SW3190701_Project Narrative_20190708

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 1.12 acres of built upon
area. This includes approximately 0.72 acres of existing impervious and 0.40 acres of new
impervious. Upon completion, the site will only be 22.80 percent impervious which would
normally be considered a low density project. However, the Town of Midland has performance
standards for low density projects based upon a points system. If a low density development
cannot meet these performance standards, then an approved stormwater control measure or
structure shall be provided, in compliance with the Town of Midland's stormwater guidelines
for water quality and flood control.
For this project, we were unable to meet the performance standards, so a sand filter will be
constructed. This sand filter will treat all of the new impervious areas. However, 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 27.12 percent impervious based upon a drainage area of 1.18 acres and 0.32 acres of built
upon impervious area. 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.