40452 Federal Register / Vol. 56, No. 157 / Wednesday, August 14, 1991 / Proposed Rules 



verifying characteristics are mandatory, 

 with the following exceptions: disturbed 

 wetlands (i.e., wetlands that met the 

 mandatory criteria prior to disturbance 

 and have had the vegetation, soils, and/ 

 or hydrology altered such that the 

 required evidence of the relevant 

 indicators for the affected criterion has 

 been removed); and specific wetland 

 types that may never meet all three 

 criteria although they are widely 

 recognized as wetlands (i.e., some 

 prairie potholes, playa lakes, vernal 

 pools and pocosins, and other special 

 wetlands that fail the hydrophytic 

 vegetation criterion such as Eastern 

 hemlock swamps, tamarack bogs, and 

 white pine bogs). Descriptions of these 

 exceptions are included in this manual. 



This manual also includes other 

 clromistances which may complicate 

 wetland delineation and which therefore 

 require special consideration (e.g^ pit 

 and mound topography, newly formed 

 hydric soils). 



The three mandatory technical criteria 

 are presented below. Background 

 information for each criterion is also 

 provided. 



Wetland Hydrology Criterion 



An area has weUand hydrology when 

 it is: 



1. Inundated for 15 or more 

 consecutive days, or saturated from 

 surface water or from ground water to 

 the surface for 21 or more consecutive 

 days during the grovdng season in most 

 years, or 



2. Periodically flooded by tidal water 

 in most years. 



Areas meeting this criterion also are 

 usually inundated or saturated for 

 variable periods during the non-growdng 

 season. The term "Inundated and/or 

 saturated at the surface" means the soil 

 is inundated or wet enough at the 

 surface to the extent that water reaches 

 the surface in an unlined borehole or 

 can be squeezed or shaken from the soil 

 at the surface. The growing season is the 

 interval between 3 weeks before the 

 average date of the last killing frost in 

 the Spring to 3 weeks after the average 

 date of the first killing frost in the Fall, 

 with exceptions for areas experiencing 

 freezing temperatures throughout the 

 year (e.g., montane, tundra and boreal 

 areas) that nevertheless support 

 hydrophytic vegetation. The term "in 

 most years" means that the condition 

 represents the prevailing long-term 

 hydrologic condition and would be 

 expected to occur in the futiire in more 

 years than not over the long term (e.g., 

 more than 5 years out of 10). 



While the above criterion must be 

 met. many times field staff will not be 



present to do wetiand determinations at 

 the right time of year or for long enough 

 to directly observe that an area is 

 inundated for 15 or more consecutive 

 days or saturated from surface water or 

 from groundwater to the surface for 21 

 or more consecutive days during the 

 growdng season in most years. 



An area meets the wetland hydrology 

 criterion above by direct measurement 

 of inundation and/or soil saturation of 

 tidal flooding or as documented by one 

 or more of the following indicators: 



1. A minimum of 3 years of hydrologic 

 records (e.g., groundwater well 

 observations foUovmig the protocol on 

 page 99, or tide or stream gauge records) 

 collected during years of normal rainfall 

 (amount and monthly distribution) and 

 correlated with long-term hydrologic 

 records for the specific geographical 

 area that demonstrates the area meets 

 the wetland hydrology criterion; or 



2. Examination of aerial photography 

 (preferably early spring or wet part of 

 the growing season) for a minimum of 5 

 years reveals evidence of inundation 

 and/or saturation in most years (e.g., 3 

 of 5 years or 6 of 10 years) and 

 correlated with long-term hydrologic 

 records for the specific geographical 

 areas demonstrate that the area meets 

 the weUand hydrology criterion; or 



3. One or more primary hydrologic 

 indicators below, which, when 

 considered with evidence of frequency 

 and duration of rainfall or other 

 hydrologic conditions, provide evidence 

 sufficient to establish that an area is 

 inundated for 15 or more consecutive 

 days or saturated from surface water or 

 from groundwater to the surface for 21 

 or more consecutive days during the 

 growing season in most years, are 

 materially present 



a. Surface water inundation; or 



b. Observed free water at the surface 

 in an unlined borehole; or 



c. Water can be squeezed or shaken 

 from a soil sample taken at the soil 

 surface; or 



d. Oxidized stains along the channels 

 of living roots (Oxidized rhizospheres); 

 or 



e. Sulfidic material (distinct hydrogen 

 sulfide, rotten egg odor) writhin 12 inches 

 of the soil surface; or 



f. Specific plant morphological 

 adaptation/responses to prolonged 

 inundation or satiu'ation: 

 pneimiatophores, prop roots, 

 hypertrophied lenticels, arenchymous 

 tissues, and floating stems and leaves of 

 floating-leaved plants grovmig in the 

 area (may be observed lying flat on the 

 soil), and buttressed trunks or stems. 



Note: Always consider the frequency and 

 duration of these primary indicators and of 



the wetness that created them, and whether 

 significant hydologic modification (e.g.. 

 Drainage) has effectively removed wetland 

 hydrology from the site. 



4. If none of the indicators in items 1, 

 2, or 3 above is present, one or more of 

 the follovydng secondary hydrologic 

 indicators should be used in conjunction 

 with corroborative information (e.g., 

 maps) that supports a wetland hydology 

 determination: 



a. Silt marks (waterbome silt 

 deposits) that indicate inundation; or 



b. Drift lines; or 



c Sturface-scoured areas; or 

 d. Other common plant morphological 

 adaptations/responses to hydrology: 

 shaUow root systems and adventitious 

 roots. 



These secondary indicators may only 

 be used in conjunction with other 

 corroborative information that indicates 

 wetiand hydrology (e.g., regional 

 indicators of saturation, hydrologic 

 gauge data, county soil surveys. 

 National Wetiandis Inventory maps, 

 aerial photographs, or reliable persons 

 with local knowledge of intmdation 

 and/or saturated conditions). This 

 information must be of siifficient quality 

 and extent that when taken together 

 with secondary indicators clearly 

 supports the presence of wetiand \ 



hydrology for the necessary time, 

 diu-ation, and frequency. This type of 

 information may also can be used to 

 support determinations based on the 

 primary indicators listed above. 



Note: Unless specifically addressed in this 

 manual as disturbed areas, areas without any 

 of the above hydrologic indicators are 

 nonwetland. In areas of suspected significant 

 hydrologic modification, follow the disturbed 

 area procedures to determine if wetland 

 hydrology still exists. 



Wetland Hydrology Background 



The driving force creating wetlands is 

 "weUand hydrology," tiiat is, permanent 

 or periodic inundation, or soil sa titration 

 for a significant period (inundated for 15 

 or more consecutive days or saturated 

 from surface water or from groundwater 

 to the surface for 21 or more consecutive 

 days) during the grov/ing season in most 

 years. Many wetiands are found along 

 rivers, lakes, and estuaries where 

 flooding is likely to occur, while otiier 

 wetiands form in isolated depressions 

 stuTOtmded by upland where surface 

 water collects. Still others develop on 

 slopes of varying steepness, in surface 

 water drainageways, or where ground /■* 

 water discharges to the land surface in v 

 spring or seepage areas. Thus, 

 landscape position provides much 

 insight into whether an area is likely to 

 be subjected to wetland hydrology. 



