T&EIPHED Committees #1&2
September 30, 2013
September 26, 2013
Planning, Housing, and Economic Development Committee
Transportation, Infrastructure, Energy and Environment Committee
Bill 13-13 Impervious Area - Calculation
Zoning Text Amendment 13-03, Impervious Area -Calculation
Zoning Text Amendment (ZTA) 13-03, sponsored by Councilmember Rice, was introduced on
May 7, 2013.
13-13, with similar content but concerning stormwater management, was also
introduced on May 7, 2013. The proposed legislation would redefine impervious surface and count
25 percent of permeable pavement as impervious. Currently, all patio, deck, sidewalk, compacted
gravel, pavement, asphalt, concrete, and stone surfaces, whether permeable or not, are counted as
Councilmember Rice believes that the Zoning Ordinance should actively encourage the provision of
Permeable pavement, when properly installed, is already approved as a
stormwater management facility in an environmentally sensitive design. ZTA 13-03 would require the
Planning Director and the DPS Director to count only a percentage of permeable pavement area
(25 percent) toward any limit on impervious surface area. Bill 13-13 would allow pervious pavement as
a means of minimizing impervious pavement.
Permeable pavement includes permeable pavers, asphalt, and concrete.
Permeable pavement is an alternative to asphalt or concrete surfaces that allows stormwater to drain through the porous
surface to a stone reservoir underneath. The reservoir temporarily stores surface runoff before infiltrating it into the subsoiL
The appearance of the alternative surface is often similar to asphalt or concrete, but it is manufactured without fine materials
and instead incorporates void spaces that allow for storage and infiltration. Underdrains may also be used below the stone
reservoir ifsoil conditions are not conducive to complete infiltration of runoff.
Permeable pavers promote groundwater recharge. Permeable interlocking concrete pavements are concrete block pavers that
create voids on the comers of the pavers. Concrete grid paver systems are composed of concrete blocks made porous by
eliminating finer particles in the concrete, which creates voids inside the blocks; additionally, the blocks are arranged to
create voids between blocks. Plastic turf reinforcing grids (PTRG) are plastic grids that add structural support to the topsoil
and reduce compaction to maintain permeability. Grass is encouraged to grow in PTRG, so the roots will help improve
permeability due to their root channels.