Charleston's Stormwater Design Standards Manual treats permeable pavement as green infrastructure: Tier I without an underdrain and Tier II with one. Its examples are porous asphalt, pervious concrete and permeable pavers, so permeable resin-bound surfacing counts toward a project's stormwater requirements only if the Department of Stormwater Management accepts it, built as a full permeable system over a stone reservoir that passes the City's soil and water table tests.
Laid over an existing slab on the peninsula or in West Ashley, it is only a finish. Rain still runs off the concrete below and into a drainage system that already struggles when the tide is high. The notes below follow the City's 2026 manual and the technical procedures that sit behind it.
The 2026 design manual's tiers and where permeable pavement sits
The Department of Stormwater Management publishes the Stormwater Design Standards Manual, most recently updated in April 2026 after a major revision in 2020. Water quality controls are sized by tier using a 24-hour rainfall depth: 1.0 inch for Tier I green infrastructure (1.5 inches within 1,000 feet of shellfish beds), 2.0 inches for Tier II green infrastructure with an underdrain, and 2.8 inches for Tier III detention. Detention and pass-through devices are not allowed for projects discharging within 1,000 feet of shellfish beds.
Permeable pavement is Tier I or Tier II depending on whether it has an underdrain. The City requires design, installation and maintenance to follow Low Impact Development in Coastal South Carolina: A Planning and Design Guide (Ellis et al. 2014), full drainage within 72 hours and a 6-inch perforated observation well with a lockable cap, and it recommends a drainage area under 10 times the pavement footprint. The manual's examples are porous asphalt, pervious concrete and permeable pavers, so a resin-bound surface needs the reviewer's acceptance.
Redevelopment has its own test. Where existing impervious cover exceeds 20 percent and improvements exceed 50 percent of site value, owners must meet one of three standards: cut impervious cover by at least 20 percent, reduce the 24-hour runoff volume from the 50 percent AEP storm by 10 percent, or cut peak flows from the 10 percent and 4 percent AEP storms by 10 percent. Permeable pavers used only for the impervious reduction and built to the coastal LID guide skip infiltration and water table testing. Whether resin-bound can use that route is the City's call.
Tides, a high water table and the base beneath the surface
The manual notes that sea level at Charleston has risen slightly more than a foot over the past century and that streets already flood during spring tides. Storm drainage designs use a 5.5-foot NAVD88 tailwater as a boundary condition, with roadways no lower than 7.5 feet. In that setting a permeable base can fill from below, so the City's technical procedures put the bottom of any infiltration practice at least half a foot above the seasonal high water table, set by at least a year of piezometer data or by soil mottling, and require a double-ring infiltration test. Inside that half foot, a 40 mil liner has to separate the practice from groundwater.
Modeling credit is specific as well. A reduced curve number is allowed only for pavement with no underdrain that is not connected to the rest of the site's system, and never where tested infiltration is below 0.5 inches per hour. Otherwise designers count either storage in the stone voids or a longer time of concentration. Sites in the Church Creek basin and other special protection areas carry extra detention rules on top.
Where it fits in Charleston
- Peninsula courtyards, drives and garden paths on redevelopment sites working toward the 20 percent impervious reduction, subject to historic review where it applies.
- Hotel, restaurant and Medical District hardscape where outdoor space doubles as storage over a lined, underdrained base.
- New neighborhoods on Johns Island, James Island and in West Ashley using Tier I or II practices to shrink pond footprints.
- Office, church and school parking stalls with conventional drive aisles draining in, kept under the recommended 10:1 drainage area ratio.
Review and supply in Charleston
The Department of Stormwater Management reviews permeable pavement as part of the project's stormwater submittal. Expect to provide a geotechnical report from a licensed professional with infiltration and water table data, the tier calculations, observation well details and a maintenance plan. State construction stormwater permitting runs through the South Carolina Department of Environmental Services (SCDES), which now holds the environmental programs formerly run by DHEC.
The City's stormwater fee, now billed annually on the county tax bill, is $132 a year for a single-family home and $132 per 2,200 square feet of impervious area for other properties. The fee page does not describe a credit for permeable surfaces.
Resin Rock does not install. We supply UV-stable binder, stone blends, trims and the Rock Crete permeable sub-base, publish technical data sheets, and train and approve installers. After the Department of Stormwater Management signs off, request an approved installer and we will usually make a match within 24 hours.
Before you specify permeable resin-bound in Charleston
- Choose Tier I or Tier II early, based on tested infiltration and the need for an underdrain.
- Collect at least a year of piezometer data, or a mottling determination, for the water table.
- Check the 1,000-foot shellfish bed rule and any special protection area.
- Keep the contributing drainage area under ten times the permeable footprint.
- Model outlets against the City's 5.5-foot NAVD88 tailwater.
- Ask whether a resin-bound surface can use the redevelopment impervious-reduction route.
Common questions about permeable resin-bound in Charleston
Does the redevelopment rule apply to my small peninsula lot?
The manual's redevelopment standards apply where existing impervious cover exceeds 20 percent and improvements exceed 50 percent of site value, but they do not apply to parcel areas under one acre or to sites with more than 80 percent existing building footprint that is staying. Small lots still need permits, so check with Stormwater Management.
Will permeable pavement lower my Charleston stormwater fee?
The City charges $132 a year for a single-family home and $132 per 2,200 square feet of impervious area for other properties, now billed on the county tax bill. The fee page lists a homestead exemption waiver and an appeals process but no credit for permeable surfaces, so ask the City before assuming any reduction.
Why does the City care so much about the water table?
Because a permeable base only works if water can leave it. Where groundwater rises close to the surface, the stone fills from below and stops storing rain. The City requires the bottom of infiltration practices to sit at least half a foot above the seasonal high water table, or be lined, with a double-ring infiltration test behind the design.
Official sources for Charleston
- City of Charleston: Stormwater Design Standards Manual
- City of Charleston: Stormwater Service Billing
- SCDES: Stormwater Program
Local rules change. We last checked these sources in October 2026. Confirm current requirements with the reviewing agency before you design, and treat this page as a starting point, not engineering or permitting advice.