Page 58 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

LEED Sustainable Sites 39

developing on previously developed areas of the site. To obtain this credit, all six of the
criteria must be met. Two important definitions to understand are those of development
footprint and previously undeveloped land. Development footprint as defined by LEED-
NC 2.2 can be found in App. B, as well as the definition of previously developed sites,
which are assumed to be the opposite of previously undeveloped land. The differences
between the two are as follows: the development footprint, as defined, does not include
landscaped areas, whereas previously developed sites as defined include areas graded
or altered by direct human activities which may include landscaped areas.
There are no calculations for this credit other than as appropriate to verify distances,
elevations, and setbacks. Confirmation that all six criteria are met must be submitted.
The second and fifth criteria are applicable only if the land in question was previously
undeveloped, but again this must be shown. There is room for “special circumstances”
or “nonstandard compliance paths” in this credit, but these must be described.
Also of note is the first criterion which refers to prime farmland. Not all farmland
or potential farmland is prime. The U.S. Department of Agriculture (USDA) definition
of prime agricultural land as stated in the applicable Code of Federal Regulations (CFR)
part is as follows:

Prime farmland is land that has the best combination of physical and chemical characteristics
for producing food, feed, forage, fiber, and oilseed crops, and is also available for these
uses (the land could be cropland, pastureland, rangeland, forest land, or other land, but not
urban built-up land or water). It has the soil quality, growing season, and moisture supply
needed to economically produce sustained high yields of crops when treated and managed,
including water management, according to acceptable farming methods. In general, prime
farmlands have an adequate and dependable water supply from precipitation or irrigation,
a favorable temperature and growing season, acceptable acidity or alkalinity, acceptable
salt and sodium content, and few or no rocks. They are permeable to water and air. Prime
farmlands are not excessively erodible or saturated with water for a long period of time,
and they either do not flood frequently or are protected from flooding. Examples of soils
that qualify as prime farmland are Palouse silt loam, 0 to 7 percent slopes; Brookston silty
clay loam, drained; and Tama silty clay loam, 0 to 5 percent slopes.
The second criterion relates to designated floodplain elevations. The 100-year
floodplain is usually as designated on the FEMA Flood Insurance Rate Maps (FIRMs). A
100-year flood is not one that occurs every 100 years, but rather is a flood with a 1 percent
probability whose magnitude or greater might occur every year. If the FEMA flood
lines are not available, then the Army Corps of Engineers or other recognized authority
maps may be substituted. There are some exceptions to building in a floodplain for
projects which have some redevelopment in the floodplain area. Another exception is
that areas can be “elevated” above the 5-ft minimum if both the 100-year floodplain is not
impacted and there are balanced cuts and fills in these areas so as not to impact storage
volumes. In LEED-NC 2.1 a credit interpretation ruling (CIR) allowed for the definition of
the facilities which needed to be at least 5 ft above the elevation of the 100-year floodplain
to be only those included in the building footprint. As the version 2.2 verbiage is more
lenient than that of version 2.1 (version 2.1 did not specifically exempt previously developed
land), it is reasonable to assume that this definition is also applicable to version 2.2,
although it is not specifically mentioned in the LEED 2009 reference guide.
As with the floodplain criterion, already existing facilities that are located within
the setbacks as defined for wetlands can remain. Maintenance and minor improvements
on these nonconforming existing facilities would normally be appropriate, whereas