20071522 Ver 1_More Info Received_20071010 (2)

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L THE JOHN R. McADAMS COMPANY, INC.
LETTER OF TRANSMITTAL
To: Ms. Lia Myott Date: October 10, 2007
NCDWQ
401 Wetlands Unit
2321 Crabtree Boulevard
*" HAND DELIVER **
Raleigh, North Carolina 27604
Re: Porto Fino -Clayton, NC
DWQ Response to Comments
Job No.: WLT-07010
EXP # 07-1522
I am sending you the following item(sl~
COPIES DATE NO. DESCRIPTION
3 Revised O eration and Maintenance A reement
3 Executed A reement 1 on final / 2 co ies
These are transmitted as checked below:
® As requested ® For your use
® For approval ^
Remarks:
Copy to: Signed:
Kevin Ya
Project Manager
FOR INTERNAL USE ONLY
^ Copy Letter of Transmittal Only to File
® Copy Entire Document to File
CIVIL ENGINEERING • LAND PLANNING SURVEYING
PO Box 14005 Research Triangle Park, NC 27709 [phone] fax (919) 361 ~6
www. ohnrmcadams.com > ; ,_~ ~ r ~ ~-I~y~? ~
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PORTO FIND
Clayton, NORTH CAROLINA
BIORETENTIONAREAS # 1-6
OPERATIONAND MAINTENANCE
AGREEMENT (Revised 10/05/07)
WLT-07010
October 2007 ~ C 2007
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SECTION I
MAINTENANCE OF EMBANKMENTS

I. MAINTENANCE OF BIORETENTION AREA EMBANKMENTS
A. Vegetation
The primary vegetative ground cover for all berm/embankments
(excluding inside the wet pond facility) is to be tall fescue. Proper
maintenance of this cover will serve to prevent erosion while providing
optimal access for inspection as well as preventing excessive sediment
from entering the facility. Woody vegetation and trees should not be
allowed to propagate on the dam embankments or top of dam. Trees and
brush, if desired, are acceptable on embankments other than the dam.
Inspection of embankment centipede sod condition should be performed
monthly or after every rainfall event greater than 0.5 inches of rainfall
over a 24-hour period.
Seeding: Seeding should be accomplished by the use of a Spiker
and large tractor aerifier to ensure proper seed and soil contact
along the top of banks. The temporary and permanent seeding
schedules are shown on the bioretention area detail sheet, which
has been included within this manual. Reseeding may be
necessary in instances where initial seeding failed or existing
areas have been compromised. The seeding schedules shown on
the original design documents for the bioretention area should be
followed for any necessary reseeding.
2. Mowing: All vegetative cover should be maintained below 6" in
height. Due to the slope of the embankments, string trimmers
(no mechanical mowers) must be utilized for mowing turf.
Mowing and maintenance should be performed once a month to
keep the maximum grass height below 6 inches and to maintain
appropriate turf cover and health of turf.
B. Erosion
Erosion is initiated when vegetative cover is insufficient and/or
concentration of runoff destabilizes centipede sod. Runoff then tends to
concentrate into channel flow, and soils tend to become entrained in the
water and be transported downstream. Unsuitable fill material,
inadequate compaction, and/or poor stabilization of centipede sod can
accelerate the erosion process. This has a negative environmental impact
on downstream features, and has the potential to undermine the stability
of the wet pond facility. Erosion can be minimized with the proper care
of centipede sod and the use of appropriate methods to repair eroded
areas and prevent recurrences of eroded areas. Appropriately, compacted
soil meeting the berm design requirements will be placed in any gullies
or rills, and then reseeded as described above. Re-occurrence of erosive
problems should be addressed with appropriate geotextile fabrics that are
installed according to manufacturer's instructions and per an engineer's
recommendation. Uneven surfaces on the crest of the berm may lead to
the formation of rills and/or gullies. It is possible to eliminate this
problem by properly filling any depressed areas such that the entire top
of berm is flat and level. Addition of fill to the top of berm should be
completed by first preparing the existing soil such that a distinct

boundary layer does not form beneath existing soil and newly placed soil.
New fill should meet all soil requirements (as to material, placement, and
compaction) as stated on the original design documents for this structure.
Inspection for erosion should be performed monthly or after every major
rainfall event.
Abutment (or toe) areas: The location where the fill of the berm
contacts the existing ground is the abutment (or toe). Erosive
channels have a tendency to form in these areas. Appropriate
geotextile fabrics, as mentioned above, may be necessary to
prevent or stop this form of erosion from occurring. An engineer
is required if erosion in this area is significant.
C. Seepage
Detection: Soft wet areas and flowing springs are an indication
of seepage. Early indicators of seepage include vegetation which
is more robust than surrounding centipede sod. Vegetation
normally associated with wetland areas such as cattails, ferns,
reeds and mosses may also indicate the initiation of seepage.
The previously described abutment (or toe) area is a common
location for seepage to occur. Another common location for
seepage problems is the area where the outlet structure exits the
berm section. This is especially true in cases where the soil
around the barrel is not compacted properly. Another problem
related to seepage may be indicated by the occurrence of `boils'
below the abutment of the dam. These boils are springs that tend
to deposit soils. Locating the occurrence of any boils should be
included in the bi-annual inspection of the facility. `Boils' are a
possible indication of piping and could lead to berm failure.
Piping occurs when a void space is formed within the interior of
the berm embankment. These void spaces tend to be preferred
paths for water to travel, which will erode the interior of the
berm and lead to failure.
D. Cracks, Slides, Sloughing and Settlement
1. Cracks: Large, well-defined cracks of greater than '/" width
indicate the potential for serious problems and the inspector of
the facility should be alert for their presence. Cracks in the berm
generally follow one of two patterns:
Transverse cracks appear perpendicular to the length of the
berm and may be caused by differential settlement.
Transverse cracks increase the likelihood of the formation of
piping and seepage.
Longitudinal cracks appear horizontally along the berm and
could serve as warnings to a future slide event. Longitudinal
cracks in newly constructed berms may be an indication of
poor compaction techniques and poor foundation preparation.
Slides: Slides and slumps have the potential to critically
undermine the integrity of the berm. Arch-shaped cracks that

expose soil indicate the initiation of slides. Detection of slides
by inspectors should be addressed in a timely manner and a
geotechnical engineer should be contacted for consultation.
Settlement: Settlement of the soil in the berm reduces freeboard
in large storm events and may even lead to overtopping.
Differential settlement of the berm can also lead to the
concentration of runoff and therefore erosion as mentioned
above. For this reason the berm should be maintained uniformly
to its original design elevation. Greater than six inches of
settlement may be indicative of significant issues within the berm
foundation and could lead to catastrophic failure. Indications of
this degree of settlement necessitate inspection by a geotechnical
engineer.
4. Inspections for cracks, slides, sloughing, and settlement should
be performed biannually. Actions to take if any of the above is
detected: Any of the problems mentioned above require that a
geotechnical or civil engineer be contacted, and that corrective
action be taken.

SECTION II
SEDIMENT MONITORING

II. SEDIMENT MONITORING
A. Bioretention Area
Accumulation of sediment within the Bioretention area should be kept to
a minimum by stabilization of the Bioretention drainage area and proper
prevention of erosion. Excess sediment accumulation within the
Bioretention area will cause suffocation of the Bioretention area -
centipede sod, thus crippling the water quality function of the
Bioretention area. Inspection for sediment deposition should be
performed biannually.
Check the depth at various points within the Bioretention area,
especially in the upland areas around the inlets to the
Bioretention area. Accumulated sediment will be removed
semiannually or when the depth reaches 0.5 inches or more. A
stake shall be set during construction to indicate 0.5 inches of
sediment accumulation. The measuring device used to determine
the sediment elevation shall be such that it will give an accurate
depth reading and not readily penetrate into accumulated
sediments.
2. Removed sediment shall be disposed of in an appropriate manner
and shall be handled in a manner that will not adversely impact
water quality (i.e. stockpiling near the Bioretention area or
surrounding streams).
3. If the elevation of the bio-retention area bottom exceeds the
planned elevation, the sediment shall be removed to design
levels. This shall be performed by removing the upper 6 inches
of soil and stockpiling the soil. The soil shall not be stockpiled
for more that 2 weeks. Any dead or damaged bio-retention area
plants must be replaced after this process per the original
planting plan.
B. Forebay
Accumulation of sediment within the forebay area should be kept to a
minimum by stabilization of the Bioretention area drainage area and
proper prevention of erosion. Excess sediment accumulation within the
forebay area will cause sediment transport to the main pool of the
Bioretention area and subsequent difficulty with maintenance procedures.
Inspection for sediment deposition should be performed biannually.
Check the depth at various points within the forebay, especially
in the upland areas around the inlets to the Bioretention area.
Accumulated sediment will be removed semiannually or when
the depth reaches 2 inches or more. A stake shall be set during
construction to indicate 2 inches of sediment accumulation. The
measuring device used to determine the sediment elevation shall
be such that it will give an accurate depth reading and not readily
penetrate into accumulated sediments.

2. Removed sediment shall be disposed of in an appropriate manner
and shall be handled in a manner that will not adversely impact
water quality (i.e. stockpiling near the pond basin or streams).
3. NCDOT class "B" rip-rap is recommended to form the forebay.
This rip-rap shall be replaced annually or when necessary
between annually replacements. Care should be taken to insure
that a 12" lip of rip-rap is maintained at all times around the
perimeter of the forebay. This lip prevents the occurrence of an
erosive environment. Loss of the lip could result in the loss of
the water quality benefits associated with the bio-retention area.
C. Principal Spillway System
If present, remove accumulated sediment from the outlet
structure. The principal spillway system should be inspected for
sediment accumulation monthly or after every rainfall event
greater than 0.5 inches of rainfall over a 24-hour period.
D. Storm Drainage System
The upstream storm drainage system should be maintained along
with the bioretention area. Trash from the site has a tendency to
be washed into the storm drainage system and become lodged in
the catch basins or pipes. The catch basins and pipes should be
cleaned of debris at the time that maintenance is performed on
the bioretention area. Sediment may accumulate in portions of
the storm drainage system where slopes are relatively flat. This
sediment may be washed out of the system, or flushed with a
garden hose. Sediment should be flushed monthly or after every
rainfall event greater than 0.5 inches of rainfall over a 24-hour
period. Steps should be taken to trap this "flushed" sediment at
the entrance to the bioretention area to prevent it from being
deposited within the wet pond.

SECTION III
MAINTENANCE OF O UTLET STRUCTURES

III. MAINTENANCE OF OUTLET STRUCTURES
The bioretention area is designed to pass stormwater quality storms through the
low flow orifice located in the secondary outlet structure and larger storm events
through the principal spillway. It is of vital importance that these structures
remain unblocked so that the hydraulic functionality is not compromised. The
outlet structure system should be inspected to ensure that it is functioning
properly.
A. Bio-Retention Underdrain System
1. The underdrain system for both bio-retention areas consists of a
series of 8-inch diameter perforated HDPE pipes. These
underdrain pipes connect to the concrete principal spillway drop
inlet via 8-inch diameter HDPE pipes. Tied to the underdrain
system are vertical HDPE cleanouts that extend up to the surface
of the mulch layer. The underdrain system is wrapped in a
nonwoven geotextile filter fabric and is installed within a gravel
jacket in order to minimize the probability of blockage.
However, in the event that the underdrain systems become
blocked, the bio-retention area will not drain appropriately and
will begin to pond up, which means that the water quality
benefits associated with the bio-retention area are lost. The
underdrain system should be inspected for blockage monthly or
after every rainfall event greater than 0.5 inches of rainfall over a
24 hour period. If inspected after a major rainfall event, all
ponded water should dissipate over 4-6 hours. Debris causing
the blockage should be promptly removed from the underdrain
system such that sufficient infiltration through the bio-retention
area may occur. The underdrain systems may be accessed /
flushed out via the HDPE cleanouts located at the top of the
mulch layer.
B. Principal Spillway
The principal spillway for the bioretention area consists of a 4' x
4' square weir box structure attached to a 18-inch O-ring RCP
barrel. The principal spillway is responsible for safely
conveying larger storm events through the facility. The principal
spillway system is expected to remain robust throughout the life
of the bioretention area, but periodic inspection of the system is
required. This inspection should occur biannually. The
inspector should check for the presence of spalling, scaling, or
cracking in the spillway system. spalling is evident when pieces
of concrete fall from the main pipe. It is defined as breaking,
chipping, or fraying of concrete slabs that leave an uneven

surface or edge, most often at joints or cracks. Scaling occurs
when the surface of the concrete begins to flake off. The
presence of cracking is indicated by separations in the concrete
that are not located in the joints. Cracking can indicate the
presence of structural problems and lead to leaks. Cracking can
cause loss of the water tightness of the system, which can lead to
piping (i.e. migration of soil particles into the pipe). If piping
occurs, the risk of failure of the dam structure is greatly
increased. Evidence of any of the above issues requires that an
engineer be contacted for additional inspection to determine the
need for repairs.
2. If the principal spillway system becomes blocked so that it does
not operate at full capacity, the risk of dam overtopping or other
uncontrolled releases may result. Therefore, to ensure hydraulic
capacity of the spillways, the principal spillway system should be
inspected for blockage monthly or after each major rainfall
event. Any vegetative growth that occurs within the principal
spillway system should be removed promptly so that the full
hydraulic capacity of the system is maintained.
C. Stormwater Pipes
The underground pipes should be inspected for any structural
damage. Structural damage includes but is not limited to
deterioration, joint failure, punctures, cracks, misalignment,
settling, leaking, deflection, and sagging. Deformations in the
ground surface directly above or near the stormwater pipe may
be a sign of failure in the system. Any structural damage
should be immediately reported to a register professional
engineer so that the appropriate course of action can be
determined.
2. The underground pipes, including inlet and outlet areas, should
be inspected for trash/debris accumulation to ensure runoff can
move freely into and out of the pipes. Any accumulated
trash/debris should be removed and disposed of in an approved
manner.
D. Ground Surface
1. The ground surface should be inspected for visual signs of sink
holes. If any signs of a sink hole are present, a registered
professional engineer should be immediately consulted for
remediation action.

SECTION IV
MAINTENANCE OF BIO-RETENTION AREA
CENTIPEDE SOD

IV. Maintenance ofBio-Retention Area Centipede sod
A. Bio-retention Area Centipede sod
1. Once the construction of the bio-retention area is complete, the
centipede sod should be watered for 14 consecutive days unless
sufficient natural rainfall in order to establish the centipede sod
appropriately.
2. The centipede sod should be visually inspected monthly (more
frequently in the summer) for disease or pest problems. If pest
treatment is necessary, use the least toxic method. All dead and
diseased centipede sod considered beyond treatment should be
removed and replaced. The centipede sod should be kept healthy
and vibrant. If necessary, it should be over seeded (usually in the
fall -September to October) at a rate of 1001bs/acre.
3. The grass within the bio-retention area should be mowed to a
height of no greater than 8 inches.
4. During extreme heat and drought conditions, the centipede sod
should be inspected for physical features of stress (i.e. wilting,
yellow, spotted, loss of, or brown leaves, etc.). During these
conditions, the bio-retention areas should be watered as
necessary.
5. Weeds and other invasive species should be removed whenever
present.
B. Planting Soil Layer
1. The planting soil layer should be visually inspected for
erosion/damage once a month. Evidence of erosion should be
promptly repaired. If erosion is present along the drainage path
within the bio-retention area, it may be stabilized using small
stones.
2. The pH of the bio-retention area should be checked twice a year.
If necessary, apply an alkaline product (such as limestone) to
maintain the appropriate pH. Please reference the detail sheet for
the bio-retention area included in this report for the appropriate
pH levels.
3. If present, accumulated trash, litter, and debris should be
removed during the monthly inspection.
4. If present, accumulated sediment should be removed per the
"Sediment Monitoring" section of this manual.

I acknowledge and agree by my signature below that I am responsible for the performance of the maintenance
procedures listed within. I agree to notify DWQ of any problems with the system or prior to any changes to the
system or responsible party.
Print name: Robert Bailey. Walthom Group
Title: Project Manager
Address
Phone:
Signatu
Date: ~
I, ~ ~~{~~. (~ ~~ , a Notary Public for the State of 1~17-'~'- ~~+c./'bl'~ ~ti.,
County of ) ~`~ ht~~~ , do hereby certify that K,~%l~.t,~tJ~ ~ I~'.li l~~-
personally appeared before me this ~ day of ~ ~~~ ~~JZ, and acknowledge the due
execution of the forgoing storm water management facility maintenance requirements. Witness my hand and
official seal,
V~~~ TAR A~'~
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SEAL
My commission expires_ _____ ~~~-, ~~, ~ ~~