SW3240804_Stormwater Narrative_20240921

STORMWATER NARRATIVE
Beckingham Estates
Subdivision
Weddington, NC
July 15, 2024
W. K. Dickson & Co., Inc.
1213 W. Morehead Street, Suite 300
Charlotte, North Carolina 28208
[phone]
NC License No. F-0374

GENERAL
Beckingham Estates is a proposed 38 lot single-family subdivision located in Weddington, North
Carolina. The project is located off Lochaven Road to the East of Providence Road (NC-16) and
South of the intersection of Providence Road and Rea Road. The project consists of 38 low
density (40k sq. ft. minimum) lots with custom-built homes, private gated roadways/community
and ditch section roadways. The design consists of preserving the shape of the land and
minimizing permanent infrastructure while meeting ordinances of the Town of Weddington for
post construction stormwater detention.
Beckingham Estates is also being submitted to Town of Weddington for Preliminary Plat &
Erosion Control and Union County Public Works for utility permitting. The project is going to
utilize public water and private septic sewers due to lack of available sewer lines in the basin.
The estimated start of construction is Spring 2025.
PROPOSED IMPROVEMENTS
The project will collect stormwater with ditch section roadways, minimal valley gutter and storm
drainage inlets. The stormwater will be conveyed in concrete storm pipes or open channel
ditches. Per the Town of Waddington's stormwater detention requirements and NCDEQ Water
Quality requirements, the stormwater will be conveyed from the storm drainage system to one
of three wetpond facilities. The stormwater, once treated for the first 1" of rainfall and detained
per the Town's requirements (2, 10, 25, 50 & 100) will be discharged from the wetponds to a rip
rap apron and vegetative filter strip.
The site has two drainage points of interest. Point of interest #1 (POI#1) is located on the
Southeast side of the site where the existing tributary #1 drains. Point of Interest #2 (POI#2) is
located at the Northeast corner of the site where the site drains towards an existing pond as
part of Mundys Run. The table below represents the pre-development and post development
discharge. The wetponds provide detention for the peak stormwater runoff for the 2, 10, 25, 50
& 100-year storm events to meet the pre-development rates. Also provided is a table that
shows the available freeboard in the three wetponds.

STORM WATER
PRE-DEVELOPMENT/POST-DEVELOPMENT TABLE
1 YEAR ir 2 YEAR
PRE(CFS) POST(CFS) DELTA PRE(CFS) POST(CFS) DELTA
POI #1 2.15 2.41 0.26 4.58 4.55 -0.03
POI #2 6.18 6.33 0.15 13.07 12.36 -0.71
10 YEAR 25 YEAR
PRE(CFS) POST(CFS) DELTA PRE(CFS) POST(CFS) DELTA
POI#1 13.64 10.95 -2.69 19.91 15.04 -4.87
POI#2 37.67 32.34 -5.33 54.87 45.69 -9.18
50 YEAR 100 YEAR
PRE(CFS) POST(CFS) DELTA PRE(CFS) POST(CFS) DELTA
POI #1 24.97 18.26 -6.71 30.14 21.51 -8.63
POI #2 68.96 56.33 -12.63 83.49 74.42 -9.07
Free Board Check
Freeboad
Peak Ely. (100YR) Top of Berm (ft)
BMP 1 618.07 619.50 1.43
BMP 2 609.81 611.00 1.19
BMP 3 588.90 590.00 1.10
* Per Town of Weddington Stormwater Design Manual a minimum of 1.00'freeboard required
* Per NCDEQ Stormwater Design Manual a minimum of 1.00'freeboard required