HomeMy WebLinkAboutAgenda - 06-21-2022; 8-l - Orange County Southern Campus Expansion Stormwater Operations and Maintenance Plan Agreement with Town of Chapel Hill (2501 Homestead Road, Chapel Hill) 1
ORANGE COUNTY
BOARD OF COMMISSIONERS
ACTION AGENDA ITEM ABSTRACT
Meeting Date: June 21, 2022
Action Agenda
Item No. 8-1
SUBJECT: Orange County Southern Campus Expansion Stormwater Operations and
Maintenance Plan Agreement with Town of Chapel Hill (2501 Homestead
Road, Chapel Hill)
DEPARTMENT: Asset Management Services,
County Attorney, &
Environment, Agriculture,
Parks & Recreation
ATTACHMENT(S): INFORMATION CONTACT:
Stormwater Operations and Maintenance Angel Barnes, Capital Projects Manager,
Plan Agreement 919.245.2628
Steven Arndt, Asset Management
Services Director, 919.245.2658
PURPOSE: To:
1) Approve a Stormwater Operations and Maintenance Plan Agreement with the Town of
Chapel Hill for the Orange County Southern Campus Expansion Stormwater Control
Measures; and
2) Authorize the Chair to sign the necessary paperwork upon final County Attorney review.
BACKGROUND: The Town of Chapel Hill has requested a Stormwater Control Measure
Operations and Maintenance Plan Agreement for the Orange County Southern Campus, Seymour
Center facility located at 2501 Homestead Road, Chapel Hill. In 2021 the stormwater system was
installed to meet the required standards. This agreement is the operations and maintenance plan
agreement per the Town of Chapel Hill Section 5.4 Land Use Management Ordinance.
FINANCIAL IMPACT: There is no financial impact associated with this Stormwater Operations
and Maintenance Plan Agreement.
SOCIAL JUSTICE IMPACT: The following Orange County Social Justice Goal is applicable to
this item:
• GOAL: ESTABLISH SUSTAINABLE AND EQUITABLE LAND-USE AND
ENVIRONMENTAL POLICIES
The fair treatment and meaningful involvement of people of all races, cultures, incomes,
and educational levels with respect to the development and enforcement of environmental
laws, regulations, policies, and decisions. Fair treatment means that no group of people
2
should bear a disproportionate share of the negative environmental consequences
resulting from industrial, governmental, and commercial operations or policies.
ENVIRONMENTAL IMPACT: The following Orange County Environmental Responsibility Goal
impact is applicable to this item:
• RESULTANT IMPACT ON NATURAL RESOURCES AND AIR QUALITY
Assess and where possible mitigate adverse impacts created to the natural resources of
the site and adjoining area.
RECOMMENDATION(S): The Manager recommends that the Board:
1) Approve the Stormwater Operations and Maintenance Plan Agreement with the Town of
Chapel Hill for the Orange County Southern Campus Expansion Stormwater Control
Measures; and
2) Authorize the Chair to sign the necessary paperwork upon final County Attorney review.
3
Stormwater Operations and Maintenance Plan
AGREEMENT
This Operation and Maintenance Agreement ("Agreement") is established this day of
20 , by Orange County ("Owner"), who is the
owner of the Property(hereinafter defined), on behalf of the Owner, the Association (if applicable), and
all successor Owners of the Property and the Town of Chapel Hill ("Town").
Owner represents, warrants, and agrees that Owner is financially responsible for the maintenance,
repair and replacement of all stormwater control structures, appurtenances and vegetation located on
the Property. Owner agrees to perform the maintenance as outlined in the Stormwater Operations and
Maintenance Plan for each Stormwater Control Measure and as may be applicable or required as part of
the regulations set forth in Section 5.4 of the Town of Chapel Hill's Land Use Management Ordinance. A
Homeowners Association or Property Owners Association shall not be the financially responsible party
unless more than 50%of the lots or units on the Property have been sold and a resident of the
Association has been named the president.
Owner agrees that the Town has the right to access the Stormwater Control Measure(s) (hereinafter
"SCM") on the Property, as deemed necessary in the Town's sole discretion, by way of the 'SCM
Maintenance &Access Easement' as recorded on the final plat. Owner recognizes and agrees that
Owner is responsible for the maintenance and upkeep of the SCM Maintenance &Access easement.
4
Owner acknowledges that Town's authorized access to the SCM(s) does not create any operation or
maintenance responsibility or obligation on the part of the Town.
Owner shall keep a maintenance record for routine maintenance performed related to SCMs on the
Property("SCM Inspection and Maintenance Log"). The SCM Maintenance Log shall be kept updated by
the Owner and be submitted to the Town each year as part of the required annual inspection report
package. Any deficiencies noted during routine maintenance shall be corrected, repaired or replaced
immediately by Owner.The Owner agrees to notify the Town of any problems with the system or prior
to any changes to the SCM.
The Owner must submit this executed Agreement with the Stormwater Operations and Maintenance
Plan applicable to the SCMs located on the Property and a copy of the approved As-Built Plans to the
Town. Once approved, the Owner shall submit these documents to Orange County Register of Deeds for
recordation, and proof of submittal shall be provided to the Town prior to issuance of the Certificate of
Occupancy. The Owner shall fulfill the requirements of this Agreement effective upon issuance of the
Certificate of Occupancy. In case the ownership of the SCM transfers,the Owner shall, within thirty (30)
days of transfer of ownership, notify the Town of such ownership transfer.
Project Name: Orange County Southern Human Services Center Phase 1:Seymour Center Expansion
Parcel Identifier Number: 9880008527
Identify the Stormwater Control Measures on site in the table below.
Stormwater Control Measures Quantity ID Number(as noted on plan)
Bioretention Cell 1
Dry Pond
Grassed Swale
Hydrodynamic Separator
Level Spreader
Other Type
Permeable Pavement
Sand Filter 1
StormFilter
Stormwater Wetland
Underground Detention 1
Wet Pond 1
5
Print Name of Owner: Renee Price
Title &Organization: Board of County Commissioners,Chair/Orange County
Street Address: 300 West Tryon Street
City, State, Zip: Hillsborough, NC 27278
Phone Number(s): 919.245.2130
rprice@orangecountync.gov
Email:
IN WITNESS WHEREOF,the Owner has hereunto set its hand and seal, or if corporate, has caused this
instrument to be signed in its corporate name by its duly authorized officers and its seal to be hereunto
affixed by authority of its Board of Directors,this the day and year first above written.
Signature of Owner:
STATE OF NORTH CAROLINA
COUNTY OF [county in which acknowledgement taken]
I, , a Notary Public of
County, North Carolina, do hereby certify that
personally appeared before me this day and acknowledge the due execution of the forgoing instrument.
Witness my hand and official stamp or seal,this day of , 20
Seal
Signature of Notary Public
My Commission Expires
6
liStormwater Operations and Maintenance e
Log Sheet
Facility Name: Orange County Southern Human Services Center Phase 1:Seymour Center Expansion Permit Number: 201920166(FPZCP-SFRS)
Address:
2501 Homestead Road,Chapel Hill,NC 27516
Owner: E-mail: Phone:
Orange County abarnes@orangecountync.gov 919.245.2628
Qualified Professional: E-mail: Phone:
Begin Date: End Date: Signature:
Date BMP Type Inspected Cause for Inspection Conditions Requiring Correction Comments and
and ID# By: Actions Taken
7
Date BMP Type Inspected Cause for Inspection Conditions Requiring Correction Comments and
and ID# By: Actions Taken
8
Instructions: Record all inspections and maintenance activities for all SCMs at the facility on this form. Use additional log sheets and/or attach
extended comments or documentation as necessary. Submit a copy of this completed Stormwater Operations and Maintenance Log Sheet in the
Annual Inspection Report. Start a new log at the time of submission. More instructions about SCM inspection submittal guidelines can be found
at this website. The following notes provide guidance for completing the Stormwater Operations and Maintenance Log Sheet.
■ BMP ID#— If applicable, use ID#from the approved site plan.
■ Inspected by— Note all inspections and maintenance activities on this form, including the required independent annual inspection.
■ Cause for inspection — Note if the inspection is routine, pre-rainy-season, post-storm, annual, or in response to a noted problem or
complaint.
■ Conditions Requiring Correction — Note any condition that requires correction or indicates a need for maintenance.
■ Comments and Actions Taken — Describe any maintenance performed or will need to be performed in the future.
9
' Stormwater Operation and Maintenance Plan
BIORETENTION CELL
Regular inspection and maintenance are necessary to preserve long-term functionality of Stormwater
Control Measures "SCMs" per the original design intent. This Plan outlines the Town of Chapel Hill
requirements for regular inspection and maintenance of Bioretention Cell SCMs. The Owner as defined
in the Agreement shall keep a copy of this Stormwater Operations and Maintenance Plan,the SCM
Inspection and Maintenance Log, and a copy of the approved As-Built Plans in a known set location and
made available to the Town of Chapel Hill upon request.
Annual inspections shall be performed by a qualified licensed Professional Engineer or Landscape
Architect. Routine maintenance and inspection shall be performed by a qualified professional with
NCSU Stormwater Inspection and Maintenance Certification or similar certification.
The qualified professional shall maintain a SCM Inspection and Maintenance Log and make available to
the Town of Chapel Hill upon request. All inspections shall be recorded in the log according to the
frequency in the Inspection and Maintenance Table (Table 1 below) and within 24 hours after storm
events that exceed 1.0 inch of rainfall. Any deficit SCM elements noted during inspection shall be
recorded in the log and immediately corrected, repaired, or replaced. All routine and
corrective/emergency maintenance activities shall be recorded in the log. The log template can be
found at the Town of Chapel Hill Stormwater Control Measures website.
An Annual Inspection and Maintenance Report shall be submitted to the Town of Chapel Hill
Stormwater Department. The report shall detail the status of the SCM and maintenance performed as
outlined in the SCM Inspection Report Guidelines. A copy of the annual report shall be submitted to the
Town of Chapel Hill Stormwater Management Division beginning one year after issuance of the
Certificate of Occupancy.
REQUIRED INSPECTION AND MAINTENANCE TASKS FOR BIORETENTION CELL
NOTE: The following inspection and maintenance table is not an exhaustive list of inspection and
maintenance tasks. It is the responsibility of the professional inspecting the facility to perform
comprehensive maintenance for the SCM to be operational.
BIORETENTION PAGE OF • • •
10
Table 1: Inspection and Maintenance Provisions for Bioretention Cell
INSPECTIONSFREQUENCY
OF MAINTENANCE ACTIVITIES
• Watering is needed twice a week until the plants become established (commonly
Upon 6-8 weeks) and then as needed during first growing season (April-October),
construction depending on rainfall.
completion • Remove and replace dead plants.
• Remove any tree stakes or wires six months after planting.
• Mow any bioretention with turf cover to a height of approximately six to eight
inches and remove grass clippings.
• Check inlet, collection system and outlet device for clogging. Remove
Once every accumulated grit, leaves, debris and any other obstructions and dispose off-site.
quarter • Inspect for ponding and bare or eroding areas and make adjustments as
necessary.
• Remove trash and/or debris from the bioretention area.
Twice during
the growing • Pull out weeds and dead, diseased, or invasives plants preferably by hand.
season
• For bioretention areas without turf cover, supplement triple shredded hard wood
mulch in devoid areas to maintain a maximum 3 inch layer.
• Prune trees and shrubs to best professional practice. Thin vegetation so that
Annually sunlight can penetrate the bioretention surface.
• Inspect the observation/cleanout wells to ensure that the underdrain is
functioning. If clogging has occurred, wash out the underdrain.
• Inspect all structural elements.
• Conduct a soil test for pH and heavy metals and determine the infiltration rate.
• For bioretention areas without turf cover, remove and replace the mulch layer
with triple shredded hard wood. The ideal time to reapply mulch is in the late
Once every
spring.
2-3 years •An extensive replanting is required if 50% minimum coverage throughout the
basin is not achieved in the bioretention after the second growing season.
Once every 5
• Perform facility"make-over'to maintain intended landscaping regime and
to 7 years address any maintenance problems detected during routine inspections. After 5
growing seasons,the vegetation should achieve 75/o coverage.
Vegetation
• If the bioretention cell suffers from dead or diseased plants or overgrown with
As Needed
(Typical invasive species, evaluate the source of the problem: soils, hydrology, species,
Problems) and/or type of disease to determine the cause of the plant failure.
o Remediate the problem by selecting new species and/or implementing an
eradication plan for invasives.
BIORETENTION PAGE 2 OF • • •
11
o Ensure appropriate plant maintenance is occurring.
o A one-time fertilizer application to establish ground cover is permissible if
a soil test indicates it is necessary. No portion of the dry detention system
shall be fertilized after the initial fertilization that is required to establish
the vegetation.
o Consult with the Town of Chapel Hill Stormwater Management Division
before any aquatic herbicide is used and site specific approval is given.
• If vegetation coverage is not achieved, add reinforcement planting to maintain
desired vegetation density and/or split out perennials to increase plant cover.
Desired vegetation coverage is 50%after 2 growing seasons and 75%after 5
growing seasons
• Remediate bare soils or erosive gullies.
o In perimeter areas, regrade the soil to remove the gully, plant a ground
cover and water until it is established. If soil test shows that the pH has
dropped, dolomitic lime shall be applied as recommended.
o Within the pretreatment area, provide erosion control devices such as
reinforced turf matting or riprap to avoid future problems with erosion.
Filter Media Failure
• If the bioretention area shows signs of clogging, identify source of sediment and
work to remediate or eliminate it before proceeding with the following
maintenance tasks.
o Flush the underdrains and capture any sediment before it enters any
downstream stream or storm drain system.
o Conduct one or more test pits to determine the depth of soil
contamination.
o Before remediating the filter bed, remove and temporary store any plants.
o Remove the accumulated sediment to the point where sediment is no
longer observed in the soil media plus an additional 2 inches of soil. Either
replace with new media or till 2 to 3 inches of sand into the upper 8 to 12
inches of soil.
o Dispose of any removed soil in an appropriate off-site location.
o Replant and mulch the area of disturbance.
• If soil test shows that the pH has dropped, dolomitic lime shall be applied as
recommended.
• If the soil test shows that heavy metals have accumulated,the toxic soils shall be
removed, disposed of properly, and replaced with new planting media.
Structural Integrity
• Replace or repair any cracked, separated or damaged inlet pipes, drop inlets,
overflow structure, outfalls, impoundment walls or other structural elements.
Functionality
• If flow is bypassing the pretreatment area, regrade to route all flow to the
pretreatment area.
• Sediment Accumulation
o Maintain stable ground cover in the drainage area.
BIORETENTION PAGE 3 OF • • •
12
o Sweep or vacuum sediment on pavement in the contributing drainage
area.
o If sedimentation or clogging is occurring in the inlet, design modification
may be needed to ensure adequate drop or slope between inlet and filter
bed.
o If sediment has accumulated in the forebay area or basin reducing its
depth to 75%of the original design depth, remove the sediment,
restabilize the area, and replace with clean rock. Search for the source of
the sediment in the drainage area and remedy the problem if possible.
• If greater than one feet of localized bed sinking and/or sediment is observed by
the underdrain or overflow, conduct a test pit excavation by hand to examine
subsurface conditions. Look for sediment across layers, discoloration,voids, loss
of material. Cause of bed sinking may be breached material layers, poor
connections, or damaged pipes. Repair the test pit to full functionality without
cross contamination of the individual material layers.
For additional information or if damage has occurred at the outlet which effects the
receiving water, contact the Town at Chapel Hill Stormwater Management at 919-
969-7246 (RAIN).
13
• Stormwater Operations and Maintenance Plan
SAND FILTER
Regular inspection and maintenance are necessary to preserve long-term functionality of Stormwater
Control Measures "SCMs" per the original design intent. This Plan outlines the Town of Chapel Hill
requirements for regular inspection and maintenance of Sand Filter SCMs. The Owner as defined in the
Agreement shall keep a copy of this Stormwater Operations and Maintenance Plan, the SCM Inspection
and Maintenance Log, and a copy of the approved As-Built Plans in a known set location and made
available to the Town of Chapel Hill upon request.
Annual inspections shall be performed by a qualified licensed Professional Engineer or Landscape
Architect. Routine maintenance and inspection shall be performed by a qualified professional with
NCSU Stormwater Inspection and Maintenance Certification or similar certification.
The qualified professional shall maintain a SCM Inspection and Maintenance Log and make available to
the Town of Chapel Hill upon request. All inspections shall be recorded in the log according to the
frequency in the Inspection and Maintenance Table (Table 1 below) and within 24 hours after storm
events that exceed 1.0 inch of rainfall. Any deficit SCM elements noted during inspection shall be
recorded in the log and immediately corrected, repaired, or replaced. All routine and
corrective/emergency maintenance activities shall be recorded in the log. The log template can be
found at the Town of Chapel Hill Stormwater Control Measures website.
An Annual Inspection and Maintenance Report shall be submitted to the Town of Chapel Hill
Stormwater Department. The report shall detail the status of the SCM and maintenance performed as
outlined in the SCM Inspection Report Guidelines. A copy of the annual report shall be submitted to the
Town of Chapel Hill Stormwater Management Division beginning one year after issuance of the
Certificate of Occupancy.
REQUIRED INSPECTION AND MAINTENANCE TASKS FOR SAND FILTERS
NOTE: The following inspection and maintenance table is not an exhaustive list of inspection and
maintenance tasks. It is the responsibility of the professional inspecting the facility to perform
comprehensive maintenance for the SCM to be operational.
SAND FILTER PAGE I OF 3 REVISED: • • •
14
Table 1: Inspection and Maintenance Provisions for Sand Filters
INSPECTIONSFREQUENCY
OF MAINTENANCE ACTIVITIES
Upon
• If a pretreatment grass filter strip has been built,water twice a week until the
completion of
construction
grass become established (commonly 6-8 weeks), depending on rainfall.
• Maintain any grass at the perimeter of the sand filter to a height of
approximately six to eight inches.
• Check inlet, outlet, and conveyance system for any obstructions or clogging.
Once every Remove accumulated grit, leaves, and debris and dispose off-site.
quarter • Remove any trash present on the sand filter surface.
• Inspect for prolonged ponding and bare or eroding areas and make adjustments
as necessary.
Twice during • Remove any vegetation growing on the surface of the sand filter preferably by
the growing
hand.
season
• Skim the first inch of sand media.
Annually • If a sedimentation chamber is present, pump out oil and grit.
Structural Integrity
• Replace or repair any cracked, separated or damaged inlet pipes, outfalls, or
other structural elements.
• Remediate bare soils or erosive gullies by regrading the soil to remove the gully,
plant ground cover and water until it is established.
• If erosion has occurred within the forebay or pretreatment area, provide
additional erosion protection such as reinforced turf matting or riprap.
Functionality
• Sediment Accumulation
As Needed o Maintain stable ground cover in the drainage area.
(Typical o Sweep or vacuum sediment on pavement in the contributing drainage area.
Problems) o If sediment has accumulated in the pre-treatment area to a depth greater
than six inches, remove the top few inches of drainage media and dispose of
it in a location where it will not cause impacts to the SCM or a stream.
Search for the source of the sediment in the drainage area and remedy the
problem.
• Filter Media Failure
o If water is ponding on the surface for more than 24 hours after a storm
event, check to see if the underdrain collection system is clogged and flush
if necessary. It water still ponds, remove the top few inches of filter bed
media and replace. If water still ponds, consult an appropriate professional.
All the sand filter media may need to be replaced.
15
For additional information or if damage has occurred at the outlet which effects the
receiving water, contact the Town at Chapel Hill Stormwater Management at 919-
969-7246 (RAIN).
SAND FILTER PAGE 3 • • •
16
smith
�,EWER C.0,H7RUCT1ON SHALL COMPLY WITH OWASA STANDARDS AND
1TO5HEF1w 1RO, All SIEI REIATEI 1-
AkCHITECTURE
ovEreaow wue wnu Urvv<wn-�m�.z�� R.III NC2.1
NOiE$: 91I—L.14lI.),
jH
vivE w,aurvours lrvvl1111
e'Ircel ,x x v^ixDicnnue N m M1H �nMµ - ...A ALL
N
xnrcxED nreEnl AS AV2,LA
— oveeaow wxx wnu — ssvwxrswxx DIPI-1 snvs ix,onu
eRIED vv vie w,nueDu x,xe Exnree b ��' y
vxovos®wwoow NHisl Dxux EI uovomi�rl
PLAN VIEW jig H
rc
w
r
z
w
E oxsw nrt art m - N Z
Dre�um�ry s[rs�`I<rc9e1� Dre�um�rvsmsl I �utn�x w O
�oIrcel oD U
DEeEa,rE 111`e,.xlrvelAT _ DEeE>sx...ox e,.x,rvel _ �LS IP"S_Ao�x�e,. _1 w a
roe of reo.E,�Anox _ ,oe of wE�a Eavnox roo or w.�a E�Ev.�ox z p
z
6
v�xm.rvexi w.rere ezEvnory _ veamAxexr wnrev erev.nox 11waee eLev.nox z C1
DII
reorcom o.reo, nxox orera�ro>AooinoxA we,.Mnoxl z
o
w > x
SAND FILTER SEDIMENT CHAMBER SECTION VIEW SAND FILTER CHAMBER SECTION VIEW SPUTTER BOX SECTION VIEW(END) w ci
r w �
z �
z a
O U
.A-AY ALIE1 D (7 p o
-LE VEw sirt crer.Dirvc vurvlmvl oaiurn iry srtvslml nn O N
eonom.o�rew uEvn�oorv--❑ —¢Doom or eor zo�nory nox FE = = rov or weire eeevxnory
.................................................
.................................................
KEY PLAN
us¢zsxuz NO SCALE
IS
zus rxnrvz mu tlegl
3p R X 3.6 WINDOW W X 1.5'WINDOW SPUTTER BOX SECTION VIEW(SIDE)
anw vme IIPIID $DESCR PT ON
UNDERDRAIN BEDDING DETAIL DMM BY: SAD
CHECKED BY: SAD
STORMWATER
MANAGEMENT
DETAILS
N17027 21 DEC 2018
C6-30
17
• Stormwater Operations and Maintenance Plan
UNDERGROUND DETENTION
Regular inspection and maintenance are necessary to preserve long-term functionality of Stormwater
Control Measures "SCMs" per the original design intent. This Plan outlines the Town of Chapel Hill
requirements for regular inspection and maintenance of Underground Detention SCMs. The Owner as
defined in the Agreement shall keep a copy of this Stormwater Operations and Maintenance Plan, any
applicable proprietary manufacturer's O&M Plan, the SCM Inspection and Maintenance Log, and a copy
of the approved As-Built Plans in a known set location and made available to the Town of Chapel Hill
upon request.
Annual inspections shall be performed by a qualified licensed Professional Engineer or Landscape
Architect. Routine maintenance and inspection shall be performed by a qualified professional with
NCSU Stormwater Inspection and Maintenance Certification or similar certification.
The qualified professional shall maintain a SCM Inspection and Maintenance Log and make available to
the Town of Chapel Hill upon request. All inspections shall be recorded in the log according to the
frequency in the Inspection and Maintenance Table (Table 1 below) and within 24 hours after storm
events that exceed 1.0 inch of rainfall. Any deficit SCM elements noted during inspection shall be
recorded in the log and immediately corrected, repaired, or replaced. All routine and
corrective/emergency maintenance activities shall be recorded in the log. The log template can be
found at the Town of Chapel Hill Stormwater Control Measures website.
An Annual Inspection and Maintenance Report shall be submitted to the Town of Chapel Hill
Stormwater Department. The report shall detail the status of the SCM and maintenance performed as
outlined in the SCM Inspection Report Guidelines. A copy of the annual report shall be submitted to the
Town of Chapel Hill Stormwater Management Division beginning one year after issuance of the
Certificate of Occupancy.
REQUIRED INSPECTION AND MAINTENANCE TASKS FOR UNDERGROUND DETENTION
NOTE: The following inspection and maintenance table is not an exhaustive list of inspection and
maintenance tasks. It is the responsibility of the professional inspecting the facility to perform
comprehensive maintenance for the SCM to be operational.
18
Table 1: Inspection and Maintenance Provisions for Underground Detention
OF MAINTENANCE ACTIVITIES 4
FREQUENCY -A
• Check detention chambers and pipes for any obstructions, clogging, or damage.
Remove accumulated grit, leaves, and debris and dispose off-site.
Biannually • Remove any trash or debris present within the drainage area and outfall area.
• Inspect the detention system for structural integrity and any accumulation of
liquids or solids within the unit.
• If the detention is in an area that is salted regularly during winter,the system
Yearly should be rinsed during the springtime to prevent salting agents from
accumulating inside the pipes.
Structural Integrity
• Repair any cracks, spalled areas, rusted areas within the detention chambers.
• Replace any crushed or collapsed pipes under the supervision of a professional
engineer.
• Replace the detention structure if it has severely deteriorated.
• Repair eroded outfall channels with additional riprap armoring or other
permanent lining material.
Functionality
• Sediment Accumulation
As Needed o Maintain stable ground cover in the drainage area.
(Typical o Sweep or vacuum sediment on pavement in the contributing drainage area.
Problems) o Any accumulated sediment in the detention unit must be disposed to a
waste handling facility.
• Other Pollutants
o Identify and eliminate any sources of excessive oil loading.
o If clogging becomes a persistent issue that prevents drawdown, a trashrack
is required on the discharge orifice within the underground detention
structure.
For additional information or if damage has occurred at the outlet which effects the
receiving water, contact the Town at Chapel Hill Stormwater Management at 919-
969-7246 (RAIN).
19
smith
�,EWE,R C.0,HTRUCT1ON SHALL COMPLY WITH OWASA STANDARDS AND
11 TO3HEET C—FOR PRDLEC.AND SHED RELATED N—
DEN 3
DATED�2/22/o
RUCNFE;r END
IL INCLUDED ON THIS SHEET FOR PROPOSED (AE_x R.AI NC'ORIFIC TO
2606
yyelpS MCCS 919 a,3rB`.'3b9a�o�
EIESr-bleb Fr .YnH--.qU"yyL
I"tlL111U1N1 -d f y
x OIEF'ItE �
Q
(Re a/oo-az1
o .g aV. J f New
.1r s
uN_1 rova(xA € ax
Barra D-atlas Ar vw PLAN VIEW Ncu u....- mR a Box L T Hill,
* E a
.awr a b"x att PBFnr,En umE� wnrtRr a� �Be
x*or•fR RN. stu € max ' '
so��EB rporBy ED
w
_ — F
l W
FBI 1F w LBOnO�GF BTr U
TO IL O 1.Ox N4.-511.�A F1EV N Z
my �rLp V O
t'oavnmw daxc F
PROFILE A-A 1m•, 5i1 w C
w a
z p
= O 2
Z = -_
w j =
O
r w �
z �
z a
O U �
eLEv-sT. WDR w E
(7 p t
r
O N
WITH�—m�ER.E STRI
UNDERGROUND DETENTION VAULT NO SCALLEAN
OUTLET STRUCTURE IMPROVEMENT DETAIL _
N S A"! DEESCRIPTION
DRAWN BV: BAD
CHECKED BY: SAD
STORMWATER
MANAGEMENT
DETAILS
N17027 21 DEC 2018
C6-20
20
• Stormwater Operation and Maintenance Plan
WET POND
Regular inspection and maintenance are necessary to preserve long-term functionality of Stormwater
Control Measures "SCMs" per the original design intent. This Plan outlines the Town of Chapel Hill
requirements for regular inspection and maintenance of Wet Pond SCMs. The Owner as defined in the
Agreement shall keep a copy of this Stormwater Operations and Maintenance Plan, the SCM Inspection
and Maintenance Log, and a copy of the approved As-Built Plans in a known set location and made
available to the Town of Chapel Hill upon request.
Annual inspections shall be performed by a qualified licensed Professional Engineer or Landscape
Architect. Routine maintenance and inspection shall be performed by a qualified professional with
NCSU Stormwater Inspection and Maintenance Certification or similar certification.
The qualified professional shall maintain a SCM Inspection and Maintenance Log and make available to
the Town of Chapel Hill upon request. All inspections shall be recorded in the log according to the
frequency in the Inspection and Maintenance Table (Table 1 below) and within 24 hours after storm
events that exceed 1.0 inch of rainfall. Any deficit SCM elements noted during inspection shall be
recorded in the log and immediately corrected, repaired, or replaced. All routine and
corrective/emergency maintenance activities shall be recorded in the log. The log template can be
found at the Town of Chapel Hill Stormwater Control Measures website.
An Annual Inspection and Maintenance Report shall be submitted to the Town of Chapel Hill
Stormwater Department. The report shall detail the status of the SCM and maintenance performed as
outlined in the SCM Inspection Report Guidelines. A copy of the annual report shall be submitted to the
Town of Chapel Hill Stormwater Management Division beginning one year after issuance of the
Certificate of Occupancy.
REQUIRED INSPECTION AND MAINTENANCE TASKS FOR WET POND
NOTE: The following inspection and maintenance table is not an exhaustive list of inspection and
maintenance tasks. It is the responsibility of the professional inspecting the facility to perform
comprehensive maintenance for the SCM to be operational.
WETPOND PAGE I OF • • •
21
Table 1: Inspection and Maintenance Provisions for Wet Pond
FREQUENCY
OF MAINTENANCE ACTIVITIES
INSPECTIONS IR
Upon • Watering is needed twice a week until the plants on the vegetated shelf and
completion of perimeter of the basin become established (commonly 6-8 weeks), depending
construction on rainfall.
• Mow grass surface areas to a height of approximately six to eight inches and
remove grass clippings.
• Check inlet system/forebay and outlet device for any obstructions or clogging.
Once a quarter Remove accumulated grit, leaves, and debris and dispose off-site.
• Remove any trash within the pond area.
• Inspect for ponding and bare or eroding areas and make adjustments before the
next rainfall as necessary.
Twice during
the growing • Pull out dead or diseased plants, weeds, or invasives preferably by hand.
season
• Have the embankment inspected by a dam safety expert.
• Remove woody species on or near embankment area and maintenance access.
Annually A dam safety specialist should be consulted to remove any trees.
• Prune trees and shrubs to best professional practice. Thin vegetation so that
sunlight can penetrate the pond surface.
Vegetation
• If the wet pond suffers from dead or diseased plants or overgrown with invasive
species, evaluate the source of the problem: soils, hydrology, species, and/or
type of disease to determine the cause of the plant failure.
o Remediate the problem by selecting new species and/or implementing
an eradication plan for invasives.
o Ensure appropriate plant maintenance is occurring.
o A one-time fertilizer application to establish ground cover is permissible
As needed if a soil test indicates it is necessary. No portion of the wet pond system
(Typical shall be fertilized after the initial fertilization that is required to establish
Problems) the vegetation.
o Consult with the Town of Chapel Hill Stormwater Management Division
If algal growth covers 50%of the area, consult a professional to remove
and control the algal growth.
• If cattails, phragmites, or other invasive plants exceed 50%of the wet pond,
remove invasives by physical removal or wiping them with a herbicide. Consult
the Town of Chapel Hill before any aquatic herbicide is used. Site specific
approval is required. Extended periods of dewatering may be a possible
treatment approach for reducing invasives.
22
• Remediate bare soils or erosive gullies.
o In perimeter areas, regrade the soil to remove the gully, plant a ground
cover and water until it is established. If soil test shows that the pH has
dropped, dolomitic lime shall be applied as recommended.
o Within the pretreatment area, provide erosion control devices such as
reinforced turf matting or riprap to avoid future problems with erosion.
Structural integrity
• Replace or repair any cracked, separated or damaged inlet pipes, outfalls,
impoundment walls or other structural elements.
• If dam embankment or emergency spillway needs maintenance, consult with a
professional.
Functionality
• Sediment Accumulation
o Maintain stable ground cover in the drainage area.
o Sweep or vacuum sediment on pavement in the contributing drainage
area.
o If sedimentation or clogging is occurring in the inlet, design modification
may be needed to ensure adequate drop or slope between inlet and
filter bed.
o If sediment has accumulated in the forebay area reducing its depth to
75%of the original design depth, remove the sediment off site,
restabilize the area, and replace with clean rock. Search for the source
of the sediment in the drainage area and remedy the problem if possible.
• If there are visible disturbances to the forebay design, make the necessary
repairs to ensure that the forebay is functioning as intended.
• If evidence of a muskrat or beaver activity is observed, contact a professional to
remove muskrat or beaver.
• If the basin must be drained for an emergency or to perform maintenance,the
flushing of sediment through the emergency drain should be minimized to the
maximum extent practical.
For additional information or if damage has occurred at the outlet which effects the
receiving water, contact the Town at Chapel Hill Stormwater Management at 919-
969-7246 (RAIN).
WETPOND PAGE 3 OF • • 1
23
N SHALL COMPLY WITH OWASA STANDARDS AND
,TaNpgRDSgND=PE�IN�AD°N3 qLL�°N3TRD�TIDNIN=IDE°F,NE
smithp HDMerEADR°gDPD4DDRI°Hr.DT_WAYSHALLDaMPLYWIrHN°DDT
�
/ j / j--- �,-- �/ ,TaNpaRD5aNp5PE�IN�aTIaN3 ALLPR°PDSEDWATERAND=ANITARY
°,o�=crl°
— ___, ,� // eFati�3N[Ei CU01 FOa PkpJeCT nND SNeEi R[Lnr[p NprFS. sinnett
_ AkCHITECTURE
LEGEND r
\\ \ EXIST,NG CONDIT,ONS LEGEND==17
arnL
rreoros[o eorveze,[ p aaE WDgs Rootl
i
�,e, % I\ \ cxreeneuner G 9. .a lol Rr - u
H: `
rreoronroScry a Y"ti w
/ � i' � \ Doan vwe _Pmcnu 44496t y F �
/� +aereseev�rioeeuc \ ` \ \ \\ ■ raorosenovovirvur q. nox Ca` j
m
raorosco c"rcx a"sin a x�iu"%pnw:plE sews '' !7
/ /� /� yO � � .4 I \ rreorosrosoreN mnrvnox c
/// _ \ 'I \ xxx w¢nue corvroure r.woel
� m
Fxunrva noeMornwnce
�I I / i/ are easaxrmie ` ——
------ , N.ralr
I I , / � oren AGrr V ` A ,oc=mr orcuree �' me g Y
----- \ I -51 a rvcs,oeNornrvn, x t w Drz�N, a 11§e
\\?ervo wn,E Ye"ie`rv�\ \`r OvCFI 91181N Y0LDME a.
ELEV AREA AVERAGE VOLUME VOLUME w
I.9 AREA {cR (eQ y z
STORAGE 0V O
SB3AG 6 D ❑ 1) S f
so4.Do 2780 88 two T.38o 1. o rc �
N \ 50B.o0 5,425 4,093 4,093 SA73 N Q
874 5,863 5,663 11 4 z
50T.00 7,]a a 7,062 7062 l8.4T$ai$
o0 0 0 `\ 507.50 8.485 B.134 4.067 22 485 z Li
\ I \ \ ` �\ eErorve mEr« 0 0 p t` / '.iDB.❑0 R.taB BA98 4pte a8.9❑2 Z o
' TE
40Pi \ \ \ �\ \ o o°o° ° o 0 0\ I ` 500.23 G+445 11 2.L43 29.045 w > _
\ \ \ o.or °o 0 0 0°p \ `\ I / SOB.SO 8A88 4.555 2.sa7 st,6$2 Z o.
o°° p oo Rsxez ` 509A0 1"46 10,206 5,103 38.755 = z
i O w
slo.00 11717 11132 11132 47886 p Lj
\ GO, ° o00 0° oa. °o N 511A0 12,967 12,342 12,342 60,228 rc
\ ` \ \\ ` �\ I 5tt.5o 738a7 tS 302 6.851 88a76 r r
°o°L GO
o° 'O t — it2.00 1a,315 t3,676 6,988 79.867 z zO
°o O \ \ \ o o° O O O ® \ FMF@AY YIX.UYE CFLd1LATld1 W E
00 °pO ` \ \ 00
Goo Qp000 \ \ \\ \ °a00o 0 OOo x u / Ln ACC. F
oop00Oo 000apO opO p \ \ \ CO0 0 0 0°oo° / ELEY AREA AVERAGE VOLUME VOLUME
o pp0000OOo 00 00 \ ` \ \ o00 000 °o ox feR (.11) O H«eresFa 0 0-00 00 0 00 0 0 O°00 r \ o o p o 0 0 0° / d IM AREA
o � I N — STORAGE S
sear«rss ° oOpO° o�p °0°ap 728 0 o o
,SIC,Ervnxc. o 0 0 0 0 oa o° o
SIC— a0°" ° °p °o o Op \ `\ o / 505.90 1A15 872 B72 872
000C °o oO° _ \ oo 506.7o 1 16 1a 1.188 2.008
°o 0 0 0°00 0 °°°
O
° ° ° — \ 507.00 7 1.57i 1 571 3,609
Ma`a"E1' �,, 000OOp tsoO °pDO, — 510 moo KEY PLAN
Ereryiihre I o CO° ° I NO SCALE
urvose rear rend n so --___ w-gPPRoxIMA GROUND ELEvanON AT TOP OF •
RCPCSED WgLL'E
------- \rreerexea'xicx _ --_--- OnOM OF PROPOSED WALL ELEVATION AT Knaw wM1aYs b20W. A—ATE
sEaRRY *auex
i_SUP+—a'""etllxk ___ Call b,,I dig. DHERCRUPnoN
APPROXIMATE AND ARE INTENDED TO 3E FORDRAWN BY: BAD
snW
, CHECKED BY: SAD
E,ERMWEDBr 'NATIONS 11ALL
THE RCA INwO WALL DE:I°NER STORMWATER
——— _ —_—— —— --- -- / MANAGEMENT
---------- ———— ———— �Y NORTH PLAN
_ — —_-- —-------------- —�—5� —
\ \ GRAPHIC SCALE C6
_00
24
smith
�,EWE,R C.0,DTIR'U.CTION SHALL COMPLY WITH OWASA STANDARDS AND
EVER TO SHEET C—NOR PROJECT All SHEET REUTEO NOTESAFtCHITECTURE
�E =r,, wA1 papaDE, aED N�a.°TxERs o,T�l
°TVATIROHaILsallo "EDIRI foaCEo,TH�EWET-. °NME.a1fA CONTRA oR
LEv-.,,o HnLLCooROINnTEwxH�EaTECHN��nLENGIrvEEa ami
alAR,NC 2 1
EIEv=.W9sp Frm 9<0 HC38
Ce�• r w aN,ISEEP couare AN,rsE,:P cowre iN PooL� a, reEeAr� NVA
OR
RsC ourvow .PLAM NE C &Aeoro,Ns F E
o3U6a w F
C`
ED
Q
CIT.11TON RT-41`N.W / CROSS SECTION OF WET POND
N.,.S. � a
g a g ' aTV
�€€,nTV
COMPAC,ED Ill
.IIIII-I IIIII- WET DETENTION BASIN CONSTRUCTION SEQUEN°CEE IT
SHALL RE" �'EITMorExao�ssJ €
—IIIII I=N IR I'IIIII= III= HN Na�D�a,x ALANREDarePAN E �ncoMP�ncEwxHTR—ALANUTOTAUR, w
EEo ND "CDz
;,'. TaenCN waH ON
DE
MN III
ANxoLE NTED =GRATTESALL N Z
sroreM DRAINAGEPIPE ANee roaTHewrs DC.TI NoasIN SHALL BE w
-11IIII °H >
-I, class a—CRETE ,racxeD
= ., w a
.I REcoMMENDAT�oNs N z o
-IIIII III a°N°M °HREDer,xEENGINEERANDRED-IREvoNSsrEP � a
i oTHIN o Z U
E mv.o Arn+lcni� is Z
—I IIIWET
wcscR�TILE1.
G--�_—; __ _ w u LENS Pusnc nEPs a—TEE coxs,auc,DH1aIRc Deunno vunTNcs TRYL NA oa NARLY wrrtea W ? _
=IIIII - ° mPiP° —
Vc wro E. O °
—II_ IN
,RENcxsoTOM �s } ouLEDarLusrlooanwaovANCEL _
I12 O
J IIIII IIIII IIII IIIII DRIED waH,HePaoJ�sPe IF'AT,
T EaANDM N,An,NEPUNT TER ,NACCORDANCE
� w
-� -� wxxArE°RIHCE RARore,,,'A RowAo�NnreD�°NaFEreREw°aK c°MPLHED z =
El
A.DIDNALEureD*o WET DETENTION BASIN CONSTRUCTION NOTES c0,] uD.01 PIPE w
oaM Pipe ALL ON LDNNHrHesaTeor NOM LCARouNA an°rowN ovSHADELL HILL.—AR.AND ENESI—ATIONE
_ x
ELEVATION TRENCH WALLS 1O Ne LT RTH,IND 11.11IT rPUN,S DTHE o ga r
ows 0 N
DISTILlEll
H 11E
EN
VENG
11
--III TarNCH wnueP� `INV our sraueD DuawcT EMALI SEAsoN oeVnrsRonD
=1 —III IIIII uueCONCa E EL N, KEY PLAN
= sru re E TN' HA NO SCALE
Mw. 1A -rwo�9BN¢5 _
-IIIII "III— TO O O O O O O O O O O O O O O OLEADS
O O O O O O O O O O O O O O _
PIPE
lReeER I.Saos�n O O O O O O O O O O O O O O
sEc,ioN DETAIL NOR LounoN� PER TPEMEW
Ki
TVIIR111THTHeI DREVUST, UREE RE,VESCRIPTIONURI DRAWNBY BAD
IIII IIIII eEIwEEN PiPEaxosrvucrureE CHECKED BY: SAD
TH ��I>"oro>a EMEr°�,'oFEAN:>areM° STORM WATER
PLAN VIEW 6DED—H.-NE ERIcifTHECDNRAlUL1SHAALLHAVETHE�R�"Ui1111I°wDEAs1RVEr°NTIEASRUILT E MANAGEMENT
ceE IIMi%F,e•
s.IN DETAILS
"'�x�a OUTLET STRUCTURE DETAILCSSAL, xON
Nx.s. oaaeer°aaDNc oe TH 201]02] 21 DEC 2018
ANTI-SEEP COLLAR DETAIL wE,Dr:,EM�oN oaS�nsHALL SETHEaESPons�sLEo'THE ConTSA,,oa.
HIS C6-10