Permeable Resin-Bound Surfacing in Austin, TX

How Austin's ECM and drainage charge treat porous pavement

Austin's water quality rules sit in Land Development Code Chapter 25-8 and the ECM. ECM Section 1.6.7, Green Stormwater Quality Infrastructure, lists porous pavement among the green controls a site can use, and a May 2024 rule update describes the water quality credit for porous pavement for pedestrian use as a deduction in the drainage area used to size water quality controls. For porous pavement the ECM goes further: it is not accepted as a water quality control anywhere in the Barton Springs Zone, which covers both its recharge and contributing zones, so there is no credit there.

That points resin-bound toward walkways, plazas, courtyards and patios that the engineer designs as porous pavement under the ECM. The ECM accepts pavers, grid pavement and porous asphalt in light vehicle areas such as parking stalls but limits porous concrete to pedestrian use, so vehicle areas are a separate conversation with the reviewer. Resin-bound is not named in the ECM, so plan to show the system data and base design rather than assume it will be treated like pervious concrete. Credit also depends on an infiltrating design, with a subgrade that drains at least 0.20 inches per hour, and a contractor certified by one of the porous pavement associations the ECM lists.

The drainage charge is calculated per property from impervious cover, a base rate of $0.0063 per square foot per month for fiscal year 2026-27 (on bills from November 2026), and an adjustment factor tied to percent impervious cover. The Stormwater Management Discount covers voluntary controls that exceed development requirements, can offset up to 50 percent of impervious cover, and lists rainwater harvesting, rain gardens, green roofs and ponds. Permeable pavement isn't on that list, so don't build a budget around a discount for it.

Balcones geology, karst and Atlas 14 rain: what the base has to handle

Austin straddles the Balcones Escarpment. To the west, thin soils over fractured Edwards limestone feed the aquifer and Barton Springs; to the east, Blackland Prairie clays shrink and swell with moisture. Over the recharge zone, the first question is whether infiltration is allowed at all. On the eastern clays, it's whether water can leave the reservoir without softening the subgrade, which usually means an underdrain.

State rules add a layer. TCEQ's Edwards Aquifer rules apply in parts of Travis, Hays and Williamson counties, and its RG-348 technical guidance allows permeable concrete in the contributing zone only. A 2017 addendum allows permeable pavers over the recharge zone only with an impermeable liner and underdrain. Neither names resin-bound surfaces. Over these zones a project engineer may specify a lined reservoir with a controlled outlet, or decide infiltration is off the table.

Rain intensity matters too. The city says Atlas 14 raises the 100-year, 24-hour storm from 10.2 inches to almost 13 inches in some areas, so overflow paths need real capacity. And a resin-bound layer over existing concrete passes rain to the slab, which still sheds it as runoff. That version should not be counted as a stormwater control.

Where porous resin-bound makes sense in Austin

The best fits are pedestrian spaces across the city's mix of dense infill and Hill Country sites:

• Plazas and courtyards in Downtown, the Domain and East Austin mixed-use projects, where pedestrian porous pavement may reduce the drainage area routed to a water quality pond or filter.
• Walkways and patios on residential infill east of I-35, built with an underdrain for the clay subgrade.
• Restaurant and hotel patios along South Congress and South Lamar, where a drained surface also cuts ponding at doorways.
• Trails and campus paths at schools, parks and institutional grounds, subject to the owner's standards.
• Hill Country homes in the contributing zone, as a lined, detention-style section where infiltration is restricted.

Getting a resin-bound section through Austin review

Commercial and multifamily projects go through the city's site plan review, which applies Watershed Protection's ECM criteria, and sites over the Edwards zones may also need a TCEQ plan. Take the porous pavement design to an early meeting with the reviewer: base section, infiltration test or liner, overflow route, aquifer zone and a maintenance plan. Credit and approval decisions stay with the city and TCEQ.

Resin Rock supplies the UV-stable binder, aggregate blends, trims and the Rock Crete permeable sub-base, with technical data sheets for your engineer and reviewer. We don't install. We match Austin owners with an approved installer, usually within 24 hours, through find an installer, and Texas contractors can learn the system through resin-bound installer training in Texas.