SW3180304_Outlet Calcs_20180509

SHABELDEEN ENGINEERING, PA
3145 TATE BLVD ● BOX A ● HICKORY, NC ● 28602 PHONE: [phone]
CIVIL/WATER/SEWER/ENVIRONMENTAL FAX [phone]
CONSTRUCTION ADMINISTRATION [e-mail]

Ltr Kontane Sand Filter

May 3, 2018
Mr. Cory Anen, PE
NC Dept. of Environmental Quality
DEMLR Stormwater Program
512 N. Salisbury St.
1612 Mail Service Center
Raleigh, NC 27699-1612

SUBJECT: Kontane Warehouse Additions – Request for Additional Information
Stormwater Permit Application
Mr. Anen:
On behalf of May Rivers Properties, LLC (Owner), Shabeldeen Engineering, PA (SE) is submitting two (2)
hardcopies of the revised plan sheets and one (1) copy of calculations for the referenced project information.
The files will be uploaded as requested. It should be noted that the stormwater control measure (SCM) has
been changed from a Wet Pond to an Open Bottom Sand Filter, therefore some of the comments are no longer
applicable.
1. Sheets C3-Grading & Drainage Plan. C6-Drainage & Utility Details and C-7 Erosion Control Details
are attached showing existing contours and cross-sectional details of the SCM, outlet structure, and
Riprap Outlet Protection.
2. SCM design:
a. Comment 2a is no longer applicable. The previously proposed Wet Pond has been replaced
with an Open Bottom Sand Filter System.
b. The side slopes are set at 3:1 (horizontal to vertical).
c. A 6’ vegetative shelf is no longer applicable. Maintenance access to the Sand Filter system
is provided within the designated Easement area as shown on Sheet C2 Grading & Drainage
Plan. The Maintenance Access includes the 26-ft. wide “Fire Lane” at the top of the SCM
as well as a 6-ft berm at the top of the 3:1 slope as recommended in your email dated April
19, 2017.
d. A landscape plan is not required for a Sand Filter system.
e. An emergency spillway has been added to the SCM. The control structure has an open top
with a trash rack. The control structure weir crest elevation has been set at the Normal Water
Level of 898.00. The 10-ft. wide emergency spillway crest elevation has been set at 898.50.
Based on the attached hydraulic analysis, the SCM has sufficient storage to retain the runoff
from the 100-Yr, 24-Hr. storm event.
Mr. Cory Anen, PE Page 2 of 2
Kontane Warehouse Additions – Stormwater Permit 5/3/2018

Ltr Kontane Sand Filter

3. Riprap Outlet Protection has been included at pipes P-1A and P-30 that discharge into the sediment
storage basin and on Pipe P-21A, which bypasses the SCM. A detail of the Riprap Outlet Protection is
provided on Sheet C7. Engineering calculations are attached.
4. Sheet C3 Grading & Drainage Plan shows the easement that encompasses the maintenance access and
SCM. The easement will be recorded once the plans are approved and the construction of the SCM is
complete.
Open Bottom Sand Filter Design
Attached are the calculations for the sand filter system. Using the NRCS Method, the treatment volume for
the 7.29-acre watershed is 21,810 cf. With the 75% discount, the required treatment volume is 16,358 cf. The
bottom elevation of the sand filter is 393.00 and the high water is 398.00. Therefore, the “ponding depth” is
5.0 feet. The required minimum surface area of the sediment control basin plus sand filter basin is 3,272 sf.
The system has been designed so half the treatment volume is held in the sediment control basin and half in
the main sand filter basin. As a result, the surface area is 3,690 sf, which exceeds the required minimum
surface area.
A cross-section of the sand filter is provided on Sheet C2 - Grading & Drainage Plan. The sand filter includes
a standpipe from the sediment storage basin to the sand filter basin and two (2) underdrains in the sand filter
basin.
I appreciate your assistance on this project. If you have any questions, please do not hesitate to contact me.

Sincerely,

Dan Shabeldeen, P.E.
Sand Filter/StormTech CALCULATIONS
Kontane Facility
Statesville, NC
Table 2 - Discrete NRCS Curve Number Method for Runoff Depth
S = 1000/(98) -10 =0.20
Where:
S = Maximum retention after rainfall begins (in)
CN = Curve Number (unitless) = 98
0.82
Where:
Q = Runoff depth (in)
P = Rainfall depth (in) = 1.00
Watershed Area (ac) 7.29
Q (in) = 0.82
Treatment Volume (ft3)21,810
Volume "Discount"75%
Treatment Volume (ft3)16,358
Bottom Length
Bottom
Width
Sediment Chamber 50% 8,179 113 26
Main Sand Filter Pool 50% 8,179 50 7
Total
Pond Data Depth Elevation
Top of Berm 900.00
Freeboard (ft) (1.00)
Emergency Overflow Weir Depth (ft) (0.50)
Emergency Spillway Crest Elevation 898.50
Control Structure Weir Height (0.50)
NWL (Control Structure Weir Elevation) 898.00
Sed. Chamber Weir Height (0.50)
Sed. Chamber Weir Crest 897.50
Sed. Chamber Depth (2.02)
Sed. Chamber Bottom Elevation 895.48
Ponding Depth 5.00
Sand Filter Main Pool Bottom Elev. 893.00
Total Depth 7.00
Ponding Depth (ft) 5.00
Sand Filter Surface Area (Min., sf) 3,272
S = 1000/CN-10
Q = (P-0.2S)/(P+0.8S)
Parameter
Q = (1.0 - 0.2*0.2)/(1.0 + 0.8*0.20)
Volume Distribution
Kontaine Calcs 8.xlsb
Rev. 5/3/2018