SW3190701_SW Report (Narrative)_20190822

STORMWATER MANAGEMENT SUMMARY
Harwood Automotive, Inc. is located on a 4.94 acre site in Midland, NC. The owner plans to
construct a 3990 sf addition to the facility. Additional pavement will be constructed around the
proposed facility. After construction, the site will have approximately 1.08 acres of built upon
area. This includes approximately 0.88 acres of existing impervious and 0.20 acres of new
impervious. Upon completion, the site will be 21.86 percent impervious. The project is
considered a high density project because the project was not designed to maximize dispersed
flows. For this project, a sand filter will be constructed to treat all of the new impervious areas.
An existing gravel parking area will be replaced with a paved parking area. This area does not
drain to the sand filter, but due to the size (0.07 acres) and current use (gravel parking), the
buffer/planting area around the parking will be sufficient for the area.
The sand filter is located southwest of the building expansion. The drainage area to the basin
is 17.25 percent impervious based upon a drainage area of 1.18 acres with 0.20 acres of new
impervious. For actual design of the sand filter, we are treating the existing and proposed
impervious (0.38 Acres). The site is is 32.2 percent impervious when considering the existing
and proposed impervious. The sand filter releases the first inch of rainfall in 1.66 days (40
hours) The system also provides stormwater detention for the 2, 10, and 25 year storms. The
maximum ponding depth for the 25 year storm is 1.89'.
The owners have provided a signed operation and maintenance plan for the sand filter. As
outlined in the document, the sand filter will require continued monitoring and maintenance to
ensure that it functions as intended.