What is my land coverage?
Land coverage is an essential element of the Tahoe Regional Planning Agency’s (TRPA) plan to protect and restore the clarity of Lake Tahoe. Permanent land disturbance is most commonly measured in terms of square feet of impervious surface, also called land coverage. It includes all human-made structures such as homes, driveways, and parking lots as well as areas of compacted soil created by human use.
When we convert Tahoe’s naturally porous and stable soil to an impervious surface we are increasing how fast and how far snow melt and stormwater runoff can travel. This runoff carries many clarity-harming pollutants, such as fine sediment, nitrogen, and phosphorus. At the same time, we are replacing some of the natural infiltration and water storage that kept those pollutants out of Lake Tahoe for millennia.
Taking a bird’s eye view of our neighborhoods and towns, small areas of land coverage add up and it is clear they are all connected to one another and the lake by roadways, streams, and stormwater systems. Lake Tahoe isn’t alone in needing to limit impervious surfaces. The U.S. Environmental Protection Agency considers land coverage a concern nationally because of its potential effect on the environment and human health.
How much land coverage can be allowed on a property depends on soil type and other factors. These are determined through either a TRPA Site Assessment or an Individual Parcel Evaluation System score (IPES).
There are two separate systems used to determine land capability and the amount of allowable coverage depending on the date of construction: Before 1987 (Bailey) or 1987 to present (IPES).
Bailey Land Capability System
The Bailey system is applied to all commercial and multi-family properties and to all residential properties that were already built upon before July 1, 1987.
The US Forest Service and TRPA developed the Bailey land capability system in the early 1970s based primarily on the official USDA soils maps for the Tahoe Region. Each soil type was assigned to a land capability class ranging from 1 to 7, with capability 1 being the most environmentally fragile and sensitive to development. Wherever land was found to be influenced by a stream or high groundwater, it was assigned to capability 1b, also known as Stream Environment Zone, or SEZ.
TRPA and the Natural Resource Conservation Service have continued to survey soil types around Lake Tahoe and are updating the original Bailey classifications. Applying for a Land Capability Verification is often the best way to find out how much coverage is allowed on residences built before 1987 and on all commercial and multi-family parcels.
|Lands Located in Land Capability District||Base Coverage|
|1a, 1b, 1c||1%|
As applied by TRPA and other regulatory agencies, the Bailey system prohibits new development on all capability 1 through 3 parcels, and restricts the amount of coverage (i.e., pavement and building footprint) that can be placed on capability 4 through 7 parcels. For parcels with Bailey scores 1 through 3, TRPA created a program for the transfer of development rights to other, less sensitive parcels. In this way, development can be moved away from the most sensitive areas and property owners can still realize value from their land.
Some Bailey scores on homes or businesses built prior to July 1, 1987, are already on file at TRPA because of a prior project or an earlier request for verification. However, a Land Capability Verification Application for commercial or multi-family properties or a Site Assessment Application for a residential property are often necessary on those parcels before TRPA can issue a permit.
From 1985 to 1987, TRPA worked with a large number of interest groups and government agencies to develop an ordinance which replaced the Bailey land capability system with an objective and more accurate classification system, the Individual Parcel Evaluation System (IPES). IPES is described in detail in the Code of Ordinances.
Understanding IPES scores
IPES assigns a numerical score to vacant parcels and ranks the parcels within each local jurisdiction according to their relative suitability for development. Any parcel with a “top rank” score may obtain an allocation from their local jurisdiction, after which a building permit may be received from TRPA or local government agencies.
Over a period of several years, the “top rank” will gradually expand to include more and more parcels, subject to a number of environmental safeguards. These safeguards include requirements for the installation of an expanded water quality monitoring program and a satisfactory rate of reduction in environmentally sensitive parcels by operation of a variety of acquisition programs.
Does IPES apply to me?
In order to put IPES into effect, TRPA needed approval of IPES from California, Nevada, and the U.S. Environmental Protection Agency. IPES does not apply to residential parcels that are already developed, nor to parcels ineligible for residential use. SEZs, which are stream environment zones – meadows and wetlands, will continue to be protected and restricted from development under IPES.
How are lots scored?
IPES field teams consisting of a soils scientist, a hydrologist, and a planner/engineer visited vacant parcels. Based on an actual onsite analysis, including digging a small pit to allow analysis of the soil profile, TRPA evaluated each parcel according to the following criteria:
|1. Relative Erosion Hazard||Based on the soil sample, slope data, and precipitation data.||450 points maximum|
|2. Runoff Potential||The potential for overland runoff, based on vegetative cover and the ease with which soil absorbs precipitation.||200 points maximum|
|3. Access||Based on the amount of excavation and vegetation removal necessary to construct driveways and parking.||170 points maximum|
|4. Stream Environment Zones||Based on the extent to which utilities, excavation, and grading will encroach on SEZs.||110 points maximum|
|5. Condition of Watershed||Considers the overall status of the watershed in which the parcel is located.||70 points maximum|
|6. Ability to Revegetate||Based on the inherent ability of the site to be revegetated, considering soil and site properties.||50 points maximum|
|7. Need for Water Quality Improvements in the Vicinity||A factor which favors areas with stable cut and fill slopes, adequate and stable drainage, and paved roads.||50 points maximum|
|8. Distance from Lake Tahoe||A factor which favors parcels which are located farthest from the shore of Lake Tahoe, from which transport of pollutants to the lake is less likely.||50 points maximum|
Coverage Exemptions for Residential Improvements
Special incentives are now available to homeowners through the TRPA Code of Ordinances to help more property owners complete home improvement projects. Homeowners may exempt certain structures from land coverage calculations for certain properties that have installed water quality Best Management Practices (BMPs). To know if the exemptions can be applied to your home improvement project, open the information packet below.
Land Coverage Exemption Worksheet (a spreadsheet will download)
Coverage Transfers Across Hydrologic Area Boundaries
Land coverage policies have been updated to encourage the removal of development from sensitive lands and add flexibility for transferring coverage across the Lake Tahoe Region’s nine Hydrologically Related Areas. Click here for the fact sheet.
Land Coverage 101
If you need a little more information than above, but not too much, use our Land Coverage 101 document.
Lake Tahoe isn’t alone in needing to limit impervious surfaces. The U.S. Environmental Protection Agency sees land coverage as a concern nationally because of its potential effect on the environment and human health.