20200579 Ver 1_Sand Filter OM and StormTrap Maintenance_20200511

ID#* 20200579 Version* 1
Select Reviewer:*
Katie Merritt
Initial Review Completed Date 05/12/2020
Mitigation Project Submittal - 5/11/2020
Is this a Prospectus, Technical Proposal or a New Site?* r Yes r No
Type of Mitigation Project:*
r Stream r Wetlands r- Buffer V Nutrient Offset
(Select all that apply)
Project Contact Information
Contact Name:*
Rebecca Stubbs, PE
Project Information
...................................................................................
ID#:* 20200579
Existing IDI#
Project Type:
Project Name:
County:
r DMS r Mitigation Bank
Whirligig Station
Wilson
Document Information
Email Address:*
[e-mail]
Version:
*1
Existing Version
Mitigation Document Type:*
Mitigation Information
File Upload: WhirligigSandFilterOM.pdf 27.64KB
StormTrap Maintenance Manual.pdf 265.06KB
Rease upload only one RDFof the conplete file that needs to be subrritted...
Signature
Print Name:* Heather Dew, PE
Signature:*

Page 1 of 9
This agreement, made and entered into this ______ day of ________, 20____, by and between
the City of Wilson, a political Municipality of the State of North Carolina (the “City”) and the North Carolina
Department of Environmental Quality (NC DEQ) for the purposes of upholding nutrient credits as provided
by the stormwater control measure (SCM), (the “Facility”), to be maintained;
WITNESSETH:
Whereas, the City has adopted through the City Unified Development Ordinance certain
stormwater management regulations applicable to the property located in the City of Wilson, North
Carolina known as “Whirligig Station” (“the Property”), recorded in Plat Book __________, Page
_________, Wilson County Registry; and
Whereas, such regulations, including but not limited to the City of Wilson Unified Development
Ordinance, Section 12, Erosion, Flood, Stormwater and Watershed Provisions, require the City to operate
and maintain the Facility to provide storage treatment of stormwater runoff as part of the development
of the Property; and
Whereas, the City has constructed an on-site stormwater control structure to satisfy the
requirements of such regulations, the boundaries and general description of such Facility being described
in Appendix A attached hereto and incorporated herein by reference; and
Whereas, the City is the Owner of the Facility; and
Whereas, as a condition of the credit generated by the Property, the City is required to operate
and maintain the Facility in perpetuity in a manner that accomplishes the stormwater control and
treatment intended, including but not limited to ongoing nutrient reduction, and to enter into an
agreement with NC DEQ securing that commitment;
Now, therefore, for and in consideration of the premises and the approval by NC DEQ of the
nutrient credits generated by the Property, the City does herby covenant and agree with NC DEQ that the
Property and Facility shall be held, operated, maintained, and encumbered pursuant to the covenants and
conditions hereinafter set forth;
1.No conveyance of Facility without new Agreement. The City covenants and agrees that it will not
convey, transfer, assign, lease or otherwise release or relinquish ownership or control of the
Facility, in whole or in part, unless and until the proposed new owner of the Facility, or any interest
therein, has entered into a SCM Operation and Maintenance Agreement with the City containing
substantially the same terms and conditions as this Agreement.
Page 2 of 9
2.Property Obligated. A legal description of all the property which is obligated to maintain the
Facility is attached hereto as Appendix A. All owners of each lot or parcel therein (or the sole
owner if there is but one parcel) at the time the obligation hereunder arises shall be ultimately
responsible for the compliance with the terms, conditions and obligations of the Agreement.
3.Operation and Maintenance. The City shall operate, maintain, repair, and, if necessary,
reconstruct the Facility in accordance with the provisions below:
a.Maintenance of the Facility shall be at least in accordance with instructions for all SCMs and
specifically, sand filters, as described in the current NC DEQ Stormwater Design Manual and
as specified in the Operation and Maintenance Plan, Appendix B. At minimum, maintenance
activities shall conform to the guidelines contained therein, and shall maintain the Facility as
designed for optimal functioning. For the project named herein, the specific SCM is described
in Appendix A.
b.An Annual SCM Certification shall be submitted by the City and approved by NC DEQ,
according to this Agreement. Annually, on or before August 15, the City shall submit to the
NC DEQ a certification, sealed by a registered Professional Engineer, that the Facility is
functioning as intended, plus a certification by the person or entity responsible for
maintenance that (1) the specific maintenance activities have occurred, (2) all nonroutine
maintenance has been listed and (3) that the Operation and Maintenance Plan is adequate to
ensure optimal functioning or that changes are recommended.
c.A notarized Operation and Maintenance Plan, Appendix B, shall be signed by the City and
submitted to NC DEQ prior to approval of this agreement. Changes to the Operation and
Maintenance Plan shall be submitted with the SCM Certification, if required to maintain
optimal functioning of the SCM or to remain in compliance with the maintenance
recommendations of the Manual. Proposed changes to the Operation and Maintenance Plan
are subject to approval by NC DEQ. Additional information may be required for reporting
purposes, as directed by NC DEQ or designee.
d.Landscaping of the area around the Facility shall not reduce the capacity or hinder operation
and maintenance of the Facility. Landscaping shall be maintained to ensure that landscape
materials live and prosper. Re-vegetation and stabilization of areas may be required by NC
DEQ or designee.
e.The Facility shall be maintained in a manner so as to control insects, odors and algae as
determined necessary by NC DEQ or designee.
f.Any fencing or other security measures shall be maintained in good condition. If no fencing
or security measures were included with original construction, they shall be added at the
City’s expense at such time as NC DEQ or designee determines that unauthorized persons are
disturbing the Facility and that security measures will help prevent such unauthorized activity.
Page 3 of 9
g.Necessary non-routine maintenance actions shall be performed in a timely manner so as to
ensure continuous performance of the Facility. All non-routine maintenance activities shall be
noted in the next yearly report.
4.Right of Inspection by NC DEQ. The City hereby grants NC DEQ the right, privilege and easement
over, upon and across the Property lying between any public street or right of way and the Facility
for the purpose of inspecting, correcting, repairing, replacing or maintaining the Facility as
provided in this Agreement. This right, privilege and easement is appurtenant to and shall run
with the Property and Facility.
5.Remedies for Violations of this Agreement.
a.If the City shall fail to satisfactorily maintain or repair the Facility as set forth herein, or
otherwise violates this Agreement, NC DEQ may order the City to undertake necessary actions
to correct such violation. If the City fails to comply with such order within thirty (30) days from
the date thereof, NC DEQ, in its sole discretion may enter the Property and perform all
necessary work to place the Facility in proper working condition. The full cost of performing
the work shall be a lien on the property as provided in G.S. 160A-193. In such event, NC DEQ
shall assess against the City all of its related costs and expenses (including but not limited to
employee time, material and supplies, vehicle and equipment use, administrative expenses,
plus all contract costs, if required for repairs, design or inspection) and the City hereby agrees
to timely pay the same. Where the City is the sole owner of the development, if this total
amount is not paid in full within three (3) months of the assessment, then each owner of
record shall become personally liable for such owner’s proportionate share of the
assessment. If the proportionate share of the assessment is not paid in full by each such owner
within thirty (30) days following receipt of notice thereof from NC DEQ, then such amount
shall be a continuing lien on the property owned by each owner, such owner’s heirs, devisees,
personal representatives, successors and/or assigns.
b.NC DEQ shall have the right to bring an action against the City and/or each individual owner
to recover all sums due, including its expenses, damages and its reasonable attorney fees,
seek injunctive and equitable relief, and/or such other and further relief as may be just and
appropriate.
c.The remedies provided by this paragraph are cumulative and are in addition to any other
remedies provided by law.
6.No Waiver of Breach. In the event of a breach of any term of this Agreement, any delay or failure
on the part of NC DEQ to exercise any rights, powers, or remedies herein provided shall not be
construed as a waiver thereof or acquiescence of such breach or any future breach.
7.Amendments. This Agreement may be amended, revised or modified only by a written document
signed by the parties.
Page 4 of 9
8.Binding Effect. The conditions and restrictions set forth herein with regard to the Facility shall run
with the land and shall bind the City and any subsequent owner(s), its heirs, successors and assigns
and all parties claiming by, through, or under them shall be taken to hold, agree, and covenant
with NC DEQ, its successors and assigns, and with each of them to conform to, comply with and
observe said conditions and restrictions. NC DEQ shall be deemed a beneficiary of the conditions
and restrictions set forth herein and such conditions and restrictions shall run with land in favor
of NC DEQ.
9.Warranties of Title. The City covenants and warrants that is lawfully seized and possessed of the
Facility and real estate described in Appendix A, that it has good right and lawful authority to
enter into this Agreement for the purposes herein expressed, and that no consent or waiver by
the holder of any mortgage, deed of trust, or other security instrument, or any other person, firm,
or corporation is required prior to entering in this Agreement.
10.Interpretation. Use of the masculine gender herein includes the feminine and neuter, and the
singular number used herein shall equally include the plural. The captions preceding the various
provisions of this Agreement are for the convenience of reference only, and shall not be used as
an aid in interpretation or construction of this Agreement. The laws of North Carolina shall govern
this agreement.
11.Severability. Invalidation of any one of these covenants or conditions by judgement or order of
any court shall in no way affect any of the other provisions, which shall remain in full force and
effect.
Page 5 of 9
City of Wilson:
Title & Organization:
Street address:
City, state, zip:
Contact Phone number(s):
Contact Email:
Signature: _______________________________________ Date: _______________________
I, ___________________________________, a Notary Public for the State of _____________________ County of
________________________, do hearby certify that _________________________________ personally appeared
before me this _______ day of _______________________ and acknowledge the due execution of the Operations
and Maintenance Agreement.
Witness my hand and official seal, _______________________.
My commission expires ______________________.
Page 6 of 9
NC DEQ:
Title & Organization:
Street address:
City, state, zip:
Contact Phone number(s):
Contact Email:
Signature: _______________________________________ Date: _______________________
I, ___________________________________, a Notary Public for the State of _____________________ County of
________________________, do hearby certify that _________________________________ personally appeared
before me this _______ day of _______________________ and acknowledge the due execution of the Operations
and Maintenance Agreement.
Witness my hand and official seal, _______________________.
My commission expires ______________________.
Page 7 of 9
Appendix A.
Description of the Facility (SCM) and Property Obligated to Maintain Facility
Stromwater control measure providing stormwater nutrient removal for the subject Property identified
as “Whirligig Station” is more particularly identified as:
“Whirligig Station Sand Filter” (SCM) located at ______________________________________
___________________________________________________, in Wilson, North Carolina.
All of the Property known as “Whirligig Station” is recorded in Book _________ Page ________ in the
Wilson County Registry.
Page 8 of 9
Appendix B.
Sand Filter Maintenance Requirements
Important maintenance procedures:
-The drainage area will be carefully managed to reduce the sediment load to the sand filter.
-The sedimentation chamber or forebay will be cleaned out whenever sediment depth exceeds six
inches.
-Once a year, sand media will be skimmed.
-The sand filter media will be replaced whenever it fails to function properly after maintenance.
The sand filter shall be inspected quarterly and within 24 hours after every storm event greater than 1.0 inches (or 1.5
inches if in a Coastal County). Records of operation and maintenance will be kept in a known set location and will be
available upon request.
Inspection activities shall be performed as follows. Any problems that are found shall be repaired immediately.
BMP element: Potential problem: How to remediate the problem:
Entire BMP Trash/debris is present. Remove the trash/debris.
Adjacent pavement (if
applicable)
Sediment is present on the pavement surface. Sweep or vacuum the sediment as
soon as possible.
Perimeter of sand filter Areas of bare soil and/or erosive gullies have
formed.
Regrade the soil if necessary to
remove the gully, and then plant a
ground cover and water until it is
established. Provide lime and a
one-time fertilizer application.
Vegetation is too short or too long. Maintain vegetation at an
appropriate height.
Flow diversion structure The structure is clogged. Unclog the conveyance and
dispose of any sediment offsite.
The structure is damaged. Make any necessary repairs or
replace if damage is too large for
repair.
The inlet device The pipe is clogged. Unclog the pipe. Dispose of the
sediment off-site.
The pipe is cracked or otherwise damaged. Replace the pipe.
Erosion is occurring in the swale. Regrade the swale if necessary to
smooth it over and provide
erosion control devices such as
reinforced turf matting or riprap
to avoid future problems with
erosion.
Page 9 of 9
Stone verge is clogged or covered in sediment (if
applicable).
Remove sediment and replace
with clean stone.
Forebay or pretreatment
area
Sediment has accumulated to a depth of greater
than six inches.
Search for the source of the
sediment and remedy the problem
if possible. Remove the sediment
and stabilize or 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 riprap 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.
Filter bed and underdrain
collection system
Water is ponding on the surface for more than 24
hours after a storm.
Check to see if the collector
system is clogged and flush if
necessary. If water still ponds,
remove the top few inches of filter
bed media and replace. If water
still ponds, then consult an expert.
The outlet device Clogging has occurred. Clean out the outlet device.
Dispose of the sediment off-site.
The outlet device is damaged Repair or replace the outlet
device.
The receiving water Erosion or other signs of damage have occurred at
the outlet.
Contact the local NC Department
of Environment and Natural
Resources Regional Office.

STORMTRAP MAINTENANCE MANUAL

1. Introduction

Regular inspections are recommended to ensure that the sys tem is functioning as designed.
Please call your Authorized StormTrap Representative if you have questions in regards to the
inspection and maintenance of the StormTrap system. Prior to entry into any underground
storm sewer or underground detention systems, appropriate OSHA a nd local safety
regulations and guidelines should be followed.

2. Inspection Schedules for Municipalities

StormTrap Stormwater Management Systems are recommen ded for inspection whenever the
upstream and downstream catch basins and stormwater pipes of the stormwater collection
system are inspected or maintained. This will economize the cost of the inspection if it is done
at the same time the Municipal crews are visiting the area.

3. Inspection Schedules for Private Development

StormTrap Stormwater Mangement Systems, for a private d evelopment, are recommended
for inspection after each major storm water event. At a minimum, until a cleaning schedule
can be established, an annual inspection is recommended. If in spected on an annual basis,
the inspection should be conducted before the stormwater season begins to be sure that
everything is functioning properly for the upcoming storm season.

4. Inspection Process

Inspections should be done such that at least 2-3 days has lapsed since the most recent rain
event to allow for draining. Visually inspect the system at all manhole locations. Utilizing a
sediment pole, measure and document the amount of silt at each manhole location (Figure
1). Inspect each pipe opening to ensure that the silt level or any forei gn objects are not
blocking the pipes. Be sure to inspect the outlet pipe(s) because this is typically the smallest

pipe in the system. It is common that most of the larger materials will be coll ected upstream
of the system in catch basins, and it is therefore important at time of inspections to check
these structures for large trash or blockages.

Remove any blockages if you can during the inspection process only if you can do so safely
from the top of the system without entering into the system. Do not go into the system
under any circumstances without proper ventilation equipment and training. Pass any
information requiring action onto the appropriate maintenance personnel if you c annot
remove the blockages from above during the inspection process. Be sure to describe the
location of each manhole and the type of material that needs to be removed.

The sediment level of the system should also be measured and recorded during the inspection
process. Recording the sediment level at each manhole is very i mportant in order get a history
of sediment that can be graphed over time (i.e. years) in order to estimate when the system
will need to be maintained next. It is also important to keep these record s to verify that the
inspection process was actually performed if anyone asks for your records in the future.

The sediment level in the underground detention system can be determined from the outside
of the system by opening up all the manholes and using a sediment pole to measure the
amount of sediment at each location. Force the stick to the bottom of the system an d then
remove it and measure the amount of sediment at that location. Again, do n ot go into the
system under any circumstances without proper ventilation equipment and training.

5. When to Clean the System

Any blockages should be safely removed as soon as practical so that the Stormwater detention
system will fill and drain properly before the next stormwater event.

The Dry Detention System should be completely cleaned whenever the sediment occupies
more than 10% to 15% of the originally designed system’s volume. The Wet Detention
System should be cleaned when the sediment occupies more than 30% or 1/3rd of the
originally designed system’s volume. NOTE: Check with your municipality in regards to

cleaning criteria, as the allowable sediment before cleaning may be more or less then
described above.

6. How to Clean the StormTrap

The system should be completely cleaned back to 100% of the originally designed storage
volume whenever the above sediment levels have been reached. Be sure to wait at least 3
days after a stormwater event to be sure that the system is completely drained (if it is a Dry
Detention System), and all of the sediments have settled to the bottom of the s ystem (if it is
a Wet Detention System).

Do not enter the System unless you are properly trained, equipped, and qualified to enter a
confined space as identified by local occupational safety and health regulations.

There are many maintenance companies that are in business to help you clean your
underground stormwater detention systems and water quality units. Please call your
StormTrap representative for referrals in your area.

A. Dry Detention System Cleaning

Maintenance is typically performed using a vacuum truck. Sediment should be flushed towards
a vacuum hose for thorough removal. For a Dry Detention System, remove the manhole cover
at the top of the system and lower a vacuum hose into one of the rows of the StormTrap
system. Open up the manhole at the opposite end of the StormTrap and use sewer jetting
equipment to force water in the same row from one end of the StormTrap row to the opposite
side. The rows of the StormTrap are completely open in one contiguous channel from one end
to the other for easy cleaning.

Place the vacuum hose and the sewer jetting equipment in the next row and repeat the
process until all of the rows have been cleaned.

When finished, replace all covers that were removed and dispose of the collected
material properly.

B. Wet Detention System Cleaning

If the system was designed to maintain a permanent pool of water, floatables and any oil
should be removed in a separate procedure prior to the removal of all sediment.

The floatable trash is removed first by using a bucket strainer to capture and remove any
floating debris.

The floatable oils are then removed off the top of the water by using the vacuum truck to
suck off any floatable fluids and liquids.

The next step is to use the vacuum truck to gently remove the clarified water above the
sediment layer.

The final step is to clean the sediment for each row as described above in the paragraph “A.
Dry Detention System Cleaning”. For smaller systems, the vacuum truck can remove all of
the sediment in the basin without using the sewer jetting equipment because of the smaller
space.

7. Inspection Reports

Proof of these inspections is the responsibility of the property owner. All inspection reports
and data should be kept on site or at a location where they will be accessible for years in the
future. Some municipalities require these inspection and cleaning reports to be forwarded to
the proper governmental permitting agency on an annual basis.

Refer to your local and national regulations for any addition al maintenance requirements and
schedules not contained herein. Inspections should be a part of your standard operati ng
procedure.

Figure 1. During inspection, measure the distance from finished grade to the top of the
sediment inside the system.

Sample inspection and maintenance log