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The definition of appropriate hydrology according to the 1987 Manual includes two important <br /> terms that must be clarified. First, the definition of a growing season is needed. The growing <br /> season is defined in the 1987 Manual as: "...the portion of the year when soil temperature <br /> (measured 19.7 inches below the surface) is above biological zero (5° C or 41° F)." According to <br /> the 1987 Manual this period of time can be approximated by using the "starting and ending dates <br /> for the growing season based on a 28° F air temperature threshold at a frequency of 5 years in <br /> 10." Based on this definition the growing season ranges approximately 160 days to 180 days in <br /> the Minneapolis/St. Paul metropolitan area(160 in the northern suburbs and greater to the south). <br /> Therefore, the required inundation or saturation to the surface for 5% of the growing season <br /> would be 8 or 9 consecutive days that ground water would need to be at the surface or saturated <br /> to the surface. <br /> The second term in the appropriate hydrology definition from the above paragraph to be clarified <br /> is "in most years". This means in 5 of 10 years hydrology must exist within a "jurisdictional <br /> wetland" for the 8 or 9 consecutive days of the growing season. This means that one observation <br /> date or even one whole year worth of detailed hydrology data may be deemed insufficient to <br /> deternune if appropriate hydrology exists at a given location. In the event that precipitation <br /> events accumulate to above or below normal during just prior to a site visit or during a more <br /> intensive hydrology study, the data may be confounded by non-normal circumstances and may <br /> be considered outside the bounds of "most years". Ideally, both antecedent soil moisture <br /> conditions and precipitation would be normal during all delineations. However, this is not a <br /> realistic impression of climate. Therefore, primary indicators of hydrology must be reviewed <br /> with scrutiny prior to determining if hydrology indeed exists. <br /> Wetland hydrology may be observed as standing water (inundation), or may be observed as <br /> freestanding water within a soil pit or auger hole (saturation)usually within the upper 12 inches. <br /> This is what would be considered primary hydrology indicators. Examination of this indicator <br /> requires digging a soil pit to a depth of 16 inches and observing the level at which water stands <br /> after sufficient time has been allowed for water to drain into the hole. The required time will <br /> vary depending on soil texture. This level represents the depth to the water table; the depth to <br /> saturated soils will always be nearer the surface due to the capillary fringe. According to the <br /> Hydrology criteria in the 1987 Delineation Manual, for soil saturation to impact vegetation, it <br /> must occur within a major portion of the root zone, typically within 12 inches of the surface. <br /> Only one primary indicator is necessary to make the deteimination that wetland hydrology is <br /> present. However, since a single observation is not enough evidence, based on the percentage of <br /> the growing season this inundation or saturation is required, these data are only valid when <br /> reviewed while also considering the abundance of recent precipitation events or the seasonal <br /> trend of climate when the site visit was made (this may be done through review of precipitation <br /> records where available). In addition to the primary indicators of wetland hydrology, there are <br /> secondary indicators (e.g. oxidized root channels, water-stained leaves, local soil survey data, <br /> FAC-Neutral test), of which two must be present to consider the sample point as having wetland <br /> hydrology. <br /> A-2 <br />