SW6230401_Stormwater Narrative_20230707

Phalanx Crossfit
Storm Water Management Statement
Harnett County, NC
Owner/Developer: Phalanx Fitness, LLC
359 Sunridge Drive, Cameron, NC 28326
Consultant:
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Contact: Jarrod E. Hilliard, PE, CFM 9p.o!;GINF:�'��P�
PO Box 249 Sanford, NC 27331 o E.
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NC License No. P-0836 Date: 12/6/22

A. Phalanx Crossfit, NC 87 South, Spout Springs, NC, Harnett County
B. Developer/Owner: Phalanx Fitness, LLC; Consultant: Hilliard Engineering, PLLC (contact
information on cover)
C. The existing project site is a vacant property, formerly residential use
1. A vicinity map is included with this Statement
2. A USGS map is included with this Statement along with a Harnett County Soil Survey for
the project area
3. This project area does not contain any water impoundments or wetlands. Water from this
project flows into Little Bridge Branch. The stream classification is as follows:
Stream Index: 18-23-29-2-1
Stream Name: Little Bridge Branch
Description: From source to Reedys Swamp
Classification: C
Date of Class.: August 31, 1974
River Basin: Cape Fear
D. The site is not located within a conservation zoning nor a watershed district
E. Impervious Area Calculations:
Buildings: 12,000 sf
Asphalt Paving: 1,896 sf
Gravel Paving: 14,983 sf
Concrete Stoop/Sidewalk: 159 sf
TOTAL IMPERVIOUS AREA: 29,038 sf
PROJECT AREA: 94,961 sf
IMPERVIOUS PERCENTAGE: 30.58
F. The project site is subject to Phase II Post Construction Storm Water regulations.
1. The project is greater than 24% impervious area, therefore it is considered high density.
2. Off-site storm water is being diverted from the site via low-velocity swales.
3. Wet Pond:
Q10 pre: 0.60 cfs
Q10 post: 4.86 cfs
Q10 wet pond outflow: 0.46 cfs

Q25 pre: 0.67 cfs
Q25 post: 5.39 cfs
Q25 wet pond: 0.47 cfs
G. Downstream Analysis, if required:
1. See drainage map within the storm water calculations for drainage areas
2. Significant increases in velocity and flooding are not anticipated from this project based
upon the use of the infiltration basin for mitigation, which is designed to contain the 100-
year storm and larger.
3. A driveway culvert is proposed for this project as show on the site plans.
4. The total drainage area in which proposed impervious area exists for this project is 0.76
acres. The point where the development becomes less than 10% of the total watershed is
at the property line for the project.
5. If erosion control measures are maintained prior to permanent stabilization, and the
infiltration basin is properly constructed and maintained, no adverse impacts are
anticipated from this project.
6. Detention is proposed for this project in the form of a wet basin.