20210224 Ver 1_12-O&M Manual - Stormwater Wetland - WETLAND 4_20220328

Operation and Maintenance Manual for
Stormwater (Constructed) Wetland
Eno Village — Wetland #4
Overview
Stormwater wetlands are constructed systems that mimic the functions of natural wetlands and
use physical, chemical, and biological processes to treat stormwater. A stormwater wetland is
designed to capture the design storm and release it slowly over a period of two to five days via
a properly designed outlet structure. The wetland shall be designed in a manner that protects
the device, the areas around the device and the receiving stream from erosion. Stormwater
wetlands temporarily store stormwater runoff in shallow pools that support emergent and
riparian vegetation. The storage, complex microtopography, and vegetative community in
stormwater wetlands combine to form an ideal matrix for the removal of many pollutants.
Stormwater wetlands can also effectively reduce peak runoff rates and stabilize flow to
adjacent natural wetlands and streams.
Below are various views of this stormwater control measure. Note that your wetland may vary
from these figures.
Figure 1: Stormwater Wetland Example - Plan View
NON-FOREBAY DEEP POOLS
FOREBAY
(a) 5% TO 15% OF THE WETLANO SURFACE AREA
(a) 10% TO 15:6 OF THE WETLAND
(b) PROVIDE THROUGHOUT A-ETLANO AND
SURFACE AREA
ADJACENT TO OUTLET STRUCTURE
(b) PROVIDE AT INLET INTO
STORWWATER WETLAND
OUTLET STRICTURE
PLACE INLETS AND OUTLETS TO
AVOID SHORT CIRCUITING AND
ZZ
DESIGN FOR EROSION
PROTECTION
EMERGENCY SPILLWAY
SHALLOW WATER ZONE ZONE
PROVIDED FOR MAJOR
la) 35% TO a5`>; OF THE WETLAND SURFACE AREA
STORMS AND DESIGNED
Ib'"TING OPTIONS.
FOR EROSION
1) 50 HERBACEOUS PLANTS PER 200 SO FT
PROTECTION
TEMPORARY INUNDATION ZONE
la) 30% TO 45% OF THE WETLAND SURFACE AREA
• A LANDSCAPE PLAN SHALL BE PROVIDED AND SHALL INCLUDE THE
IO)PLANTING OPTIONS
FOLLOWING
1) 50 HERBACEOUS PLANTS PER 200 SO FT
(a) DELINEATION OF PLANTING ZONES
218 SHRUBS PER 200 SO FT
(b) PLANT LAYOUT VATH SPECIES NAMES AND LOCATIONS AND
3) ONE TREE AND 40 GRASS LIKE HERBACEOUS
(c) TOTAL N1.IUBER AND SIZES OF ALL PANT SPECIES
PLANTS PER 100 SO FT
• CATTAILS SHALL NOT BE PLANTED IN WETLAND

Figure 2: Stormwater Wetland Example — Schematic Cross -Section
EMBANKMENT AND PERIVIETER FILL SLOPES
PLANT WITH NON -CLUMPING TURF GRASS. NO TREES OR
WOODY SHRUBS
FOREBAY
W ENTRANCE SHALL BE DEEPER THAN EXIT
(b) DEPTH$/-40' BELOW PERMANENT POOL
(b) IF DEPTH -15'. CLEAN OUT FOREBAY
TEMPORARY INUNDATION ZONE
0
L_
Z
SEDIMENT STORAGE AIDUST THE PH. COMPACTION.
AND OTHER ATTRIBUTES OF
THE FIRST 12* DEPTH OF TILE
SOIL IF NECESSARY TO
PROMOTE PLANT
ESTABLISHMENT AND GROWTH
TEMPORARY INUNDATION ZONE
(a) DRAW DOWN BFT%VEFN 9 AND 5 DAYS
(b) WETLAND MAY TEMPORARILY POND PEAK ATTENUATION
WXUME AT A DEPTH EXCEEDING 15'
(C) DEPTH. 0-15' ABOVE PERMANENT POOL
SHALLO'A' WATER ZONE
DEPTH 0-9' BELO'N PERMANENT POOL
NON-FOREBAY DEEP POOL
(a) DESIGN TO RETAIN WATER
BETWEEN STORM EVENTS
(b) DEPTH. A MINIMUM OF18- BELOW
PERMANENT POOL
Figure 3: Stormwater Wetland Example - Riser
TRASH RACK (REQUIRED)
WEIR (OR OTHER METHOD) TO
ESTABLISH TEMPORARY POOL
1 /////MRIMM \
'�•
OUTLET TO ESTABLISH
NORMALPOOL
MUST DRAW DOWN
TEMPORARY POOL IN TWO
TO FIVE DAYS
DE'NATERING METHOD /
PROVIDE A METHOD TO DRAW DO'NN
STANDIYG WATER TO FACILITATE
MAI%TENANCE AND INSPECTION
(E G . SKIIAMER OR PUMP)
i
1 1
1 1
1 1 OUTLET PIPE
1 1
1 1
1
1
•�J• .. .. •� t
ANTI -FLOTATION SLAB ANTI -SEEP MEASURES
ARE RECOMMENDED

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Maintenance
Although wetland plants require water for growth and reproduction, they can be killed by
drowning in excessively deep water. Usually, initial growth is best with transplanted plants in
wet, well -aerated soil. Occasional inundation followed by exposure to air of the majority of the
vegetation enables the plants to obtain oxygen and grow optimally. Conversely, frequent soil
saturation is important for wetland plant survival.
Dramatic shifts can occur as plant succession proceeds. The plant community reflects
management and can indicate problems or the results of improvements. For example, a
requirement of submerged aquatic plants, is light penetration into the water column. The
disappearance of these plants may indicate inadequate water clarity. The appearance of
invasive species or development of a monoculture is also a sign of a problem with the
aquatic/soil/vegetative requirements. For instance, many invasive species can quickly spread
and take over a wetland. If cattails become invasive, they can be removed by a licensed aquatic
pesticide applicator by wiping aquatic glyphosate, a systemic herbicide, on the cattails.
Unlike maintenance requirements for wet or dry stormwater ponds, sediment should only be
selectively removed from stormwater wetlands, primarily from the forebay. Sediment removal
disturbs stable vegetation cover and disrupts flowpaths through the wetland. The top few
inches of sediment should be stockpiled so that it can be replaced over the surface of the
wetland after the completion of sediment removal to re-establish the vegetative cover using its
own seed bank. Accumulated sediment should be removed from around inlet and outlet
structures.
Important maintenance procedures for Stormwater Wetlands include:
It is recommended that this facility be inspected/monitored monthly and after any rain event
that produces at least 1" of rainfall during a 24-hour period.
No portion of the Stormwater Wetland should be fertilized after the first initial fertilization that
is required to establish the plants on the vegetated shelf.
Stable groundcover should be maintained in the drainage area to reduce the sediment load to
the stormwater control measure.
If the pond must be drained for an emergency or to perform maintenance, the flushing of
sediment through the emergency drain should be minimized as much as possible.
The dedicated access easement needs to be maintained so that a clear pathway to and around
the stormwater control measure is present. No obstructions should be present within this
pathway.
The stormwater control measure shall be certified annually in accordance with the City of
Durham's Annual SCM Maintenance Certification Protocol. Annual inspection reports by
individuals certified by the City of Durham as a BMP Maintenance Certifier (BMC) shall be
submitted to the City for each stormwater control measure by its established anniversary date.
If functional issues arise during the year, a qualified SCM inspector should be contacted to

provide a supplemental assessment and recommendation for remediation of any functional
deficiencies.
Maintenance Provisions for This Stormwater Control Measure
SCM element:
Potential problems:
How to remediate the
problem:
The entire SCM
Trash/debris are present
Remove the trash/debris
Areas of bare soil and/or
Regrade the soil if necessary
erosive gullies have formed.
to remove the gully, and then
plant a ground cover and
water until it is established.
Perimeter of Wetland
Provide lime and a one-time
fertilizer application.
Vegetation is too short or too
Maintain vegetation at an
long.
appropriate height (6"-12"
with no scalping).
Areas of bare soil and/or
• Stabilize any bare soil
erosion are present
with vegetation or
Areas draining into the SCM
ground cover.
• Remove sediment.
• Investigate source of
sedimentation.
The pipe is clogged (if
Unclog the pipe. Dispose of
applicable)
the debris offsite.
The pipe is cracked or
Replace the pipe
otherwise damaged (if
applicable)
Inlet device: pipe or swale
Erosion is occurring in the
Regrade the swale if
swale (if applicable)
necessary to smooth it over
and provide erosion control
devices such as reinforced
turf matting or rip rap to
avoid future problems with
erosion.
Sediment has accumulated to
Search for the source of the
a depth of less than 15" or
sediment and remedy the
Forebay
that inhibits the forebay from
problem if possible. Remove
function well.
the sediment and dispose of
it in a location where it will

not cause impacts to streams
or the BMP.
Erosion has occurred.
Provide additional erosion
protection such as reinforced
turf matting or rip rap if
needed to prevent future
erosion problems.
Weeds are present
Remove the weeds,
preferably by hand. If a
pesticide is used, wipe it on
the plants rather than
spraying.
Algal growth covers over 30%
Consult a professional to
of the deep pool and shallow
remove and control the algal
water areas.
growth.
Cattails, phragmites, or other
Remove invasives by physical
invasive plants cover over
removal or by wiping them
30% of the deep pool and
with pesticides (do not spray)
shallow water areas.
—consult a professional.
The temporary inundation
Unclog the outlet device
zone remains flooded more
immediately.
than 5 days after a storm
event
Deep pool, shallow water,
Plants are dead, diseased, or
Determine the source of the
and shallow land areas
dying
problem: soils, hydrology,
disease, etc. Remedy the
problem and replace plants.
Provide a one-time fertilizer
application to establish the
ground cover if necessary.
Sediment has accumulated
Search for the source of the
and reduced the depth of
sediment and remedy the
75% of the original design
problem if possible. Remove
depth of the deep pools.
the sediment and dispose of
it in a location where it will
not cause impacts to streams
or the BMP.
A tree has started to grow on
If tree is <6" in diameter,
Embankment
the embankment
remove the tree. If >6" in
diameter, consult a dam

safety specialist to remove
the tree.
An annual inspection by
Make all needed repairs
appropriate professional
shows that the embankment
needs repair.
Evidence of muskrat or
Consult a professional to
beaver activity is present
remove muskrats or beavers
and repair any holes or
erosion
Sediment has accumulated
Search for the source of the
and reduced the depth to
sediment and remedy the
75% of the original design
problem if possible. Remove
Micropool
depth
the sediment and dispose of
it in a location where it will
not cause impacts to streams
or the BMP.
Clogging has occurred
Unclog the device. Dispose
Outlet device / control
of the debris offsite.
structure
The device is damaged
Repair or replace the outlet
device. Investigate cause.
Erosion or other signs of
Repair erosion as necessary.
Receiving water
damage have occurred at the
outlet
Add additional energy
dissipation such as fresh rip
rap as necessary

Maintenance Record -Keeping
Per Durham Stormwater Division requirements, all inspection and maintenance
record -keeping shall be maintained by the owner (or the owner's representative).
An inspection log for the Stormwater Control Measure is attached. For this facility,
the owner's representative contact information is:
Name: Keith Brown
Company: Point Ridge Park LLC
Mailing Address: 388 Old Piedmont Circle, Chapel Hill, NC 27516
Phone: [phone]
E-mail: [e-mail]

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