SW5200602_As-Built Designer Certification - Level Spreader/Filter Strip_20220516

State Stormwater Management
Permit No. SW5200602
AS -BUILT DESIGNER'S CERTIFICATION LEVEL SPREADER AND
VEGETATED FILTER STRIPS MDC
I hereby state that I am a licensed professional and I certify by my signature and seal below, that I
have observed the construction of the project named above to the best of my abilities with all due care
and diligence, and that the project meets the below listed Level Spreader and Vegetated Filter Strip
MDC found in NCAC 02H.1059 in accordance with the permit documents, plans and specifications on
file with or provided to the Division, except as noted on the "AS -BUILT" drawings, such that the intent
of the stormwater rules and statutes has been preserved.
Check here if this is a partial certification. Section/phase/SCM #?
Check here if this is a part of a Fast -Track As -Built Package Submittal per .1044(3).
Check here if the designer did not observe the construction, but is certifying the project.
Check here if pictures of the SCM are provided.
Printed /f
Name Signature
NC Registration Number Date
SEAL:
Consultant's Mailing Address:
City/State/ZIP
Phone Number
Consultant's Email address:
O Circle N if the as -built value differs from the Plan. If N is circled, provide an explanation on Page 2.
ON/E = not evaluated (provide explanation on page 2) ON/A = not applicable to this SCM or project.
Consultant's Certification NCAC 02H.1059
OAs-built
ON/EON/A
A. SIZING
4. The length of the Level Spreader is a minimum of 10 feet
Y or N
per 1 cfs.
5. The Level Spreader receives flow directly from the
Y or N
Drainage Area, and is sized based on the flowrate for a
design storm of 0.75 inches per hour.
6. The Level Spreader receives flow from an SCM and is
Y or N
sized based on the drawdown rate of the design volume.
7. The Level Spreader has a flow bypass system for larger
Y or N
storm events.
8. The Level Spreader is sized to handle the 10 year storm
Y or N
flow and does not provide a flow bypass system.
9. The minimum width of the Vegetated Filter Strip is 30
Y or N
feet measured perpendicular to the level lip.
10. A blind swale or other means of ponding water is
Y or N
provided upslope of the Level Spreader.
11. The blind swale provides for uniform overtopping into the
Level Spreader.
B. LEVEL SPREADER SPECIFICATIONS
4. The lip of the Level Spreader is at a uniform elevation
Y or N
and has a construction tolerance of ±0.25 inches at any
point along its length.
5. The Level Spreader is constructed of concrete or other
Y or N
stable material.
6. The shape of the Level Spreader is straight or convex in
Y or N
plan view.
Page 7 of 8

State Stormwater Management
Permit No. SW5200602
Y or N
7. Downslope of the Level Spreader, there is a 1-3 inch
Y or N
drop followed by a Transition Zone at least 12 inches
wide that is protected from erosion by aggregate or high
performance turf reinforcement matting.
C. FILTER STRIP SPECIFICATIONS
4. The filter strip does not contain any draws or channels.
Y or N
5. The filter strip has been graded with a uniform transvers
Y N
slope of eight percent or less.
or
6. The pH, compaction and other attributes of the first 12"
of soil within the filter strip have been adjusted to
promote plant establishment and growth.
7. The filter strip and side slopes have been planted with
non -clumping deep-rooted grass sod.
8. During construction, the soil was stabilized with
temporary measures until the permanent vegetation took
root, or the runoff was directed elsewhere until the
vegetation established.
Provide an explanation for every MDC that was not met, and for every item marked "N/A" or "N/E",
below. Attach additional pages as needed:
Page 8of8

Level Spreader —Filter Strip Calculation:
LS_FS Width (ft)
LS_FS Length (ft)
Structure Name
*Q10 (cfs)
Size Provided
(Min. Reqd.)
(Q10 x 10)
Sandfilter 1 LS FS
2.85
30
28.50
30' x 40'
Sandfilter 2 LS FS
1.20
30
12.00
30' x 20'
*Q10 is derived from Hydragraph Output pg 1

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LEVEL SPREADER FILTER STRIP 1 SECTION A -A
N.T.S.
NOTE:
1. LEVEL SPREADER —FILTER STRIP IS SIZED FOR HANDLE THE FLOW
DURING 10-YEAR STORM EVENT.
2. CONSTRUCTION OF LEVEL SPREADER_ FILTER STRIP COMPLY WITH
NCDEQ STORMWATER BMP MANUAL C-9.
3. MAINTENANCE AND INSPECTION REQUIREMENT COMPLY WITH NCDEQ
STORMWATER BMP MANUAL C-9.
LEVEL SPREADER FILTER STRIP 1 SECTION B-B
N.T.S.
NCDEQ Stormwater BMP Manual
Maintenance
A LS-FS that is not maintained properly may become a source of pollution rather than a
pollutant removal mechanism. During the first two years after construction, the LS-FS should be
inspected after every major storm event for proper distribution of flows and signs of erosion.
After the first two years, the LS-FS may be inspected quarterly. If evidence of erosion exists, the
eroded areas should be filled in and reseeded and the cause of the erosion should be
determined and eliminated.
Maintenance of an FS involves routine mowing and replanting grass when necessary. Strips
that receive excessive sediment may require periodic regrading and reseeding of their upslope
edge because deposited sediment can kill grass and prevent the LS-FS from achieving diffuse
flow. Figures 12 through 14 show a number of common maintenance issues with LS-FS
systems.
The job of a forebay is to collect leaves, trash and sediment before stormwater is discharged to
the blind swale. Therefore, this is the part of the LS-FS that needs the most frequent
maintenance. The forebay must be checked frequently and will need to be cleaned out
throughout the year, particularly in the fall. In case you can't see the LS, it is immediately to the
left of the yellow line. The vegetation in the blind swale has become overgrown and taken up
nearly all the capacity of the blind swale. The blind swale was likely undersized in its design.
Figure 12: Clogged Forebay (left) and Unmaintained Blind Swale (right)
C-9. Level Spreader -Filter Strip 13 Revised: 1-3-2017
NCDEQ Stormwater BMP Manual
During the mowing season, the FS should be mowed at least every other week. The mowing
allows an opportunity for the FS to be inspected and also helps to prevent clumping of grass.
This is a view upslope of the same FS at right. The clumping of the unmown grasses and
resulting channelization of flow is evident from this view. The eroding areas in this FS need to
be filled in and revegetated before the problem becomes worse.
Figure 13: Unmaintained Blind Swale and Unmown FS
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Figure 14: Erosion in the FS
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C-9. Level Spreader -Filter Strip 14 Revised: 1-3-2017
NCDEQ Stormwater BMP Manual
Important maintenance procedures:
• Immediately after the FS is established, grass will be watered twice weekly if needed until
the plants become established (commonly six weeks).
• Stable groundcover will be maintained in the drainage area to reduce the sediment to the
LS-FS.
• Every two weeks during the growing season, the FS will be mowed. Turf grass should not
be cut shorter than 4-6 inches and may be allowed to grow as tall as 12 inches depending
on aesthetic requirements (NIPC, 1993).
• Once a year, the soil will be aerated if necessary and the FS will be reseeded to maintain
a dense growth of vegetation.
• Once a year, soil pH will be tested and lime will be added if necessary.
For the first two years after the LS-FS is established, it will be inspected quarterly and within
24 hours after every storm event greater than 1.0 inch (or 1.5 inches if in a Coastal
County). After two years of successful performance, the LS-FS will be inspected quarterly.
Records of operation and maintenance will be kept in a known set location and will be available
upon request.
If the soil in the FS becomes compacted, consider coring to alleviate this condition. Use a
device that removes soil cores. Coring should be accomplished when the lawn is actively
growing so that it can recover from any injury. Core cool -season grasses in fall or early spring.
Core warm -season grasses in late spring or early summer. Some lawn care and landscape
companies offer coring service if rental equipment is not available. Inspection and maintenance
shall be performed per Table 3 below.
Table 3: Sample Operation and Maintenance Provisions for LS-FS
Potential problem How to remediate the problem
The entire LS-FS Trash/debris is present. Remove the trash/debris.
The flow splitter device The flow splitter device is Unclog the conveyance and dispose of
(if applicable) clogged. any sediment off -site.
The flow splitter device is Make any necessary repairs or replace if
damaged. damage is too large for repair.
The blind swale The swale is clogged with Remove the sediment and dispose of it
sediment. off -site.
The swale is overgrown with Mow vegetation. Re -grade and vegetate
vegetation. if the swale has become silted in.
The LS The level lip is cracked, Repair or replace lip.
settled, undercut, eroded or
' otherwise damaged.
C-9. Level Spreader -Filter Strip 15 Revised: 1-3-2017
NCDEQ Stormwater BMP Manual
There is erosion around the Regrade the soil to create a berm that is
end of the level spreader that higher than the level lip, and then plant a
shows Stormwater has ground cover and water until it is
bypassed it. established. Provide lime and a one-time
fertilizer application.
Trees or shrubs have begun Remove them.
to grow on the swale or just
downslope of the level lip.
The bypass channel Areas of bare soil and/or Regrade the soil if necessary to remove
erosive gullies have formed. the gully, and then reestablish proper
erosion control.
Turf reinforcement is Study the site to see if a larger bypass
damaged or ripap is rolling channel is needed (enlarge if necessary).
downhill. After this, reestablish the erosion control
material.
Grass is too short or too long Maintain grass at a height of
(if applicable). approximately three to six inches.
Areas of bare soil and/or Regrade the soil if necessary to remove
erosive gullies have formed. the gully, and then plant a ground cover
and water until it is established. Provide
lime and a one-time fertilizer application.
Sediment is building up on Remove the sediment and restabilize the
the filter strip. soil with vegetation if necessary. Provide
lime and a one-time fertilizer application.
Grass is dead, diseased or Determine the source of the problem:
dying. soils, hydrology, disease, etc. Remedy
the problem and replace plants. Provide
a one-time fertilizer application.
Nuisance vegetation is Remove vegetation by hand if possible.
choking out grass. If pesticide is used, do not allow it to get
into the receiving water.
The receiving water Erosion or other signs of Contact the NC Division of Water
damage have occurred. Resources.
C-9. Level Spreader -Filter Strip 16 Revised: 1-3-2017
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ARCHITECT:
16150 Main Circle Drive, Suite 100
St. Louis, MO 63017
[phone] / fax [phone]
CONSULTANTS:
CIVII:
Stantec
801 Jones Franklin Road, Suite 300
Raleigh, NC 27606
ME_
SSC Engineering, Inc.
18207 Edison Ave.
Chesterfield, MO 63005
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DESCRIPTION
DATE
ADDENDUM #2
07/10/2020
ERC/STRM COMMENTS
08/14/2020
PROFESSIONAL RECORD
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DATE
07-10-2020
PROJECT NUMBER
19.025
TITLE
LEVEL SPREADER
_FILTER STRIP DETAIL
SHEET
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