SW6220603_Stormwater Narrative_20220711

Harnett Self Storage
Storm Water Management Statement
Harnett County, NC
Owner/Developer: Land 2020, Inc
350 Wagoner Drive, Fayetteville, NC 28303
Consultant:
HILLIARD
ENGINEERIN('
Contact: Jarrod E. Hilliard, PE, CFM
PO Box 249 Sanford, NC 27331
[phone]
NC License No. P-0836 Date: 6/2/22

A. Harnett Self Storge, Alpine Drive, Sanford, NC
B. Developer/Owner: Land 2020, Inc.; Consultant: Hilliard Engineering, PLLC (contact information
on cover)
C. The existing project site is an undeveloped sandy non -wooded tract of land
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. Storm water from this
project flows into Kiln Branch. The stream classification is as follows:
Stream Index: 18-20-13-4
Stream Name: Kiln Branch
Description: From source to Barbeque Creek
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:
Proposed Buildings and Asphalt: 258,531 sf
TOTAL IMPERVIOUS AREA: 258,531 sf
PROJECT PROPERTY AREA: 7.5 ac = 326,700 sf
IMPERVIOUS PERCENTAGE: 79.1 %
F. The project site is located within the unincorporated area of a Phase II Tipped County and is
therefore subject to Phase II Post Construction Storm Water regulations.
1. The project is over the high density threshold of 24% impervious area and as such, the
project proposes to utilize an existing storm water BMP in accordance with NC DEQ
regulations.
2. Minimal off -site runoff flows to this project. See drainage area map in erosion and storm
water report.
3. Skimmer Basin 01 (Prior to discharge to existing wet pond):
Q10 pre: 6.04 cfs
Q10 post: 45.27 cfs
Q25 pre: 6.70 cfs
Q25 post: 50.28 cfs

G. Downstream Analysis, if required:
1. See drainage map within the site development plans for drainage areas
2. There are no existing streams or ditches within the project area. Kiln Branch is
approximately % mile along the runoff path from the discharge point of this project.
Significant increases in velocity and flooding are not anticipated from this project based
upon the use of the existing storm water BMP. This BMP was originally designed for a
much higher runoff rate. A minor modification is being submitted to NCDEQ for this BMP
to reflect these changes.
3. A culvert is used for the driveway to this project and it flows into the aforementioned
BMP.
4. The total drainage area in which proposed impervious area exists for this project is 7.67
acres. The point where the development becomes less than 10% of the total watershed is
approximately 100 downstream of the source to Kiln Branch. The drainage area to that
point is approximately 79 acres.
5. As long as erosion control measures and the permanent storm water BMP are maintained
prior to permanent stabilization, no adverse impacts are anticipated from this project.
6. No additional phases to this project are proposed.