compliance.
Section I
1.01
Wetlands
The delineation and jurisdictional approval of wetlands as identified under Section 404
of the Clean Water Act is regulated by the US Army Corps of Engineers. For proj ects located in
Augusta, the Savannah office of US ArnlY Corp of Engineers provides review and enforcement
activities. Although compliance of section 404 of the Clean Water Act is the responsibility of
the property owner, Augusta-Richmond County Commission is dedicated to insuring the
protection of natural resources and working with the Corps of Engineers in identifying, accessing
and evaluating the impact of proposed developments on a existing wetland areas. Should
characteristics typical of wetland be identified within a specific project area, the City Engineer
may request additional information concerning the impact of the proposed development on this
area and/or the jurisdictional on delineation of the area.
For projects impacting wetland areas, appropriate documentation of design approval by
the US Army Corps of Engineers will be required; for projects impacting lands within 25 feet of
state waters shall require appropriate variances for Georgia Department of Natural Resources.
Section II Water Quality Requirements:
2.01
The water quality of stormwater runoff depends on a number of factors including:
magnitude and duration of rainfall events, soil types, time between storms, land use type and
specific activity, illicit connections or illegal dumping, and the ratio of the runoff per volume to
the receiving water flow volumes. The stomi water management policy adopted by Augusta-
Page 14
Richmond County Commission recognizes that the use of structural and non-structural controls
for stormwater management programs are beneficial in the controlling pollution of the receiving
waters. Therefore, best management practices (BMP'S) are encouraged in stormwater plans in
project design and construction. BMP's may include a maintenance and activities schedule for
drainage facilities, soil erosion and sedimentation control practices, etc. All developments must
comply with the Soil Erosion and Sedimentation Control Ordinance, current edition, as minimum
structural and non-structural standards for project design.
Section III Local Regulations: .
3.01
In response to specific requirements in the Clean Water Act of 1993, Augusta has been
given authority by the Georgia Department of Natural Resources, Environmental Protection
Division to permit the National Pollution Discharge Elimination System permit program. The
local program requires the use of best management practices based on the current Soil Erosion
and Sedimentation Control Ordinance adopted by Augusta-Richmond County Commission. The
application of these regulations includes the use in stabilization, mulching, straw, grass, silt
fences, sediment traps, and other temporary/permanent structures for minimizing soil erosion and
the transportation of sediment into receiving waters. All developers shall comply with these
regulations.
PART III
MATERIALS FOR CONSTRUCTION
SECTION I STORM DRAINS:
Page 15
1.01 General:
For public systems, all storm drain pipe, manholes, junction boxes, catch basins, inlets,
etc. and appurtenances shall comply with GA Department of Transportation construction
standards and specifications. Additionally, bedding material, when required, and select backfill
shall comply with these regulations. The following specific design criteria will be required for
new developments:
1.02 Desien Guidelines:
a. All storm drain pipe located under pavement or longitudinal pipe as part of the
roadway drainage system shall be reinforced concrete pipe. A minimum class III
reinforce concrete pipe shall be used. All concrete pipe shall be manufactured and
installed in compliance with GA Department of Transportation standards and
specifications. Concrete arch pipe shall only be allowed with special approval by
the City Engineer.
b. Outside of right-of-way limits, other suitable pipe materials may be used.
Installation shall be in accordance with GA Department of Transportation
construction specifications.
c. Catch basins, drop inlets, junction boxes, grate inlets, hoodback traps, storm
manholes, etc. shall be constructed in accordance with GA Department of
Transportation construction specifications and standards.
c. Catch basins installed along roadways with raised edge asphalt sections, shall
include concrete transition lengths standards for construction. The construction of
the transition curb shall be of concrete as per construction standards and tie into
the raised edge asphalt. The face of the proposed catch basin shall be located at
the back of the raised asphalt section "not at the gutter line" .
Augusta recognizes that private developments may be designed and constructed in the
County. Private developments not constructed in accordance with GA Department of
Transportation Construction standards, as noted herein, can not be accepted into the county
system for improvement and/or maintenance unless improved to minimum county standards and
accepted by the county..
Page 16
Section II CUL VERTS:
2.01
Culverts shall be constructed of Class III reinforced concrete pipe, Class IV reinforced
concrete pipe, as appropriate, or concrete box culverts. Design of said facilities shall be in
accordance with GA Department of Transportation standards specifications and construction
standards.
Section III Soil and Rock Structures:
3.01 General:
Soil and rock structures shall include earthen embankments for roadways, earth and/or
earthrock structures for dam construction, dikes, containment embankments, and structural earth
berms for the support of facilities or structures, impoundment of water, or diversion of runoff.
Earth and earthrock structures do not include landscaping berms. For earthen dam construction,
sufficient design information regarding the construction of the proposed impoundment
embankment shall be provided. This data shall include the suitability of the materials and design
cross-sections to ensure geometric stability of the structure. Soil for embankments impounding
water shall have at least 15% clay content and be compacted to a minimal of 95% of standard
proctor dry density at or near optimum moisture content. For earthen structures, design data
shall include sufficient information to indicate the stability of the soil structure and provisions to
prevent piping, excess seepage, etc. Earthen structures that must comply with the GA Safe Dams
Act shall be submitted to the Department of Natural Resources Dam Safety Division for review.
Earthen structures will also include the construction of swales. The type of erosion
control practices required for construction of swales will depend on the velocity of runoff for the
design storm. Construction of swales shall be accomplished in accordance with the Manual for
Erosion and Sediment Control in Georgia.
Section IV GRASSING
4.01
Temporary and permanent grassing are required to comply with the Soil Erosion and
Sedimentation Control Ordinance adopted by Augusta-Richmond County Commission.
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Grassing schedules shall be submitted in accordance with the Manual for Erosion and Sediment
ControL
Section V Fencing
5.01
Fencing is required around all impoundments designed as permanent stormwater runoff storage
facilities to be dedicated to Augusta-Richmond County Commission. In some cases, a hold
harmless agreement may be executed by the owner of the project to eliminate the installation of
fencing for the subject stormwater storage facility (see Appendix). Where fencing is required, all
fencing shall be 11 gage (minimal) and 6 feet in height. The fencing shall contain three (3)
strands of barbed wire or ribbon wire to inhibit unauthorized access and shall include access
gates, minimum 14 feet total width. All fencing shall include a top rail in accordance with GA
Department of Transportation Standards.
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PART IV UPDATE
This Development Document is to be updated annually by the Subdivision Review Committee
appointed by the Richmond County Commission appointed by the Richmond County
Commission in October 1995.
This review and update will take place in June of each year.
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:- ~
REFERENCES:
Augusta-Richmond County Subdivision Regulations
Columbia County Subdivision Regulation Manual, April 1993
Drainage Criteria Manual, City of Austin, Texas, Revised 1989
Drainage Procedures Manual DeKalb County, Revised 1978
Environmental Criteria Manual, City of Austin, Texas, Revised 1991
Highway Drainage Guidelines, AASHTO 1987
Manual for Erosion and Sediment Control in Georgia, Fourth Edition, 1996
Manual on Drainage Design for Highways, Georgia Department of Transportation, revised 1988
Manual on Drainage Design Fulton County Department of Planning & Community
Development, 1983
Municipal Stormwater Management by Debo and Reese, 1995
Regulation of Storm water Management Systems, Saint Johns River Water Management District,
Palatka, Florida, revised April 1994
Urban Stormwater Management Special Report No. 49, American Public Works Association
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APPENDIX
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