HIGHLAND LAKES WATERSHED ORDINANCE

AND THE LOOKOUT MOUNTAIN WEST SUBDIVISION

As part of the highland lakes area, the Lookout Mountain West subdivision falls under the jurisdiction of the Lower Colorado River Authority (LCRA).  The LCRA, as stewards of the highlands lakes, maintains a watershed ordinance specifically designed to minimize degradation of the Colorado River due to pollution and/or erosion stemming from new commercial or residential developments.

To meet the standards and requirements of the Highland Lakes Watershed Ordinance (HLWO) all residential lots within the Lookout Mountain West subdivision are subject to impervious cover restrictions.  The maximum impervious cover allowed to be constructed on any single lot is 4,790 square feet.  Impervious cover includes, but is not limited to, pavement, rooftops and other surfaces that prevent the infiltration of water into the soil.  Impervious cover for any structure, such as a multi-story home, is based on the effective footprint of the structure and not the overall interior square footage.

There are provisions in the HLWO that allow exceptions to the impervious cover restrictions placed on each lot.  The approved “stormwater credits” listed and explained below can be used to effectively reduce the impervious cover on any lot so as to bring the lot into compliance with the HLWO.

LCRA Approved Stormwater Credits

Porous Pavement (concrete) or Paver Blocks – A credit is given when porous pavement and/or paver blocks are used in driveways and sidewalks.  These technologies can be used to reduce the effective impervious cover attributed to paved areas such as driveways or sidewalks by up to 90%.  Porous pavement must satisfy the design and installation requirements found in the HLWO.

Rainwater Harvesting (cisterns) – A credit is given when rainwater collection systems are used to retain roof runoff resulting in the reduction of the development impervious cover.  Approved rainwater collection systems can reduce the effective impervious cover attributed to rooftops by up to 75%.  Overflows from rainwater tanks should be diverted to grassy swales and/or lawns to promote infiltration of excess runoff.

Soil Amendment – The Soil Amendment Credit relies on native soils, appropriate soil depths and low maintenance turf grasses to reduce the runoff volume.  Approved soil amendment plans may be used to reduce the effective impervious cover of the lot by 2%.  Home builders must coordinate with LCRA during soil placement.

Conservation Landscaping – The Conservation Landscaping Credit is based upon planting a reduced turf area and incorporating native plants, shrubs, trees and perennials to retain stormwater on site and require minimal chemicals to sustain a native landscape.  Approved conservation landscaping plans may be used to reduce the effective impervious cover of the lot by 5%.  Home builders must coordinate with LCRA during landscape installation.

Rooftop Disconnection – A credit is given when rooftop runoff is disconnected via drainage pipes and directed to a pervious area where it can either infiltrate into the soil or filter over it.  If a rooftop is adequately disconnected, i.e. the runoff is taken far enough away; the disconnected impervious cover area can be deducted directly from the total impervious cover for the site.  The contributing area of a rooftop to a single disconnected discharge point shall be 800 square feet or less.

Additional information pertaining to stormwater credits and the Highland Lake Watershed Ordinance may be found at the following web link.