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



40479 



Note: Only those areas showing signs of 

 wetness should be considered to meet the 

 wetland hydrology criterion. 



(Q Examine additional aerial photos, 

 National Wetland Inventory maps, or 

 other infonnation for indication of 

 wetland or signs of wetland hydrology. 

 If other information, coupled with the 

 previous infonnation is substep B, 

 indicates that the area is wet more often 

 than not (e.g., 3 of 5 years or 8 of 10 

 years), or indicates Uiat the area is wet 

 half of the time (e.g., 3 of 6 years or 5 of 

 10 years), then the wetland hydrology 

 criterion is presiuned to be met. If other 

 information, coupled with the previous 

 information in substep 2, provides 

 indication that the area is wet less often 

 than not (e.g., 2 of 5 years or 4 of 10 

 years), then the wetland hydrology 

 criterion is presumed not to be met. If it 

 is perceived after reviewing additional 

 information that wetland hydrology is 

 still inconclusive, proceed to substep D. 



(D) Inspect the site for direct evidence 

 of inundation or prolonged soil 

 saturation or other field evidence of 

 wetland hydrology (excluding soil 

 properties resulting from long-term 

 hydrology) to determine whether the 

 wetland hydrology criterion is met. 

 Ideally, such inspection should be done 

 during the early or wet part of the 

 growing season during a normal rainfall 

 year. Avoid periods after heavy rainfall 

 or immediately after more normal 

 rainfaUs. After conducting the onsite 

 inspection, if necessary, proceed to 

 substep E in areas where vegetation has 

 not been removed or cultivated or to 

 substep G in cultivated areas to perform 

 a more rigorous assessment of 

 vegetation and/or hydrology and 

 document your reason for doing so. 



(E) Inspect the site on the ground to 

 assess changes in the plant community. 

 If OBL or OBL and FACW plant species 

 (especially in the herb stratum) are 

 dominant or scattered throughout the 

 site and UPL species are absent or not 

 dominant, the area is considered to meet 

 the wetland hydrology criterion and 

 remains wetland. If UPL species 

 predominate one or more strata (i.e., 

 they represent more than 50 percent of 

 the dominants in a given stratiun) and 

 no OBL species are present, then the 

 area is considered effectively drained 

 and is no longer wetland. 



Note: Make sure that the UPL species are 

 materially present and dominate a valid 

 stratum. 



If the vegetation differs from the 

 above situations, then the vegetation at 

 this site should be compared if possible 

 with a nearby undisturbed reference 

 area, so proceed to substep F; if it is not 

 possible to evaluate a reference site and 



the area is ditched, chaimelized or tile- 

 drained, go to substep G. 



(F) Locate a nearly undisturbed 

 reference site v«th vegetation, soils, 

 hydrology, and topography similar to the 

 subject area prior to its alteration, 

 examine the vegetation (following an 

 appropriate onsite delineation method), 

 and compare it with the vegetation at 

 the project site. If the vegetation is 

 similar (i.e., has the same dominants or 

 the subject area has different dominants 

 with the same indicator status or wetter 

 as the reference site), then the area is 

 considered to be wetland — the wetland 

 hydrology criterion is presumed to be 

 satisfied. If the vegetation has changed 

 to where FACU and UPL species or UPL 

 species alone predominate and OBL 

 species are absent, then the area is 

 considered effectively drained and is 

 nonwetland. If the vegetation is different 

 than indicated above, additional work is 

 required — go to substep G. 



(G) Select one of the following 

 approaches to further assess the area's 

 hydrology: 



(1) Determine the "zone of influence" 

 of the drainage structure and its effect 

 on the water table using existing SCS 

 soil drainage guides, the ellipse 

 equation, or similar drainage model 

 (SCS soil drainage guides and the ellipse 

 equation relate only to water table and 

 do not address surface water), and 

 determine the effect of the drainage 

 structure on surface water (ponding and 

 flooding). Factors to consider when 

 analyzing the effect of the drainage 

 structure on surface water are: (a) The 

 type of drainage system (e.g., size, 

 spacing, depth, grade, and outlet 

 conditions); (b) surface inlets; (c) 

 condition of the drainage system; (d) 

 how surface water is removed; and (e) 

 soil type as it related to runoff. 



(2) Conduct detailed ground water 

 studies, making direct observations of 

 inundation and soils saturation 

 throughout the area in question. Data 

 should be collected in the follovmig 

 manner 



(a) Depth of Wells. Well should be 

 placed within 24 inches of the soil 

 surface or to the top of the restrictive 

 horizon, if shallower. 



(b) Annual Observation Period. 

 Observations should be made during the 

 expected high water table period 

 including both the nongrowdng and 

 growing seasons; the recommended 

 period of observation will vary 

 regionally. At a minimum the period 

 should encompass a three month period 

 during the wettest part of the growing 

 season and include the month before the 

 start of the growing season if the wettest 

 part is in the Spring. 



(c) Frequency of Observation. During 

 the observation periods, the wells 

 should be observed a minimum of two 

 times per week at a reg\ilar interval not 

 to exceed four days between 

 observations; for soils with anticipated 

 rapid fluctuations of the water table 

 (e.g., sandy soils), a one or two day 

 observation interval is recommended. 



(d) Length of Study. A minimum of 

 three annual observation periods, each 

 having at least 90% of average yearly 

 precipitation and at least 90% of normal 

 monthly distribution. Also, the year 

 prior to the water table study must have 

 had 90% of the monthly and aimual 

 precipitation. The observation study 

 may cease after the minimum 

 consecutive time period required for 

 meeting the wetland hydrology criterion. 



Note: Data from any year that does not 

 have 90% of average precipitation cannot be 

 counted toward the three-year study duration 

 unless it can be adequately justified in a 

 specific case. 



Precipitation information should be 

 locally derived (not necessarily site- 

 specific) from the nearest NOAA- 

 approved weather station or other 

 available sources of technically valid 

 information (e.g.. university branch 

 stations or research sites, media 

 weather stations, USGS stations, stale 

 agency stations, etc.). These 

 precipitation stations must be located 

 within 25 miles of the monitored water 

 table study. If this is not possible, 

 consult appropriate regulatory agency 

 for alternatives. 



If the wetland hydrology criterion is 

 met, return to the applicable step in the 

 onsite determination method being used 

 and continue delineating the wetland. 



Appendix 8. Procedures for Exceptions 

 to the Three Criteria 



Wetlands that are exceptions to the 

 three criteria are to be identified using 

 the procedures below. 



1. What is the reason for the 

 exception? (Identify vegetation or 

 hydrology as the reason for the 

 exception.) 



If vegetation is the reason for the 

 exception, go to 2a. If hydrology, go to 

 2b. 



2a. Is the plant community growing on 

 a soil that meets the hydric soil 

 criterion? 



If no, the area is non-wetland. 



If yes, document the reasons for this 

 conclusion and go to 3a. 



3a. Are one or more of the following 

 conditions satisfied? 



• Hydrologic records or aerial 

 photography combined with hydrologic 

 records (items 1 and 2 of wetlands 



