Permeable Resin-Bound Surfacing in Wilmington, NC

Wilmington's own stormwater permit and the coastal rules behind it

Since its ordinance took effect on November 1, 2009, the City of Wilmington has run its own stormwater permit process for many projects inside city limits, in place of the process administered by NCDEQ's Division of Energy, Mineral and Land Resources. Permits are required for new development, redevelopment and expansion of existing development, through either a Full Stormwater Review or a Drainage Plan Review. Projects proposing permeable pavements for credit submit the state SCM supplement, and the City publishes an operation and maintenance agreement specifically for permeable pavements.

The state framework still applies. North Carolina's coastal stormwater rule covers the 20 coastal counties, and Chapter C-5 of the NCDEQ Stormwater Design Manual says the built-upon area credit for infiltrating pavement cannot be used to escape coastal permit requirements, because the pavement must still be reviewed against the design criteria. C-5 sets a surface infiltration rate of at least 50 inches per hour and asks for proof of long-term performance for surfaces other than pavers, pervious concrete or porous asphalt.

Standards are changing locally too. The City says it will move from a Phase II to a Phase I NPDES permit with added requirements, and it is rewriting its Technical Standards Manual, including a stormwater chapter that was open for public comment through June 2026. Check which version applies on your submittal date.

Sand, shallow groundwater and tides: base design questions

Wilmington's sandy soils often drain well; the constraint is the seasonal high water table. C-5 requires at least two feet between the bottom of an infiltrating base and the seasonal high water table, reducible to one foot with a hydrogeologic evaluation, and one foot for a detention design. On low sites that usually means a shallow reservoir, a raised grade or an underdrain. An impermeable liner can isolate a detention base where groundwater or contamination is a concern, but it lowers the TSS removal credit from 85 to 70 percent.

Tides and tropical storms add a separate problem. Low streets near the river and creek mouths flood from the downstream side, and no permeable surface helps once the ground is saturated or under water. Outlets should be checked for backwater conditions, and wind-blown sand on the surface is a clogging risk that calls for regular vacuum sweeping.

Where it fits in Wilmington

• Commercial and mixed-use sites in the Bradley Creek and Hewletts Creek watersheds, where the City's cost-share program supports permeable pavement retrofits.
• HOA common areas and amenity parking in those watersheds and in areas draining to the Intracoastal Waterway.
• Downtown courtyards and side yards where a small permeable footprint can take roof downspouts, subject to any historic district review.
• Medical office, retail and campus parking along the College Road and Military Cutoff corridors, with permeable stalls beside conventional drive aisles.

Permitting, rebates and supply in Wilmington

Start with the City's stormwater permit staff: confirm the review track, whether permeable pavement will be counted for credit, and what the permeable pavement O&M agreement will ask of the owner. Bring seasonal high water table data, borings, the reservoir and outlet design, and manufacturer data on surface infiltration.

For retrofits, Heal Our Waterways offers a first-come rebate for commercial, mixed-use and high-density properties and HOA common areas in the Bradley Creek, Hewletts Creek and connected Intracoastal Waterway watersheds. It lists permeable pavement among the large-scale practices it supports, with rebates up to $20,000 based on project type and size. The residential full-funding track does not cover permeable pavement.

Resin Rock does not install. We supply binder, aggregate blends, trims and the Rock Crete permeable sub-base, and we train and approve installers through our North Carolina installer training. When the design is settled, request an approved installer.