Permeable Resin-Bound Surfacing in Bethesda / Montgomery County, MD

The Water Quality Protection Charge credit and the RainScapes rebate

The Department of Environmental Protection (DEP) bills the Water Quality Protection Charge (WQPC) on impervious area with property taxes. Permeable pavement is on DEP's list of eligible practices, and the credit is based on the volume of water a practice captures. Multifamily and nonresidential properties can earn up to 60% off where environmental site design (ESD) and conventional systems together treat the site, and up to 80% where the property is fully treated by ESD. Credits are renewed every three years, and applications are due September 30.

The separate RainScapes permeable pavement retrofit rebate pays $14 per square foot of existing impervious surface replaced, with a 100-square-foot minimum for homes and 200 square feet for commercial and institutional sites, up to a maximum of $7,500 per residential parcel and $20,000 for commercial, HOA, multifamily and institutional parcels. As written, the rebate requires permeable interlocking concrete pavers installed by a contractor certified for them through the Concrete Masonry and Hardscapes Association (CMHA), built to the RainScapes Permeable Paver Manual or the county's paver specifications. A resin-bound surface would qualify only if RainScapes grants an exception, so ask before you build, not after.

Piedmont soils, steep stream valleys and a dense downtown

Bethesda sits on Piedmont ground: weathered schist and gneiss under silty, mica-rich soils, with infiltration that ranges from useful to poor over short distances. Little Falls Branch, Willett Branch and Cabin John Creek cut steep valleys toward the Potomac, and the east side drains to Rock Creek. Maryland's ESD criteria for permeable pavement want soils in Hydrologic Soil Groups A, B or C, a surface that passes at least eight inches of water per hour, and slopes no steeper than 5%, with terracing on steeper grades.

MDE's subbase is clean, washed, open-graded stone of about 30% porosity, typically 6, 9 or 12 inches thick, with no filter cloth between subbase and soil subgrade. Shallow rock or saprolite on some lots limits depth, and that is where the project engineer may trade reservoir depth for an underdrain. Downtown Bethesda parcels are nearly all redevelopment sites, where existing impervious area inside the limit of disturbance sets the treatment target.

Snow and freeze-thaw are routine. MDE's maintenance guidance asks for at least two vacuum sweepings a year, plow blades set an inch higher than normal, and no plowed snow piles on the permeable surface.

Where permeable resin-bound fits across Bethesda and the county

• Single-family driveways and front walks in Bethesda, Chevy Chase and Kensington, where a design DEP accepts could earn a WQPC credit, though the RainScapes rebate as written covers only certified permeable pavers.
• Courtyards, plazas and through-block walkways in downtown Bethesda and the Pike District, where redevelopment projects need treatment inside tight footprints.
• HOA common areas in Potomac and Olney, such as paths, pool surrounds and overflow parking.
• Private schools, places of worship and office parks in Rock Spring and along Rockville Pike, where large paved areas drive the WQPC bill.

DPS concept review, DEP credits and how Resin Rock supports the submittal

For development, the Department of Permitting Services (DPS) reviews the stormwater management concept, and that approval comes before the Planning Board acts on a preliminary plan. Anything other than a single-family house on a residential lot generally needs one, and sites in a Special Protection Area follow added water quality plan steps. Credits and rebates for existing properties are handled by DEP, separately from permitting.

Resin Rock is a manufacturer-supplier, not an installer. We supply the UV-stable binder, natural stone blends, trims and the Rock Crete permeable sub-base, plus technical data sheets your engineer can attach to a DPS or DEP submittal. We train and approve installers, and through find an installer we usually match a Montgomery County project with one within 24 hours. Contractors who want to add the system can start with our Maryland installer training.